YELLOW.——_a._ A solution of sesquioxide or rust of iron, 1/2 lb., in

hydrochloric acid, 1 quart, diluted with water.——_b._ To a strong

decoction of French berries add a little alum.——_c._ A simple solution of

chromate or bichromate of potash in distilled water.——_d._ A solution of

equal parts of nitre and either chromate or bichromate of potash, in

water.

_Obs._ Most of the above require filtering, which should be done through

powdered glass, placed in a glass funnel, and never through paper. They

usually need a second filtration, after being exposed to the light for

some weeks; hence it is convenient always to make a little more of them

than is required to fill the bottle, as several of them, when diluted

after filtration, become again turbid. Distilled water or filtered rain

water should be used.

=SHRIMP.= See SHELL-FISH.

=SHRUB.= A species of concentrated cold punch, prepared with lemon juice,

spirit, sugar, and water. When the word is used in its unqualified form,

RUM SHRUB is alluded to.

=Shrub, Brandy.= _Prep._ 1. Take of brandy, 1 gall.; orange and lemon

juice, of each 1 pint; peels of 2 oranges; do. of 1 lemon; digest for 24

hours, strain, and add of white sugar, 4 lbs., dissolved in water, 5

pints; in a fortnight decant the clear liquid for use.

2. As RUM SHRUB (below), but using brandy.

=Shrub, Lemon.= _Syn._ LEMONADE SHRUB. Concentrated lemonade, either with

or without the addition of a little spirit. Used to make lemonade or lemon

sherbet.

=Shrub, Punch.= Concentrated punch, made with equal parts of spirit and

water. Used to make punch.

=Shrub, Rum.= _Prep._ 1. As BRANDY SHRUB, but substituting rum for brandy.

2. Take of rum, at proof, 34 gall. (or, if of any other strength, an

equivalent quantity); essential oils of orange and lemon, of each 2 oz.,

dissolved in rectified spirit, 1 quart; good lump sugar, 300 lbs.;

dissolved in water, 20 galls.; mix well by ‘rummaging,’ and gradually and

cautiously add of Seville orange juice, or of a solution of tartaric acid

in water, q. s. to produce a pleasant but scarcely perceptible acidity;

next ‘rummage’ well for 15 minutes, then add sufficient water to make the

whole measure exactly 100 galls., and again ‘rummage’ well for at least

half an hour; lastly, bung the cask down loosely, and allow it to repose

for some days. In a fortnight, or less, it will usually be sufficiently

‘brilliant’ to be racked. The product is 100 galls., at 66 u. p.

_Obs._ Rum shrub is the kind in the greatest demand, and that having a

slight preponderance of the orange flavour is the most esteemed. If wholly

flavoured with lemon it is apt to acquire a kind of ‘dead’ or ‘musty’

flavour by long keeping. The substitution of a few gallons of brandy for a

portion of the rum, or the addition, after racking, of about 1 oz. each of

bruised bitter almonds, cloves, and cassia, the peels of about 2 dozen

oranges, and a ‘thread’ of the essences of ambergris and vanilla, render

it delicious.

=SIAL′OGOGUES.= Medicines which increase the flow of saliva. Mercurials

and pellitory of Spain belong to this class.

=SICK′NESS.= Nausea and vomiting frequently arise from the use of improper

food, and other articles which offend the stomach; at other times it is

symptomatic of some disease, as colic, cholera, dyspepsia, head

affections, incipient fever, &c.; in which case the primary affection

should be attended to. Nausea lowers the pulse, contracts the small

vessels, occasions cold perspiration, severe rigors, and trembling; and

diminishes, as long as it lasts, the actions, and even the general powers,

of life. The act of retching, and vomiting more especially, on the

contrary, rouses rather than depresses, puts to flight all the preceding

symptoms, and often restores the system to itself.

The best remedies or palliatives in these affections are effervescing

saline draughts, either with or without the addition of a few drops of

tincture of henbane, or tincture of opium. A glass of genuine lemonade,

iced, or a spoonful of crushed ice in a wine-glassful of mint water, is

also very serviceable. Pepsin (Bullock and Reynolds) and oxalate of cerium

are said to be most valuable remedies in the sickness of pregnancy. See

DRAUGHTS, PREGNANCY, SEA SICKNESS, &c.

=SIFT′ING= is to pulverulent substances what filtration is to liquids; but

in this case the medium through which the substance passes is, usually, of

a simpler and coarser description. Sieves are commonly employed for the

purpose, which are fitted with silk or brass-wire gauze for fine purposes,

and horsehair cloth, or wire netting, for coarser ones. Drum sieves are

such as are furnished with covers and an enclosed space to receive the

fine powder that passes through, by which dust and loss are prevented.

=SIGHT.= See VISION.

=Sight, Effect of Gaslight on.= The German Minister of Instruction has

recently issued a report on the influence of gaslight on the eye. The

conclusion arrived at in this report——the result of frequent conference

with well-known physicians——is that no evil results follow a moderate use

of gas, if the direct action of the yellow flame on the eye is prevented.

For this purpose screens or shades are employed. Very great objections,

however, exist to the use of zinc or lead shades, most evils affecting the

eye being traceable to them. Their use, it is said, inevitably tends to

blindness or inflammation, and other harmful effects. The milky-white

glass shade is the best, as it distributes the light and has a grateful

effect on the eyes. The burner should not be too close to the head, as

congestions of the forehead and headaches result from the radiated heat.

The glass plate below the gas, employed in some places, is especially

useful for the purpose, as it causes an equal distribution of the

light——necessary where a number are working at one burner——prevents the

radiation of heat, and tends to a steady illumination by shielding the

flames from currents of air. In cases of highly-inflamed eyes, dark-blue

globes can be very beneficially employed. With precautions of this kind no

evil effects from the burning of gas need be feared.

=SIG′NATURES (Fac-similes of).= These may be readily obtained as

follows:——

1. Let the name be written on a piece of paper, and, while the ink is

still wet, sprinkle over it some finely-powdered gum Arabic, then make a

rim round it, and pour on it some fusible alloy in a liquid state.

Impressions may be taken from the plates formed in this way, by means of

printing ink and the copper-plate press.

2. By the use of transfer ink and lithography.

=SILBER LIGHT.= This light is thus described in ‘Dingler’s Polytechnic

Journal,’[161]——This mode of illumination is recommended where gas cannot

be had.

[Footnote 161: ccix, 79 (‘Journ. Chem. Society,’ vol. xi, new series,

1273).]

The material used is oil, which is converted into gas before combustion

takes place, whereby the combustion of the wick is greatly lessened (one

wick may last a year); the accumulation of impurity is obviated, and the

prevention of smell completely effected. The light is regular and uniform,

and of a white colour. The light, with a burner 1-1/4 inch wide, is equal

to that of 28 sperm candles, each consuming 120 gr. per hour, and with one

1-3/4 inch wide a light is obtained equal to 50 such candles.

The burning apparatus consists of a row of concentrically enclosed double

cylinders, perpendicularly arranged at definite intervals. The innermost

cylinder contains the wick between its two walls, the hollow space in the

interior serving to convey fresh air to the interior of the flame. The

second cylinder conveys air to the outer side of the wick, and the third

contains oil, and is in direct communication with both wick and reservoir.

The mouths of all these chambers have a dome-shaped head, and form a

suitable opening in this; the gas streams forth in such a manner that it

comes in contact with a current of air, and thus a complete combustion is

attained.

According to the nature of the oil burnt the construction is somewhat

varied in its minor details. Rape oil or light hydrocarbon oils are

mentioned.

=SIL′ICA.= SiO_{2}. _Syn._ SILICIC ANHYDRIDE, SILICIC ACID, SILEX,

SILICEOUS EARTH†, EARTH OF FLINTS†. This exists in quartz and rock crystal

in a nearly pure state. The sands of rivers and the sea-shore, flint, and

almost all the scintillating stones, chiefly consist of it.

Silica occurs under two conditions——the crystalline and the amorphous. The

former variety has a sp. gr. of 2·642; the amorphous of 2·2-2·3. Some of

our well-known native gems and precious stones consist almost wholly of

one of the above forms of silica. In agate and calcedony the two varieties

are combined. Amethyst is silica, coloured purple by ferric oxide. Onyx is

formed of calcedony arranged in layers of different colours. Cornelian is

a red or brown variety of silica coloured with ferric oxide, whilst opal

is amorphous silica combined with varying quantities of water. Silica is

present in the stems of certain plants, such as wheat, many grasses, to

which the shining appearance of the stems is due, &c. The Italians polish

marble with the ashes of burnt straw, the usefulness of which for such a

purpose depends upon the silica contained in the straw; for similar

reasons the Dutch rush is thus employed. Silica also occurs in solution in

many natural waters. In the geysers, or boiling springs of Iceland, it

exists in large quantity.

It may be obtained in a state of absolute purity by passing gaseous

fluoride of silicon into water, collecting the resulting gelatinous

precipitate on a calico filter, washing it with distilled water, drying

it, and heating it to redness. Another method is to precipitate a solution

of silicate of soda or potassa (soluble glass) with dilute hydrochloric

acid, and to treat the precipitate as before.

Nearly pure silica may also be procured by heating colourless quartz to

redness, and plunging it into cold water, by which treatment the quartz is

rendered so friable as to be easily reducible to fine powder. Ordinary

flints, subjected to this method, are found to yield silica in a condition

approaching to purity. Amorphous silica is much more easily attacked by

solvents than the crystalline variety. The artificial forms of silica are

all amorphous.

The test for a silicate consists in fusing the suspected body with sodic

or potassic carbonate, heating the residue with acid, and evaporating to

dryness. If the residue be then treated with hot water the silica remains

undissolved in the form of a white powder, which will yield a colourless

bead when fused with sodic carbonate upon a piece of platinum foil before

the blowpipe flame. If silica be fused with borax it becomes slowly

dissolved, forming a clear, colourless bead.

Chapman contests Plattner’s opinion that, when silicates are fused with

phosphor salt, the ‘silica skeleton’ that results is especially due to the

presence of alkalies or earthy bases.

Chapman says: “It is true enough that silicates in which these bases are

present exhibit the reaction; but as other silicates——practically all,

indeed——exhibit the reaction also, the inference implied in the above

statement is quite erroneous.

“The opalescence of the glass arises entirely from precipitated silica.

“If some pure silica (or a silicate of any kind), in a powdered condition,

be dissolved before the blowpipe flame in borax until the glass be

saturated, and some phosphor salt be then added, and the blowing be

continued for an instant, a precipitate of silicate will immediately take

place, the bead becoming milky white (or, in the case of many silicates,

opaque) on cooling. This test may be resorted to for the detection of

silica in the case of silicates, which dissolve with difficulty in

phosphor salt alone, or which do not give the pronounced ‘skeleton’ with

that reagent.”[162]

[Footnote 162: Chapman on ‘Blow-pipe Reactions.’]

_Prop., &c._ A fine, white, tasteless, infusible powder, insoluble in all

acids, after being heated, except the hydrofluoric; requires the heat of

the oxyhydrogen blowpipe for its fusion; approaches the precious stones in

hardness; soluble in strong alkaline solutions; its salts are called

SILICATES. Sp. gr. 2·66. See GLASS, GLASS, SOLUBLE, &c.

=Silica, Hydrates of.= By pouring a dilute solution of sodium silicate

into a considerable excess of hydrochloric acid the whole of the silica is

retained in solution, together with the chloride of sodium formed by the

action of the hydrochloric acid upon the soda. By subjecting this solution

to dialysis (see DIALYSIS) the hydrochloric acid and chloride of sodium

are removed, whilst the hydrate of silica is left behind, in solution, in

the dialyser. Graham recommends a stratum of the liquid four tenths of an

inch in depth, to be subjected for four or five days to dialysis, the

water in the outer vessel to be changed every twenty-four hours.

If the solution so obtained be carefully evaporated down in a flask, and

any drying of the silicic acid at the edges of the liquid being prevented,

a solution may be obtained containing 14 per cent. of silica.

The solution has a very feebly acid reaction, and is without taste or

colour. It cannot be preserved in the liquid state for more than a very

few days, even in well-closed vessels, but becomes converted into a

transparent gelatinous mass, which separates from the water. Hydrochloric

acid, as well as small quantities of caustic potash or soda, retard the

coagulation.

When the solution is evaporated _in vacuo_ at 59° F. over sulphuric acid,

a lustrous transparent glass is left behind, which consists of 22 per

cent. of water, which closely accords with the formula SiO_{2}H_{2}O.

By the action of moist air upon silicic ether a transparent glassy hydrate

was obtained by Ebelmen, to which this chemist assigned the formula

2SiO_{2},3H_{2}O. Two hydrates of silica were obtained by Fuchs, one

having the formula 3SiO_{2},H_{2}O, the other, 4SiO_{2},H_{2}O.

=Silicic Chloride.= _Syn._ SILICIC TETRACHLORIDE. (SiCl_{4}.) This

compound is rarely, if ever, obtained by the direct method, viz. by

heating silicon in chlorine, but by the following indirect process:——A

paste is made of finely divided silica, oil, and charcoal, and heated in a

covered crucible. The fragments of the charred substance (consisting of

silica and carbon) are then placed in a porcelain tube, which is raised to

a red heat in a furnace, and during the ignition of the fragments a

current of dry chlorine is passed into and over them; the silicic chloride

which is thus formed being made to distil over into a bent tube

surrounded by a freezing mixture of ice and salt, whereby it becomes

condensed.

Silicic chloride is a very voluble and strongly fuming gas, transparent

and colourless, with an irritating and pungent smell. It is immediately

decomposed by water into hydrochloric acid and hydrated silica, which

deposits in the vessel.

=Silicic Fluoride.= _Syn._ SILICIC TETRAFLUORIDE. (SiF_{4}.) This gas is

best prepared by heating in a capacious flask or retort equal parts of

finely powdered fluorspar and white sand, or glass with ten or twelve

times their weight of strong sulphuric acid. This gas must be collected

over mercury, and in jars that are free from the least trace of moisture.

Silicic fluoride is a colourless gas, with a very pungent odour, fuming

strongly in the air, and neither burning nor supporting combustion.

Faraday succeeded in liquefying it under great pressure, and Natterer

states that at a temperature of -220° F. it may be solidified. By water it

is partially decomposed and partially dissolved, yielding silicic acid and

hydrofluosilic acid.

