CHEMICALS.
Bromine and its Compounds—Iodine and its Compounds—Chlorine and its
compounds—Cyanide of Potassium—Hyposulphite of Soda—Hyposulphite of
Gold—Nitric Acid—Nitro-Muriatic Acid—Hydrochloric Acid—Hydrofluoric
Acid—Sulphuric Acid—Accelerating Substances—Liquid Sensitives—Dry
Sensitives, etc., etc.
BROMINE.
An article so extensively used in the practice of the Daguerreotypic
art as Bromine, is deserving of especial attention, and accordingly
every person should endeavor to make himself familiar with its
properties and applications.
History.—This element was discovered in 1826 by M. Balard, in the
mother-liquor, or residue of the evaporation of sea-water. It is named
from its offensive odor (bromos, bad odor). In nature it is found in
sea-water combined with alkaline bases, and in the waters of many
saline springs and inland seas. The salt springs of Ohio abound in the
compounds of bromine, and it is found in the waters of the Dead Sea.
The only use which has been made of bromine in the arts is in the
practice of photography. It is also used in medicine In a chemical
point of view it is very interesting, from its similarity in
properties, and the parallelism of its compounds to chlorine and
iodine.
Dr. D. Alter, of Freeport, Pa., is the only American manufacturer, and
furnishes all of the “American Bromine.” Yet we understand much
purporting to be of German manufacture is prepared from that made in
Freeport. This is done by individuals in this city, who get well paid
for the deception.
For the successful application of bromine as an accelerating agent, we
are indebted to Mr. John Goddard of London, who at the time was
associated with Mr. John Johnson, now a resident of this city.
Preparation.—The mother-liquor containing bromides is treated with a
current of chlorine gas, which decomposes these salts, setting the
bromine free, which at once colors the liquid to a reddish brown color.
Ether is added and shaken with the liquid, until all the bromine is
taken up by the ether, which acquires a fine red color and separates
from the saline liquid.
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Solution of caustic potash is then added to the ethereal solution,
forming bromide of potassium and bromate of potash. This solution is
evaporated to dryness, and the salts being collected are heated in a
glass retort with sulphuric acid and a little oxide of manganese. The
bromine is distilled, and is condensed in a cooled receiver, into a red
liquid.
Properties.—Bromine somewhat resembles chlorine in its odor, but is
more offensive. At common temperatures it is a very volatile liquid, of
a deep red color, and with a specific gravity of 3, being one of the
heaviest fluids known. Sulphuric acid floats on its surface, and is
used to prevent its escape. At zero it freezes into a brittle solid. A
few drops in a large flask will fill the whole vessel when slightly
warmed, with blood red vapors, which have a density of nearly 6.00, air
being one. It is a non-conductor of electricity, and suffers no change
of properties from heat, or any other of the imponderable agents. It
dissolves slightly in water, forming a bleaching solution.
Chloride of Bromine.—This as an accelerating agent is by many
considered superior {75} to the other Bromide combinations. It can be
readily prepared by passing a current of chlorine through a vessel
containing bromine. A mixture of two parts muriatic acid and one of
black oxide of manganese, should be put into a flask having a bent tube
to conduct the chlorine vapor into the bromine in another vessel. This
last vessel should also be supplied with a bent tube for conducting the
combined vapors with a third vessel or receiver. On the application of
the heat from a spirit lamp to the bottom of the flask, a current of
chlorine gas will be disengaged, and pass into the bromine, when it
readily combines, and gives off a vapor, which, when condensed in the
third vessel, forms a volatile yellowish-red liquid. It is best, even
at ordinary temperature, to place the receiver in an ice bath. For
manner of using, see farther on, under head of Accelerators.
Bromides.—A bromide treated with oil of vitriol, disengages
chlorohyadic acid; but vapors of bromine are constantly disengaged, at
the same time imparting a brown color to the gas. If the bromide be
treated with a mixture of sulphuric acid, and peroxide of manganese,
bromide is only disengaged. A solution of a bromide gives, with of
nitrate {76} silver, a light yellowish white precipitate of bromide of
silver, which is insoluble in an excess of acid, and readily dissolves
in ammonia. The precipitated bromide is colored by light like the
chloride, but is immediately tinged brown, while the chloride assumes
at first a violet hue. The bromides, in solution, are readily
decomposed and chloride being set free, colors the liquid brown.
In the whole range of heliographic chemicals there is probably not
another collection less understood and being so productive of
interesting investigation as the bromides.
Bromide of Iodine.—M. de Valicours furnishes us with the best method
for preparing this mixture:
“Into a bottle of the capacity of about two ounces, pour thirty or
forty drops of bromine, the precise quantity not being of importance.
Then add, grain by grain, as much iodine as the bromine will dissolve
till quite saturated. This point is ascertained when some grains of the
iodine remain undissolved. They may remain in the bottle, as they will
not interfere with the success of the preparation.
“The bromide of iodine thus prepared, from its occupying so small a
space, can very easily be carried, but in this state it is much too
concentrated to be used. When it is to be employed, pour a small
quantity, say fifteen drops, by means of a dropping-tube, into a bottle
containing about half an ounce of filtered river water. It will easily
be understood that the bromide of iodine can be used with a greater or
less quantity of water without altering the proportion which exists
between the bromine and iodine.”
This article forms a very good dry accelerator, and is by some persons
thought superior to all others, as it works with great uniformity, and
is less liable to scum the plate in coating at high temperatures, or
when the thermometer indicates a heat above 60 deg.
Bromide of Potassium—Is prepared by mixing bromine and a solution of
pure potass together, and evaporating to dryness; it crystallizes in
small cubes, and dissolves readily in water. This agent is extensively
employed in the paper and glass processes.
Bromide of Lime. This the principal accelerator used in the American
practice, and is the best of all dry combinations at present employed.
There are many reasons why the dry is advantageous; these are too
familiar to repeat.
“The bromide of lime may be produced by allowing bromine vapor to act
upon hydrate of lime for some hours. The most convenient method of
doing this is to place some of the hydrate at the bottom of the flask,
and then put some bromine into a glass capsule supported a little above
the lime. As heat is developed during the combination, it is better to
place the lower part of the flask in water at the temperature of about
50 deg. Fah.; the lime gradually assumes a beautiful scarlet color, and
acquires an appearance very similar to that of the red iodide of
mercury. The chloro-iodide of lime may be formed in the same manner; it
has a deep brown color. Both these compounds, when the vapor arising
from them is not too intense, have an odor analogous to that of
bleaching powder, and quite distinguishable from chlorine, bromine, or
iodine alone.”
Farther on, I have given, in connection with accelerators, a process I
adopt, which is far less tedious and equally reliable.
Bromide of Silver—May be formed by pouring an alkaline bromide into a
solution of nitrate of silver, in the shape of a white, slightly
yellowish precipitate, which is insoluble in water and nitric acid, but
readily dissolves in ammonia and the alkaline hyposulphites. Chlorine
easily decomposes bromide of silver, and transforms it into chloride.
M. Biot has expressed his opinion, that it is not possible to find any
substance more sensitive to light than the bromide of silver. This is
true to a certain extent, but in combination with deoxidizing agents,
other preparations have a decided superiority over the pure bromide of
silver.
Bromide of Gold—Is readily prepared by adding a little bromide to the
brown gold of the assayers, and allowing it to remain some time under
water, or assisting its action by a gentle heat. It forms a salt of a
bright crimson color, but in its general properties is precisely
similar to the chloride used in gilding.
