2. =Perox'ide of Hydrogen.= (HO.) _Syn._ HYDROXYL, BINOXIDE OF HYDROGEN,
DEUTOXIDE OF H., OXYGENATED WATER; HYDROGENIIBINOXYDUM, L. This singular
fluid was discovered by M. Thénard in 1818.
_Prep._ (Odling.) A known quantity of pure hydrochloric acid, diluted with
8 or 10 times its volume of distilled water, is placed in a glass beaker
surrounded with ice or a freezing mixture. A quantity of binoxide of
barium rather less than sufficient to neutralise the acid is then ground
to a fine paste with distilled water, and added gradually to the acid in
which it should dissolve without effervescence. Diluted sulphuric acid is
next added cautiously, to precipitate the barium, and reproduce
hydrochloric acid to act upon a fresh quantity of peroxide. The liquid
having been filtered from the insoluble sulphate of baryta, a second
proportion of binoxide of barium paste is added gradually, as before. The
treatment with sulphuric acid, filtration and addition of binoxide, is
repeated 6 or 7 times. Sulphate of silver is then very carefully added, so
as exactly to precipitate in the form of chloride of silver the whole of
the chlorine. After filtration, pure baryta, first as a paste and then in
solution, is cautiously added, to precipitate exactly the sulphuric acid
set free from the sulphate of silver. Filtration is again resorted to, and
the clear liquid (aqueous solution of peroxide of hydrogen) is placed in a
dish over oil of vitriol in vacuo, in order that the water mixed with it
may evaporate.
_Prop., &c._ A colourless, transparent, somewhat syrupy liquid, of sp. gr.
1·452. It has a metallic taste, and corrodes the skin. It is easily
resolved into oxygen and water. It mixes freely with water, and becomes
more permanent by the dilution. It bleaches organic substances, and acts
as a powerful oxidating agent. Under certain circumstances, however, it
plays the part of a reducing agent. To the chemist, peroxide of hydrogen
and its analogue, binoxide of barium, have been of great service as
instruments of research. Binoxide of hydrogen has been applied in the arts
to restore the blackened lights of paintings which have become darkened by
sulphuretted hydrogen; it is also sold by hair-dressers for bleaching
human hair.
=Hydrogen, Phosphuret'ted.= See PHOSPHORUS.
=Hydrogen, Sulphides of.= See SULPHUR.
=HYDROMEL.= _Syn._ HYDROMELI, L. An aqueous solution of honey. _Prep._ (P.
Cod.) Honey, 2 oz.; boiling water, 32 oz.; dissolve, and strain. A
refreshing and slightly laxative drink; in fevers, hoarseness, sore
throats, &c.
=HYDROM'ETER.= _Syn._ AREOMETER, GRAVIMETER; HYDROMETRUM, L. An instrument
for ascertaining the specific gravities of liquids, and hence their
strength, the latter being either in inverse or direct proportion to the
former. Hydrometers are of two kinds:--1. Those which are always immersed
to the same depth in distilled water, and the liquid to be tried, small
weights being used for the purpose, as in FAHRENHEIT'S and NICHOLSON'S
hydrometers; and 2nd, those which are suffered to rise or sink freely in
the liquid, until they come to a state of rest, as in SYKE'S, BAUMÉ'S, &c.
In both cases a correction must be made for any variation in temperature.
Of the two kinds, the first give the most accurate results, and have the
great advantage of being applicable to liquids either lighter or heavier
than water, but the second are the readier in practice, requiring less
time and less skill to use them. The following are those best known:--
BAUMÉ'S HYDROMETER or AREOMETER, which is very generally employed on the
Continent, consists of two distinct instruments, the one for liquids
heavier than water, the other for liquids lighter than that fluid. The
first floats at the 0, or 'zero,' of the scale, in distilled wafer, at the
temperature of 58° Fahr., and each degree, marked downwards, indicates a
density corresponding to one per cent. of common salt. The hydrometer for
liquids lighter than water is poised so that the 0 of the scale is at the
bottom of the stem, when it is floating in a solution of 1 oz. of common
salt in 9 oz. of water, and the depth to which it sinks in distilled water
shows 10°; the space between these fixed points being equally divided, and
the graduation continued upwards to the top of the scale.