With twice its volume of ammoniacal gas silicic fluoride combines to form

a crystalline volatile. Silicic hydride has an acid reaction.

=Silicic Hydride.= (H_{4}Si?) To procure this gas silicide of magnesium is

decomposed with cold diluted hydrochloric acid.

The silicide of magnesium may be prepared as follows:——Mix intimately 40

parts of fused magnesic chloride, 35 of dried sodic silico-fluoride, and

10 of fused sodic chloride; these are mixed in a warm, dry tube, with 20

parts of sodium in small fragments, and thrown into a red-hot Hessian

crucible, which is immediately covered, the operation being finished when

the vapours of sodium cease to burn.

Silicic hydride becomes spontaneously ignited in the air, and in doing so

gives off white fumes, which consist of amorphous silica (SiO_{2}). A cold

body, such as a piece of porcelain or glass, introduced into the flame,

becomes covered with a brown deposit of reduced silicon. Passed into

solutions of cupric sulphate, argentic nitrate, and palladium chloride,

this gas throws down the metals, in most cases combined with silicon.

=SILICOFLUORIC ACID.= See FLUOSILICIC ACID.

=SIL′ICON.= Si. _Syn._ SILICIUM. An elementary substance forming the base

of silica.

This element was first obtained by Sir Humphry Davy, by acting upon silica

with potassium. It is now procured much more easily by the decomposition

of silico-fluoride of potassium, at an elevated temperature, with

potassium or sodium. By heating a mixture of fluorspar and ground flints

with sulphuric acid a gaseous tetra-fluoride of silicon is formed, which,

being partially soluble in water, yields an acid solution of the

tetra-fluoride. Caustic potash is then added to the acid solution of the

tetra-chloride until it becomes neutralised, and the sparingly soluble

silico-fluoride of potassium thus formed is thoroughly dried and mixed in

a glass or iron tube with eight or nine tenths of its weight of potassium

or half its weight of sodium, and heated. The following equation explains

the reaction that takes place:

2KF,SiF_{4} + 2K_{2} = Si + 6KF.

The resulting mass, consisting of potassic fluoride, and reduced silicon

in partial combination with the excess of potassium, is treated with cold

water, when a copious evolution of hydrogen gas ensues, owing to the

decomposition of the water by the excess of potassium. The potassic

fluoride is got rid of by washing with cold water, its entire removal

being indicated by the water ceasing to have an alkaline reaction on test

paper, whilst amorphous silicon is left behind in the form of a brown

powder.

Another method by which silicon may also be procured is by passing the

vapour of silicic chloride over heated potassium or sodium, placed on a

porcelain tray in a glass tube. In this operation it is advisable to

protect the lining of the tube with thin plates of mica.

The silicon obtained by the above processes is known as _amorphous

silicon_, and, as already stated, occurs as a brown powder. It is dull in

colour, and, being heavier than water, as well as insoluble in it, sinks

in that fluid. It is a non-conductor of electricity, is unaffected by

nitric or sulphuric acid, but dissolves readily in hydrofluoric acid, and

in a warm solution of caustic potash. It burns with great brilliancy when

heated in air or oxygen, and becomes converted into silica, which, owing

to the great heat of combustion, fuses, and thus forms a superficial crust

over the unburnt silicon. A _crystalline_ variety of silicon may also be

procured by heating the brown amorphous silicon, already described,

intensely in a platinum crucible, with exclusion of air. This crystalline

silicon so obtained is much darker in colour than the amorphous, and also

considerably denser; besides which it differs widely in properties from

the latter. It will not take fire if heated strongly in the air or oxygen,

even if before the blowpipe flame. Its density is such that it sinks in

strong sulphuric acid, and hydrofluoric acid fails to dissolve it,

although it is soluble in a mixture of hydrofluoric and nitric acids. It

does not become oxidised, even if fused with potassic nitrate or chlorate,

unless a white heat is obtained, when it burns brilliantly, giving rise,

on so doing, to the formation of silica.

In addition to the above, a _graphitoid_ form of silicon, occurring in

plates, has been described by Deville and Wöhler. These chemists obtained

this last modification from an alloy of silicon and aluminium, which was

treated in succession with boiling hydrochloric and hydrofluoric acids.

The plates of silicon which are left have a metallic lustre, and a sp.

gr. of 2·49. The graphitoid bears a great resemblance in properties to the

crystalline silicon. It is a conductor of electricity. Like the

crystalline variety, it dissolves in a mixture of hydrofluoric and nitric

acids, although slowly, but, unlike the crystalline, it undergoes no

change when heated to whiteness in a current of oxygen.

Deville states that silicon requires a temperature between the melting

points of iron and steel to fuse it. He effected its fusion in a platinum

crucible lined with lime, the platinum crucible being then placed in a

clay crucible, which was then exposed to intense heat in a wind furnace.

By passing the vapour of silicic chloride over pure aluminium, placed on a

porcelain tray, and raised to an intense heat, the aluminium becomes

volatilised as aluminic chloride, whilst the silicon remains behind in

crystals possessing a reddish lustre. These crystals occur in regular

six-sided prisms, terminated by three-sided pyramids, derived from the

octohedra, and are so hard that glass may be cut by them, in the same way

as by the diamond.

With oxygen silicon forms only one oxide, silica, described above.

=SILK.= As an article of clothing, as far as “roundness of fibre, softness

of texture, absence of attraction for moisture, and power of communicating

warmth, are concerned, silk is greatly superior to both linen and cotton;

moreover, it gives the sensation of freshness to the touch which is so

agreeable in linen. But, with all these advantages, silk (when worn next

the body) has its defects; on the slightest friction it disturbs the

electricity of the skin, and thus becomes a source of irritation.

Sometimes, it is true, this irritation is advantageous, as causing a

determination of blood to the surface; but when this action is not

required, it is disagreeable, and quite equal, in a sensitive

constitution, to producing an eruption on the skin. I have seen eruptions

occasioned in this manner, and, when they have not occurred, so much

itching and irritation as to call for the abandonment of the garment.”

(Eras. Wilson.)

Silk is characterised by its fibres appearing perfectly smooth and

cylindrical, without depressions, even under a magnifying power of 160.

Its fibres (even when dyed) acquire a permanent straw-yellow colour when

steeped in nitric acid of the sp. gr. 1·20 to 1·30. The fibres of white or

light-coloured silk are similarly stained by a solution of picric acid. A

thread of silk, when inflamed, shrivels and burns with difficulty, evolves

a peculiar odour, and leaves a bulky charcoal. By these properties silk is

distinguished from cotton and linen.

Cotton, wool, and silk may be easily distinguished from each other by

means of the microscope.

The cotton fibre will be seen to consist of only one cell; wool (as well

as hair and alpaca) is made up of numerous cells in juxtaposition; whilst

silk fibre is similar to the secreted matter of spiders and caterpillars.

[Illustration: FIG. 1-3.]

The silk fibre (fig. 1) is smooth, cylindrical, devoid of structure, not

hollow inside, and equally broad. The surface is glossy, and only seldom

are any irregularities seen on it. If it is desired to detect in a woven

fabric the genuineness of the silk, it is best to cut a sample to pieces,

place it under water under the object-glass of a microscope, magnifying

120 to 200 times, covering it with a thin piece of glass. The round,

glazed, equally proportioned silk fibre (fig. 1), is easily distinguished

from the unequalled and scaled wool fibre (W in fig. 2), and from the

flat, band-like, and spiral cotton fibre (B, fig. 3). Under the microscope

also the mixture of inferior with superior fibres of silk can be easily

detected.

Black silk, the weight of which has been augmented by extensive

sophistication, is not uncommon in English, French, and German markets. It

is known as ‘weighted’ or ‘shotted’ silk, and very frequently contains no

more——and frequently less——than one third of its weight of silk, the

remaining two thirds consisting, according to Persoz, of a combination of

iron salts, with some astringent substance, salts of tin, and cyanides. It

is easily distinguishable from genuine silk by its want of elasticity and

tenacity, and its much greater combustibility. Persoz found a specimen of

this adulterated silk to yield, upon incineration, more than 8 per cent.

of ferric oxide.

The cleaning and renovation of articles of wearing apparel made of silk

are matters requiring some care. No silk goods look well after being

washed, however carefully it may be done; and this method should,

therefore, never be resorted to but from absolute necessity. It is

recommended to sponge faded silks with warm water and curd soap, then to

rub them with a dry cloth on a flat board, and afterwards to iron them on

the wrong side with an ordinary smoothing iron. Sponging with spirit,

benzol, or pure oil of turpentine, also greatly improves old silk, and is

often preferable to any other method. The odour of the benzol passes off

very quickly, that of the turpentine after exposure for a few days. When

the ironing is done on the right side thin paper should be spread over the

surface to prevent ‘glazing.’ See DYEING, GILDING, &c.

=Silk Material, a New.= The ‘Textile Manufacturer’ contains the

following:——The utilisation of new substances as raw material for

manufactures is a distinguishing feature of the scientific investigations

of the nineteenth century. One of the most recent suggestions is the

result of the researches of Herr Tycho Tulburg, an eminent German

naturalist, on the products of the mussel. It will be remembered it was

from one of the mussel species the famous purple dye was in past ages

obtained, and this colour gained an imperishable renown from its being

adopted by the Roman emperors, and the imperial purple became the symbol

of sovereignty. In these latter days animal products have been displaced

by aniline dyes, and there is no likelihood of their regaining their

former celebrity. The researches of Tulburg have not, however, been in the

direction of dyes, but in the adaptation of animal products other than the

silkworm for silk yarns. The mussel (_Mytilus edulis_) fastens itself to

the rocks by strong threads, called by naturalists _byssus_, and it is

this substance which it is proposed to utilise for the manufacture of

silk. The material is of a silky texture and very tough, and the

experiments that have been made prove that it is well adapted to be made

into yarn. Already the _Pinna_, one of the mussel tribe, has been already

manufactured into fabrics, although it is not of general use, nor at

present of much commercial value, and the same obstacles to the use of the

_byssus_ of the common mussel are apparent. Notwithstanding the abundant

supply of this popular shell fish, it is difficult to see how a sufficient

quantity of _byssus_ can be collected to enable manufacturers to purchase

the raw material at rates low enough for a marketable remuneration on the

manufactured article. But the records of industrial progress testify to

greater difficulties than these having been successfully overcome; and

should the commercial value of the new material be satisfactorily

demonstrated, there is no doubt some agency will be developed whereby the

requisite supply may be obtained.

At present it is sufficient to notice the discovery that has been made,

and to welcome another instance of the results of scientific labour being

for the advantage of manufacturers.

=SILK′WORM, Diseases of.= Silkworms are liable to a disease known as

_pébrine_, which Pasteur has shown to be due to the presence, on the body,

the egg, and in the blood of the insect, of peculiar parasitic corpuscles.

Pasteur states that the black specks which constitute these bodies are

very easily distinguishable in the moth of the silkworm, but that in the

earlier stages of its development, such as in the egg and worm condition,

the detection of them becomes difficult, if not impossible. Pasteur

further adds that sound moths produce sound eggs, and unsound moths the

reverse, and that although the unsound eggs show no sign of disease, they

never give rise to healthy worms.

Pasteur advises the silk cultivator, therefore, to ensure breeding from

healthy moths at starting, and to abandon the old and useless precaution

of hatching apparently healthy eggs.

The loss resulting from the silkworm disease in Italy may be seen from the

following tables, which are calculated for bales of 102 lbs.

weight:[163]——

[Footnote 163: ‘British Manufactory of Industries,’ Stamford.]

Average production prior to disease, 81,600.

1863 Bales, 50,600 Deficit, 38 per cent.

1864 ” 38,000 ” 53 ”

1865 ” 38,700 ” 52 ”

1866 ” 39,600 ” 51 ”

1867 ” 44,000 ” 46 ”

1868 ” 41,000 ” 49 ”

1869 ” 47,300 ” 42 ”

1870 ” 69,900 ” 14 ”

1871 ” 76,300 ” 6 ”

1872 ” 68,000 ” 16 ”

The value of the cocoons grown in the whole world in 1870 was said to be

as follows:——France, £4,334,000; Italy, £11,260,000; Spain and other

European countries, £984,000; giving a total for Europe of £16,588,000.

China, £17,000,000; India, £4,800,000; Japan, £3,200,000; Persia,

£920,000; other Asiatic states, £2,192,000; giving a total for Asia of

£28,112,000. Africa, £68,000. America, £20,000. Making a general total of

£44,788,000.

=Silkworm Gut.= See GUT.

=SIL′LABUB.= _Prep._ Grate off the yellow peel of a lemon with lump sugar,

and dissolve the sugar in 3/4 pint of wine; add the juice of 1/3 a lemon,

and a 1/4 pint of cream; beat the whole together until of a proper

thickness, and then put it into glasses.

_Obs._ 3/4 to 1 pint of new milk is often substituted for the cream, and

strong cider or perry for the wine. Grated nutmeg is often added. When

‘whipped’ to a froth it is called ‘WHIPPED SILLABUB,’ See CREAM (Whipped).

=SILVER.= Ag. _Syn._ ARGENTUM, L. This metal, like gold, appears to have

been as much valued in the remotest ages of antiquity of which we have any

record, as at the present time. It is found in nature, both in the

metallic state and mineralised, in the state of alloy, and combined with

sulphur, chlorine, and other metallic sulphurets. In Great Britain it is

found in combination chiefly with lead. It is extracted from its ores

principally by the process of amalgamation, founded on its easy solubility

in mercury, and by subsequent cupellation. It is only prepared on the

large scale.

Chemically pure silver may be obtained by the methods noticed

subsequently.

_Prop._ Pure silver has a very white colour, a high degree of lustre, is

exceedingly malleable and ductile, and is the best conductor of heat and

electricity known. Its hardness is between that of copper and gold; its

sp. gr. is 10·475 to 10·500; it melts at about 1873° Fahr.; or bright

redness (Daniell); is freely soluble in nitric acid, and dissolves in

sulphuric acid by the aid of heat; it refuses to oxidise alone at any

temperature, but, when strongly heated in open vessels, it absorbs many

times its bulk of oxygen, which is again disengaged at the moment of

solidification; its surface is rapidly tarnished by sulphuretted hydrogen

and by the fumes of sulphur.

