gi-a 



NOTES AND QUERIES. 



[No. 281. 



precipitate. Call this precipitate No. 1. Then take the 

 liquid and add to it cautiously, and shaking it well after 

 each addition, some nitrate of silver : this throws down a 

 precipitate, undistinguishable from the first, of yellow 

 iodide of silver ; call this precipitate No. 2. But if careful 

 in the addition to let the precipitate settle each time, 

 Mr. Reade will find that on a sudden a different coloured 

 precipitate will fall down, much lighter in colour than the 

 former, and soluble in ammonia ; whereas the precipitates 

 No. 1. and No. 2., if the experiment has been carefully 

 performed, are almost completely insoluble, except perhaps 

 the last portions of No. 2., which may possibly carry down 

 some portions of bromide, from there not being enough 

 iodide of potassium left in the liquid to decompose the 

 last drop of nitrate. Separate then the liquid once more 

 by filtration, and wash the precipitate with distilled 

 water, and having added the washings to the liquid, pre- 

 cipitate it completely with nitrate of silver. We thus 

 obtain a precipitate which has every property of, and 

 which I assert to be, pure bromide of silver, and if the 

 experiment has been carefully performed, will have almost 

 the exact weight of the bromide first added to the iodide 

 of potassium. 



In regard to the colour produced on the paper, to which 

 he alludes in his last letter, that merely depends on the 

 degree of washing to which the iodized paper has been 

 subjected ; as, if we wash only a little, the paper will be 

 almost white when dry, but if well washed it will be of a 

 fine yellow colour. I have also a few words to say on the 

 subject of positives in answer to Dk. Diamond, with 

 whom I quite agree in thinking that there is the greatest 

 probability that many owe their fading to salts contained 

 in the mounting card ; but also I feel certain that there are 

 two very sure causes, viz. gases which act on the picture, 

 especially when their action is aided by a damp atmo- 

 sphere, and sulphur set free in the paper by the action of 

 free acids on the hyposulphite; and secondly, imperfect 

 washing of the proof, thereby leaving hj'posulphite of 

 soda and silver in the paper. ' For the latter of these we 

 have our remedy in simply well washing in many waters, 

 and lastly in warm water ; but for the others I know of 

 no sure process yet proposed, but I think perhaps that one 

 I can here give will meet the difficulty in many points. 

 It is a modification of the process of Monsieur Le Gray, 

 Take paper, which we will suppose plain, salted with 

 chloride of ammonium, and sensitise it on a bath of nitrate 

 of silver, 20 to 25 per cent. Then print it very strongly, 

 so that paying no attention to the deep shades, which may 

 without risk be allowed to become green, the lightest 

 parts of the picture are even twice or three times as 

 strong as they are wished to be ultimately. The proof is 

 now to be placed in pure water, where most of the nitrate 

 will dissolve out (this bath, after being used some time, 

 may be precipitated by some common salt to recover the 

 silver as chloride). Then place the proof in a weak so- 

 lution of common salt, say two per cent., and then place 

 it in the following bath : 



Terchloride of gold - - - - 15 grs. 



Hydrochloric acid - . - « 6 drs. 



Distilled water ----- 2 pints. 

 Here the proof must be carefully watched till the details 

 of the deep shades are well out, and it is then immediately 

 to be taken out and placed in a bath of carbonate of soda, 

 half an ounce to the pint of distilled water. Bubbles will 

 here appear at the surface of the proof, and the acid will 

 be neutralised. It is now to be placed for a minute in a 

 bath of clean water, and then placed in a bath prepared 

 as follows : 



Hypo. - - - - - - 5 oz. 



Water --.... i pint. 



Liquor ammonise - - - - ^ oz. 



This bath should have a piece of glass kept over it to 

 prevent the ammonia from flying off. Here the whites of 

 the proof become beautifully transparent, while the de- 

 tails appear even in the deepest shades. The proof is now 

 to be placed in new 20 per cent, hypo., composed as 

 before with ammonia ; after remaining in the other bath 

 till quite disgorged, and having remained there at least a 

 quarter of an hour, to be finally washed in many waters, 

 and lastly in tepid water. The operator must not be 

 frightened at the number of baths here proposed, as surely 

 the production of really beautiful, and quite stable, pho- 

 tographic positives, is a desideratum to be purchased at 

 any trouble; and, after all, if the baths be ranged one 

 beside the other on a table, I think no time is really lost. 

 Having then washed and dried the proof, cut it to the 

 size wished, and then gum it at the back with a thin so- 

 lution of dextrine, and place it on a piece of drawing- 

 paper ; then polish it with a varnish made as follows : 



Venice turpentine - . - - i part. 



White wax ----- 6 parts. 



Melt these together, and add spirits of turpentine, so that 

 when cold the varnish shall have the consistence of thick 

 cream. Take some of this on a bit of flannel and rub it 

 well into the face of the proof, and after five minutes 

 polish it with a bit of clean flannel till it looks clear and 

 well defined ; then cut down the paper to the size of the 

 drawing, and mount it on a card. 



By this means we first recover all the free nitrate, 

 which by the ordinary processes is wasted ; we next in- 

 sure by the saline bath the absence of nitrate of silver ; 

 we then colour the proof with the gold solution ; we then 

 neutralise the acid, and then place the proof in a strongly 

 alkaline solution of hypo., which disgorges it much more 

 rapidly than ordinary hypo. ; and lastly, in a second bath 

 of the same, which ensures the complete removal of every 

 trace of the double hyposulphite of soda and silver which 

 might remain from the last bath ; and then we inclose 

 each fibre of the paper in a case, as it were, of varnish, 

 insoluble and impervious, and which at the same time 

 gives a beauty to the proofs which, in my estimation, 

 surpasses that of the albumen. F. Maxwell Lyte. 



Pau. 



Dr. Diamond's Formula. — I shall personally feel much 

 obliged, if you (perhaps in " Notices to Correspondents ") 

 would acquaint me with the quantities of iodide and of 

 bromide which Dr. Diamond recommends to be used in 

 the paper process. I would not give this trouble, but 

 having looked over the whole of the Numbers of " N. & Q." 

 from the communication he first made, " On the Sim- 

 plicity of the Calotype Process," and not having found it, 

 and wishing to try that plan, as it is said to give the 

 various gradations in foliage, so much to be desired, I 

 should, as I have before said, be exceedingly obliged. 



I have tried a great many highly spoken of formulae 

 for the paper, wax-paper, &c., but have found Du. Dia- 

 mond's first the best of all. Mr. Stewart's is very 

 sensitive and beautiful in the various details, but, in my 

 hands, does not come out so pure as is desirable, and in- 

 deed requisite. T. L. Merbitt. 



[Having submitted this Query to Dr. Diamond, we 

 have been favoured with the following reply : 



" If Mr. Merritt will mix 45 grains of nitrate of 

 silver, dissolved in a little distilled water, with 45 grains 

 of iodide of potassium similarly dissolved, he will obtain 

 iodide of silver. Then, in the like manner, let him 

 dissolve separately 38 grains of nitrate of silver and 

 25 grains of bromide of potassium, and, mixing the solu- 

 tions, bromide of silver will be the result. Now, having 

 washed and mixed these two precipitates, put them to- 