The temperature at which these instruments were originally adjusted by
Baumé was 12·5° Centigrade (54·5° Fahr.). They are now commonly adjusted
in this country at 58° or 60° Fahr. Hence arise the discrepancies
observable in the published tables of the "correspondence between degrees
of Baumé and real specific gravities."
CARTIER'S HYDROMETER, which is much used in France for light liquids, has
the same point for the zero of its scale as Baumé's, but its degrees are
rather smaller, 30° Baumé being equal to 32° Cartier.
FAHRENHEIT'S HYDROMETER consists of a hollow ball, with a counterpoise
below, and a very slender stem above, terminating in a small dish. The
middle, or half-length of the stem, is distinguished by a fine line across
it. In this instrument every division of the stem is rejected, and it is
immersed in all experiments to the middle of the stem, by placing proper
weights in the little dish above. Then, as the part immersed is constantly
of the same magnitude, and the whole weight of the hydrometer is known,
this last weight, added to the weights in the dish, will be equal to the
weight of fluid displaced by the instrument, as all writers on
hydrostatics prove. And accordingly, the specific gravities for the common
form of the tables will be had by the proportion--
_As the whole weight of the hydrometer and its load, when adjusted in
distilled water_, is to the _number_ 1000, so is the _whole weight when
adjusted in any other fluid, to the number expressing its specific
gravity._
GAY-LUSSAC'S ALCOHOLOMETER is used to determine the strength of spirituous
liquors. It, at once, indicates on the stem, the per-centage of absolute
alcohol in the liquid examined. The original experiments of Gay-Lussac
having been made on liquids at a temperature of 59° Fahr., all examples
examined by the alcoholometer, must either be brought to that temperature
previous to being tested, or a correction made in the strength found.
NICHOLSON'S HYDROMETER is constructed on the same principle as
Fahrenheit's. It has in addition to the small dish for weights above, a
little cup attached below, for holding any solid body whose weight in
water is required. It is chiefly intended for taking the sp. gr. of
minerals.
RICHTER'S HYDROMETER resembles, for the most part, Gay-Lussac's.
SYKE'S HYDROMETER is that adopted by the Revenue authorities in England
for ascertaining the strength of spirits, and has been already fully
noticed.
TRALLES'S HYDROMETER resembles Gay-Lussac's (nearly).
TWADDELL'S HYDROMETER is much used in the bleaching establishments of
Scotland, and in some part of England. According to this scale, 0 is equal
to 1000 or the sp. gr. of distilled water, and each degree is equal to
·005; so that, by multiplying this number by the number of degrees marked
on the scale, and adding 1·, the real specific gravity is obtained.
_Obs._ Hydrometers, unless manufactured with great care and skill, merely
afford approximate results; but which are nevertheless sufficiently
correct for all ordinary purposes. They also require several ounces of
liquid to float them, and hence cannot be used for very small quantities.
Those of Fahrenheit, Nicholson, and Sykes are the most accurate, both in
principle and application. They are all employed with a tall glass
cylinder termed a sample, test, or hydrometer glass, in the way already
noticed; but the thermometer for ascertaining the temperature must be
covered with a glass case, or arranged with a folding scale to allow of
its immersion in corrosive liquids.
ALCOHOLOMETERS, ELAIOMETERS, SACCHAROMETERS, URINOMETERS, &c., are simply
hydrometers so weighted and graduated as to adapt them for testing
spirits, syrups, urine, &c. See ALCOHOLOMETRY, ALONHOLMETRY, AREOMETER,
SPECIFIC GRAVITY, &c.