_Pur._ “Entirely soluble in diluted nitric acid. This solution, treated

with an excess of muriate of soda, gives a white precipitate entirely

soluble in ammonia water, and a fluid which is not affected by

sulphuretted hydrogen.” (Ph. E.)

_Tests._ 1. The compounds of silver, mixed with carbonate of soda, and

exposed on a charcoal support to the inner flame of the blowpipe, afford

white, brilliant, and ductile metallic globules, without any incrustation

of the charcoal.——2. The salts of silver are non-volatile and colourless,

but most of them acquire more or less a black tint by exposure to full

daylight.

The soluble salts of silver give——1. A white curdy precipitate (chloride

of silver) with hydrochloric acid and the soluble metallic chlorides,

which is soluble in ammonia and insoluble in nitric acid, and blackened by

exposure to light;——2. White precipitates with solutions of the alkaline

carbonates, oxalates, and ferrocyanides;——3. Yellow precipitates with the

alkaline arsenites and phosphates;——4. With the arseniates, red

precipitates;——5. With the fixed alkalies, brown precipitates;——6. With

sulphuretted hydrogen and hydrosulphuret of ammonia, a black powder, which

is insoluble in dilute acids, alkalies, alkaline sulphurets, and cyanide

of potassium, but readily soluble, with separation of sulphur, in boiling

nitric acid; and——7. With phosphorus, and with metallic copper or zinc,

pure silver.

_Assay._ 1. The method of assaying silver by cupellation has been

explained under ASSAY and CUPELLATION; and that method is alone applicable

when the alloy contains a very small quantity of silver, as a few ounces

only per ton. When the reverse is the case, as with the silver of

commerce, the following is a much more accurate method:——

2. _Humid assay of silver._——_a._ Dissolve 10 gr. of the silver for assay

in 100 gr. of nitric acid, sp. gr. 1·28, by the aid of heat, the solution

being made in a tall stoppered glass tube, furnished with a foot; then

place it in a very delicate balance, bring it into an exact state of

equilibrium, and add the test solution (see _below_), gradually and

cautiously, until the whole of the silver be thrown down, the number of

grains now required to restore the equilibrium of the balance or scales

gives the exact quantity of pure silver in 1000 parts of the

sample.——_Obs._ To ensure accuracy, after each addition the stopper should

be placed in the tube, and the latter violently agitated for a short time,

when the liquor will rapidly clear and enable us to see when the operation

is concluded. We must then, as a check, add a small quantity of a solution

of nitrate of silver to the liquor in the tube, after having first

carefully taken the weight. If too much of the test liquor has been added,

this will produce a fresh precipitate, and the assay cannot then be

depended on.——Instead of weighing the quantity of test liquor used, a tube

graduated into 100 parts, and holding 1000 gr., may be employed, every

division of which, required to throw down the silver, will represent the

1/10th of a grain. See ALKALIMETRY and ACIDIMETRY.

_b._ The precipitate of chloride of silver may be collected in a paper

filter, and be dried, washed, fused, and weighed. The previous weight of

the paper, deducted from the gross weight of the filter and its contents,

gives the quantity of chloride of silver present, which multiplied by

0·75278, gives the weight of the pure silver in the sample.

_Test liquor._ Dissolve 54·27 (54-1/4) gr. of pure sea salt in 9945·73 gr.

(or 22 oz. and 320-3/4 gr. avoirdupois) of distilled water; filter, and

keep the liquor in a stoppered bottle for use. Pure sea salt is obtained

by boiling together, for a few minutes, in a glass vessel, a solution of

common salt with a little pure bicarbonate of soda; then adding to the

filtered liquor sufficient hydrochloric acid to render it neutral to

litmus and turmeric paper, and, lastly, evaporating and crystallising.

_Obs._ The presence of mercury, lead, or sulphuret of silver, interferes

with the accuracy of the above assay. When mercury is present, the

precipitate blackens less readily by exposure to light; and when it

contains 4/1000 or 5/1000 of chloride of mercury, it remains of a dead

white; with 3/1000 it is not sensibly discoloured by the diffused light of

a room, with 2/1000 only slightly darkened, with 1/1000 more so, but with

pure chloride of silver, the effect is very rapid and intense. When this

metal is present, which is, however, seldom the case, the assay sample

must be placed in a small crucible, and exposed to a full red heat, before

solution in the acid. Another method, proposed by M. Levol, and modified

by M. Gay-Lussac, is to add to the nitric solution of the silver

sufficient acetate of ammonia or crystallised acetate of soda to saturate

all the nitric acid existing in the liquor, either in the free state or

combined with the silver. When the alloy contains lead, shown by the

precipitated chloride being partly soluble in water, it may either be

laminated and subjected to the action of acetic acid before solution in

the nitric acid; or, the test solution of chloride of soda should be

replaced by one of chloride of lead; (139·355 gr. of the latter are equiv.

to 58·732 gr. of the former). The presence of sulphuret of silver is

detected whilst dissolving the sample in nitric acid, by the black flakes

which may be observed floating about in the liquor in an insoluble state.

These flakes may be dissolved by fuming nitric acid, or by adding pure

concentrated sulphuric acid to the solution, which should be then heated

for about a 1/4 hour in a steam-bath. When thus treated, the precipitate

produced by the test liquor represents the whole of the silver contained

in the alloy.

Dr Gräger[164] gives the following process of the preparation of pure

metallic silver:——He dissolved the alloy of silver in nitric acid, taking

care to use as small a quantity of the acid as possible. The solution is

then transferred to a large-sized porcelain basin, and gradually

neutralised with previously lixiviated chalk free from chlorine. The

neutralised liquid is next boiled, and chalk again added to it, while

boiling, until the fluid has become colourless. (In order to test more

accurately, a drop of the liquid is poured on a piece of white

filtering-paper, and next to that drop is placed one of a solution of

ferrocyanide of potassium; as long as the well-known red colouration,

copper reaction, hereby ensues, chalk is added.) The fluid is next

filtered to separate the carbonate of copper, and the filtrate (a solution

of nitrate of silver, and nitrate of lime) is again boiled, and either

further treated with carbonate of lime, or better still, with carbonate of

soda. The bright yellow-coloured precipitate thereby ensuing, a mixture of

carbonate of silver, and carbonate of lime, is washed, dried, and ignited,

leaving a greyish-white mass of metallic silver, mixed with carbonate of

lime. This mixture is treated with dilute hydrochloric acid, washed with

distilled water, and then fused along with borax, yielding pure silver.

The bright green coloured carbonate of copper can be used as a pigment for

painting purposes.

[Footnote 164: ‘Chemical News,’ xxv, No. 641, 119.]

Krüger says:——In frequently experimenting with silver salts, a mixture of

solution of precipitates is obtained, in which silver exists in all kinds

of combination. When such mixtures are shaken up with an ethereal solution

of phosphorus, the solution and the precipitate soon separate, the former

being more or less yellow, the latter intensely black. If light-coloured

particles are perceived in the precipitate, the quantity of phosphorus

solution employed is not sufficient, and more must be added till the

precipitate is uniformly black. The precipitate is next filtered, washed,

and dried, or placed while still damp, in a porcelain dish and boiled with

potash solution. Pure metallic silver is thus obtained. If a solid fused

mass is required, pure potassium hydrate is fused in a crucible, and to

this the dried precipitate is added in small portions.

_Uses, &c._ Metallic silver, unless in a state of very minute division,

has no action on the human body. A plate of silver is ordered, in the Ph.

L., as a test of the presence of nitric acid in the acetic and phosphoric

acids; and metallic silver (preferably granulated) is employed by the

other colleges in the preparation of the nitrate. Its numerous

applications in the arts are well known. The standard silver of England

contains 111 parts of silver and 9 parts of copper.

_Concluding Remarks._ The researches of Tillet, D’Arcet, and Gay-Lussac

have clearly shown that the percentage of silver in an alloy, as indicated

by cupellation, is always below its real richness in that metal, owing to

loss in the process; and, that the cupelled button always retains a trace

of lead and copper, the precise quantity of which is variable. The

following table exhibits the additions to be made on this score, when the

quantity assayed (assay pound) is 20 gr.:——

+-------------------------+---------------+--------------+

| |Actual richness| Percentage |

|Weight after cupellation.| in _pure_ |of richness in|

| | _silver_. |_pure silver_.|

+-------------------------+---------------+--------------+

| 19·979 | 20 | 100 |

| 18·95 | 19 | 95 |

| 17·92 | 18 | 90 |

| 16·917 | 17 | 85 |

| 15·914 | 16 | 80 |

| 14·91 | 15 | 75 |

| 13·905 | 14 | 70 |

| 12·905 | 13 | 65 |

| 11·906 | 12 | 60 |

| 10·906 | 11 | 55 |

| 9·906 | 10 | 50 |

| 7·921 | 8 | 40 |

| 5·948 | 6 | 30 |

| 3·949 | 4 | 20 |

| 1·982 | 2 | 10 |

+-------------------------+---------------+--------------+

In assaying lead ores very poor in silver the best quantity to be taken

for cupellation is 500 gr.; and from that quantity 0·0148 of silver,

including compensation for loss, represents one ounce of silver to the

ton. A cupel may absorb its own weight of lead. If the quantity of lead to

be absorbed is more considerable, another cupel may be turned topsy-turvy,

and the cupel in which the assay is to be made may be placed upon it. See

Assay, and M. Gay-Lussac’s elaborate memoir on the ‘_Humid Assay of

Silver_,’

For the recovery or reduction of silver from the chloride and its other

compounds, several methods are employed:——

_a._ The washed chloride is placed in a zinc or iron cup, along with a

little water strongly acidulated with sulphuric acid; or in a glass or

porcelain cup along with a zinc plate; the whole may then be left to

itself for some hours; or, to hasten the reduction, gently heated, or even

boiled; the precipitated silver is washed with pure water, and dried.

_b._ (Hornung.) Digest the chloride with some ammonia and pure copper

filings, for 24 hours, then wash and dry the powder.

_c._ (M. Levol.) The washed chloride is mixed with an equal weight of

sugar, and the mixture is digested in an excess of a moderately strong

solution of caustic potassa, with occasional agitation for 24 hours; or

the whole is boiled for some time; the reduced silver is washed with

distilled water.

_d._ (Mohr.) The dry chloride is mixed with 1-3rd of its weight of

powdered black resin, and moderately heated in a crucible until the flame

ceases to have a greenish-blue colour; the heat is then suddenly increased

so as to melt the metal into a button or ingot.

_e._ (M. Gay-Lussac.) If the chloride, dry it, and throw it, in successive

portions, into twice its weight of carbonate of potassa fused in a red-hot

Hessian crucible; effervescence ensues, and the pure silver subsides to

the bottom.——If a “soluble salt,” as the nitrate, acidulate the solution,

and precipitate it by means of a polished plate of copper; the silver is

then obtained in the form of powder. The products of the above processes,

when the latter are carefully conducted, are chemically pure silver.

=Silver, Acetate of.= _Syn._ ARGENTI ACETAS, L. _Prep._ By adding a

solution of acetate of potassa to a like solution of nitrate of silver,

washing the precipitate with cold water, redissolving it in a little hot

water, and setting the solution aside to crystallise. Small colourless

needles.

=Silver, Ammoniuret of.= See FULMINATING SILVER (Berthollet’s, Nos. 1 and

2, _page_ 768).

=Silver, Ammonio-chloride of.= _Syn._ ARGENTOCHLORIDE OF AMMONIA; ARGENTI

AMMONIO-CHLORIDUM, L. _Prep._ Add, gradually, chloride of silver (recently

precipitated and well washed) to concentrated liquor of ammonia, as long

as it is dissolved on agitation, applying a gentle heat towards the end;

then heat the solution to the boiling-point, concentrate a little, and

allow it to cool very slowly; collect the crystals which form, dry them by

pressure (with care) between folds of bibulous paper, and at once preserve

them from the light and air.——_Dose_, 1/16 to 1/8 gr.

=Silver, Ben′zoate of.= AgC_{7}H_{5}O_{2}. Thin transparent plates, which

are blackened by exposure to the light. See BENZOATE.

=Silver, Bro′mide of.= AgBr. Resembles the chloride.

=Silver, Car′bonate of.= Ag_{2}CO_{3}. _Syn._ ARGENTI CARBONAS, L. A white

insoluble powder, obtained by precipitating a cold solution of nitrate of

silver with another of carbonate of sodium. It is decomposed by heat.

=Silver, Chlo′′ride of.= AgCl. _Syn._ ARGENTIC CHLORIDE. _Prep._

Precipitate a solution of nitrate of silver by dilute hydrochloric acid or

a solution of common salt; wash the precipitate, and dry it in the

shade.——_Dose_, 1/4 to 3 gr., thrice daily; in epilepsy, chronic

dysentery, cholera, diarrhœa, &c. Dr Perry regards it as preferable to the

nitrate. When fused, chloride of silver forms horn silver, the ‘luna

cornea’ of the older writers.

=Silver, Cy′anide of.= AgCN. _Syn._ ARGENTIC CYANIDE, HYDROCYANATE OF

SILVER. _Prep._ Add dilute hydrocyanic acid to a solution of nitrate of

silver, as long as a precipitate falls; wash this with distilled water,

and dry it.

_Prop., &c._ Cyanide of silver is a white powder, soluble in ammonia, and

decomposed by contact with vegetable substances; light turns it

violet-coloured.——_Dose_, 1/16 to 1/8 gr.; in syphilis, &c. It has been

proposed as a source of hydrocyanic acid. (Everitt.)

=Silver Hyposul′phite of.= Ag_{2}S_{2}O_{3}. _Syn._ ARGENTI HYPOSULPHIS,

L. A white substance, insoluble in water, and very prone to decomposition.

It is very soluble in the alkaline hyposulphites, forming compounds

possessing an intensely sweet taste. See HYPOSULPHUROUS ACID.

=Silver, I′odide of.= AgI. _Syn._ ARGENTIC IODIDE; ARGENTI IODIDUM, L.

_Prep._ Precipitate a solution of nitrate of silver with another of iodide

of potassium; wash the precipitate with distilled water, and dry it in the

shade. Pale greenish-yellow; insoluble in water and in liquor of ammonia;

soluble in a solution of hyposulphite of soda. Used in some of the French

hospitals in the stomach affections of scrofulous subjects: also in

epilepsy.——_Dose_, 1/12 to 1 gr.

