copper take a copper plate silvered on the etching side. Trace on this
plate, either with varnish or lithographic ink, the design. When the
tracing is dry, place the plate in an iron bath, using a battery. The
designs traced with the varnish or ink are not attacked by the etching
fluid. When the plate is taken from the bath and has been washed and
dried, remove the varnish or ink with essence of turpentine; next pour
mercury on the places reserved by the varnish or ink; the mercury will
attack the silvered portions and the etching is quickly made. When the
mercury has done its duty gather up the excess and return to the bottle
with a paper funnel. Wash the plate in strong alum water, and heat.
II.—The plate must be first polished either with emery or fine pumice
stone, and after it has been dried with care, spread thereon a varnish
composed of equal parts of yellow wax and essence of turpentine. The
solution of the wax in the essence is accomplished in the cold; next
a little oil of turpentine and some lampblack are added. This varnish
is allowed to dry on, away from dust and humidity. When dry, trace the
design with a very fine point. Make a border with modeling wax, so as
to prevent the acid from running off. Pour on nitric acid if the plate
is of copper, or {325} hydrochloric acid diluted with water if the
plate is of zinc, allow the acid to act according to the desired depth
of the engraving; wash several times and remove the varnish by heating
the plate lightly. Wash with essence of turpentine and dry well in
sawdust or in the stove. For relief engraving the designs are traced
before the engraving on the plate with the resist varnish instead of
covering the plate entirely. These designs must be delicately executed
and without laps, as the acid eats away all the parts not protected by
the varnish.
«Etching Fluids for Copper.»—I.—A new etching fluid for copper plate
is hydrogen peroxide, to which a little dilute ammonia water is added.
It is said to bite in very rapidly and with great regularity and
uniformity.
II.—Another fluid is fuming hydrochloric acid (specific gravity,
1.19), 10 parts; water, 70 parts. To this add a solution of potassium
chlorate, 2 parts, dissolved in 20 parts of hot water. If the articles
to be etched are very delicate and fine this should be diluted with
from 100 to 200 parts of water.
«ETCHING ON GLASS.»
Names, designs, etc., can be etched on glass in three ways: First,
by means of an engraving wheel, a method which requires some manual
skill. Second, by means of a sand blast, making a stencil of the name,
fixing this on the glass, and then, by means of a blast of air, blowing
sand on the glass. Third, by the use of hydrofluoric acid. The glass
is covered with beeswax, paraffine wax, or some acid resisting ink or
varnish; the name or device is then etched out of the wax by means of a
knife, and the glass dipped in hydrofluoric acid, which eats away the
glass at those parts where the wax has been cut away.
Fancy work, ornamental figures, lettering, and monograms are most
easily and neatly cut into glass by the sand-blast process. Lines and
figures on tubes, jars, etc., may be deeply etched by smearing the
surface of the glass with beeswax, drawing the lines with a steel
point, and exposing the glass to the fumes of hydrofluoric acid. This
acid is obtained by putting powdered fluorspar into a tray made of
sheet lead and pouring sulphuric acid on it, after which the tray is
slightly warmed. The proportions will vary with the purity of the
materials used, fluorspar (except when in crystals) being generally
mixed with a large quantity of other matter. Enough acid to make a thin
paste with the powdered spar will be about right. Where a lead tray
is not at hand, the powdered spar may be poured on the glass and the
acid poured on it and left for some time. As a general rule, the marks
are opaque, but sometimes they are transparent. In this case cut them
deeply and fill up with black varnish, if they are required to be very
plain, as in the case of graduated vessels. Liquid hydrofluoric acid
has been recommended for etching, but is not always suitable, as it
leaves the surface on which it acts transparent.
There are two methods of marking bottles—dry etching, or by stamping
with etching inks. The first process is usually followed in glass
factories. A rubber stamp is necessary for this process, and the
letters should be made as large and clean cut as possible without
crowding them too much. Besides this, an etching powder is required.
A small quantity of the powder is poured into a porcelain dish, and
this is placed on a sand bath or over a gentle fire, and heated until
it is absolutely dry, so that it can be rubbed down to an impalpable
powder.
The bottle or other glass to be marked must be perfectly clean and dry.
The etching powder takes better when the vessel is somewhat warm.