=HYDROM'ETRY.= _Syn._ AREOMETRY. The art of determining the specific
gravity of liquids, and hence their strength and commercial value. The
instruments used are noticed above; their action depends upon the fact
that a floating body displaces a bulk, equal to itself in weight, of the
fluid in which it floats, and consequently that a body of a given weight
sinks deeper in a lighter than in a heavier fluid. In hydrometric
determinations the temperature of the samples must be carefully attended
to, for fluids expand as their temperature is increased. The hydrometers
used in England are generally adjusted to the standard temperature of 60°
Fahr., and when 'Hydrometer Tables,' giving the corrections for the
variations of the thermometer, are not accessible, the fluids to be
examined should be brought to this standard temperature by applying heat
directly to the vessel, when the temperature is below the standard, or by
surrounding the vessel, with cold water, when it is above the standard.
The principal applications of hydrometry are described in different parts
of this work. See ACETIMETRY, ALCOHOLOMETRY, CHLOROMETRY, SPECIFIC
GRAVITY, &c.
=HYDROP'ATHY.= _Syn._ WATER CURE; HYDROPATHIA, L. A mode of curing
diseases by the copious use of pure cold water, both internally and
externally, together with dry sweating, and the due regulation of diet,
exercise, and clothing. This "treatment of diseases undoubtedly includes
powerful therapeutic agents, which, in the hands of the educated and
honourable practitioner, might be most beneficially resorted to as
remedial agents." (Pereira.)
=HYDROPHO'BIA.= _Syn._ CANINE MADNESS; RABIES CANINA, L. A disease which
is generally considered as the result of a morbid poison being introduced
into the system by the bite of a rabid animal. A clear case of idiopathic
or spontaneous hydrophobia has never yet been known to occur in the human
subject.
The common symptoms of hydrophobia are great excitability and horror at
the sight of water, or the attempt to drink, fever, vomiting, excessive
thirst, spitting of viscid saliva, difficult respiration, irregular pulse,
convulsions, syncope, delirium, and death.
The whole materia medica has been, unfortunately, unsuccessfully sought
without the discovery of a single remedy for this disease, or even a
palliative of its severer symptoms. See CURARINE.
The treatment of recent bites of venomous animals has been fully
explained, and need not be repeated here. To prevent secondary or
constitutional effects arising, the use of lemon juice, or arsenical
solution, has long been popular. (Graham, and others.) Dr Buchan remarks
that "vinegar is of considerable use, and should be taken freely."
=HYDROSULPHU'RIC ACID.= See SULPHUR.
=HYGIENE'.= _Syn._ HYGIENE, Fr. Health; its preservation, promotion, and
restoration. That department of medicine and civil government which
relates to health. See AIR, BATH, EXERCISE, FLANNEL, FOOD, NUTRITION,
SLEEP, VENTILATION, &c.
=HYGROMETER.= An instrument for measuring the amount of moisture in the
atmosphere.
Amongst the various contrivances for accomplishing this end are Daniel's
dew-point hygrometer; and the wet bulb hygrometer.
By the first, the quantity of moisture in the atmosphere, is determined by
noting with a sensitive thermometer, the temperature at which a film of
dew mass, to deposit on one of the bulbs of a species of cryophorus,
disappears; the tension of the aqueous vapour present in the air at that
period, being readily ascertained from tables constructed for the purpose,
the corresponding proportion of moisture can thus be readily ascertained.
The wet bulb hygrometer consists of two small thermometers placed side by
side, the bulb of them being surrounded by cotton films kept constantly
damp by a simple contrivance. According to the rate of evaporation of the
bulb so moistened, with the fall of the thermometer to which the moistened
bulb belongs, the depression, of course, being greater the further the
surrounding atmosphere is from the saturation point, and tables are
furnished for determining the degree of saturation for all differences of
temperature within the ordinary atmospheric range.
=HYOCHO'LIC ACID.= C_{25}H_{40}O_{4}. _Syn._ GLYCOHYOCHOLALIC ACID. A
compound peculiar to the gall of pigs, discovered by Strecker and
Gundelach.