=Silver, Ni′trate of.= AgNO_{3}. _Syn._ ARGENTI NITRAS, L. This article is

found in commerce under two forms:——

1. CRYSTALLISED. _Prep._ By dissolving grain silver in nitric acid diluted

with about twice its weight of water, evaporating the solution until it is

strong enough to crystallise on cooling, and then allowing it to cool very

slowly. Colourless; transparent, anhydrous rhombic prisms or tables;

soluble in an equal weight of cold and in half their weight of boiling

water; soluble in alcohol; fuse when heated, and at a higher temperature

suffer decomposition; blackened by light, and by contact with organic

substances. Its solution in distilled water is not sensibly darkened by

light, in the absence of organic matter. Used for solutions, and in

photography.

2. FUSED (LUNAR CAUSTIC; ARGENTI NITRAS——B. P., Ph. L. & E., A. N.

FUSUM——Ph. D.). _Prep._ (Ph. D.) Refined silver, 3 oz.; pure nitric acid,

4 fl. oz.; distilled water, 5 fl. oz.; mix in a glass flask, and apply in

a gentle heat until the metal is dissolved; transfer the solution to a

porcelain capsule (or a large porcelain crucible), decanting it off a

heavy black powder which appears at the bottom of the flask, and, having

evaporated it to dryness, raise the heat (in a dark room) until the mass

liquefies; then pour it into a brass mould (iron moulds——Ph. E. & Ph. L.

1836), furnished with cylindrical cavities of the size of a goose-quill,

and which then admits of being opened by a hinge; preserve the concreted

salt in well-stopped bottles, impervious to the light. The formulæ of the

Ph. E. & Ph. L. 1836 are similar.

_Obs._ In preparing this salt care should be had that the silver is free

from copper. Pure nitrate of silver may, however, be prepared from silver

containing copper, by evaporating the nitric solution to dryness, and

cautiously heating the mixed nitrates to fusion. A small portion of the

melted mass is examined from time to time, until a little dissolved in

water, and treated with ammonia in excess, ceases to strike a blue colour.

When this point is arrived at, the fused nitrate is allowed to cool, when

it is redissolved in water, filtered or decanted from the insoluble black

oxide of copper, and evaporated in the usual way.

The heat employed in preparing the fused nitrate should not exceed 420°

Fahr., and the fusion should be effected completely, but with moderate

expedition, to prevent loss of nitric acid. Formerly, a mass of

well-tempered white clay, perforated by means of a well-greased

goose-quill, was used instead of metal moulds. In the Ph. E. & Ph. L. 1836

the moulds are ordered to be greased; when this is done, the sticks of

caustic should be wiped clean before rolling them in paper. The moulds

should be gently heated before pouring the fused nitrate into them. Mr

Benzoin, the celebrated Danish pharmaceutist, recommends mould formed of

the massive white Bohemian talc or of English slate.

_Pur., &c._ Pure nitrate of silver, whether crystallised or fused, is

entirely soluble in water, yielding a colourless solution, from which

metallic silver is precipitated by a piece of bright copper; both are

originally white, but are darkened by exposure to light and contact with

organic matter.

_Uses, &c._ Nitrate of silver is a powerful tonic, antispasmodic,

astringent and escharotic.——_Dose_, 1/8 to 1 gr., gradually increased,

twice or thrice a day, made into a pill with crum of bread; in cholera,

epilepsy, &c., preceded by purgatives. It has been highly extolled by Mr

Ross as a remedy in cholera. Its continued use permanently colours the

skin. It is also extensively employed externally as a caustic. It is

powerfully poisonous. A solution of common salt, emetics, and demulcents,

constitute the treatment in such cases. Nitrate of silver is much employed

in the manufacture of ‘indelible ink’ for linen, and hair dyes.

=Silver, Di′oxide of.= Ag_{2}O_{2}. _Syn._ ARGENTI SUBOXYDUM, L. _Prep._

From dry citrate of silver heated to 212° Fahr., in a stream of hydrogen

gas, until it turns dark brown, when it is dissolved in water; the

solution is next treated with potassa, and the precipitate is carefully

washed and dried. A black powder, easily decomposed, and soluble in

ammonia.

=Silver, Oxide of.= Ag_{2}O. _Syn._ PROTOXIDE OF SILVER; ARGENTI OXYDUM,

A. PROTOXYDUM, L. _Prep._ 1. (Lane.) Nitrate of silver, 2 parts; hydrate

of potassa, 1 part; dissolve each separately in distilled water, mix the

solutions, and, after frequent agitation during an hour, collect and wash

the precipitate, and dry it by a gentle heat in the shade. A pale brown

powder.

2. Recently precipitated chloride of silver is boiled in a solution of

hydrate of potassium of the sp. gr. 1·25, with frequent stirring and

trituration, until, on testing a little of it, it is found to be entirely

soluble in dilute nitric acid, when it is washed and dried, as before. A

black and very dense powder. Chemically pure.

3. Nitrate of silver, 1/2 oz.; water, 4 fl. oz., dissolve, and pour the

solution into a bottle containing lime water, 2 quarts, or q. s.; agitate

the mixture well, collect and wash the sediment, and dry it at a heat not

exceeding 212° Fahr. A dark olive-brown powder. Pure.

_Prop., &c._ Very soluble in solutions of ammonia and of the alkaline

hyposulphites; slightly soluble in water; reaction alkaline; decomposed by

light.——_Dose_, 1/2 to 2 gr.; in epilepsy, gastralgic irritations, &c. It

is much used in France, and has been highly extolled in menorrhagia. By

some, however, it is not considered superior to the nitrate.

=Silver Pencils, Nitrate of.= According to A. Huber, very thin pencils of

nitrate of silver, such as are sometimes required for intra-uterine

applications may be prepared in the following manner:——Silver nitrate is

fused in a capsule, and the liquid drawn up by slow and cautious suction

into a glass tube, the calibre of which is a trifle larger than the

required diameter of the pencil. Especial care is to be taken that no

cavities filled with air-bubbles are produced in the contents of the tube.

When entirely cold the tube is warmed by turning over a spirit-lamp until

the outer surface of the stick has become soft, when it may be easily

pushed out by means of a knitting needle. With a little practice very

handsome pencils of considerable length may be obtained in this manner.

=Silver, Perox′ide of.= _Syn._ ARGENTI PEROXYDUM, L. A black crystalline

substance which forms on the positive electrode of a voltaic arrangement

employed to decompose solution of nitrate of silver.

=Silver, Sul′phate of.= Ag_{2}SO_{4}. _Syn._ ARGENTI-SULPHAS, L. _Prep._

By boiling silver in sulphuric acid; or, by precipitating a solution of

the nitrate by another of sulphate of sodium. It dissolves in 80 parts of

hot water, and falls in small colourless needles as the solution cools.

=Silver, Sul′phide of.= Ag_{2}S. _Syn._ SULPHURET OF SILVER; ARGENTI

SULPHURETUM, L. Prepared by passing sulphuretted hydrogen through a

solution of nitrate of silver; or, by melting its constituents together.

It possesses a greyish-black colour, and is a strong sulphur-base.

=Silver, Ox′idised.= The high appreciation in which ornamental articles in

oxidised silver are now held, renders a notice of the process followed

interesting. There are two distinct shades in use, one produced by

chlorine, which has a brownish tint, and the other by sulphur, which has a

bluish-black tint. To produce the former, it is only necessary to wash the

article with a solution of sal ammoniac. A much more beautiful tint may,

however, be obtained by employing a solution composed of equal parts of

sulphate of copper and sal ammoniac dissolved in vinegar. A fine black

tint may be produced by a slightly warm solution of sulphide of potassium

or of sodium. (‘Chem. Techn.’)

=SILVER DUST.= _Syn._ SILVER POWDER; ARGENTI CROCUS, A. PULVIS, L. _Prep._

1. Pure pulverulent silver, obtained by any of the methods explained on

the previous page. Used to coat pills, by japanners, &c.

2. Heat oxide of silver to dull redness in a porcelain crucible, cool,

triturate the powder in an agate mortar, and pass it through a fine sieve.

Used at the hospital of Montpellier.

=SILVER SHELLS.= These are prepared and used like gold shells.

=SIL′VERING.= The art of covering the surfaces of bodies with a thin

coating of silver. Leather, paper, wood, &c., are silvered by covering

them with silver leaf, by a similar process to that employed for gilding

them.

=Silvering of Glass.= Two distinct methods are adopted for this

purpose——one of which consists in employing a layer of tin-foil and

mercury, falsely called ‘silvering,’ the other in using a coating of real

silver precipitated from a solution of that metal.

1. Plane surfaces, as those of mirrors, &c., are commonly silvered as

follows:——A sheet of tin-foil corresponding to the size of the plate of

glass is evenly spread on a perfectly smooth and solid marble table, and

every wrinkle on its surface is carefully rubbed down with a brush; a

portion of mercury is then poured on, and rubbed over the foil with a

clean piece of very soft woollen stuff, or a hare’s foot, after which two

rules are applied to the edges, and mercury poured on to the depth of a

crown-piece, when any oxide on the surface is carefully removed, and the

sheet of glass, made perfectly clean and dry, is slid along over the

surface of the liquid metal, so that no air, dirt, or oxide can possibly

either remain or get between them. When the glass has arrived at its

proper position, gentle pressure is applied, and the table sloped a little

to carry off the waste mercury, after which it is covered with flannel and

loaded with heavy weights; in 24 hours it is removed to a wooden table and

further slanted, and this position is progressively increased during a

month, until it becomes perpendicular.

For silvering convex or concave surfaces a mould of plaster of Paris is

employed, so that the amalgamated foil may be accurately fitted to the

surface.

Globes and other hollow vessels are commonly silvered by the application

of one of the silvering amalgams noticed at page 117.

2. In the HUMID WAY.——_a._ (Drayton.) A mixture is first made of nitrate

of silver (in coarse powder), 1 oz., ammonia, 1/2 oz., and water, 2 oz.,

which, after standing for 24 hours, is filtered (the deposit upon the

filter, which is silver, being preserved), and an addition is made thereto

of spirit (by preference, rectified spirit at 60% o. p.), or naphtha, 3

oz.; from 20 to 30 drops of oil of cassia are then added; and, after

remaining for about 6 hours longer, the solution is ready for use. The

glass to be silvered (first well cleaned and polished) is placed in a

horizontal position, and a wall of putty, or other suitable material,

formed around it; the above solution is then poured over it to the depth

of from 1/8 to 1/4 inch; from 6 to 12 drops of a mixture of oil of cloves

and spirit of wine (in the proportion of 1 part, by measure, of oil of

cloves, to 3 of spirit of wine) are next dropped into it, at different

places; or the diluted oil of cloves may be mixed with the solution before

it is poured upon the glass, a larger quantity, in both cases, increasing

the rate of the deposit. When the glass is sufficiently silvered, the

solution is poured off; and as soon as the silver on the glass is

perfectly dry, it is varnished with a composition formed by melting

together equal quantities of beeswax and tallow. The solution, after being

poured off, is allowed to stand for 3 or 4 days, in a close vessel; as it

still contains silver, and may be again employed after filtration, and the

addition of a sufficient quantity of fresh ingredients to supply the place

of those which have been used. 18 gr. of nitrate of silver are sufficient

for one square foot of glass. Hollow vessels may he silvered by pouring

the solution into them. By the addition of a small quantity of oil of

caraway, oil of cloves, or oil of thyme, the colour of the silver may be

varied. (‘Patent Journ.’)

_b._ (Thomson & Mellish.) Nitrate of silver, 2 oz.; water and rectified

spirit, of each 3 fl. oz.; dissolve, add of spirit of hartshorn or liquor

of ammonia, 1 fl. oz., mix, and after a short time filter the solution; to

each ounce of this add of grape sugar, 1/4 oz., previously dissolved in a

mixture of rectified spirit and water, of each 1/2 pint; after 3 or 4

hours’ repose it is fit for use. This solution is applied to the glass,

heated to about 160° Fahr., in a similar manner to the last. Patented.

_c._ The best plan of silvering plain or slightly curved surfaces is,

however, the method employed for coating the specula of the silvered-glass

Newtonian telescopes. This method is very easy, and has the advantages of

giving a brilliant and durable surface on both sides, and the film is

sufficiently firm to admit of being polished with rouge and fine

wash-leather.

One half ounce of pure nitrate of silver is dissolved in 4 oz. of

distilled water, and divided into two equal portions. One is treated with

dilute ammonia until the brownish precipitate is entirely redissolved; and

to this clear solution, 1/2 oz. of pure hydrate of potassium dissolved in

8 oz. of water added; and the brown precipitate, and grey sediment that

remains after the brown precipitate disappears, dissolved by the cautious

addition of ammonia, stirring well all the time. The remaining nitrate of

silver solution is now added, stirring well until it gives a greyish

precipitate that does not disappear after well stirring. The bulk of the

solution is next made up to 100 oz., and allowed to settle, when the clear

solution is poured off for use.

The reducing solution is prepared by dissolving 1/2 oz. of pure milk

sugar in 10 oz. of hot water, and adding 10 minims of pure alcohol.

This quantity of silvering solution will coat over two square feet of

glass surface with a brilliant film of pure silver. The glass must be

perfectly clean, and is to be suspended face downwards on the surface of

the solution and allowed to stand one hour; the temperature of the

solution being best about 80° Fahr.

_d._ (R. Siemens.) As a reducing agent, acetic aldehyde is used in the

form of aldehyde ammonia, prepared by passing dry ammoniacal gas into

aldehyde. Four grams of silver nitrate and 2-1/2 grams of aldehyde ammonia

are separately dissolved in a litre of distilled water, and the solutions

mixed and filtered. The article to be silvered, after washing out with

potassium carbonate, and then with spirits of wine and distilled water, to

remove every trace of grease, is filled with this solution (as far as it

is desired to silver), and then hung up in the water bath.

It is now gradually heated, and as soon as the temperature reaches 50° C.

the separation of the silver mirror begins, and soon spreads over the

whole inner glass surface. Its formation is soon finished, usually between

55° or 60°. When the beauty of the silver surface reaches a maximum it is

time to withdraw the article from the water bath, and pour off the

contents, or the brilliancy of the mirror will be impaired. The article is

finally rinsed in distilled water.