Bromide of Magnesia—Is prepared in the same manner as bromide of lime.
This mixture is particularly adapted for hot climates, and is used in
this country by some few who regard its use as a valuable secret.
Bromide of Starch.—This preparation is much used, but not alone. It is
combined with lime by putting about one part in measure of starch to
four of lime. It is prepared by adding bromine to finely pulverized
starch, in the same manner as bromide of lime. (See Accelerators.)
Experiments with Bromine.—Place in a very flaring wine glass a few
drops (say ten) of bromine, then place a small piece of phosphorus
about one-twentieth of an inch in diameter. Place the latter on the end
of a stick from five to ten feet in length. So place it that the
phosphorus can be dropped into the glass, and in an instant combustion
giving a loud report will be the result.
b. Expose a daguerreotype plate to the vapor of bromine, it assumes a
leaden-grey color, which, blackens by light very readily. Exposing this
to mercury will not produce any decided action upon the lights. Immerse
it in the solution of the muriate of soda, and the parts unacted upon
by light becomes a jet black, while the parts on which the light has
acted will be dissolved off, leaving a clean coating of silver. This
will be a most decided black picture on a white ground.
c. Expose an impressioned plate, that has been sufficient time in the
camera to become solarized, to the vapors of bromine, and the
impression will be fully developed and exhibit no signs of
solarization. The exposure over the bromine most be very brief.
Chlorine or iodine will produce the same result. The latter is
preferable.
Again, should the impressioned plate be exposed too long over the vapor
of bromine, the impression would be rendered wholly insensitive to the
mercurial vapor. Hence this method is resorted to for restoring the
sensibility of the plate when there is reason to believe that the
impression would not be a desirable one; as, for example, if a likeness
of a child be wanted, and it had moved before the plate had been
sufficiently long exposed in the camera, the plate may be restored to
its original sensitiveness by re-coating over bromine, as above, thus
saving the time and labor of re-preparing the plate for the chemicals.
d. If by accident (we would not advise a trial to any extent of this),
you should inhale a quantity of the vapor of bromine, immediately
inhale the vapor of aqua ammonia, as this neutralizes the dangerous
effect of the bromine vapor. Every operator should be provided with a
bottle of ammonia, as a little sprinkled about the chemical room soon
disinfects it of all iodine or bromine vapor, and also tends to
facilitate the operation in the camera.
IODINE.
History of Iodine.—This is one of the simple chemical bodies which was
discovered in 1812 by M. Courtois, of Paris, a manufacturer of
saltpetre, who found it in the mother-water of that salt. Its
properties were first studied into by M. Gay Lussac. It partakes much
of the nature of chlorine and bromine. Its affinity for other
substances is so powerful as to prevent it from existing in an isolated
state. It occurs combined with potassium and sodium in many mineral
waters, such as the brine spring of Ashby-de-la-Zouche, and other
strongly saline springs. This combination exists sparingly in
sea-water, abundantly in many species of fucus or sea-weed, and in the
kelp made from them. It is an ingredient in the Salt Licks, saline, and
brine springs of this country, especially of those in the valley of the
Mississippi. It is sparingly found in fresh-water plants, as well also
in coal, and in combination with numerous other bodies.
Fermented liquors contain iodine; wine, cider, and perry are more
iodureted than the average of fresh waters. Milk is richer in iodine
than wine; independently of the soil, with which it varies, the
proportion of iodine in milk is in the inverse ratio of the abundance
of that secretion. Eggs (not the shell) contain much iodine. A fowl’s
egg weighing 50 gr. contains more iodine than a quart of cow’s milk.
Iodine exists in arable land. It is abundant in sulphur, iron, and
manganese ores, and sulphuret of mercury: but rare in gypsum, chalk,
calcareous and silicious earths. Any attempt to extract iodine
economically should be made with the plants of the ferro-iodureted
fresh waters. Most of the bodies regarded by the therapeutists as
pectoral and anti-scrofulous are rich in iodine.
It is probably to the application of this body that we owe the
discovery of the daguerreotype. There is no record of the precise date
when Daguerre commenced experimenting with iodine, but by the published
correspondence between him and M. Neipce, his partner, it was previous
to 1833. There is no doubt, however, that the first successful
application was made in 1838, as the discovery was reported to the
world early in January, 1839.
Preparation.—Iodine is mostly prepared from kelp, or the half vitrified
ashes of seaweed, prepared by the inhabitants of the western islands,
and the northern shores of Scotland and Ireland. It is treated with
water, which washes out all the soluble salts, and the filtered
solution is evaporated until nearly all the carbonate of soda and other
saline matters have crystallized out. The remaining liquor, which
contains the iodine, is mixed with successive portions of sulphuric
acid in a leaden retort, and after standing some days to allow the
sulphureted hydrogen, etc., to escape, peroxide of manganese is added,
and the whole gently heated. Iodine distills over in a purple vapor,
and is condensed in a receiver, or in a series of two-necked globes.
Properties.—Iodine is solid at the ordinary temperature, presenting the
appearance of dark-grey or purple spangles, possessing a high degree of
metallic lustre. It somewhat resembles plumbago, with which it is
sometimes diluted, particularly when it is fine. Operators should
endeavor to secure the larger crystals. It melts at 224.6 deg., forming
a brown or nearly black liquid. It boils at about 356 deg., and emits a
very deep violet colored vapor. It gives off a very appreciable vapor,
sufficient for all purposes of forming the iodide of silver on the
daguerreotype plate, at a temperature of 45 deg. or even lower. Iodine
crystallizes readily. Every operator has found upon the side of the jar
in his coating-box, perfectly regular crystals, deposited there by
sublimation.
Water dissolves but a small proportion of iodine, requiring 7000 parts
of water to dissolve one of iodine, {85} or one grain to the gallon of
water. Alcohol and ether dissolve it freely, as does a solution of
nitrate or hydrochlorate of ammonia and of iodides.
The density of solid iodine is 4.95; that of its vapor 8.716. It
greatly resembles chlorine and bromine in its combinations, but its
affinities are weaker. It does not destroy the majority of organic
substances, and vegetable colors generally resist its action. It
combines with several organic substances, imparting to them peculiar
colors. It colors the skin brown, but the stain soon disappears.
Chloride of Iodine—Is formed by passing chlorine into a bottle
containing some iodine. This can be readily done by pouring one ounce
and a half of muriatic acid upon a quarter of an ounce of powdered
black oxide of manganese, and heat it gradually in a flask, to which is
adapted a bent glass tube. This tube must connect with the bottle
containing the iodine, and the yellowish-green gas disengaged will
readily combine with the iodine, forming a deep red liquid, and the
operation is complete. The use of chloride of iodine will be referred
to in connection with the Accelerators.
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Iodides.—The iodide treated with the oil of vitriol, instantly produces
a considerable deposit of iodine; and if the mixture be heated, intense
violent vapors are disengaged. The reaction is due to the decomposition
of oil of vitriol by iodohydric acid, water and sulphurous acid being
formed, and iodine set free. The iodides in solution are decomposed by
chlorine, iodine being precipitated, the smallest quantity of which in
solution is instantly detected by its imparting to starch an intensely
blue color.
Iodide of Potassium.[4]—This compound is easily made in the following
manner: Subject to a moderate heat a mixture of 100 parts of iodine, 75
of carbonate of potash, 30 of iron filings, and 120 parts of water.