The stamp should be provided with a roller which is kept constantly
supplied with a viscid oil which it distributes on the stamp and which
the stamp transfers to the glass surface. The powder is dusted on
the imprint thus made, by means of a camel’s-hair brush. Any surplus
falling on the unoiled surface may be removed with a fine long-haired
pencil. The printed bottle is transferred to a damp place and kept for
several minutes, the dampness aiding the etching powder in its work on
the glass surface. The bottle is then well washed in plain water.
Glass cylinders, large flasks, carboys, etc., may be treated in a
somewhat different manner. The stamp here is inserted, face upward,
between two horizontal boards, in such a manner that its face projects
about a quarter of a millimeter (say 0.01 inch) above the surface. Oil
is applied to the surface, after which the cylinder, carboy, or what
not, is rolled along the board and over the stamp. The design is thus
neatly transferred to the glass surface, and the rest of the operation
is as in the previous case.
For an etching ink for glassware the following is recommended:
Ammonium fluoride 2 drachms
Barium sulphate 2 drachms
Reduce to a fine powder in a mortar, {326} then transfer to a lead dish
and make into a thin writing-cream with hydrofluoric acid or fuming
sulphuric acid. Use a piece of lead to stir the mixture. The ink may be
put up in bottles coated with paraffine, which can be done by heating
the bottle, pouring in some melted paraffine, and letting it flow all
around. The writing is done with a quill, and in about half a minute
the ink is washed off.
Extreme caution must be observed in handling the acid, since when
brought in contact with the skin it produces dangerous sores very
difficult to heal. The vapor is also dangerously poisonous when inhaled.
«Hydrofluoric Formulas.»—I.—Dissolve about 0.72 ounces fluoride of
soda with 0.14 ounces sulphate of potash in 1/2 pint of water. Make
another solution of 0.28 ounces chloride of zinc and 1.30 ounces
hydrochloric acid in an equal quantity of water. Mix the solutions and
apply to the glass vessel with a pin or brush. At the end of half an
hour the design should be sufficiently etched.
II.—A mixture consisting of ammonium fluoride, common salt, and
carbonate of soda is prepared, and then placed in a gutta-percha
bottle containing fuming hydrofluoric acid and concentrated sulphuric
acid. In a separate vessel which is made of lead, potassium fluoride is
mixed with hydrochloric acid, and a little of this solution is added to
the former, along with a small quantity of sodium silicate and ammonia.
Some of the solution is dropped upon a rubber pad, and by means of a
suitable rubber stamp, bearing the design which is to be reproduced, is
transferred to the glass vessel that is to be etched.
«Etching with Wax.»—Spread wax or a preservative varnish on the glass,
and trace on this wax or varnish the letters or designs. If letters
are desired, trace them by hand or by the use of letters cut out in
tin, which apply on the wax, the inside contours being taken with a
fine point. When this is done, remove the excess of wax from the glass,
leaving only the full wax letters undisturbed. Make an edge of wax all
along the glass plate so as to prevent the acid from running over when
you pour it on to attack the glass. At the end of 3 to 4 hours remove
the acid, wash the glass well with hot water, next pour on essence of
turpentine or alcohol to take off the wax or the preservative varnish.
Pass again through clean water; the glass plate will have become dead
wherever the acid has eaten in, only the letters remaining polished.
For fancy designs it suffices to put on the back of the plate a black
or colored varnish, or tin foil, etc., to obtain a brilliant effect.
«Etching Glass by Means of Glue.»—It is necessary only to cover a piece
of ordinary or flint glass with a coat of glue dissolved in water in
order to see that the layer of glue, upon contracting through the
effect of drying, becomes detached from the glass and removes therefrom
numerous scales of varying thickness. The glass thus etched presents
a sort of regular and decorative design similar to the flowers of
frost deposited on windowpanes in winter. When salts that are readily
crystallizable and that exert no chemical action upon the gelatin are
dissolved in the latter the figures etched upon the glass exhibit a
crystalline appearance that recalls fern fronds.
Hyposulphite of soda and chlorate and nitrate of potash produce nearly
the same effects. A large number of mineral substances are attacked
by gelatin. Toughened glass is easily etched, and the same is the
case with fluorspar and polished marble. A piece of rock crystal, cut
at right angles with the axis and coated with isinglass, the action
of which seems to be particularly energetic, is likewise attacked
at different points, and the parts detached present a conchoidal
appearance. The contraction of the gelatin may be rendered visible by
applying a coating of glue to sheets of cardboard or lead, which bend
backward in drying and assume the form of an irregular cylinder.