_e._ (Martin.) M. Martin makes use of four liquids, viz., first, a 10 per

cent. solution of nitrate of silver; second, liquor ammoniæ, sp. gr. ·970;

third, a 4 per cent. solution of caustic soda; and fourth, a 12-1/2 per

cent, solution of white sugar, to which he adds 2-1/2 per cent. of nitric

acid, and after twenty minutes’ boiling he adds to it 25 parts of alcohol

and water, to make up the bulk to 250. The silvering solution is made by

mixing together 12 parts of solution No. 1, 8 parts of No. 2, 20 parts of

No. 3, and 60 parts of distilled water, and finally, in twenty-four hours,

10 parts of No. 4. The object to be silvered is then immersed, when it

will be covered with a film of reduced silver, which in ten minutes’ time

will be sufficiently thick for use. After having been washed with

distilled water and dried the surface may be polished with chamois leather

and rouge.

=Silvering of Metals.= 1. (LEAF SILVERING.) This is performed with leaf

silvering in the way described under GILDING for the gilding of polished

metals.

3. (COLD SILVERING.) Mix chloride of silver, 1 part, with pearlash, 3

parts, common salt, 1-1/2 part, and whiting, 1 part; and well rub the

mixture on the surface of the brass or copper (previously well cleaned),

by means of a piece of soft leather, or a cork moistened with water and

dipped into the powder. When properly silvered the metal should be well

washed in hot water slightly alkalised, and then wiped dry.

3. (ELECTEO-SILVERING.) This is described under ELECTROTYPE.

=Silver, A New Imitation of.= A patent for an alloy has been taken out by

M. Lemarquand, which is said to bear a close resemblance to silver in

appearance, and to be unaffected by atmospheric influences. It has the

following composition:——

Pure copper 750 parts.

Nickel 140 ”

Black oxide of cobalt 20 ”

Tin, in sticks 18 ”

Zinc 72 ”

=SIMAROU′BA.= _Syn._ SIMARUBA (Ph. E. & D.), L. The root-bark of _Simaruba

amara_ or _officinalis_, the mountain damson. Tonic, bitter, and

astringent.——_Dose_, 20 to 30 gr.; in intermittents, obstinate diarrhœa,

dysentery, and dyspepsia.

=SIN′AMINE.= C_{4}H_{6}N_{2}. A basic substance formed, along with

sulphide of lead, when thiosinamine is treated with oxide of lead. It is

very bitter tasted, has a powerful alkaline reaction, and, when slowly

obtained from its concentrated aqueous solution, forms brilliant

colourless crystals.

=SIN′APISM.= _Syn._ SINAPISMUS, L. A mustard poultice.

=SIN′APOLINE.= C_{7}H_{12}N_{2}O. A basic substance, formed, along with

carbonic acid, when the volatile oil of mustard, or sulphocyanide of

allyl, is treated with oxide of lead. It is soluble in water and alcohol,

has an alkaline reaction, and crystallises in colourless plates.

=SINKS.= “In no case,” says Mr Eassie,[165] “should the waste pipe of

sink, laboratory, or bath lead direct into the drains; yet how frequently

is this the case, and a special card sent out to disease and death.

[Footnote 165: ‘Healthy Houses,’ by Wm. Eassie, C.E. Simpkin, Marshall &

Co.]

“It must also be remembered it is every whit as dangerous if these waste

conduits lead into the soil pipe of a closet. Waste pipes from the

above-named places should be led down to within 12 or 18 inches from the

ground, and should deliver on to the grating of a gully or yard trap.”

This subject has been already treated in the article on “Sanitation,

Domestic,” wherein we have embodied the practical suggestions of Mr

Collins, another sanitary house reformer, as well as in our article on

“Drainage,” in which will be found details for carrying out the system

recommended by Messrs Eassie and Symonds, and thus preventing the

admission into our dwelling-houses of the poisonous sewer gas.

The matter has so important a bearing upon health, that we shall make no

apology for having thus reiterated and emphasised it by quoting Mr

Eassie’s words of warning. See TRAPS.

=SIT′FASTS.= These hard tumours, possessing but little sensibility, are

situated in those superficial parts of the horse’s body which have been

exposed to the unequal pressure of the collar, the saddle, or the harness.

The tumour should be removed by the veterinary surgeon, if the previous

application of either blisters, biniodide of mercury ointment, or a seton

have been tried and failed to disperse it. The precursor of the sitfast is

always a swelling filled with serum and lymph, caused, as before stated,

by badly-fitting harness. Hence the soundest treatment is to prevent its

development into the hard form, by proper means, directly it shows itself,

the best remedies being the application of salt and water or Goulard

water, and correcting the defects of the harness.

=SIZE.= Obtained, like glue, from the skins of animals, but is evaporated

less, and kept in the soft state. See GOLD and GOLD SIZE.

=Size, Oil.= This may be made by grinding yellow ochre or burnt red ochre

with boiled linseed oil, and thinning it with oil of turpentine.

=SKATE.= The _Raia batis_ (Linn.). Other varieties of _Raia_ also pass

under the name. It is a coarse fish, and is principally salted and dried

for exportation.

=SKIN (The).= _Syn._ CUTIS, DERMIS, PELLIS, L. Every person must be

familiar with the external appearance and general properties of the skin;

but there are many of our readers who may not be aware of its peculiar

compound character. The skin, then, although apparently a single membrane,

is composed of three distinct layers or membranes, each of which performs

its special duties:——1. The exterior of these is called the cuticle,

epidermis, or scarf-skin. It is an albuminous tissue, possessing no

sensibility, and is found thickest on those parts of the body most exposed

to friction or injury.——2. The mucous net, or rete mucosum, which is a

thin layer of soft pulpy matter, which lies immediately under the cuticle,

and is supposed to be the seat of the colour of the skin.——3. The derma,

cutis vera, or true skin, is a highly sensitive, vascular, gelatinous

texture, the third, and last in succession from the surface of the body.

It is this which, when the scarf-skin and hair have been removed, is

converted by the process of tanning or tawing into leather.

The skin, because of its tough, elastic, flexible nature and its

underlying layer of fat, is admirably adapted for covering the various

internal parts and organs, as well as for bodily movement and exertion.

Besides this, it exercises, in common with the lungs, the liver, and the

kidneys, the important function of a depurator, and may, with the organs

above specified, be regarded as one of the main outlets for the waste

products of the body; the effete and noxious matters of which, when in a

healthy condition, it effects the removal, are those contained in the

perspiration, and in addition carbonic acid, and, in the case of unhealthy

subjects, nitrogen. The importance of the removal of these substances from

the organism will be realised when it is stated that, when this excretory

function of the skin has, in the course of experiments upon animals, been

prevented by covering their bodies over with a coat of varnish or some

other impermeable agent, the animal has quickly perished.

The perspiration is variable in amount, owing to various causes, such as

temperature, the amount of exercise taken, the more or less hygroscopic

condition of the surrounding atmospheres, the quantity of fluid swallowed,

the season of the year, &c., with the exception of that which occurs under

the armpits and upon the soles of the feet, it has generally an acid

reaction, due to the presence in it of uncombined formic and lactic acids.

Under ordinary conditions of life it averages daily about 2 lbs. in

quantity, being, as might be expected, more abundant than the urine in

summer, and less in winter. The perspiration is of very complex

composition, and contains lactates, butyrates, and acetates of sodium and

ammonium, sodic chloride, phosphate of calcium, and sulphates——these

latter, however, occurring in but small quantities. It also contains a

peculiar nitrogenous substance that very quickly decomposes, and a

peculiar odorous principle. According to Anselmino the proportion of solid

matter in the perspiration varies from 5 to 12·5 parts in 1000.

Various observers have arrived at different conclusions respecting the

amount of carbonic acid exhaled from the skin. Professor Scharling

believed it to be from a fortieth to a sixtieth the amount given off by

the lungs. Recent observations seem, however, to have shown that this

estimate was too high. Dr Edward Smith, operating upon himself by placing

every part of his body except the head in a caoutchouc bag, and

subsequently collecting the evolved carbonic acid (the experiment being

performed in the summer time), found the quantity evolved to be 6 grains

per hour, or about a hundredth part of that passing off from the lungs.

Aubert’s experiments led him to the conclusion that it was about half the

amount given by Smith; whilst Reinhart estimated it at 34 or 35 grains a

day.

These excretory processes of the skin are effected by means of very minute

vessels called the _sudoriparous_ or _sweat-glands_. These glands abound

in almost every part of the human skin. They are of largest size under the

axillæ or arm-pits, where perspiration is most profuse. They are also very

abundant upon the palms of the hand. Professor Erasmus Wilson says that as

many as 3528 of these sweat-glands exist in a square inch of surface on

the palm of the hand; and as every tube, when straightened out, is about

a quarter of an inch in length, it follows that, in a square inch of skin

from the palm of the hand, there exists a length of tube equal to 882

inches, or 73-1/2 feet. These glands, as we have seen, vary in number for

different parts of the human body; but if we take Professor Wilson’s

average for the superficial area of a man of ordinary stature, viz., 2800

of them to the square inch, it follows “the total number of pores on such

a man’s skin would be about _seven millions_, and the length of

perspiratory tubing would then be 1,750,000 inches, or 145,833 feet, or

48,611 yards, or nearly 28 miles.”[166]

[Footnote 166: Carpenter’s ‘Human Physiology.’]

[Illustration: _Sudoriferous Gland_ from the palm of the hand magnified 40

diam.:——_a, a_, contorted tubes, composing the gland, and uniting in two

excretory ducts; _b, b_, which unite into one spiral canal that perforates

the epidermis at _c_, and opens on its surface at _d_; the gland is

imbedded in fat-vesicles, which are seen at _e, e_.]

In addition to the _sudoriparous_, the skin also possesses _sebaceous_

glands which stud almost every part of its surface except the palms of the

hands and the soles of the feet. The sebaceous glands secrete a

semi-fluid, greasy kind of substance, the office of which is probably to

aid in rendering the skin soft and supple, and to prevent the too rapid

evaporation of moisture from it. The sebaceous glands are more

particularly found on the scalp, the anus, and the nose, their locality in

the skin of this last feature being sometimes marked by small black specs,

which when squeezed yield a little white mass resembling a maggot in

appearance. This is merely the solidified secretion from the sebaceous

gland. A parasite known as the _Acarus folliculorum_ infests the sebaceous

glands. In the cartilaginous part of the external passage of the ear are

other glands, the _ceruminous_, which secrete the wax that forms a

protective film for the membrane of the tympanum or drum, and guards it

against dust, insects, &c. See EXERCISE, PERSPIRATION.

=SKIN BALSAM, Glycerin——Glycerin Haut, Balsam.= A mixture of 1000 parts

glycerin, 120 parts orange-flower water, 1 part each oils of neroli and

bitter almonds. (Hager.)

=SKIN COSMET′ICS.= The simplest, cheapest, and most generally employed

cutaneous cosmetics are soap and water, which at once cleanse and soften

the skin. Soap containing a full proportion of alkali exercises a solvent

power upon the cuticle, a minute portion of which it dissolves; but when

it contains a small preponderance of oily matter, as the principal part of

the milder toilet soaps now do, it mechanically softens the skin and

promotes its smoothness. Almond, Naples, and Castile soaps are esteemed

for these properties, and milk of roses, cold cream, and almond powder

(paste), are also used for a similar purpose. To produce an opposite

effect, and to harden the cuticle, spirits, astringents, acids, and

astringent salts, are commonly employed. The frequent use of hard water

has a similar effect. The application of these articles is generally for

the purpose of strengthening or preserving some particular part against

the action of cold, moisture, &c.; as the lips, or mammæ, from chapping,

or the hands from contracting chilblains; but in this respect oils,

pommades, and other oleaginous bodies, are generally regarded as

preferable.

Another class of cutaneous cosmetics are employed to remove freckles and

eruptions. Among the most innocent and valuable of these is Gowland’s

lotion, which has long been a popular article, and deservedly so, for it

not only tends to impart a delightful softness to the skin, but is a most

valuable remedy for many obstinate eruptive diseases which frequently

resist the usual methods of treatment. Bitter almonds have been

recommended to remove freckles (Celsus), but moistening them with a lotion

made by mixing 1 fl. oz. of rectified spirit, and a teaspoonful of

hydrochloric acid with 7 or 8 fl. oz. of water, is said to do this more

effectually. A safe and excellent cosmetic is an infusion of horseradish

in cold milk. (Withering.)

Hermann prescribes the following lotion:——Blanched almonds, 2 oz.; rose

water, 8 oz.; orange-flower water, 2 oz. Make an emulsion, strain, and add

sal ammoniac, 1 dr.; simple tincture of benzoin, 2 dr.

Skin paints and skin stains are employed to give an artificial bloom or

delicacy to the skin. Rouge and carmine are the articles most generally

used to communicate a red colour. The first is the only cosmetic that can

be employed, without injury, to brighten a lady’s complexion. The other,

though possessing unrivalled beauty, is apt to impart a sallowness to the

skin by frequent use. Starch powder is employed to impart a white tint,

and generally proves perfectly harmless. The American ladies, who are very

fond of painting their necks white, use finely-powdered magnesia, another

very innocent substance. Several metallic compounds, as the trisnitrate,

chloride, and oxide of bismuth (pearl white, Fard’s white, &c), carbonate

of lead (flake white), white precipitate, &c., are frequently used to

revive faded complexions; but they are not only injurious to the skin, but

act as poisons if taken up by the absorbents. Trisnitrate of bismuth

(pearl white), probably the least injurious of these articles, has been

known to cause spasmodic tremblings of the muscles of the face, ending in

paralysis. (‘Voght. Pharm.’) The employment of liquid preparations

containing sugar of lead, which are commonly sold under the name of milk

of roses, cream of roses, &c., is equally injurious. Another disadvantage

of these metallic preparations is, that they readily turn black when

exposed to the action of sulphuretted hydrogen gas, or the vapours of

sulphur, such as frequently escape into the apartment from coal fires.

There are many instances recorded of a whole company being suddenly

alarmed by the pearly complexion of one of its belles being thus

transformed into a sickly grey or black colour.

In conclusion, it may be remarked that the best purifiers of the skin are

soap and water, followed by the use of a coarse but not a stiff cloth, in

opposition to the costly and smooth diapers that are commonly employed;

and the best beautifiers are health, exercise, and good temper.

=Skin, Goldbeat′er’s.= See GOLDBEATER’S SKIN.