This mass must be thoroughly dried and then heated to redness; the
resulting reddish powder is to be washed with water, and the solution
obtained filtered, and evaporated to dryness. It is found that 100
parts of iodine yield 135 parts of very white, but slightly alkaline,
iodide of potassium.
[4] I shall present the preparation of only a few iodides, and such as
are more intimately connected with the Daguerreotype.
Experiment.—On projecting dry pulverized iodide of potassium into fused
anhydrous phosphoric acid, a violent disengagement of iodine takes
place, attended by a transient ignition; fused hydrate of phosphoric
acid liberates iodine abundantly from iodide of potassium; this
reaction is accompanied by the phenomenon of flame and formation of a
considerable quantity of hydriodic acid.
Iodide of Mercury.—For the preparation of iodide of mercury, Dublanc
recommends to cover 100 grms. of mercury with 1 kilogrm. of alcohol, to
add 124 grms. of iodine gradually in portions of ten grms., and
agitating between each fresh addition, until the alcohol becomes
colorless again. After the addition of the last 4 grms. the alcohol
remains colored, the whole of the mercury having become converted into
iodide. The resulting preparation is washed with alcohol; it is
crystalline and of a hyacinth color.
Iodide of Silver.—This compound is formed upon every plate upon which a
Daguerreotype is produced. The vapor of iodine coming in contact with
the silver surface, forms an iodide which is peculiarly sensitive to
light.
The various colors produced are owing to the thickness of the coating,
and the maximum sensibility of the coating, as generally adopted, is
when it assumes a deep yellow, or slightly tinged with rose color.
This compound is largely employed in most photographic processes on
paper, and may be easily prepared by the following formula: By adding
iodide of potassium to a solution of nitrate of silver, a
yellowish-white precipitate of iodide of silver is obtained, which is
insoluble in water, slightly soluble in nitric acid, and soluble in a
small degree in ammonia, which properties seem easily to distinguish it
from the chloride and bromide of silver. Chlorine decomposes it and
sets the iodine free, and chlorohydric acid converts it into a
chloride. It fuses below a red heat. Although the effect of light on
the iodide is less rapid than on the chloride, the former sooner
turning black, assuming a brown tinge; but when in connection with
gallic acid and the ferrocyanate of potash, it forms two of the most
sensitive processes on paper.
Iodide of silver dissolves easily in a solution of iodide of potassium,
and the liquid deposits in evaporation crystals of a double iodide.
Iodide of Gold.—If a solution of potassium be added to a solution of
chloride of gold, a precipitate of iodide of gold takes place, soluble
in an excess of the precipitate. A little free potash should be added
to combine with any iodide that may chance to be set free by the
chloride of gold.
Iodide of Lime is prepared by adding iodine to hydrate of lime (which
will be referred to farther on) until the mixture assumes a light
yellow shade, when wanted for combinations with accelerators, or to a
dark brown when employed for the first coating. This latter mixture has
been sold in our market under the name of “Iodide of Brome.”
Iodide of Bromine.—(See page 76.)
Experiments with Iodine.—Place a plate which has been exposed in the
camera over the vapor of iodine for a very brief period, and it will
present the appearance of the impression having been solarized.
b. Upon a Daguerreotype plate, from which an impression has been
effaced by rubbing or otherwise, the picture may be made to reappear by
merely coating it over with iodine.
c. Place in a vessel a little water, into which put the smallest
possible quantity of free iodine and add a little starch, and the
liquid will instantly assume a blue color. Advantage is taken of this
fact in the laboratory to detect the presence of iodine in liquids. The
starch should be dissolved in boiling water and allowed to cool. There
are numerous other interesting experiments that can be performed by the
aid of iodine, but it is unnecessary here to consume more space.
CHLORINE.
History.—The Swedish chemist, Scheele, in 1774, while examining the
action of hydrochloric acid on peroxide of manganese, first noticed
this element. He called it dephlogisticated muriatic acid. It was
afterwards, by the French nomenclaturists, termed oxygenated muriatic
acid, conceiving it to be a compound of oxygen and muriatic acid. This
view of its notice was corrected by Sir H. Davy (in 1809), who gave it
the present name. In 1840-41, this gas vas employed for accelerating
the operation of light upon the iodized Daguerreotype plate. John
Goddard, Wolcott & Johnson, Claudet, Draper, Morse and others, were
among the first made acquainted with its use. Count Rumford, Ritter,
Scheele, Seebert and others, experimented with chlorine in regard to
its effect when exposed to the action of light in combination with
silver. In 1845, M. Edward Becquerel announced that he had “been
successful in obtaining, by the agency of solar radiations, distinct
impressions, of the colors of nature.”
On the 4th of March, 1851, Neipce, St. Victor, a former partner of
DAGUERRE, announced that he had produced “all the colors by using a
bath of bichloride of copper, and that a similar phenomenon occurs with
all salts of copper, mixed with chlorine.”
Preparation.—This is easily accomplished by putting about two parts of
hydrochloric (muriatic) acid on one of powdered black oxide of
manganese, and heating it gradually in a flask or retort, to which may
be adapted a bent glass tube. A yellowish-green gas is disengaged,
which being conducted through the glass tube to the bottom of a bottle,
can readily be collected, being much heavier than the air, displaces it
completely and the bottle is filled (which can be seen by the green
color); a greased stopper is tightly fitted to it, and another bottle
may be substituted.
In all experiments with chlorine, care should be taken not to inhale
the gas!
Properties.—Chlorine is a greenish-yellow gas (whence its name, from
chloros, green), with a powerful and suffocating odor, and is wholly
irrespirable. Even when much diluted with air, it produces the most
annoying irritation of the throat, with stricture of the chest and a
severe cough, which continues for hours, with the discharge of much
thick mucus. The attempt to breathe the undiluted gas would be fatal;
yet, in a very small quantity, and dissolved in water, it is used with
benefit by patients suffering under pulmonary consumption.
Under a pressure of about four atmospheres, it becomes a limpid fluid
of a fine yellow color, which does not freeze at zero, and is not a
conductor of electricity. It immediately returns to the gaseous state
with effervescence on removing the pressure.
Water recently boiled will absorb, if cold, about twice its bulk of
chlorine gas, acquiring its color and characteristic properties. The
moist gas, exposed to a cold of 32 deg., yields beautiful yellow
crystals, which are a definite compound of one equivalent of chlorine
and ten of water. If these crystals are hermetically sealed up in a
glass tube, they will, on melting, exert such a pressure as to liquefy
a portion of the gas, which is distinctly seen as a yellow fluid, not
miscible with the water which is present. Chlorine is one of the
heaviest of the gases, its density being 2.47, and 100 cubic inches
weighing 76.5 grains.
Chlorine Water.—This combination, which is used in conducting M.
Neipce’s process, can be readily prepared by conducting the gas into a
bottle containing distilled water. One part water dissolves two parts
of chlorine.
Chlorides.—The metallic chlorides are nearly all soluble in water; that
of silver and protochloride of mercury being the only exceptions. A
metallic chloride, treated with oil of vitriol, disengages chlorohydric
acid. Heated with a mixture of peroxide of manganese and sulphuric
acid, chlorine is given off, which is easily recognized by its odor and
other physical properties.
The chlorides dissolve in water; give with nitrate of silver, a white
precipitate, even in highly diluted solutions, becoming violet colored
and finally black when exposed to the light. The rapidity of the change
of color is proportioned to the intensity of the light. It is insoluble
in nitric acid, but readily soluble in ammonia; it fuses without
decomposition, forming, when cold, a tough, horny mass, and is reduced
by hydrogen and by fusion with carbonate of soda, or with resin.