Such etching of glass and different mineral substances by the action of
gelatin may be employed for the decoration of numerous objects.
Dissolve some common glue in ordinary water, heated by a water bath,
and add 6 per cent of its weight of potash alum. After the glue has
become perfectly melted, homogeneous, and of the consistency of syrup,
apply a layer, while it is still hot, to a glass object by means of a
brush. If the object is of ground glass the action of the glue will
be still more energetic. After half an hour apply a second coat in
such a way as to obtain a smooth, transparent surface destitute of air
bubbles. After the glue has become so hard that it no longer yields
to the pressure of the finger nail (say, in about 24 hours), put the
article in a warmer place, in which the temperature must not exceed
105° F. When the object is removed from the oven, after a few hours,
the glue will detach itself with {327} a noise and removes with it
numerous flakes of glass. All that the piece then requires is to be
carefully washed and dried.
The designs thus obtained are not always the same, the thickness of the
coat of glue, the time of drying, and various other conditions seeming
to act to modify the form and number of the flakes detached.
It is indispensable to employ glass objects of adequate thickness,
since, in covering mousseline glass with a layer of glue, the
mechanical action that it has to support during desiccation is so
powerful that it will break with an explosion. Glue, therefore, must
not be allowed to dry in glass vessels, since they would be corroded
and broken in a short time.
«Indelible Labels on Bottles.»—To affix indelible labels on bottles an
etching liquid is employed which is produced as follows:
Liquid I, in one bottle.—Dissolve 36 parts of sodium fluoride in 500
parts of distilled water and add 7 parts of potassium sulphate.
Liquid II, in another bottle.—Dissolve zinc chloride, 14 parts, in 500
parts of distilled water, and add 65 parts of concentrated hydrochloric
acid.
For use mix equal parts together and add a little dissolved India ink
to render the writing more visible.
The mixing cannot, however, be conducted in a vessel. It is best to use
a cube of paraffine which has been hollowed out.
«Etching on Marble or Ivory» (see also Ivory).—Cover the objects with
a coat of wax dissolved in 90 per cent alcohol, then trace the desired
designs by removing the wax with a sharp tool and distribute on the
tracing the following mixture: Hydrochloric acid, 1 part; acetic acid,
1 part. Repeat this operation several times, until the desired depth is
attained. Then take off the varnish with alcohol. The etching may be
embellished, filling up the hollows with any colored varnish, by wiping
the surface with a piece of linen fixed on a stick, to rub the varnish
into the cavities after it has been applied with a brush. The hollows
may be gilded or silvered by substituting “mixtion” for the varnish
and applying on this mixtion a leaf of gold or silver, cut in pieces
a little larger than the design to be covered; press down the gold by
means of a soft brush so as to cause it to penetrate to the bottom; let
dry and remove the protruding edges.
«Etching on Steel.»—The print should be heavily inked and powdered
with dragon’s blood several times. After each powdering heat slightly
and additional powder will stick, forming a heavy coating in 2 or 3
operations. Before proceeding to heat up, the plate should receive a
light etching in a weak solution of the acid described later on. The
purpose of this preliminary etching is to clean up the print, so that
the lines will not tend to thicken, as would be the case otherwise.
Next a good strong heating should be given. On top the dragon’s blood
plumbago may be used in addition. For etching use nitric acid mixed
with an even amount of acetic acid. Some operators use vinegar, based
on the same theory. When commencing the etching, start with a weak
solution and increase as soon as the plate is deep enough to allow
another powdering. If the operator is familiar with lithography, and
understands rolling up the print with a lithoroller, the etching of
steel is not harder than etching on zinc.
«Liquids for Etching Steel.»—
I.—Iodine 2 parts
Potassium iodide 5 parts
Water 40 parts
II.—Nitric acid 60 parts
Water 120 parts
Alcohol 200 parts
Copper nitrate 8 parts
III.—Glacial acetic acid 4 parts
Nitric acid 1 part
Alcohol 1 part
IV.—Mix 1 ounce sulphate of copper, 1/4 ounce alum, 1/2 teaspoonful
of salt (reduced to powder), with 1 gill of vinegar and 20 drops of
nitric acid. This fluid can be used either for etching deeply or for
frosting, according to the time it is allowed to act. The parts of the
work which are not to be etched should be protected with beeswax or
some similar substance.