_Prep._ The fresh gall of pigs is mixed with a solution of sulphate of
sodium; the precipitate is dissolved in absolute alcohol, and decolourised
by animal charcoal. From this solution ether throws down hyocholate of
sodium, which, on the addition of sulphuric acid, yields hyocholic acid as
a resinous mass, which is dissolved in alcohol, re-precipitated by water,
and dried. When heated with alkaline solutions, glycocine and a new
crystalline acid (hyocholalic acid) are formed. When boiled with acids, it
yields glycocine and hyodyslysin.
=HYOSCY'AMINE.= _Syn._ HYOSCYAMIA, HYOSCYAMINA, DATURINE, DATURIA. An
alkaloid obtained from common henbane (_Hyoscyamus niger_), and also from
the thorn apple (_Datura stramonium_). See DATURA.
=HYPNOT'ICS.= _Syn._ HYPNOTICA, L. Agents or medicines which induce sleep,
as opium, morphia, henbane, Indian hemp, lactucarium, &c. Agents which
prevent sleep are called agrypnotics (_Agrypnotica_, L.), or anthypnotics
(_Anthypnotica_, L.).
=HYPOCHLO'RIC ACID.= See CHLORINE.
=HYPOCHONDRI'ASIS.= _Syn._ HYPOCHONDRIACISM. The 'hip' or 'hyp,' the
'vapours,' depression of spirits, 'blue devils.' This disease chiefly
affects persons of the melancholic temperament, and is commonly induced by
hard study, irregular habits of life, want of proper social intercourse,
living in close apartments, and insufficient out-of-door exercise. The
treatment may, in most cases be similar to that recommended for DYSPEPSIA,
observing, however, that success depends more on amusing and engaging the
mind, and in gradually weaning it from old conceits, than in the mere
administration of medicine. When the patient is tormented with a visionary
or exaggerated sense of pain, or of some concealed disease, or a whimsical
dislike of certain persons, places, or things, or groundless apprehensions
of personal danger or poverty, or the conviction of having experienced
some dreadful accident or misfortune, the better way is to avoid any
direct attempts to alter his opinions, but to endeavour to inspire
confidence in some method of relief. Greding mentions the case of a
medical man who conceived that his stomach was full of frogs, which had
been successively spawning ever since he had bathed, when a boy, in a pool
in which he had perceived some tadpoles; and he had spent his life in
endeavouring to get them removed. One patient, perhaps, fancies himself a
giant; another as heavy as lead; a third a feather, in continual danger of
being blown away by the wind; and a fourth a piece of glass, and is hourly
fearful of being broken. Marcellus Dentatus mentions a baker of Ferrara
who thought himself a lump of butter, and durst not sit in the sun, or
come near the fire, for fear of being melted. The writer of this article
once knew a man who always put on his coat the wrong side in front,
because he conceived his face looked behind him. In such cases it is
useless to argue with the patient, as it only causes irritation, and
increases the malady. The restoration of the bodily health, and a sudden
surprise or change of scene, will often effect a cure.
=HYPONI'TRIC ACID.= See NITROGEN.
=HYPONI'TROUS ACID.= See NITROGEN.
=HYPOPHOS'PHITES.= See PHOSPHORUS.
=HYPOPHOS'PHITE.= A salt of hypophosphorous acid.
=HYPOSUL'PHATE.= _Syn._ DITHIONATE; HYPOSULPHAS, L. A salt of
hyposulphuric acid.
=HYPOSUL'PHITE.= _Syn._ THIOSULPHATE; HYPOSULPHIS, L. A salt of
hyposulphurous acid.
=HYPOSUL'PHUROUS ACID.= See SULPHUROUS ACID.
=HYRA'CEUM.= A substance produced by the Cape badger (_Hyrax Capensis_),
and proposed as a substitute for CASTOREUM. Pereira considered it to be
inert and useless.