Chloride of Bromine. (See page 74.)
Chloride of Iodine. (See page 85.)
Chloride of potassium.—or (Muriate of Potassa).—Dissolve half an ounce
of carbonate of potassa in water, and neutralize with muriatic acid.
Upon concentrating the solutions, cubic crystals will be obtained,
having a taste similar to common salt. They consist of potassium and
chloride, and when dissolved in water they may be regarded as muriate
of potassa.
Chloride of Lime.—Mix half an ounce of slacked lime (hydrate of lime)
with six ounces of water, and conduct into this milk of lime, with
frequent agitation, as much chlorine gas as will evolve from two ounces
of muriatic acid and half an ounce of black oxide of manganese. The
liquid clarifies by standing; may be regarded as a solution of chloride
of lime, and must be protected from the air and light. It may also be
made without putting in the water with the hydrate of lime, by merely
passing the chlorine into the hydrate of lime. This last is by some
used in preparations for accelerating the operation of taking
Daguerreotypes, but when used for this purpose it is in small
quantities.
Chloride of Calcium.—To one part of water add two parts of muriatic
acid, and add pieces of common chalk until effervescence ceases; then
filter through cotton cloth and evaporate it by placing it in all
earthen or porcelain dish, over a slow fire, to the consistency of a
syrup. When cooling, large prismatic crystals of chloride of calcium
are formed. These must be quickly dried by pressing between folds of
blotting paper and kept carefully excluded from the air, as it readily
attracts hydrogen. For most daguerreotype purposes, the syrup may be at
once evaporated to dryness. This is frequently placed in the iodine
coating box for the purpose of keeping the atmosphere dry. It is so
easily made that every operator can provide himself with it in a short
time, and at little expense.
Chloride of Gold.—Is prepared by dissolving gold in aqua regia, a
composition of one part of nitric to two parts of muriatic acid. Gold
foil is the best for our purposes; coin, however, answers, in most
cases, for the daguerreotype operator, as the alloy, being so slight is
not noticed in the gilding process. When the latter is used, it will
facilitate the operation to beat it out, forming a thin sheet, and then
cutting in small strips. Where purity is required, foil is better. The
gold is placed in three or four times its own weight of the above
acids. For this purpose, an evaporating dish is best (a common saucer
will do); a moderate heat may be applied to favor the action. The
mixture should be stirred often with a glass rod; care should be
observed not to apply too much heat, for at a temperature of about 300
deg. the chlorine would be expelled and leave a metallic precipitate,
which would require re-dissolving. Acid may at any time be added if
necessary to dissolve the gold, but it is advisable to add as little
excess as possible, as it would require more time to evaporate. After
all the gold has dissolved, and the liquid assumes a deep red color,
the solution should be allowed to cool, being stirred nearly all the
time. This salt is of a reddish-brown color. It is rarely we find in
our market good chloride of gold, as common, salt is used for the bulk;
and when the bottles are labelled “15 grains,” “20 grains,” nine-tenths
do not in reality contain exceeding five grains of chloride of gold.
The salt is mixed with the above solution when it is cooling, and gives
bright yellow crystals, which some of our uninformed operators conceive
to be the best quality.
Chloride of Silver.—(Oxide of Silver.)—Take any quantity of silver coin
or other silver, roll or hammer it thin; cut in small pieces. This in
order to save time. Put the silver in a glass or earthen vessel
(Florence flask is best); pour in nitric acid and water, about three
parts of the former to one of the latter. The operation of cutting up
the silver may be facilitated by applying a gentle heat. This blue
solution consists of oxide of silver and oxide of copper, both combined
with nitric acid. Should the operator wish a pure solution of silver,
which, however, is not always used, he may obtain it in the following
manner:
To separate the two metals contained in the above solution from each
other, put some bright copper coins into the solution and set it aside
in a warm place for three or four days, occasionally giving it a
circular motion. The separated laminae are pure silver, which is to be
digested with ammonia until it ceases to be colored blue. The silver,
after being washed and dried, is again dissolved in nitric acid, and
the liquid, diluted with water, is kept as solution, of silver.
Either of the above solutions (the one of oxide of silver and copper,
and the pure silver solution) may be prepared for use by putting them
in a bottle, with a quantity of water, and adding common fine salt, you
obtain a white curdy precipitate of chloride of silver. No matter how
much salt is used, provided enough be added to throw down all the
chloride of silver. This solution should be well agitated and then
allowed to stand for a few minutes; thus the white precipitate is in
the bottom of the bottle. When the water has become clear, pour it off
with care, leaving the sediment behind, then add a fresh quantity of
clean water, shake, let settle, and pour off as before. Repeat the same
for several times, and the excess of salt will disappear, leaving the
white precipitate, which may be drained of the water and dried in the
dark, and kept free from light and air.
CYANIDE OF POTASSIUM.
Cyanide of Potassium.—This important article is worthy the undivided
attention of every Daguerreotypist. I here give Mr. Smee’s process for
its preparation. This is from that author’s work entitled, “Electro
Metallurgy,” American edition:
“The cyanide of potassium, so often alluded to while treating of the
metallo-cyanides, may be formed in several ways. It may be obtained by
heating to a dull redness the yellow ferrocyanate of potash, in a
covered vessel, filtering and rapidly evaporating it. The objection to
this method, however, is that without great care the whole of the
ferrocyanate is not decomposed, a circumstance which much reduces its
value for electro-metallurgy. By boiling, however, the ignited residue
with spirits of wine this difficulty is said to be overcome, as the
ferrocyanate is absolutely insoluble in that menstruum, while the
cyanuret, at that heat, freely dissolves, and is as easily re-deposited
on cooling.
“There is, however, a much better process by which this salt may be
formed, viz. by simply transmitting hydrocyanic acid through potassium.
Although the modes of making this acid are very numerous, there is but
one which is likely to be employed on a very large scale, and that is
its formation from the yellow ferrocyanate by means of sulphuric acid.
This process is performed as follows: any given weight of the yellow
salt is taken and dissolved in about five times its weight of water;
this is placed in a retort, or some such analogous vessel, to which is
then added a quantity of strong sulphuric acid, twice the weight of the
salt, and diluted with three or four times its quantity of water. A
pipe is carried from the neck of the retort to the receiving bottle,
which should be kept as cool as possible.
“For small operations, those invaluable vessels, Florence flasks,
answer well: a bent tube being connected at one end to its month, the
other passing into the second vessel; heat should be cautiously applied
by means of an Argand lamp, a little vessel of sand being placed under
the flask, which helps the acid to decompose the salt. Prussic acid is
then generated and passes through the tube to the recipient vessel,
which is to be charged with liquor potassae.
“When the potash is saturated, the operation is completed. The Germans
recommend a strong, alcoholic solution of potassa to be used in the
second vessel, for in this case, the hydrocyanic or prussic acid
combines with the potassa, forming a hydrocyanate of potassa, or, the
water being abstracted, the cyanuret of potassium, which spontaneously
precipitates, on the saturation of the fluid, the cyanuret, being
insoluble in strong alcohol. The ferrocyanate of potash may be
considered as containing three equivalents of hydrocyanic acid, two of
potash and one of iron; but, unfortunately, we can only obtain half the
acid from the salt, owing to the formation of a compound during its
decomposition which resists the action of the acid. The decomposition
of this salt taking 2 equivalents or 426 grains (to avoid fractions)
would afford 3 equivalents or 81 grains of hydrocyanic, or prussic
acid, capable of forming 198 grains of cyanuret of potassium, while in
the retort there would remain 384 grains or 3 equivalents of bisulphate
of potash, and 1 equivalent or 174 grains of a peculiar compound, said
to contain 3 equivalents of cyanogen, 1 of potassium, and one of iron
(Pereira). It is manifest that, but for this later compound, we might
double the quantity of hydrocyanic acid from the yellow salt.”