V.—Nitric acid, 60 parts; water, 120 parts; alcohol, 200 parts; and
copper nitrate, 8 parts. Keep in a glass-stoppered bottle. To use
the fluid, cover the surface to be marked with a thin even coat of
wax and mark the lines with a machinist’s scriber. Wrap clean cotton
waste around the end of the scriber or a stick, and dip in the fluid,
applying it to the marked surface. In a few minutes the wax may be
scraped off, when fine lines will appear where the scriber marked the
wax. The drippings from a lighted wax candle can be used for the {328}
coating, and this may be evenly spread with a knife heated in the
candle flame.
VI.—For Hardened Steel.—Heat an iron or an old pillar-file with a
smooth side, and with it spread a thin, even coat of beeswax over the
brightened surface to be etched. With a sharp lead pencil (which is
preferable to a scriber) write or mark as wanted through the wax so
as to be sure to strike the steel surface. Then daub on with a stick
etching acid made as follows: Nitric acid, 3 parts; muriatic acid, 1
part. If a lead pencil has been used the acid will begin to bubble
immediately. Two or three minutes of the bubbling or foaming will be
sufficient for marking; then soak up the acid with a small piece of
blotting paper and remove the beeswax with a piece of cotton waste wet
with benzine, and if the piece be small enough dip it into a saturated
solution of sal soda, or if the piece be large swab over it with a
piece of waste. This neutralizes the remaining acid and prevents
rusting, which oil will not do.
If it is desired to coat the piece with beeswax without heating it,
dissolve pure beeswax in benzine until of the consistency of thick
cream and pour on to the steel, and even spread it by rocking or
blowing, and lay aside for it to harden; then use the lead pencil,
etc., as before. This method will take longer. Keep work from near the
fire or an open flame.
EUCALYPTUS BONBONS FOR COLDS AND COUGHS: See Cold and Cough Mixtures.
EXPECTORANTS: See Cold and Cough Mixtures.
«Explosives»
Explosives may be divided into two great classes—mechanical mixtures
and chemical compounds. In the former the combustible substances are
intimately mixed with some oxygen supplying material, as in the case
of gunpowder, where carbon and sulphur are intimately mixed with
potassium nitrate; while gun cotton and nitro-glycerine are examples
of the latter class, where each molecule of the substance contains the
necessary oxygen for the oxidation of the carbon and hydrogen present,
the oxygen being in feeble combination with nitrogen. Many explosives
are, however, mechanical mixtures of compounds which are themselves
explosive, e. g., cordite, which is mainly composed of gun cotton and
nitro-glycerine.
The most common and familiar of explosives is undoubtedly gunpowder.
The mixture first adopted appears to have consisted of equal parts
of the three ingredients—sulphur, charcoal, and niter; but some time
later the proportions, even now taken for all ordinary purposes, were
introduced, namely:
Potassium nitrate 75 parts
Charcoal 15 parts
Sulphur 10 parts
────
100 parts
Since gunpowder is a mechanical mixture, it is clear that the first aim
of the maker must be to obtain perfect incorporation, and, necessarily,
in order to obtain this, the materials must be in a very finely divided
state. Moreover, in order that uniformity of effect may be obtained,
purity of the original substances, the percentage of moisture present,
and the density of the finished powder are of importance.
The weighed quantities of the ingredients are first mixed in gun metal
or copper drums, having blades in the interior capable of working in
the opposite direction to that in which the drum itself is traveling.
After passing through a sieve, the mixture (green charge) is passed
on to the incorporating mills, where it is thoroughly ground under
heavy metal rollers, a small quantity of water being added to prevent
dust and facilitating incorporation, and during this process the
risk of explosion is greater possibly than at any other stage in the
manufacture. There are usually 6 mills working in the same building,
with partitions between. Over the bed of each mill is a horizontal
board, the “flash board,” which is connected with a tank of water
overhead, the arrangement being such that the upsetting of one tank
discharges the contents of the other tanks onto the corresponding mill
beds below, so that in the event of an accident the charge is drowned
in each case. The “mill cake” is now broken down between rollers, the
“meal” produced being placed in strong oak boxes and subjected to
hydraulic pressure, thus increasing its density and hardness, at the
same time bringing the ingredients into more intimate contact. After
once more breaking down the material (press cake), the powder only
requires special treatment to adapt it for the various purposes for
which it is intended.