=SKINS (of Animals).= The preparation and preservation of fur skins are

noticed under PELTRY; the preparation and uses of the skins of the larger

animals under LEATHER, TANNING, TAWING, &c.

=SLACK.= Small coal, such as is used for kilns.

=SLAG.= The semi-vitrified compounds, produced, on the large scale, during

the reduction of metallic ores by fluxes. Those from iron and copper works

are often used for building materials, mending roads, &c.

According to Egleston[167] the following are some of the industrial

applications to which the slag from blast furnaces is put.

[Footnote 167: Dingler’s ‘Polytech. Journ.,’ ‘Journ. Chem. Society.’]

When required for building stones the slag is run from the blast furnace

into a semicircular vessel on moving wheels, and having its bottom covered

three centimetres deep with sand and coke dust. By means of a bent iron

instrument the slag is mixed with sand and coke dust till the escape of

gases has nearly ceased and the mass is sufficiently tough. With the same

tool it is next pressed into a mould furnished with a lid, which is forced

down as soon as the escape of gas ceases. The red-hot stone is then placed

in the cooling oven, covered with coke dust, and allowed to remain three

or four days to cool completely. These stones are impervious to damp, and

make good foundations. According to another method the slag, which should

contain from 38 to 44 per cent. of silica, is run down a shoot into a

large cavity, and then covered over with sand and ashes, and left to cool

from five to ten days, when it is distributed in moulds, and there

hardens. In certain parts of Belgium slag is poured upon iron plates and

cooled by water, and thus a kind of glass is manufactured.

In other districts the slag is granulated as it flows from the blast

furnace by means of a stream of water. The granulated slag is preferred by

the puddlers to the sand for the moulds of pig iron. The slag gravel may

be advantageously substituted for sand in mortar making, a more rapid

hardening being thus secured, a matter of great moment in building

foundation walls.

Artificial stone is also manufactured from the granulated slag, and used

for building purposes, furnishing warm dry houses of handsome appearance.

When stones for building with enamelled surfaces are required they are

obtained in some parts of Europe as follows:——The unburnt bricks are

covered with granulated slag, and after drying are burnt in a furnace

where they do not come in contact with carbon. The stones are completely

glazed, and according to the different kinds of slag used are tinted of

different colours. This operation is also employed advantageously with

tiles, pipes, and earthenware.

If, in the preparation of fire-proof bricks, a certain proportion of

mixture of clay and granulated slag be added to the mixture, very hard and

durable fire bricks are obtained. These have been tested in a brass

furnace, and experiments are being tried as to their applicability to

building puddling furnaces. This granulated slag may also be

advantageously used for manure. Blast furnace slag has also been drawn out

in fine threads or filaments, furnishing the so-called ‘furnace wool.’

This substance, being a very bad conductor of heat, has suggested various

household and other uses. A cheap and valuable cement, said to be equal to

Portland cement, has been prepared from the finely granulated slag, which

will also resist well the action of acids.

Mr Britten in 1876 patented a process for the manufacture of glass from

blast furnace slag. Large works for the purpose of carrying out this

invention, under the title of ‘Britten’s Patent Glass Company,’ have been

erected at Finedon in Northamptonshire, and are, we believe, successfully

worked in manufacturing glass bottles.

The method consists in removing molten slag in a ladle from the blast

furnace, and pouring into a Siemen’s furnace, when certain amounts of

carbonate of sodium and silica are added, depending upon the quality of

the slag used, and of the glass required.

=SLATE.= The excellence of this material for water cisterns deserves a

passing notice here.

Irish slate (_Lapis Hibernicus_) is an argillaceous mineral, said to

contain iron and sulphur, found in different parts of Ireland. It is a

common remedy, among the vulgar, for internal bruises, taken in a glass of

gin.

=SLEEP.= During the period of our waking hours the exercise of the animal

functions entails a waste or destruction of tissue in the organs

performing them, which, unless duly repaired, would soon lead to the

enfeeblement and consequent failure of the powers of the organs

themselves. For the animal economy therefore to be maintained in a state

of efficiency the repair of the reduced tissues is a necessity; and this

essential condition is effected by the agency of sleep, during which

respiration, circulation, digestion, &c., continue to be carried on

simultaneously with assimilative processes which end in the regeneration

of the impaired tissue.

A proper amount of sleep is therefore as great or even a greater necessity

than a proper supply of food; and any one failing to obtain it soon

perishes of exhaustion. Thus it is that any great mental emotion——such as

intense remorse, grief, anxiety, or the depressing effect of a reverse of

fortune——so frequently expedites death. Like Macbeth “it murders sleep,”

one of the great needs of man’s existence.

Infants and children it is well known require much more sleep than adults.

In these latter the organism, being already matured, demands only so much

sleep as will enable it to make up for the daily waste of the body, which

waste falls very far below the amount of nutrition required by the growing

infant. In a still earlier state of development, viz., the fœtal one,

life may be said to be passed entirely in slumber; whilst children

prematurely born scarcely ever wake except for food. We may assume that,

as a general rule, infants take treble the amount of sleep that adults do,

and that very young infants thrive the better the larger the amount of

sleep they get, is borne out by the experience of medical practitioners,

who affirm that they have known many children who were born small and

weakly, but who slept the greatest part of their early existence,

afterwards became strong and healthy; whilst those children on the

contrary who, being born large and strong, were not good sleepers, became

subsequently enfeebled and unhealthy. As regards the sleep of adults, if

the slumber has been of average length, or the subject of it awakes fully

refreshed therefrom, a second sleep instead of being conducive is

prejudicial to health, and should never be encouraged.

During sickness a patient, if in a very helpless and enfeebled state, may

often be exposed whilst asleep to great peril, unless the nurse who

attends him exercises intelligence and a proper amount of vigilance. In

his work on ‘Household Medicine’ Dr Gardner has pointed out the dangers

that beset the sleeping patient, and the means by which they may be

avoided. “Having disposed,” he says, “of the patient in bed in the best

manner, be careful that no part of the pillow can project over the mouth

or nose, and that the bedclothes do not cover the mouth.

“The attendant should be particularly attentive to these points, when a

narcotic has been taken, when the disease is paralysis, fever, head

diseases, bronchitis, or any pulmonary complaint. The patient should be

watched until he sleeps, and during his sleep, if a nurse is not

constantly present, should be visited frequently, to observe whether the

mouth and nostrils are free, and nothing obstructs the breathing.

“Very little suffices for an obstruction in such cases, which may

extinguish life. Hundreds, perhaps we may say thousands of persons die

prematurely from suffocation during sleep, in a low condition of the vital

energies.

“How often does it happen that a patient left in a calm sleep is found

dead upon being visited an hour or two after. Soft yielding pillows, in

which the head and face get buried, are the instruments of suffocation to

weakly persons, very, very often.”

The larger amount of sleep indulged in by the very old, over adults, is

referable to the incapacity of the aged for exercise, and to their

enfeebled powers of nutrition. Besides age, temperament, habit, and

surrounding circumstances exercise considerable influence on the amount of

sleep necessary for man. Persons of lymphatic temperament are generally

great sleepers; whilst those of a nervous and active nature are mostly the

reverse. The late Earl Russell was we believe in the years of his active

political life a very small sleeper, his slumbers seldom extending over

five hours. So, likewise was the Duke of Wellington; General Elliott, the

defender of Gibraltar, seldom slept more than four hours out of the

twenty-four. As a contrast to these cases may be mentioned that of Dr

Reid, the metaphysician, of whom it is stated that he could take as

sufficient food and afterwards as much sleep as would suffice for an

ordinary man for two days.

Several well-attested cases of excessive slumber are on record in which

the sleep lasted in some cases for weeks, and in others even for months.

In the ‘Comptes Rendus’ for 1864 Dr Blanchet records the case of one of

his patients, a lady of 24 years of age, who had slept for 40 days when

she was 18 years of age. Two years later she had a sleep lasting 50 days.

Upon a subsequent occasion she fell asleep on Easter Sunday, 1862, and did

not wake till March, 1863. She was fed during this period with milk and

soup. She continued motionless and insensible, the pulse was low, the

breathing scarcely perceptible, there were no evacuations, and she

betrayed no signs of wasting away, whilst her complexion is described as

florid and healthy.

This, however, as well as other cases of a similar kind, must not be

regarded as an extreme instance of healthy slumber, but as a form of

lethargy or coma, as indicative of disease, as the opposite condition or

sleeplessness, that is frequently an accompaniment of certain forms of

fevers, inflammatory affections, and brain disorders.

Mr Durham, of Guy’s Hospital, seems to have disposed of the condition that

sleep is caused by the pressure of the distended veins on the brain.

A piece of bone being removed from a dog’s skull so that the animal’s

brain could be observed when sleeping, it was found, 1, the veins were not

distended. 2. During sleep the brain is in a comparatively bloodless

condition, and the blood in the encephalic vessels is not only diminished

in quantity, but moves with diminished rapidity; and this is corroborated

by the observations of Dr Hughlings Jackson on the ophthalmoscopic

condition of the retina during sleep, the optic disk being then whiter,

the arteries smaller, and the retina generally more anæmic than in the

waking state. 3. The condition of the cerebral circulation during sleep is

from physical causes, that which is most favorable to the nutrition of the

brain tissue. See BED, WATCHFULNESS.

=SLEEPLESSNESS AND COLD FEET.= The association betwixt cold feet and

sleeplessness is much closer than is commonly imagined. Persons with cold

feet rarely sleep well, especially women. Yet the number of persons so

troubled is considerable. We now know that if the blood-supply to the

brain be kept up, sleep is impossible. An old theologian, when weary and

sleepy with much writing, found that he could keep his brain active by

immersing his feet in cold water; the cold drove the blood from the feet

to the head.

Now, what this old gentleman accomplished by design is secured for many

persons much against their will. Cold feet are the bane of many women.

Light boots keep up a bloodless condition of the feet in the day, and in

many women there is no subsequent dilatation of the blood-vessels when the

boots are taken off. These women come in from a walk and put their feet to

the fire to warm——the most effective plan of cultivating chilblains. At

night they put their feet to the fire, and have a hot bottle in bed. But

it is all of no use; their feet still remain cold. How to get their feet

warm is the great question of life with them——in cold weather. The

effective plan is not very attractive at first sight to many minds. It

consists in first driving the blood-vessels into firm contraction, after

which secondary dilatation follows. See the snowballer’s hands! The first

contact of the snow makes the hands terribly cold; for the small arteries

are driven thereby into firm contraction, and the nerve-endings of the

finger-tips feel the low temperature very keenly. But as the snowballer

perseveres, his hands commence to glow; the blood-vessels have become

secondarily dilated, and the rush of warm arterial blood is felt agreeably

by the peripheral nerve-endings. This is the plan to adopt with cold feet.

They should be dipped in cold water for a brief period; often just to

immerse them, and no more, is sufficient; and then they should be rubbed

with a pair of hair flesh gloves, or a rough Turkish towel, till they

glow, immediately before getting into bed. After this a hot-water bottle

will be successful enough in maintaining the temperature of the feet,

though without this preliminary it is impotent to do so. Disagreeable as

the plan at first sight may appear, it is efficient; and those who have

once fairly tried it continue it, and find that they have put an end to

their bad nights and cold feet. Pills, potions, lozenges, “night-caps,”

all narcotics, fail to enable the sufferer to woo sleep successfully: get

rid of the cold feet, and then sleep will come of itself.——_British

Medical Journal._

=SMALLPOX.= See POX.

=Smallpox in Sheep.= _Syn._ VARIOLA OVINA. This disease, although bearing

the same name as that which attacks the human subject, is a perfectly

distinct malady, and incapable of being communicated to man either by

inoculation or contagion. In about ten days from the time of the animal’s

having imbibed the contagion feverish symptoms set in accompanied with a

mucous discharge of a purulent character from the nose. Red inflammatory

pimples then begin to develop, first appearing where the skin is thin.

After the pimples have been out about three days they assume a white

appearance, and are filled with serum and pus. “Some of the vessels dry

up, leaving brown scabs; others, especially in the severer cases, run

together, and the scarf skin is detached, leaving an ulcerated surface. It

is in this ulcerated stage that the prostration reaches its height, and

that most sheep die. The mortality from smallpox in sheep ranges from 25

to 90 per cent.”[168]

[Footnote 168: Finlay Dun.]

The disease being a very infectious one, the affected animals must be kept

separate from the healthy ones. Thirty grains of chlorate of potash should

be given three times a day, whilst the food should be nutritious and such

as to tempt the animal’s appetite. It may consist of bruised oilcake,

bran, and steeped oats. Professor Simonds recommends inoculation as a

prophylactic measure.

=Smallpox Marks, Prevention of.= 1. For preventing disfigurement from

smallpox marks, Dr Bernard suggests that the pustules as soon as they have

acquired a certain size should be punctured with a fine needle, and then

repeatedly washed with tepid water.

2. Dr Thorburn Patterson prescribes the following ointment:——Carbonic

acid, 20 to 30 minims; glycerine, 1-1/2 dr.; ointment of oxide of zinc, 6

dr.

3. Cream smeared on the pustules, frequently during the day, with a

feather. See also OINTMENTS.

=SMALTS.= _Syn._ AZURE, POWDER BLUE, SILICEOUS B., SMALT, AZURUM, SMALTA,

L. This consists, essentially, of glass coloured by fusing it with oxide

of cobalt.

_Prep._ 1. Cobalt ore is roasted, to drive off the arsenic, then made into

a paste with oil of vitriol, and heated to redness for an hour; the

residuum is powdered, dissolved in water, and the ferric oxide

precipitated with carbonate of potassium, gradually added, until a

rose-coloured powder begins to fall; the clear portion is then decanted,

and precipitated with a solution of silicate of potassium (prepared by

fusing together, for 5 hours, a mixture of 10 parts of potash, 15 parts of

finely ground flints, and 1 part of charcoal); the precipitate after being

dried is fused, and reduced to a very fine powder. A very rich colour.

2. Roasted cobalt ore and carbonate of potassium, of each 1 part;

siliceous sand, 3 parts; fuse them together, and cool and powder the

residuum. Used as a blue pigment, also to colour glass, and for ‘blueing’

the starch used to get up linen. See BLUE PIGMENTS.

=SMELL′ING SALTS.= See SALTS, SMELLING.