The decomposition just described is the one usually received; but too
much reliance must not be placed on its accuracy, for the analysis of
the several compounds is too difficult for the results to be fully
admitted. The residue left in the retort speedily turns to one of the
blues, identical with, or allied to, Prussian blue. This is at best a
disagreeable process to conduct, for the hydrocyanic acid formed
adheres so strongly to the glass, that, instead of being freely given
off, bubbles are evolved suddenly with such explosive violence as
occasionally to crack the vessel. This may be remedied as far as
possible by the insertion of plenty of waste pieces of platinum—if
platinized, so much the better, as that facilitates the escape of the
gas. The heat should be applied to every part of the vessel, and the
flame should not be allowed to play upon one single part alone. Large
commercial operations are performed in green glass or stone-ware
retorts.
“Now for one word of advice to the tyro: Remember that you are working
with prussic acid; therefore, never conduct the process in a room, the
fumes being quite as poisonous as the solution of the acid itself;
moreover, have always a bottle of ammonia or chlorine by your side,
that should you have chanced to inhale more than is pleasant, it will
be instantly at hand to counteract any bad effects. It is stated by
Pereira, that a little sulphuric acid or hydroferrocyanic acid passes
to the outer vessel, but probably the amount would be of no consequence
for electro-metallurgy, otherwise, it might be as well to use a
Woulfe’s apparatus, and discard the salt formed in the first vessel. To
the large manufacturer it may be worth considering whether some other
metallo-cyanuret, formed in a similar manner to the ferrocyanuret,
might not be more advantageously employed, because the residue of the
process last described contains a large quantity of cyanogen which the
acid is unable to set free.
“There are other modes of procuring prussic acid, besides the one which
has been so tediously described; but these are found to be more
expensive. The only one which I shall now notice is the process by
which it is obtained from bicyanide of mercury. The bicyanide of
mercury itself is formed when peroxide of mercury is digested with
Prussian blue, the peroxide of mercury abstracting the whole of the
cyanogen from the blue, and leaving the oxides of iron at the bottom of
the vessel. The solution may be evaporated to dryness, and one part of
the salt dissolved in six of water; one part of muriatic acid, sp. gr.
1.15, is then added, and the solution distilled, when the whole of the
hydrocyanic acid passes over, and by being conducted into a solution of
potassa, as in the former process, forms cyanuret of potassium. This
process, though easier than the first described, is rather given as a
resource under peculiar circumstances than as one to be adopted by the
large manufacturer. The expense is the only objection, but in a small
quantity this cannot be a consideration.
“In giving this very rough outline of the general mode of forming
salts, the minutiae necessary for chemical work have altogether been
avoided, and those parts alone are entered upon which are more
immediately necessary for the electro metallurgist to know and practice
for himself. This will account for the long description of the cyanuret
of potassium, while the preparation of the equally important and even
more used acids, the sulphuric, muriatic, etc., commonly found in
commerce, are altogether neglected.
“In using solutions of cyanide of potassium, the workman should not
immerse his arms into them, otherwise it occasionally happens that the
solution produces very troublesome eruptions over the skin.”
HYPOSULPHITE OF SODA.
Hyposulphite of Soda.—This salt forms one of the important chemicals
for the Daguerreotype operator. Its application to this art is of an
interesting nature. It is used to dissolve the sensitive salt of silver
which remains unchanged during the exposure in the camera. It has the
property of readily dissolving the chloride, bromide and iodide of
silver. It should be pure and free from sulphuret of sodium; should
this last be present, it will cause brown spots of sulphurated silver
upon the Daguerreotype impression. This annoyance is a great source of
complaint from many operators, and ever will be, so long as it is
prepared by men who have no reputation to lose, and whose eyes are
blinded by the “Almighty Dollar.”
A good article may be prepared as follows:
“Mix one pound of finely pulverized carbonate of soda with ten ounces
of flowers of sulphur, and heat the mixture slowly in a porcelain dish
till the sulphur melts. Stir the fused mass, so as to expose all its
parts freely to the atmosphere, whereby it passes from the state of a
sulphuret, by the absorption of atmospheric oxygen, into that of a
sulphite, with the phenomenon of very slight incandescence. Dissolve in
water, filter the solution, and boil it immediately along with flowers
of sulphur. The filtered concentrated saline liquid will afford, on
cooling, a large quantity of pure and beautiful crystals of
hyposulphite of soda.”
Hyposulphite of Gold.—This compound salt is by a few considered
preferable to the chloride of gold, but our experience has induced us
to use the latter, believing we are enabled to produce a more brilliant
and warm-toned impression with it. When the hyposulphite of gold is
used in gilding, it requires less heat and a longer application, as
there is some danger of producing a glossy scum over some parts of the
surface of the plate. I prepare this salt as follows:
Dissolve one part chloride of gold and four parts hyposulphite of soda
in equal quantities of distilled water: pour the gold into the
hyposulphite solution, in the same manner as in mixing the gilding
solution; let it stand until it becomes limpid; filter and evaporate to
dryness. Re-dissolve and add a few grains of burnt alum.
After standing a few hours, filter and evaporate again. If not
sufficiently pure, repeat the crystallization until it is so. For
gilding, dissolve in water and use in the same manner as the common
gilding solution.
N.B.—The four following mixtures were employed in Neipce’s process in
his earliest experiments:
Aqueous Solution of Bichloride of Mercury.—Eight grains of bichloride
of mercury in 10,000 grains of distilled water.
Solution of Cyanide of Mercury.—A flask of distilled water is saturated
with cyanide of mercury, and a certain quantity is decanted, which is
diluted with an equal quantity of distilled water.
Acidulated White Oil of Petroleum.—This oil is acidulated by mixing
with it one tenth of pure nitric acid, leaving it for at least 48
hours, occasionally agitating the flask. The oil, which is acidulated,
and which then powerfully reddens litmus paper, is decanted. It is also
a little colored, but remains very limpid.
Solution of Chloride of Gold and Platinum.—In order not to multiply the
solutions, take the ordinary chloride of gold, used for fixing the
impressions, and which is composed of 1 gramme of chloride of gold and
50 grains of hyposulphate of soda, to a quart of distilled water.
With respect to chloride of platinum, 4 grains must be dissolved in 3
quarts of distilled water; these two solutions are mixed in equal
quantities.
Acids.—I shall not go into the preparations of the various acids
employed in the Daguerreotype. This would be useless to the operator,
as there are few, if any, that it would be advisable to prepare. It is
only necessary for the experimenter to be made acquainted with their
properties, and this in order to prevent any haphazard experiments,
which are too common among operators. Any person who may be desirous to
try an experiment, should first study the agents he wishes to employ.
By so doing much time and money will be saved; while the searcher after
new discoveries would rarely become vexed on account of his own
ignorance, or be obliged to avail himself of the experience of others
in any department of science.