=HYSTERICS.= _Syn._ HYSTERIA, PASSIO HYSTERICA, L. In _pathology_, a
nervous affection peculiar to women, attacking in paroxysms or fits,
preceded by dejection; tears, difficult breathing, sickness, and
palpitation of the heart. The treatment of this disease varies with the
causes and the symptoms. Bleeding, cupping, and depletives, are generally
had recourse to in robust and plethoric habits, and stimulants and tonics
in those of a weakly or relaxed constitution. Affusion of cold water and
nasal stimulants will frequently remove the fit in mild cases. Exercise,
proper amusements and regular hours and diet, are the best preventives.
See DRAUGHT (Antihysteric and Hydrocyanic), &c.
=ICE.= _Syn._ GLACIES, L. Water in the solid state. On being cooled, water
gradually contracts until the temperature has fallen to 39·9° Fahr., when
it begins to expand. At the freezing-point, 32° Fahr., under ordinary
conditions, water crystallises or freezes, and in consequence of the
continued expansion, the sp. gr. of ice, as compared with that of water at
39·9°, is as ·94 to 1·00. Ice has the peculiar property of reuniting by
the contact of adjoining surfaces after having been broken into fragments
(REGELATION). Coloured water and salt water, by freezing, produce
colourless and fresh ice; and clean solid ice, when thawed, furnishes
water equal in purity to that which has been distilled.
The use of ice in the preparation of ICE-CREAMS, ICED-LIQUORS, &c., is
noticed elsewhere. The confectioner collects his ice as early as possible
during the winter, and stores it in a well-drained well or excavation,
somewhat of the form of an inverted sugar-loaf, contained in a small shed
or building called an ICE-HOUSE. This building should always be situated
on a dry sandy soil, and, if possible, on an eminence. The door should be
on the north side, and the roof should be conical and thickly thatched
with straw.
In _medicine_, ice is frequently employed externally in inflammation of
the brain, to resolve inflammation, to stop hæmorrhage, to constringe
relaxed parts, and an anodyne, to deaden pain. For these purposes it is
pounded small, in a cloth, and placed in a bladder or bag of gauze
(ICE-CAP, ICE-POULTICE) before applying it. Internally, ice or ice-cold
water has been given with advantage in heartburn, typhus, inflammation and
spasms of the stomach, to check the vomiting in cholera, and to arrest
hæmorrhage, whether bronchial, gastric, nasal, or uterine. Very recently,
ice has been proposed as a remedy in the treatment of diphtheria. Small
lumps of ice, or a small glassful of pounded ice-and-water, will often
temporarily restore the tone of the stomach and nervous system during hot
weather, when all other means fail. Ice-creams, taken in moderation, act
in the same way.
In the warmer climates of Europe an ICE-HOUSE or an ICE-SAFE (a
REFRIGERATOR) is a necessary appendage to every respectable dwelling, not
merely for the purpose of pleasing the palate with iced beverages, but to
enable the residents to preserve their provisions (fish, meat, game, milk,
butter, &c.) in a wholesome state from day to day. In addition to large
cargoes of ice imported yearly from Norway, and principally consumed in
England, Germany and France, ice is now manufactured to no inconsiderable
amount, in these three countries artificially, the principal consumption
of the factitious article being by brewers, who use it for the cooling of
their worts. The artificial manufacture of ice is effected by the means of
the condensation of elastic vapours in machines expressly made for the
purpose. In Siebe's ice-making machine the vapour of ether is made to
traverse metallic tubes surrounded with a concentrated solution of common
salt, by which it becomes recondensed to the liquid state, to be again
utilised in the production of the vapour; the solution of salt becoming at
the same time so reduced in temperature, as to convert into ice, water,
contained in proper vessels, placed in it. In Carré's machine the same end
is accomplished by means of ammoniacal gas, a solution of calcic chloride
being used for absorbing the cold instead of common salt. Reece's is a
modification, (he states an improvement) of Carré's. Ice machines are also
made, in which ice is produced, by bringing water into contact with air,
which has been greatly reduced in temperature by cooling it when in the
compressed state, and subsequently allowing it to expand. Liquid carbonic
and sulphurous acids have likewise been used in the preparation of
artificial ice, but not when it has been required in any considerable
quantity. See REFRIGERATION.