=SMELT.= A beautiful little abdominal fish abounding in the Thames, and a

few other rivers, between the months of November and February. It is

esteemed a great delicacy by epicures, but sometimes proves offensive to

the delicate and dyspeptic.

=SMOKE PREVEN′TION.= Although the full consideration of this subject

belongs to public hygiene and civil engineering, its immediate

application and advantages are interesting and important to everybody.

The history of smoke burning scarcely commences before the year 1840, at

which date Mr Charles Wye Williams obtained a patent for this purpose.

Since that time a ‘thousand-and-one’ schemes, either patented or

non-patented, professedly for the same object, have been brought before

the public. Most of these have been supported by the most reckless

statements regarding their value, made by interested parties; and the most

serious inconvenience and losses have often followed their adoption.

Williams’s method is to admit an abundant supply of cold air through a

large number of small perforations in the door and front part of the

furnace. Lark’s method is based on the admission of heated air, under due

regulation, both through the door, and at the bridge or back of the

furnace, by which means combustion is rendered more complete, and smoke

thereby prevented.

Ivison’s plan consists in the introduction of steam by minute jets over

the fire, which is thus greatly increased in intensity without the

production of smoke, and with a saving of fuel. In Jucke’s arrangement the

grate bars of a furnace are replaced by an endless chain web, which is

carried round upon two rollers, in such a way that each part of the fuel

is exposed to conditions most favorable for perfect combustion. Other

inventions are based upon supplying fuel to the fires from beneath, so

that the products of combustion must pass through the incandescent coals

above.

For household fires, the smokeless grate, invented by Dr Arnott, will be

found entirely successful, and most economical. Its general introduction

would be a great advance in both domestic and public hygiene; and, being

hence of national importance, should be enforced by law.

=SMO′′KING.= This is done, on the large scale, by hanging up the articles

(previously more or less salted) in smoking rooms, into which smoke is

very slowly admitted from smothered dry-wood fires, kindled in the cellar,

for the purpose of allowing it to cool and deposit its cruder part before

it arrives at the meat. This process requires from six days to as many

weeks to perform it properly, and is best done in winter. In farm-houses,

where dry wood is burnt, hams, &c., are often smoked by hanging them up in

some cool part of the kitchen chimney. When the meat is cut into slices,

or scored deeply with a knife, to allow the smoke to penetrate it, it is

called ‘BUCANING,’

“The quality of the wood has an influence upon the smell and taste of the

smoke-dried meat; smoke from beech wood and oak being preferable to that

from fir and larch. Smoke from the twigs and berries of juniper, from

rosemary, peppermint, &c., impart somewhat of the aromatic flavour of

these plants.” (Ure.) The occasional addition of a few cloves or allspice

to the fuel gives a very agreeable flavour to the meat.

Hung beef, a highly esteemed variety of smoked beef, is prepared from any

part, free from bone and fat, by well salting and pressing it, and then

drying and smoking it in the usual manner. It is best eaten shredded. See

PUTREFACTION, SALTING, &c.

=SNAKE-POISONING, Mortality from.= The ‘Lancet’[169] quoting a letter from

T. B. Beighton, Esq., of the Bengal Civil Service, magistrate of the Culna

district of the Burdwan province of Bengal, says:——“The Culna district

comprises, we presume, 80 or 100 square miles, and has a population of

about 300,000. Mr Beighton says that deaths from snakebite are singularly

common in the subdivision. An average of one per day is reported through

the police. The actual deaths are probably double the number reported. If

this daily average is meant to apply the whole year round, we should thus

get in a comparatively small district the frightful death of 700 persons

from snakebite. It is lamentable to think that despite the supposed

remedial discoveries in this direction, we still seem to be without an

agent to neutralise the effects of the bites of poisonous snakes.”

[Footnote 169: ‘Analyst,’ 11th, 1870.]

=SNAKE-ROOT.= See SENEGA. For ‘Virginian snake-root’ see SERPENTARY.

Snakeweed (_Bistortæ radix_) is the root of _Polygonum Bistorta_ (Linn.).

=SNIPE.= The _Scolopax Gallinago_, a well-known bird indigenous to this

country. It is fine-flavoured, but rather indigestible.

=SNOW, Foreign Bodies in.= M. Bondier[170] having lately made an

examination of snow, records that of the solid matters floating in the air

and retained in the snow, the most abundant was found to be soot; next

some cells of _Protococcus virictis_, and spores and filaments of other

cryptograms; then granules of starch and cells and fibres of various

plants. Epithelial cells and hairs of animals were also present, as well

as fibres of wool and silk. These last, being dyed, indicated the presence

of man, as did also the fibres of hemp, cotton, and indigo. The amount of

foreign matter was greatest in the snow collected at the lowest levels,

especially in the vicinity of human habitations and of woods, which are

both fertile sources of floating particles. Permanganate of potassium was

used to estimate the amount of organic matter dissolved by the filtered

snow water.

[Footnote 170: ‘Journ. Ch. Soc.’]

Immediately mixed with the soot were the ferruginous corpuscles observed

by Tissandier. These are regarded by the author, in opposition to the

opinion of Tissandier, as of terrestrial origin.

=SNUFF.= _Syn._ PULVIS TABACI, L.; TABAC EN POUDRE, Fr. A powder, prepared

from tobacco, for the purpose of being sniffed up the nose as a stimulant

or intoxicant.

The finer kinds of snuff are made from the soft portions of the best

description of manufactured leaf-tobacco, separated from the damaged

portion; but the ordinary snuffs of the shops are mostly prepared from the

coarser and damaged portions, the mid-ribs, stems, or stalky parts that

remain from the manufacture of ‘shag tobacco,’ the dust or powder sifted

from the bales, and the fragments that are unfit for other purposes.

_Prep._ The proper material being chosen, and if not in a sufficiently

mature state rendered so by further fermentation, they are sufficiently

dried by a gentle heat or exposure to the air to admit of being

pulverised. This is performed, on the large scale, in a mill, and on the

small scale, with a kind of pestle and mortar. During the operation the

tobacco is frequently sifted, that it may not be reduced to too fine a

powder, and is several times slightly moistened with rose or orange-flower

water, or eau d’ange, which are the only liquids fit for the superior

kinds of snuff. In preparing the dry snuffs no moisture is used. The scent

or other like matters are next added, and, after thorough admixture, the

snuff is packed in jars or canisters.

_Adult._ During the grinding of tobacco it is frequently mixed with

dark-coloured rotten wood, various English leaves, colouring, and other

matter. Ammonia, hellebore, euphorbium, and powdered glass are common

additions to snuffs to increase their pungency. We have seen powdered sal

ammoniac sent by the hundredweight at one time to a certain celebrated

London tobacconist. The moist kinds of snuff are generally drugged with

pearlash, for the triple purpose of keeping them damp and increasing their

pungency and colour. The dry snuffs, especially ‘Scotch’ and ‘Welsh,’ are

commonly adulterated with quicklime, the particles of which may be

occasionally distinguished even by the naked eye. This addition causes

their biting and desiccating effect on the pituitary membrane. “We were

once severely injured by taking snuff which, after our suspicions were

awakened, we found to contain a mixture of red lead and umber.” (Cooley.)

The following circumstance related by Dr Garrod[171] in a lecture at

King’s College Hospital leads to the inference that the custom of packing

snuff in lead is not free from danger. The doctor says:——A gentleman, a

resident in India, began to suffer some time since from nervous

exhaustion, anæmia, and debility of both extremities; he was a great snuff

taker, taking on an average as much as an ounce in the course of a day. He

consulted several medical men in India, and they attributed his symptoms

to inordinate snuff taking. He, however, continued to take snuff and to

get worse, and at last came to England to seek further advice. When Dr

Garrod saw him he discovered a blue line on the gums. His suspicions were

directed to the snuff, which he found to contain a considerable quantity

of lead. To ascertain whether or not the presence of lead in this

circumstance was an accidental circumstance, six packets were ordered from

the house in Calcutta with which the gentleman had been in the habit of

dealing. The snuff was contained in sheet-lead packages, which were all

found to contain lead to about the same extent as the first specimen. Dr

Garrod exhibited a solution, which he tested in the following way:——Ten

grains of snuff were burned in a platinum crucible, and the ash was

treated with nitric acid, the crystallised result was dissolved in water

with the addition of a small quantity of acetic acid, and then tested with

iodide of potassium, which threw down an abundant precipitate of yellow

iodide of lead. The leaden packages were labelled ‘best brown rappee,’ and

bore the name of a well-known English firm, from which they had been

exported to India. The snuff itself was rather moist. Where it adhered to

the sides of the case it was dotted with white spots, probably consisting

of carbonate of lead, formed by, Dr Garrod suggests, the fermentation of

the damp snuff.

[Footnote 171: ‘Lancet.’]

Since Dr Garrod’s attention has been directed to this subject, he has

spoken to a medical man recently returned from Calcutta, who told him that

he had quite lately met with three cases of lead-poisoning, which, on

investigation, were found to be due to the use of snuff.

_Var._ Snuffs are divided into two kinds——DRY SNUFFS, as ‘Scotch,’

‘Irish,’ ‘Welsh,’ and ‘Spanish snuff,’ ‘Lundyfoot,’ &c.; and MOIST SNUFFS,

or RAPPEES, including ‘black’ and ‘brown rappee,’ ‘carrotte,’ ‘Cuba,’

‘Hardham’s mixture,’ ‘prince’s mixture,’ ‘princeza,’ ‘queen’s snuff,’ &c.

The last three also come under the denomination of SCENTED SNUFFS.

The immense variety of snuffs kept in the shops, independently of the

above-named conditions, depend for their distinguishing characteristics on

the length of the fermentation, the fineness of the powder, the height to

which they are dried, and the addition of odorous substances. Tonquin

beans, essence of tonquin bean, ambergris, musk, civet, leaves of orchis

fusca, root and oil of calamus aromaticus, powder and essence of orris

root, and the essences or oils of bergamot, cedra, cloves, lavender, petit

grain, neroli, and roses (otto), as well as several others, either alone

or compounded, are thus employed. TABAC PARFUMÉE AUX FLEURS is perfumed by

putting orange flowers, jasmins, tuberoses, musk roses, or common roses,

to the snuff in a close chest or jar, sifting them out after 24 hours, and

repeating the treatment with fresh flowers, as necessary. Another way is

to lay paper, pricked all over with a large pin, between the flowers and

the snuff.

MACOUBA SNUFF is imitated by moistening the tobacco with a mixture of

treacle and water, and allowing it to ferment well.

SPANISH SNUFF is made from unsifted ‘Havannah snuff,’ reduced by adding

ground Spanish nutshells, sprinkling the mixture with treacle water, and

allowing it to sweat for some days before packing.

YELLOW SNUFF is prepared from ordinary pale snuff moistened with a mixture

of yellow ochre diffused in water, to which a few spoonfuls of thin

mucilage have been added; when dry, the colour that does not adhere to the

snuff is separated with a fine sieve.

RED SNUFF. As last, but using red ochre.

=Snuff, Asarabac′ca.= _Syn._ CEPHALIC SNUFF, COMPOUND POWDER OF

ASARABACCA; PULVIS ASARI COMPOSITUS, L. _Prep._ 1. (Ph. D. 1826.)

Asarabacca leaves, 1 oz.; lavender flowers, 1 dr. (both dried); mix and

powder them.

2. (Ph. E. 1817.) Asarabacca leaves, 3 dr.; leaves of marjoram and flowers

of lavender, of each 1 dr.; as before. Both are used as errhines in

headaches and ophthalmia. See SNUFF, CEPHALIC, ASARABACCA, &c.

=Snuff, Cephal′ic.= _Prep._ 1. From asarabacca leaves and Lundyfoot snuff,

of each 2 oz.; lavender flowers, 1/4 oz.; essence of bergamotte and oil of

cloves, of each 2 or 3 drops; mixed and ground to a powder, the perfume

being added last.

2. (Boeli’s.) From tobacco or pure snuff and valerian root, of each 1/2

oz.; reduced to powder, and scented with the oils of lavender and

marjoram, of each 5 or 6 drops.

_Obs._ The first formula is an excellent one; and the product is very

useful in nervous headaches, dimness of sight, &c. See SNUFF, ASARABACCA

(_above_).

=Snuff, Eye.= _Prep._ From finely levigated tribasic sulphate of mercury

(‘Turpeth mineral’), 1/2 dr.; pure dry Scotch or Lundyfoot snuff, 1 oz.;

triturate them well together. A pinch of this, occasionally, has been

recommended in inflammation of the eyes, dimness of sight, headache,

polypus, &c.; but it should be used with caution, and not too often.

=SOAP.= _Syn._ SAPO, L.; SAVON, Fr. SPANISH, CASTILE, or HARD SOAP, made

with olive oil and soda (SAPO, SAPO EX OLIVÆ OLEO ET SODÂ CONFECTUS——Ph.

L.; SAPO DURUS——B. P., Ph. E., & D.), and SOFT SOAP, made with olive oil

and potash (SAPO MOLLIS——B. P., Ph. L., & E., SAPO EX OLIVÆ OLEO ET

POTASSÂ CONFECTUS——Ph. L.), are the only kinds directed to be employed in

medicine. The former is intended whenever ‘soap’ is ordered, and is the

one which is principally employed internally; the latter is used in

ointments, &c., and in some of the officinal pills.

_Prep._ The fatty or oleaginous matter is boiled with a weak alkaline lye

(soap-lye) rendered caustic by quicklime, and portions of stronger lye are

added from time to time, the ebullition being still continued, until

these substances, reacting on each other, combine to form a tenacious

compound, which begins to separate from the water; to promote this

separation and the granulation of the newly-formed soap, some common salt

is generally added, and the fire being withdrawn, the contents of the

boiler are allowed to repose for some hours, in order that the soap may

collect into one stratum, and solidify; when this happens it is put into

wooden frames or moulds, and when it has become stiff enough to be handled

it is cut into bars or pieces, and exposed to the air, in a warm

situation, to further harden and to dry.

In the print works of Alsace, where an immense quantity of egg albumen is

consumed, there collect, as a necessary result, enormous quantities of the

yolks of egg. Amongst other purposes to which these are applied that of

soap-making is one. According to Kingzett, the olein is not the only

ingredient of the yolk which reacts upon the soda or potash, and thus

produces soap; but the yolk also contains another body, which, absorbing

water under the influence of the bases, splits up into oleic and margaric

acids.