Nitric Acid—Exists in combination with the bases, potash, soda, lime,
magnesia, in both the mineral and vegetable kingdoms, and is never
found insoluble. It has the same constituents as common air, but in
different proportions. The strongest nitric acid contains in every
pound, two and a quarter ounces of water. Pure nitric acid is
colorless, with a specific gravity of 1.5, and boiling at 248 deg.. It
is a most powerful oxidizing agent, and is decomposed with more or less
rapidity, by almost all the metals, to which it yields a portion of its
oxygen.
The nitric acid of commerce, is generally the article used by the
Daguerreotypist. This usually contains some chlorine and sulphuric
acid. It is obtained by the distillation of saltpetre with sulphuric
acid. It is employed in the Daguerreotype process for dissolving
silver, preparing chloride or oxide, nitrate of silver, [the former
used in galvanizing,] and in combination with muriatic acid for
preparing chloride of gold, used in gilding. It is also used by some
for preparing the plate.
Acidulated Solution.—This solution is used for cleaning the surface of
the Daguerreotype plate. It has the property of softening the silver,
and bringing it to a state in which it is very susceptible of being
either oxidized or iodized, hence it contributes to increase the
sensibility of the plate. The proportions are to one drop of acid add
from 15 to 20 drops of water, or make the solution about like sharp
vinegar to the taste.
Nitro-Muriatic Acid.—Aqua Regia is a compound menstruum invented by the
alchemists for dissolving gold. It is composed of colorless nitric acid
(aqua-fortis) and ordinary muriatic acid; the mixture is yellow, and
acquires the power of dissolving gold and platinum. These materials are
not properly oxidized; it nearly causes their combination with
chlorine, which is in the Muriatic acid.
Hydrochloric Acid (Muriatic Acid).—This acid forms a valuable addition
to the chemicals employed by the practical Daguerreotypist. This acid
is formed by acting upon common salt (which is chloride of sodium) by
concentrated sulphuric acid. The water of the acid is decomposed, and
its hydrogen combines with the chloride of the salt to form muriatic
acid, and this unites with the sulphuric acid to form sulphate of soda;
60 parts of common salt and 49 parts of concentrated sulphuric acid,
afford, by this mutual action, 37 parts of muriatic acid and 72 parts
of sulphate of soda. The muriatic acid of commerce has usually a
yellowish tinge, but when chemically pure it is colorless. The former
is commonly contaminated with sulphurous acid, sulphuric acid,
chlorine, iron, and sometimes with arsenic.
Muriatic acid, from the fact of the presence of the chlorine, is used
in the Daguerreotype process for dissolving gold, and in combination
with various accelerators. Its presence can be detected by ammonia. A
strip of paper dipped in this and waved to and fro will emit a thick
white smoke if the acid vapor be in the atmosphere. The ammonia
neutralizes the acid fumes. By reversing the experiment we can
determine whether vapor of ammonia be in the air, and also deprive
these suffocating and dangerous gases of their injurious properties,
and remove them from the air. Every Daguerreotype operator should be
furnished with, at least, a six ounce bottle of aqua ammonia. Its
operation is very nearly the same on bromine and iodine vapor.
Hydrofluoric Acid (Fluorohydric Acid).—This acid is used to form some
of the most volatile and sensitive compounds employed in the
Daguerreotype. It is one of the most dangerous bodies to experiment
with: it is volatile and corrosive, giving off dense white fumes in the
air. It combines with water with great heat. At 32 deg. it condenses
into a colorless fluid, with a density 1.069. It is obtained from
decomposition of fluorspar by strong sulphuric acid. It readily
dissolves the silica in glass, and consequently cannot be kept in a
vessel of that material. It is prepared and kept in lead. It is
employed in accelerators on account of its fluorine.
One small drop on the tongue of a dog causes death. The operator who
wishes to use it should pour some of the liquid for which he intends it
into a graduate, or other vessel, and then add the desired quantity of
acid. If by accident any of the spray should fall upon the skin, it
should at once be copiously drenched with water.
Sulphuric Acid.—There are two sorts of this acid: one is an oily,
fuming liquid; this is made in Nordhausen, in Saxony, and is commonly
called “Nordhausen sulphuric acid,” or oil of vitriol. The other which
is the kind used in connection with the Daguerreotype, is common
sulphuric acid. It is somewhat thinner, and when undiluted is not
fuming. This acid may be obtained in a solid and dry state, called
anhydrous sulphuric acid.
The common sulphuric acid is made by burning sulphur, which forms
sulphurous acid. To convert this into sulphuric acid and gain more
oxygen, nitric acid, which is rich in that body, is added. It forms a
limpid, colorless fluid, of a specific gravity of 1.8. It boils at 620
deg.; it freezes at 15 deg. It is acrid and caustic, and intensely acid
in all its characters, even when largely diluted.
Its attraction for basis is such that it separates or expels all other
acids, more or less perfectly, from their combinations. Its affinity
for water is such that it rapidly absorbs it from the atmosphere, and
when mixed with water much heat is evolved. It acts energetically upon
animal and vegetable substances, and is a poisonous, dangerous
substance to get on the skin. It is a powerful oxidizing agent; hence
its use in the galvanic battery, for which purpose it is mostly used by
the Daguerreotypist. The fumes of this being so much more offensive
than nitric acid, the latter is sometimes used. It is also employed in
some of the more sensitive accelerators.
ACCELERATING SUBSTANCES.
Remarks on the Accelerating substances Used in the Daguerreotype.—I
have now arrived at a point in this work, where the eye of the
Daguerreotype public will intently search for something new. This
search will prove in vain, at least so far as regards those who have
enjoyed and embraced the opportunities for studying the principles of
our art. Every experienced operator has in a degree become familiar
with the mechanical uses of all the agents employed, while I fear but
few understand the properties, and laws governing those properties,
which are so indispensable to produce an image impressed upon the
silver surface.
There are three substances which form the bases for producing a
Daguerreotype; silver, iodine and bromine. Each forms a separate body
which is indispensable to the operators success as the art is now
practiced in America. With these three, compounds of great variety are
formed.
The silver surface is first thoroughly cleaned and freed from all
organic matter, then exposed to vapor of iodine, producing an iodide of
silver. The plate upon which is this salt, is again exposed to the
vapor of bromine, forming a bromo-iodide of silver, a salt also.
As most of the various accelerators are compounds of bromine, with
either chlorine or fluorine combination, they partake somewhat of the
nature of these latter, giving results which can be detected by the
experienced operator. Thus muriatic acid is added for its chlorine,
which can generally be detected by the impression produced, being of a
light, soft, mellow tone, and in most cases presenting a brilliant
black to that colored drapery. Those who wish to experiment with agents
for accelerating substances, should first study to well understand
their peculiar nature and properties; as well, also, to endeavor to
find out what will be the probable changes they undergo in combination
as an accelerator. This should be done before making the experiments.
From the foregoing it will be seen that numerous compounds are formed
from the same basis, and, consequently, it would be a waste of time and
a useless appropriation to devote more of our space than is necessary
to give the principal and most reliable combination.
In America, the words “Quick” and “Quick Stuff,” are more generally
used for and instead of the more proper names, “Sensitives,” or
“Accelerators,” etc. As it has by use become common, I frequently use
it in this work.
