Silver bromide

“ If the worker himself does not know that his silver bromide print is faulty, he is inclined to ascribe the difficulties which he finds in making the bromoil print and his dissatisfaction with the results, to the bromoil process itself. Most of the unsatisfactory results in bromoil work must be ascribed to the imperfect quality of the bromide print which is used, and this is the more important as this lack is not perceptible to the eye after the bleaching is completed. ”

“ The silver bromide is much more sensitive than the chloride, so that the printing can be done in artificial light. Since the darkest places on the negative cut off the most light, it is evident that the lights of the print will be the reverse of those of the negative, and will therefore correspond to those of the object photographed. ”

“ I would also beg to mention that a certain portion of the bromide of silver introduced into the iodized paper seems much to accelerate its power of receiving the green colour, as it undoubtedly does in the collodion. Although it does not accelerate its general action, it is decidedly a great advantage for foliage. Its best proportions I have not been able accurately to determine; but I believe if the following quantity is added to the portion of solution of iodide of silver above recommended to be made, that it will approach very near to that which will prove to be the most desirable. ”

“ Without a restrainer, the tendency is for those parts to be first reduced, but the action extends to that which has not been acted upon by the light. It has been usually said that alkaline development is only available for bromide of silver, but my experience has taught me that iodide of silver is as amenable to alkaline development as the bromide, although not so rapidly, and that chloride is very amenable to it, and will give most beautiful pictures. ”

“ Lastly, the bath may of itself get too weak, and then it will be best to place it on one side, and recover the silver by any of the usual methods, and make a new bath. One word about the addition of the bromide of {158}silver to the double iodide, as recommended by Dr. Diamond. I tried this, and feel most confident that it produces no difference; as soon as the bromide of silver comes in contact with the iodide of potassium, double decomposition ensues, and iodide of silver is formed. ”

“ It is only possible to use papers whose swelling power has not been too completely removed in process of manufacture by the use of hardeners. The principle of the bromoil process is that a tanning of the gelatine shall occur simultaneously with the bleaching of the silver bromide image. As we have already remarked, this does not affect the high lights and leaves them still absorbent, while the shadows are tanned and therefore become incapable of taking up water. The half-tones are tanned or hardened to an intermediate degree and therefore can take up a certain amount of water. ”

“ The atomic weight of silver was also determined by Stas by means of the synthesis of silver sulphide and the analysis of silver sulphate. The combining weight obtained by this method was 107·920. The synthesis of silver iodide and the analysis of silver iodate gave the figure 107·928. The [439] synthesis of silver bromide with the analysis of silver bromate gave the figure 107·921. The synthesis of silver chloride and the analysis of silver chlorate gave a mean result of 107·937. ”

“ The residual potassium bromide is estimated by means of standard silver nitrate solution. Bromoform is specially suitable for this purpose for several reasons. It is very readily formed by the action of bromine and potash on acetone, and although very volatile in steam, it is not liable to loss due to its own evaporation. Further, its high molecular weight and large percentage of bromine conduce to accurate results, 58 grms. of acetone being responsible for the formation of 357 grms. ”

“ A direct transformation of one modification into the other has not yet been accomplished. The effect of the light upon these substances is incipient reduction, and we might hence suppose that the more reducible indigo sensitive variety would be the more sensitive to light. But this is not the case, because it is not chemical reducibility, but the absorption power for light that is of the greatest importance. Now the blue sensitive silver bromide has a greater absorption power than the indigo sensitive variety, and hence its greater sensitiveness. ”

“ The sub-bromide formed by light and that subsequently produced in the act of development are therefore reduced. A large proportion of gelatin compared with the silver salt in a film enables an alkaline developer to be used without any chemical restrainer; but when the gelatin bears a small proportion to the silver such a restrainer has to be used. With collodion films the particles of bromide are more or less unenveloped, and hence in this case some kind of chemical restrainer is absolutely necessary. ”

“ The film is transformed into different quantities of sub-iodide and sub-bromide of silver, according to brilliancy of light. In addition, there is on the plate an amount of unchanged silver nitrate which becomes useful in the second stage, or development. The image is not seen as yet, being latent, and requiring the well-known developing solution of sulphate of iron, acetic acid, alcohol, and water. Practically we all recognize the effect of a nicely-balanced wave of developer worked round a plate. The high lights are first to appear as a darker color, till the details of shadow come out ”

“ Silver occurs native, or in ores. The latter are as follows:—The sulphide, or the vitreous silver (argentite) ; antimonial silver; and the combined sulphides, of antimony and silver. There are many silver minerals, such as the chloride (horn silver, or kerargyrite) , bromide, and carbonate of silver, bismuthic silver, etc. The bromide and iodide are bromargyrite and iodargyrite. Silver occurs most frequently associated with gold; natural alloys of these two metals are found, containing from 0·16 to 38·7 per cent. of silver, which causes considerable variations both of colour and density. ”

“ We make, then, a solution of recrystallized silver nitrate in distilled water, containing in every 12 ounces of solution 11⁄4 ounces of the salt.
The next material we require is a soluble bromide. I have here specimens of various bromides which can be employed, such as ammonium, potassium, barium, and zinc bromides; as a rule, however, either the ammonium or potassium salt is used, and I should like to say a few words respecting the relative efficiency of these two salts.
1. As to ammonium bromide. This substance is a highly unstable salt. ”

