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62. ations, I ociety, I id and I soluble I glass, I ty had I y Dr a, not I je, but say be ‘epart ooked g, but 1 who e well takes ithout I letely | mar I dered, I cts to case. places little 1 and sition n the ortake table as by I It is olour, ff all I tirely I that I ess in I hoto- j $ in vhid f n igit mW ne of i what 530) they iown has ctet- arly ably I ■the soa It eery ged rery est, ave E. out kill I to- I JUNE 27,1862.] THE PHOTOGRAPHIC NEWS. 305 graphic department, a notice of which we must defer till a future occasion. Messrs. Huskisson and Sons (536) exhibit a beautiful series of iodides, bromides, &c. One remarkable point about their case is the attention they seem to have paid to the crystallographic characteristics of the various salts exhi bited. We may notice especially some large jars of iodide and bromide of potassium, the crystals of the former salt being in some cases nearly an inch and a half cube. They also exhibit some pure neutral iodide of potassium for pho tographic purposes, as well as iodides of ammonium, cal cium, magnesium, silver, mercury, lead, iron, zinc, anti mony, arsenic, phosphorus, and sulphur. Their iodide of arsenic is a magnificent preparation; it is exhibited in a large hemispherical bowl with a flat glass cover. The sides are lined with a fine mass of brilliant red crystals, resembling a beautiful collection of miniature ferns or sea-weeds, and totally unlike the ordinary run of chemical crystals. The companion dish of iodide of mercury is also exceedingly fine; but the third of iodine will be looked upon with especial interest. There are many exhibitors of iodine in this department, but few, if any, show a specimen equal to this. J. Ward and Co.’s case (619) will be regarded by the scientific photographer with some interest, illustrating as it does the utilisation of kelp, the technical name of the ash obtained by the incineration of sea-weeds; it is valuable from the potash salts and iodine which it contains. We have here exhibited a beautiful specimen of crystallized iodine, and several samples of iodide of potassium extracted from this source. W. Bailey and Son, Wolverhampton (465), also exhibit some good chemicals, nearly every article used in photo graphy being manufactured by this house. They prepare an impervious varnish for the preservation of paper photo graphs, and specially adapted for taking colour, which is said to render the touch equal to working on ivory; and also an encaustic paste, which produces an equal and homo geneous surface on the picture that neither damp nor water "’ill effect, making the colour transparent like glazing in oil. The value of this is most apparent when uncoloured photo graphs are stippled with sepia or the like, which on albu- menized paper injures the surface and spoils the effect. The paste is to be gently rubbed all over the picture with the finger, and after remaining there for ten minutes, rubbed off again, when the photograph will be found to have ac- United great brilliancy and clearness of detail. AWARDS OF JURORS. fire following official circular, relative to the declaration of the awards of the juries, has been issued by order of the commissioners:— 1 . The declaration of the awards of the juries at a State teremony on Friday, 11th July, 1862, at one o’clock, will be made by an International representative body of Royal and distinguished personages, specially named by the various nations which have taken part in the Exhibition. 2 , The Queen has named his Royal Highness the Duke of Cambridge, K.G., as her Majesty’s representative to receive and distribute the awards to the exhibitors of the United Kingdom "nd its colonies and dependencies. The special representatives of foreign countries will receive and distribute the awards to 'oreign exhibitors. n 3 The various ceremonies will take place in the Exhibition Buildings and in the Horticultural Gardens, which will be 4 m, as part of the Exhibition for that day. The special representatives will be received by her Majesty’s irommissioners, 011 the upper terrace of the Horticultural Gardens, tor 18 weather be favourable ; if unfavourable, in the Conserva- t X’ and the International juries will then deliver their awards "Ehespecial representatives. will•n ™ special representatives after receiving the awards Build’ 88 1,1 procession along the arcades to the Exhibition ngs, and at various stations will deliver the awards to the chairmen of the British Class Committees, to the Colonial Com missioners, and to the Foreign Commissioners in or near those parts of the buildings where the principal objects of each class or country are placed. 6. Upon the arrivals of the special representatives at the dif ferent stations for distributing the awards, the national airs of the respective nations will be played by military bands, British and foreign. After the distribution, &c., the procession will assemble again on the upper terrace, when “God save the Queen” will be performed by all the military bands. 7. The public will bo admitted between the hours of 10 and 12.30 by season tickets or by special tickets to be purchased before the 8th July at 5s. each. On and after that day the price will be 7s. 6d. each. Tickets will be ready for issue on the 30th June. 8. Exhibitors who may not have season tickets may obtain a free ticket of admission upon personal application at the offices in the Exhibition Road, on or before the 8th July. DECOMPOSITION IN COLLODION. BY M. AUG. TESTELIN.* In studying the decomposition of collodion, we began by examining the reciprocal action which each of the con stituent elements of this product exercises upon the others, and we also, though very incompletely, indicated the reactions and the principal products resulting from them. We now proceed to the examination of the changes in pro perty which the collodion undergoes. Collodion, properly so called, that is to say, the simple solution of pyroxyline in ether and alcohol, has never pre sented to us a very striking example of spontaneous decom position. Still, however, we believe that this collodion will ultimately become decomposed when it is not protected from the influence of light. But when the pyroxyline is not chemically pure, and retains traces of the salts which have served in its prepara tion, or of the hyponitric acid which, in some extremely rare cases, is left behind, then the collodion is always decom posed in the course of a very limited space of time. For nitric acid very readily decomposes ether, even without com bining with it: this reaction gives rise to a great number of products, the nature of which varies according to the degree of concentration of the acid, and the temperature at which these reactions are manifested. When the acid is very diluted, or the temperature is very low, there arc formed simply nitric ether and aldehyde; but if the acid be con centrated, there are formed beside, oxalic acid, carbonic acid, acetic acid, formic acid, and formic and acetic ether. These several products are very injurious to the photo graphic preparation, because they always acidify it in the course of a short space of time, and because some of them, as acetic ether for example, cause the pyroxyline to undergo a molecular modification which renders it unfit for photo graphic purposes ; the film given by a collodion thus modi fied is of a dull white colour, and non-adherent to the glass. The gun-cottons of commerce always retain a greater or lesser quantity of free acid. To prove this fact, it is suffi cient to put a specimen of 10 or 20 drachms into a glass- stoppered bottle ; upon opening the bottle at the expiration of a few days, a very strong odour of hyponitric acid escapes, which will be found fixed between the capillary fibres of the cotton, and which repeated washings fail to remove. Now, at the moment when the cotton becomes dissolved in any liquid, these capillary spaces are distended, and even become dissolved, upon disengaging the acids they contain; from which necessarily follows a partial decomposition of the solvent, when the latter is susceptible of being destroyed by oxygenizing bodies as energetic as hyponitric acid. The solution of pyroxyline in ether is then a prime cause of acidification, for beside the substances whose formation we have indicated, the compound ethers also produced at * Continued from p. 222.