Liquid Accelerator, No. 1.—This mixture was used by me in 1849, and is
given as it appeared in my “System of Photography,” published at the
above date:
Take pure rain or distilled water, one quart, filter through paper into
a ground stopper bottle, and add, for warm weather, one and a half
ounce chloride of iodine; or for cold, one ounce; then add one ounce
bromine, and shake well. Now with care not to allow the vapor to
escape, add drop by drop, thirty drops of aqua ammonia, shaking well at
each drop. Care must be taken not to add more at a time, as it evokes
too much heat. This mixed, in equal proportions with John Roach’s
quick, forms an excellent chemical combination. For this purpose, take
one and a half ounce of each, to which add ten ounces water, for warm
weather, or from six to seven for cold. Pour the whole into a large
box, and it will work from two to four months. I am now using (1849)
one charged as above which has been in constant use for three months,
and works uniformly well. The above is right for half or full size
boxes, but half of it would be sufficient for a quarter size box.
Coat to the first shade of rose over iodine, change to a deep rosy red
over quick, and black about one tenth the first.
I would not now recommend the addition of “John Roach’s quick,” as I
believe equally good results can be produced without it. This liquid is
now used by many, and is very good for taking views.
Lime Water Quick.—This mixture is more used at present than all the
other liquids ever introduced. It produced the most uniform results,
giving the fine soft tone so characteristic in pictures produces from
accelerators containing chlorine. To one quart of lime water (this can
be had of any druggist) add one and a half ounce of pulverized alum.
This should be shook at intervals for twenty—four hours; then add one
ounce of chloride of iodine and three fourths ounce of bromine.
Lime Water.—This is easily prepared by putting lime into water, say a
piece of quick-lime about the size of an egg into one quart of water.
This should be shook occasionally for two or three days and allowed to
settle, when the water can be poured off and used.
Use.—To one part of quick add six parts of water; coat to a light
yellow over the iodine, to a rose color over the quick, and recoat
about one tenth. The above coating may be increased or diminished, it
matters not, so that there is not too much, and the proper proportions
are preserved. Some add to the above a small quantity of magnesia, say
about a teaspoonful to the quart of liquid.
Liquid Accelerator, No. 2.—The following was for a long time used by
one of the first houses in the United States, and probably was one of
the first liquids ever used. It produces a fine-toned picture, but is
not considered as sure as the lime water quick:
Take rain water one quart, add pulverized alum until it is a little
sour to the taste, and a small piece, say one half inch square, of
magnesia. Filter through paper, and add chloride of iodine one half
ounce, bromine sufficient to take it up, which is a little less than
half an ounce.
Charge with one of quick to six of water; coat over iodine to a soft
yellow, nearly, but not quite, bordering on a rose; over quick to a
dark purple, or steel, and back one sixth to one tenth.
Wolcott’s American Mixture.—Van Loan Quick.—This mixture was first
formed and used by T. Wolcott & Johnson and gained great celebrity for
its productions. I have now a bottle hermetically sealed that contains
about a half ounce of this mixture prepared in 1841 by John Johnson,
now a resident of this city, and the former partner of Mr. Wolcott. The
preparation of this mixture, as furnished by Mr. Johnson himself, is
given as follows:
“One part of bromine, eight parts of nitric acid, sixteen parts of
muriatic acid, water one hundred parts. This mixture should be allowed
to stand for several days; it improves by age.
“Use.—A few drops say, 6 to 12, of this mixture, should be put into
about 6 or 8 ounces of water; it will require frequent replenishing by
the addition of a few more drops. The plate should be coated over the
dry iodine to a red just bordering on a slate, and then exposed to the
mixture only sufficiently long to change the color. If this is not done
in less than six seconds it is not strong enough. Re-coat over the
iodine full one fourth as long as first coating.”
This exceedingly volatile compound is difficult to control from its
instability; it is but little used. The impressions successfully
produced by this mixture are very brilliant, and possess a pleasing
peculiarity.
DRY SENSITIVES.
Hydrate of Lime.—The operation by which water is combined with lime is
called slaking. Take a piece of quick lime, common lime used in mortar,
and immerse it in warm water for about fifteen seconds; then place it
in an iron or tin vessel. It will soon begin to swell, evolving a great
deal of heat and emitting steam, and soon falls into a fine powder,
hydrate of lime. This should be well stirred and allowed to cool, and
then bottled in order to prevent it from giving off the hydrate and
recovering the carbonic acid from the atmosphere. The last is
detrimental to its use with bromine, and is one cause of the complaint
that “it will not take bromine.” The hydrate of lime should, not be
dried over a heat, as has been supposed by many, for in that case the
hydrogen is expelled and it returns to a carbonate. It is advisable to
cool it in a damp place like a ground cellar. Much of the lime in our
market will not, except it be quite damp, combine with the bromine.
This is owing to impurities. Nothing is equal to oyster-shell lime,
which I use altogether.
Bromide of Lime.—In preparing large quantities of this, we adopt the
following method: Fill a four-quart bottle about two-thirds full of
hydrate of lime; pour into this about one or two ounces of bromine;
then shake well, add more of the bromine, shake well and let it stand
for a few hours, adding sufficient bromine to give it a fine red color.
It is better when kept in the large bottles, as it forms a more perfect
combination: in other words it improves by age.
Use.—Coat over the iodine to a rose red and then over this mixture to a
purple or slate; recoat over the first about one fourth as long as
first coating.
Gurneys American Compound.—Of this compound there are two combinations,
one for use, when the temperature of the atmosphere is above 65 or 70
deg., and the other at a lower temperature. The first is called No. 1,
the second No. 2.
No. 1 is prepared by placing hydrate of lime in a bottle, say to three
quarts of the hydrate of lime, add one ounce of pulverized burnt alum,
and as much chloride of lime as can be put on a quarter of a dollar,
and from 15 to 30 grains of dry pulverized iodine, or enough to change
the color of the hydrate of lime, to the slightest possible tinge of
yellow. There had better be less than carry the color to a deeper
shade. The object of using the iodine is to form a compound with
bromine that is not so volatile as the bromine itself. No matter how
little iodine is combined with the bromine, the vapors possess their
relative proportion; hence, only enough iodine to prevent “flaring,” or
as it is often termed a “scum-coating,” is used. The iodine should be
thoroughly combined with the lime, which will take about one or two
days. Should add bromine the same as in bromide of lime, until the
compound assumes a light red color.
No. 2 is prepared in the same manner as No. 1, except the addition of
the iodine, which is omitted.
Use.—No. 1. Coat over the iodine to a bright yellow color, then over
the compound, No. 1, to red color, recoat over iodine, about one sixth
as long, as the time occupied in first coating.
No. 2. Coat over iodine same as above, except recoat over the iodine
about one fourth to one half as long as first coating.
Dry Quick, No. 1.—Bromide of Lime and Starch.—The following compound
forms an excellent accelerator, and is used by many. It is claimed for
this preparation, that it will hold the bromine longer than others
where starch is not employed. As regards this claim we do not think it
can be substantiated. Our experience in practice has led us to the
conclusion that there is no great difference as respects durability,
but there is some little difference as regards the tone of the
impressions produced by its use.
To one quart of hydrate of lime add one quart of finely pulverized
starch. To this mixture add bromine, until it assumes a deep yellow or
pink color.
Starch may be added to any of the dry mixtures.
Use.—Coat over the iodine to a deep yellow, then over this quick to a
red color, recoat about one sixth of the time of first coating.
I will here again remark, that the exact color of the coating is not
essentially provided a proper proportion is preserved.