=Ice, Medicated.= Mr Martin, of Weston-super-Mare, writing to the
'Lancet,' says:--"Every practitioner has at times to face the difficulties
of the scarlatinal throat in young children. It may sadly want topical
medication; but how is he to apply it? Young children cannot gargle, and
to attempt the brush or the spray fills them with terror. In many cases
neither sternness nor coaxing avails. Yet these little ones in almost
every case will greedily suck bits of ice. This has long been my chief
resource where I could not persuade the child to submit to the sulphurous
acid spray. Lately, I have been trying an ice formed of the frozen
solution of the acid (or some other antiseptic). Though, of course, not so
tasteless as pure ice, the flavour is so much lessened by the low
temperature, and probably also through the parched tongue, very little
appreciating any flavour, that I find scarcely any complaint on that score
from the little sufferers; they generally take to it very readily. The
process of making it is very simple. A large test-tube immersed in a
mixture of ice and salt is the only apparatus required, and in this the
solution is easily frozen. When quite solid a momentary dip of the tube in
hot water enables one to turn out the cylinder of ice, as the cook turns
out her mould of jelly. I have tried the three following formulæ, all of
which answer, although I think I prefer the first.
"1. Sulphurous acid, 1/2 dr.; water, 7-1/2 dr.; mix and freeze.
"2. Chlorate of potass, 1 scruple; water, 1 oz.; dissolve, and freeze.
"3. Solution of chlorinated soda, 1/2 dr.; water, 1 oz.; mix and freeze.
"However, the form is of secondary importance, as each practitioner can
construct his own. Boracic acid, salicylic acid, or any other harmless
antiseptic with not too much taste, would doubtless be as useful as those
indicated."
=ICE'LAND MOSS.= _Syn._ CETRARIA (B. P.), LICHEN ISLANDICUS, L. The lichen
termed _Cetraria Islandicus_. It is much employed, both as a nutritious
food and as a mild mucilaginous tonic, in catarrh and consumption. It may
be purified from its bitter principle by a little cold solution of
potassa.
=Iceland Moss, Saccharated.= _Syn._ (P. C.), SACCHARUM LICHENIS. Iceland
moss, 1 lb.; refined sugar 1 lb.; macerate the moss in water to extract
the bitterness, express, boil in water for an hour, strain, let settle,
decant, add the sugar, evaporate to dryness with a gentle heat, constantly
stirring, and finally reduce to powder.
=ICES.= (In _confectionery_.) These are commonly composed of cream or
sweetened water, variously flavoured, and congealed by ice or a freezing
mixture. Sometimes, instead of cream, the materials of a custard are used.
The mixed ingredients are placed in a tin furnished with a handle at top,
called a 'freezer,' or 'freezing-pot,' which is then plunged into a bucket
containing ice broken small, and mixed with about half its weight of
common salt, and is kept in rapid motion, backwards and forwards, until
its contents are frozen. As the cream congeals and adheres to the sides,
it is broken down with the ice-spoon, so that the whole may be equally
exposed to the cold. As the salt and ice in the tub melt, more is added,
until the process is finished. The 'ice-pot,' with the cream in it, is
next placed in a leaden 'ice-stand,' is at once surrounded with a mixture
of ice and salt, and closely covered over. In this state it is carried
into the shop. The glasses are filled as required for immediate use, and
should have been previously made as cold as possible.
PLAIN ICE-CREAM, or CREAM FOR ICING, is commonly made by one or other of
the following formulæ:--
1. New milk, 2 pints; yolks of 6 eggs; white sugar, 4 oz.; mix, strain,
heat gently and cool gradually.