“Besides the olein contained in the free state, there is,” says Mr

Kingzett, “present a body called _lecithine_ of the formula

C_{42}H_{84}NPO_{9}.” Gobloy, Diakonow, Strecker, Thudicum, and Kingzett

have studied this substance, and express its chemolysis as follows:——

Lecithine. Water. Glycero-phosphoric

acid.

C_{42}H_{84}NPO_{9} - 3H_{2}O = C_{3}H_{9}PO_{6}

Choline. Oleic acid. Palmitic

acid.

+ C_{5}H_{15}NO_{2} + C_{18}H_{34}O_{2} + C_{16}H_{32}O_{2}.

That is to say, bases have the power, by abstracting water, to split up

_lecithine_ into, among other products, oleic and palmitic acid; so that

when eggs are used for soap-making this process actually occurs, the soda

or potash employed being sufficient to effect the necessary decomposition,

and the resulting soap being, therefore, the product from not only the

olein, but from the fatty acids so formed.

Tessie du Mothay has proposed a method for the recovery of potash, soda,

&c., from soap water, which is as follows:——He decomposes the soap water

by calcium, barium, or magnesium carbonate, and then passes carbonic acid

through the liquid. The bicarbonate form precipitates organic matter and

other impurities, and these settle down. The solution is then evaporated

or treated with baryta water, which precipitates the last portion of

foreign matters, and leaves a solution of caustic alkali. At a particular

stage of the process an acid is used in order to hasten the separation of

the resinous substances, and, in certain cases, of the sulphides of sodium

and calcium, or barium and calcium and ferric oxide, and then passes

carbonic acid into the liquid. The precipitated metallic substances carry

down with them the humus-like substances present.

_Var._ The principal varieties of soap found in commerce are:——

ALMOND SOAP (SAPO AMYGDALINUS), made from almond oil and caustic soda, and

chiefly used for the toilet.

The P. Codex gives the following formula for its preparation:——Solution of

caustic soda (1·334), by weight, 10 oz.; oil of almonds, by weight, 21

oz.; add the lye to the oil in small portions, stirring frequently; leave

the mixture for some days at a temperature of from 64° to 68° Fahr.,

stirring occasionally, and when it has acquired the consistence of a soft

paste, put it into moulds until sufficiently solidified. It should be

exposed to the air for one or two months before it is used.

ANIMAL SOAP. SAPO ANIMALIS, CURD SOAP (B. P.). A soap made with soda and a

purified animal fat consisting principally of stearin (P. Cod.). Put 5

parts of beef marrow with 10 parts of water into a porcelain or silver

basin, heat, and when melted add by portions, with constant stirring,

2-1/2 parts of liquor sodæ (1·33); when saponified, add 1 part of salt;

stir, remove the soap from the surface, drain it, melt it with a gentle

heat, and pour it into moulds.

CASTILE SOAP, SPANISH S., MARSEILLES S.; SAPO CASTILIENSIS, SAPO

HISPANICUS. An olive-oil soda soap, kept both in the white and marbled

state. The former is said to be the purest, the latter the strongest.

CURD SOAP, made with tallow (chiefly) and soda (see _above_).

MEDICATED SOAPS, containing various active ingredients. The chief of these

are noticed _below_.

MOTTLED SOAP, made with refuse kitchen-stuff, &c.

SOFT SOAP (of commerce), made with whale, seal, or cod oil, tallow, and

caustic potash.

N. Gräger[172] gives the following method for the easy determination of

the fat and alkali in soft (potash) soaps:——25 to 50 grammes of soap are

dissolved in 150 c.c. of water by aid of heat, cooled, and mixed with an

excess of salt, so that a soda-soap separates out; the latter is washed on

a paper filter with a saturated solution of salt. In the filtrate the free

alkali is estimated by a normal acid. The precipitate is decomposed by

warming with excess of normal acid, and the quantity of acid neutralised

by the combined alkali, determined by a standard soda solution. The cake

of fat which separates in the last operation, is dried and weighed after

adding to it, while melted, a known weight of stearin or paraffin to give

it hardness.

[Footnote 172: ‘Dingler’s Journal’ (‘Journ. of Chem. Soc.,’ vol. ix, new]

TOILET SOAPS, prepared from any of the preceding varieties, and variously

coloured and scented. Formulæ are given _below_.

YELLOW SOAP, RESIN SOAP, made with tallow, resin, and caustic soda.

Soluble glass is now largely employed in place of resin.

Soaps are also divided into SOFT or POTASH SOAPS, and HARD or SODA SOAPS.

_Assay._ 1. For the WATER. A piece, fairly taken from the sample, and

weighing 100 gr., is reduced to thin shavings, which are dried by the heat

of boiling water, until they cease to lose weight. The loss indicates the

proportion of free water. This should not exceed 35% for ordinary curd and

mottled soap, 45% for yellow soap, and about 15% to 16% for Castile soap.

2. For the ALKALI. 100 gr. of the soap are dissolved in 4 or 5 fl. oz. of

boiling water, and the solution tested by the common method of

alkalimetry. Curd and yellow soap usually contain from 6% to 7%, mottled

soap from 7% to 8%, and Castile soap 8% to 9% of soda.

3. For the OIL or FAT. The solution tested for alkali (see No. 2) is

heated, and then allowed to cool slowly; when cold the floating fatty

matter is removed, freed from water, and weighed. When the fat or oil has

little consistence, 100 gr. of pure white wax is added to the soap

solution before heating it. The weight obtained, in grains in the one

case, and the excess above 100 gr. in the other, give the proportion of

oil or fat present. This, in ordinary mottled soap, should be about 68%;

in yellow soap, 65%; in curd soap, 60%; and in Castile soap, 75%.

4. UNSAPONIFIED FATTY MATTER.——_a._ Pure soap is entirely soluble in

distilled water and insoluble in saline solution; if a film of fatty

matter forms on its solution in the former, after repose, that portion has

not been saponified.

_b._ The fat separated from soap (see No. 2), when it has been perfectly

saponified, is entirely soluble in alcohol.

5. OTHER IMPURITIES. Pure soap is soluble in rectified spirit, forming a

colourless or nearly colourless solution. The undissolved portion, if

exceeding 1%, is adulteration.

ANOTHER METHOD OF SOAP ASSAY (M. Moffit). The constituents to be

determined in an analysis of soap are alkalies (combined and free),

carbonates, fatty acids, resin, glycerin, salts, colouring matters, and

water.

Three portions of the finely divided soap are weighed off, containing

respectively 10 grams, 20 grams, and 40 grams. Ten grams are digested with

alcohol on the water-bath and filtered. The residue containing carbonates

and other salts, colouring matter, &c., is dried at 100°, weighed,

digested with water, and titrated with normal oxalic acid. Every c.c. of

acid used indicates 0·053 Na_{2}CO_{3}.

Regard must be had to a slight precipitate of calcium oxalate. The weight

of Na_{2}CO_{3} found is subtracted from the total residue insoluble in

alcohol, the difference is the weight of the salts and foreign matters.

The filtrate is subjected to a stream of carbonic acid, filtered, and the

precipitate dissolved in water and titrated with oxalic acid. Each c.c.

of acid indicates 0·031 free soda, or 0·042 free potash. No precipitate

shows the absence of free alkalies. The filtrate from the precipitate

produced by the carbonic acid is, after the addition of 15 c.c. of water,

evaporated to remove the alcohol. The aqueous solution, treated with

normal oxalic acid to acid reaction, shows for every c.c. of acid 0·031

soda, or 0·042 potash in combination. Sulphuric acid is then added, and

the whole is heated on a water bath with pure beeswax to separate the

fatty acids and resin, which are then weighed, the weight of the beeswax

being subtracted.

Forty grams of the soap are next dissolved in water and mixed with

sulphuric acid, as long as any precipitate is formed. On standing the

fatty acids separate, and can be dried and weighed. These fatty acids are

digested with a mixture of equal volumes of water and alcohol, till the

liquid on cooling ceases to appear milky. The solid layer is again

weighed, and the difference between the weight and that obtained above

shows the weight of the resin.

The melting point of the acids is next determined. Ten grams are then

dissolved in alcohol, and sulphuric acid diluted with alcohol is added,

till a precipitate is no longer formed. The liquid is filtered, mixed with

barium carbonate, and again filtered. The sweet residue left after

evaporation of the alcohol is glycerin. The weights of the carbonates,

salts, and foreign matters, free and combined alkalies, fatty acids,

resin, and glycerin are added together, and the sum subtracted from 10

grams gives the weight of the water.

See also Soap analysis, ‘Chem. News,’ xxxv, 2. The article is too long to

allow of insertion here.

_Uses, &c._ The common uses of soap need not be enumerated. As a medicine

it acts as a mild purgative and lithontriptic, and it has been thought by

some to be useful in certain affections of the stomach arising from

deficiency of bile. _Externally_ it is stimulant and detergent.——_Dose_, 3

to 20 or 30 gr., made into pills, and usually combined with aloes or

rhubarb.

_Concluding Remarks._ Prior to the researches of Chevreul, no correct

ideas were entertained as to the constitution of soap. It was long known

that the fixed oils and fats, in contact with caustic alkaline solutions

at a high temperature, undergo the remarkable change which is called

saponification; but here the knowledge of the matter stopped. Chevreul

discovered that if the soap, so produced, be afterwards decomposed by the

addition of an acid, the fat which separates is found to be completely

changed in character; to have acquired a strong acid reaction when applied

in a melted state to test paper, and to have become soluble with the

greatest facility in warm alcohol; in other words——that a new substance,

capable of forming salts, and exhibiting all the characteristic properties

of an acid, has been generated out of the elements of the neutral fat

under the influence of the base. Stearin, when thus treated, yields

stearic acid, palmitin gives palmitic acid, olein gives oleic acid, and

common animal fat, which is a mixture of several neutral bodies, affords,

by saponification by an alkali and subsequent decomposition of the soap, a

mixture of the corresponding fatty acids. These bodies are not, however,

the only products of saponification; the change is always accompanied by

the formation of a very peculiar sweet substance called glycerin, which

remains in the mother liquor from which the acidified fat has been

separated. The process of saponification itself proceeds with perfect

facility, even in a closed vessel; no gas is disengaged; the neutral fat,

of whatsoever kind, is simply resolved into an alkaline salt of the fatty

acid, which is soap, and into glycerin, a neutral body resembling syrup,

and, like that liquid, miscible with water in every proportion.

“When yellow soap is made with the cheaper kinds of fat it will hardly

acquire a sufficient degree of firmness or hardness to satisfy the thrifty

washerwoman. It melts away too rapidly in hot water, a defect which may be

well remedied by the introduction into the soap of a little (1·20th) fused

sulphate of soda; and this salt concreting gives the soap a desirable

hardness, whilst it improves its colour, and renders it a more desirable

article for the washing tub.” (Ure.) This process was patented by Dr

Normandy, but soon proved a source of annoyance and molestation to him on

the part of the Board of Excise, it being an enormous crime in law to

attempt to improve and cheapen soap.

“Soda which contains sulphurets is preferred for making mottled or marble

soap, whereas the desulphuretted soda makes the best white curd soap.”

“The Barillas always contain a small proportion of potash, to which their

peculiar value, in making a less brittle or more plastic hard soap than

the factitious sodas, may, with great probability, be ascribed.” (Ure.)

The mottled appearance is usually given, in the London Soap-works, by

watering the nearly finished soap with a strong lye of crude soda, by

means of a watering can furnished with a rose spout. For ‘Castile soap’ a

solution of sulphate of iron is so employed. See SOAPS (Medicated and

Toilet).

=Soap, Arsen′ical.= _Syn._ SAPO ARSENICALIS, L. _Prep._ (Bécœurs.) From

carbonate of potash, 12 oz.; white arsenic, white soap, and air-slaked

lime, of each 4 oz.; powdered camphor, 3/4 oz.; made into a paste with

water, q. s. Used to preserve the skins of birds, and other small animals.

=Soap, Black.= _Syn._ SAPO NIGER, S. MOLLIS COMMUNIS, L. A crude soft

soap, made of fish oil and potash; but the following mixture is usually

sold for it:——Soft soap, 7 lbs.; train oil, 1 lb.; water, 1 gall.; boil to

a proper consistence, adding ivory black or powdered charcoal, q. s., to

colour. Used by farriers.

=SOAPS (Med′icated).= A few only of these deserve notice here:——

=Soap, Antimo′′nial.= _Syn._ SAPO ANTIMONIALIS, SAPO STIBIATUS, L. _Prep._

(Hamb. Cod. 1845.) Golden sulphuret of antimony, 2 dr.; solution of

caustic potassa, 6 dr. (or q. s.); dissolve and triturate the solution

with medicated (Castile) soap (in powder), 1-1/2 oz., until the mass

assumes a pilular consistence. It should be of a greyish-white colour.

=Soap, Chlorina′ted.= _Syn._ SAPO CALCIS CHLORINATÆ, L.; SAVON

ANTISYPHILITIQUE, Fr. _Prep._ From Castile soap (in powder), 11 oz.;

chloride of lime (dry and good), 1 oz.; mix, beat them to a mass with

rectified spirit, q. s.; (holding in solution) oil of verbena or of ginger

grass, 1/4 oz.; lastly, form the mass into flat tablets, and wrap these in

thin sheet gutta percha. A most excellent detergent and stimulant soap in

various affections, admirably adapted for hospital use, and for removing

stains from the skin and rendering it white. It is the most powerful known

agent against infection from contagious diseases communicable by contact.

=Soap, Cod-Liver Oil.= _Syn._ SAPO OLEI JECORIS (Deschamps). _Prep._

Cod-liver oil, 2 oz.; caustic soda, 2 dr.; water, 5 dr.; dissolve the soda

in the water, and mix it with the oil. An ioduretted soap is made by

mixing with the above, 1 dr. of iodide of potassium dissolved in 1 dr. of

water.

=Soap, Cro′ton.= _Syn._ SAPO CROTONIS, L. _Prep._ From croton oil and

liquor of potassa, equal parts; triturated together in a warm mortar until

they combine. Cathartic.——_Dose_, 1 to 3 gr.

=Soap of Gamboge.= _Syn._ SAPO GAMBOGIÆ. (Soubeiran.) _Prep._ Mix 1 part

of gamboge with 2 of soap, dissolve it with a little spirit, and evaporate

to a pilular consistence.