I have never seen it stated, though it be a fact worthy of note, that a
proportionate time for coating over the iodine and accelerator, will
not answer. For example: if a plate exposed to the vapor of iodine be
perfectly coated in sixteen seconds, and then exposed to an
accelerator, (not having iodine in its combination) receives its
coating in four seconds, it will be found that a proper proportionate
coating cannot be preserved by adopting, a proportion of time, but on
the contrary, the time will diminish; for exposure over the
accelerator, as in the above example, if it be desired to coat the
plate with twice as much iodine as in the above example, the time would
be, over iodine thirty-two seconds, and over the accelerator (to
possess a proper proportion) from six to seven seconds. Hence it is
that many inexperienced operators, when wishing to vary their usual
manner of coating, fail in producing a favorable result. They coat
calculating a proportion of time when they should not.
Dry Quick, No. 2.—Bromide of Lime and Magnesia.—To one quart of hydrate
of lime add one quart of magnesia, and mix them well together; add
bromine same as in preparing bromide of lime; coat the same as over dry
quick No. 1. This combination produces very uniform results, and is
worked with much success by beginners.
Chloro-Bromide of Lime.—To the bromide of lime add chloride of bromine
until the mixture becomes a pale yellow color, resembling sulphur. It
should be shook well, and enough of the chloride of bromine added to
bring the compound to a deep blood red color.
Use.—Coat over the iodine to a pink color, and then over the above to a
red, or just changing the color. It should be remembered that
accelerators containing chlorine do not admit of a great change of
color of coating on the plate.
Iodide of Starch.—This mixture can be employed for coating over in warm
weather, and prevent the flashing resulting at high temperatures. It
may be used the same as the iodide alone.
To six ounces of finely pulverized starch, add one fourth ounce of dry
iodine.
Use.—Same as the dry iodine alone.
The same combination may be made with lime, magnesia and other
substances.
Concentrated Solution of Iodine for First Coating.—It may appear
strange to some of our old operators that an aqueous solution of iodine
can be used for coating the plate and forming the iodide of silver. It
has long been a cry among most operators that it is impossible to
succeed when the iodine box contains dampness. Now this is a great
mistake, and we will here state that in all cases where dampness
appears upon a properly prepared Daguerreotype plate, it is the result
of a different temperature of the metal from the air which surrounds
it. Mr. Senter, of Auburn, was the first of our operators who used a
solution of iodine for coating the plate, and we several years since
saw his results, which would rival the production of any other
operator. A concentrated solution of iodine is prepared by putting into
a common bottle two thimblesful of hyposulphite of soda and a rather
larger quantity of iodine, so that there may be more than sufficient.
Add to it about 40 ounces of common water (heated to 60 or 70 degrees),
by little and little, moving, the bottle to warm it, for fear of
breaking. After shaking it a short time, the water is rapidly and
strongly colored. The solution should be poured into a bottle with a
ground stopper, and when cool used for iodizing.
A solution of sufficient strength can be made by moistening or just
covering the iodine with water.
Chloride of Iodine as an Accelerator.—This is probably one of the best
accelerators that can be used for coating the plate for taking views;
it works too slow, however, to meet the wants of the operating room,
yet its use was formerly, for a long time, adhered to by some of our
best professors. In producing views with this, we are successful in
obtaining well-developed impressions, with a depth of tone and richness
of appearance not to be met with in the productions of any other
substances. I give its use as furnished me by an old and experienced
operator, and published in Humphrey’s Journal, vol. i. p. 180:
“As the process of using chloride of iodine may be of interest to some
of our subscribers, I take pleasure in giving the following
manipulation. To one ounce of chloride of iodine add two ounces of
water; place this mixture in a coating-box, the same as quick stuff;
coat the plate with dry iodine to a light yellow, or lemon color; then
bring the coating to a deep pink over the chloride. The plate must be
recoated over the dry iodine.”
This combination has been very successfully used in one of our most
extensive establishments in this city, and the superiority of the
pictures produced by it was considered as an equivalent for the
additional time required to bring out the impressions.
Chlorine as an Accelerator.—I shall here refer to but a single
experiment in which I employed chlorine gas for coating the plate. I
was provided with a retort, the neck of which was fitted to the jar of
my coating-box, through a hole drilled for its reception. This was
fitted perfectly tight in my coating-box. I placed some pure undiluted
bromine water and the agents necessary for producing chlorine gas (in
small quantity) in the retort. The result was that my first experiment
produced an impression completely solarized in all its parts by an
exposure of four seconds of time, which would have required an exposure
of twenty seconds to produce a perfectly developed impression by the
usual process.
Another trial immediately produced one of the finest toned impressions
I ever saw, perfectly developed in one second of time.
My next two or three experiments proved total failures. I was unable to
produce even a sign of an impression. By accident my retort was broken,
and not being in a locality convenient to obtain another, my
experiments were necessarily suspended.
My attention was not called to this subject again for several years,
when I noticed an account of some similar experiments by F. A. P.
Barnard and Dr. W. H. Harrington, the latter of whom is now of the firm
of Dobyns & Harrington, of New Orleans.
From reading this article, I found my own difficulties explained. Too
much of the chlorine gas was present in my coating jar. I would like to
see some of our enterprising operators investigate this combination.
It is a singular fact, that the vapors of bromine and chlorine
combining upon the iodide of silver, produce a more sensitive coating
than when the two are combined in solution, as in chloride of bromine
solution. Those having Humphrey’s Journal at hand, can refer to vol. i.
p. 142.
To use Bromine Water or other Accelerators in Hot Weather.—An excellent
plan for using bromine water is as follows:
Fill a two-ounce bottle quarter full of it, and then fill the bottle
with fine sand, which serves to preserve a low temperature; then place
the bottle in a porous cup, same as used in the battery; fill this also
with sand, and close the end with plaster of Paris. Place this in a
coating-box, and it will be found to act with great uniformity and be
quite permanent.
Bromide of Lime, another accelerator, can be used in the same manner,
except it is, only necessary, when a solid sensitive is used, to mix it
with the sand without placing it in a bottle. This method is employed
with great success by a few, who have regarded it as a secret worth
keeping.
A Combination, requiring the Use of only One Coating-box.—It is often
wondered by beginners, why some solution requiring only one coating
cannot be employed. This can be done, but the results are not so
satisfactory as when two or more are employed. Such an accelerator may
be produced by adding alcoholic solution of iodine to a solution of
chlorate of potash, until the latter will take up no more of the
former, and to each ounce, by measure of this solution, ten drops of a
saturated solution of bromide in water are added. The solution of
chlorate of potash is made by diluting, one part of a saturated
solution of the salt with ten parts of water. The use of the chlorate
is simply as a solvent of iodine.
Fats as Accelerators.—The use of fats, oils, or greasy substances, has
been one of the most emphatic prohibitions about the Daguerreotype
plate. Yet it has been proved that its presence in a small quantity
upon the silver surface has the effect of reducing the time of exposure
in the camera from two-thirds to three-fourths. An application may be
made as follows: Pour sweet oil, or rub beef or mutton fat, on a common
buff, which is free from all polishing powders. With this, buff a
well-cleaned plate, and it will leave a scum, which should be mostly
removed by using another buff, which should be clean. Coat the plate in
the usual manner, and the result will be a great reduction in the time
of exposure in the camera. The impression produced upon a plate so
prepared presents, when coming from the vapor of mercury, a grey,
scummy appearance, which, on the application of heat in gilding, does
not improve; hence its use is not generally adopted.
We have instituted some investigations upon this subject, and in the
present volume, we shall not refer to it further. Those wishing to
learn more fully the effect of light upon organic substances will find
Robert Hunt’s “Researches on Light” an invaluable work.