“ The hornsilvers all occur under similar conditions and are often associated together; they are found in metalliferous veins with native silver and ores of silver, and are usually confined to the upper oxidized parts of the lodes. They are important ores of silver (the pure chloride contains 75.3% of silver) , and have been extensively mined at several places in Chile, also in Mexico, and at Broken Hill in New South Wales. The chloride and chloro-bromide have been found in several Cornish mines, but never in very large amounts. ”

“ The imaginary principles or elements of the alchemists were termed salt, sulphur, and mercury. About sixty-four different kinds of matter are at present recognised as elementary bodies. They are substances having the most diverse characters. The great majority exist in the solid state; bromide and mercury are liquid; while oxygen, hydrogen, nitrogen, and chlorine, are gaseous. About four fifths of the elements are metallic, as instanced by gold, silver, copper, iron, &c. ”

“ The sensitiveness with this developer is at least equal to that when iron developer is used, frequently even greater.
The addition of bromides is superfluous, sometimes injurious. Bromides in quantities, as added to ammoniacal pyro, would reduce the sensitiveness to 1/10 or 1/20; will even retard the developing power almost entirely.
Must a restrainer be resorted to, 1 to 3 min. of a 1:10 solution of potassium bromide is quite sufficient. ”

“ 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. ”

“ A salt which is obtained from hydrobromic acid, bromide of iron, &c., by similar processes to those adopted for the iodide. The following process for the preparation of bromide of ammonium is from the formula for the new medicaments adopted by the Paris Pharmaceutical Society: “Add bromine very slowly to a solution of ammonia, with continual stirring, until the liquid remains faintly and persistently coloured by a slight excess of bromine.” It forms white prismatic crystals; and, in its general properties, resembles bromide of potassium. It is volatile, and easily decomposed. ”

“ As the iron developer is not really suited to this purpose on account of certain unpleasant qualities inherent in it, it is advisable to use amidol for the development of bromide paper for bromoil printing whenever possible, and the best developer is composed as follows:
The sodium sulphite is first dissolved in water, and the easiest way is to pour the necessary quantity of water into a developing dish and sprinkle the pulverized or granular dry sodium sulphite into it while the dish is constantly rocked ”

“ They come inevitably as the alarm clock; when the hands of circumstance touch the hour, the bromidic remark will surely go off.
But, lest one make too much of this particular symptom, let us consider a few other tendencies. The Bromide has no surprises for you. When you see one enter a room, you must reconcile yourself to the inevitable. No hope for flashes of original thought, no illuminating, newer point of view, no sulphitic flashes of fancy—the steady glow of bromidic conversation and action is all one can hope for. He may be wise and good, he may be loved and respected—but he lives inland ”

“ Development should be stopped when the shadows and half-tones are blackened, and there is still a whitish film of silver chloride in the high lights. Observation of the negative by looking through it is not advisable, for the negative very soon appears dense by transmitted light, because the metallic silver formed in development masks the silver chloride. ”

“ It is the bore who, at times, unconsciously to himself, amuses you to the point of repressed laughter. These terms are fluent—your friends have a way of escaping from the labeled boxes into which you have put them; they seem to defy your definitions, your Orders and Genera. Fifteen minutes’ consideration of the great Sulphitic Theory will, as the patent medicines say, convince one of its efficacy. A Bromide will never jump out of his box into that ticketed “Sulphite.” ”

“ The decomposition of 2HBr into H2 + Br2 only requires, if the bromine be obtained in a gaseous state, a consumption of about 24,000 units, whilst in the decomposition of 2HI into H2 + I2 as vapour about 3,000 heat units are evolved; [68] these facts, without doubt, stand in causal connection with the great stability of hydrogen chloride, the easy decomposability of hydrogen iodide, and the intermediate properties of hydrogen bromide. ”

“ Bromine does not occur in nature in the uncombined condition, but in combination with various metals is very widely but sparingly distributed. Potassium, sodium and magnesium bromides are found in mineral waters, in river and sea-water, and occasionally in marine plants and animals. Its chief commercial sources are the salt deposits at Stassfurt in Prussian Saxony, in which magnesium bromide is found associated with various chlorides, and the brines of Michigan, Ohio, Pennsylvania and West Virginia, U.S.A. ”

“ Nerve sedative; diminishes reflex excitability and depresses the motor area of the cortex. Similar to sodium bromide, but more likely to disturb digestion.
Dosage: 1 Gm. or 15 grains (U.S.P.) ; preferably administered by itself in simple dilute solutions; increased if necessary. Long-continued administration should be [Pg 170] interrupted occasionally to prevent bromism and accumulation in the system.
Elixir Potassii Bromidi (Elix. Pot. Brom.) , Elixir of Potassium Bromide, N.F.—Potassium bromide (17.5%) in syrup, water and aromatic elixir; may be colored with compound tincture of cudbear. ”

“ Sulphites, those who are over that age. In some dim future incarnation, perhaps, the Bromide will leap into sulphitic apprehension of existence. It is the person who is Absolutely Young who says, “Alas, I never had a youth—I don’t understand what it is to be young!” and he who is Absolutely Old remarks, blithely, “Oh, dear, I can’t seem to grow up at all!” One is a Bromide and the other a Sulphite—and this explanation illuminates the paradox. ”

“ For prints and transfers which should show the greatest possible fineness and modeling, it is better to choose a smooth bromide paper.
The prepared print is swollen and pigmented as in making an ordinary bromoil print. It is not necessary, when planning to make a transfer, to produce a higher relief by a warm water or ammonia bath, which requires the use of softer inks and limits artistic freedom in working up. One’s whole attention must be focused on a single point: the shadows must be clean, the lights pure white. ”