The products of the combustion of powder and its manner of burning are
{329} largely influenced by the pressure, a property well illustrated
by the failure of a red-hot platinum wire to ignite a mass of powder
in a vacuum, only a few grains actually in contact with the platinum
undergoing combustion.
Nitro-glycerine is a substance of a similar chemical nature to gun
cotton, the principles of its formation and purification being very
similar, only in this case the materials and product are liquids,
thereby rendering the operations of manufacture and washing much
less difficult. The glycerine is sprayed into the acid mixture by
compressed-air injectors, care being taken that the temperature during
nitration does not rise above 86° F. The nitro-glycerine formed readily
separates from the mixed acids, and being insoluble in cold water, the
washing is comparatively simple.
Nitro-glycerine is an oily liquid readily soluble in most organic
solvents, but becomes solid at 3° or 4° above the freezing point of
water, and in this condition is less sensitive. It detonates when
heated to 500° F., or by a sudden blow, yielding carbon dioxide,
oxygen, nitrogen, and water. Being a fluid under ordinary conditions,
its uses as an explosive were limited, and Alfred Nobel conceived the
idea of mixing it with other substances which would act as absorbents,
first using charcoal and afterwards an infusorial earth, “kieselguhr,”
and obtaining what he termed “dynamite.” Nobel found that “collodion
cotton”—soluble gun cotton—could be converted by treatment with
nitro-glycerine into a jellylike mass which was more trustworthy in
action than the components alone, and from its nature the substance was
christened “blasting gelatin.”
Nobel took out a patent for a smokeless powder for use in guns, in
which these ingredients were adopted with or without the use of
retarding agents. The powders of this class are ballistite and filite,
the former being in sheets, the latter in threads. Originally camphor
was introduced, but its use has been abandoned, a small quantity of
aniline taking its place.
Sir Frederick Abel and Prof. Dewar patented in 1889 the use of
trinitro-cellulose and nitro-glycerine, for although, as is well known,
this form of nitro-cellulose is not soluble in nitro-glycerine, yet by
dissolving the bodies in a mutual solvent, perfect incorporation can be
attained. Acetone is the solvent used in the preparation of “cordite,”
and for all ammunition except blank charges a certain proportion of
vaseline is also added. The combustion of the powder without vaseline
gives products so free from solid or liquid substances that excessive
friction of the projectile in the gun causes rapid wearing of the
rifling, and it is chiefly to overcome this that the vaseline is
introduced, for on explosion a thin film of solid matter is deposited
in the gun, and acts as a lubricant.
The proportion of the ingredients are:
Nitro-glycerine 58 parts
Gun-cotton 37 parts
Vaseline 5 parts
Gun cotton to be used for cordite is prepared as previously described,
but the alkali is omitted, and the mass is not submitted to great
pressure, to avoid making it so dense that ready absorption of
nitro-glycerine would not take place. The nitro-glycerine is poured
over the dried gun cotton and first well mixed by hand, afterwards in
a kneading machine with the requisite quantity of acetone for 3 1/2
hours. A water jacket is provided, since, on mixing, the temperature
rises. The vaseline is now added, and the kneading continued for a
similar period. The cordite paste is first subjected to a preliminary
pressing, and is finally forced through a hole of the proper size in
a plate either by hand or by hydraulic pressure. The smaller sizes
are wound on drums, while the larger cordite is cut off in suitable
lengths, the drums and cut material being dried at 100° F., thus
driving off the remainder of the acetone.
Cordite varies from yellow to dark brown in color, according to its
thickness. When ignited it burns with a strong flame, which may be
extinguished by a vigorous puff of air. Macnab and Ristori give the
yield of permanent gases from English cordite as 647 cubic centimeters,
containing a much higher per cent of carbon monoxide than the gases
evolved from the old form of powder. Sir Andrew Noble failed in
attempts to detonate the substance, and a rifle bullet fired into the
mass only caused it to burn quietly.
«Dynamite.»—Dynamite is ordinarily made up of 75 per cent
nitro-glycerine, 25 per cent infusorial earth; dualine contains 80
per cent nitro-glycerine, 20 per cent nitro-cellulose; rend-rock
has 40 per cent nitro-glycerine, 40 per cent nitrate of potash, 13
per cent cellulose, 7 per cent paraffine; giant powder, 36 per cent
nitro-glycerine, 48 per cent nitrate of potash, 8 per cent sulphur, 8
per cent rosin or charcoal.