254 



NOTES AND QUERIES. 



[No. 229. 



PHOTOGRAPHIC CORRESPONDENCE. 



A Prize for the best Collodion. — Your " Hint to the 

 Photographic Society" (Feb. 25) I much approve of, 

 but I have always found more promptness from indi- 

 viduals than from associated bodies ; and all photo- 

 graphers I deem to be under great obligations to you 

 in affording us a medium of communication before a 

 Photographic Society was in existence. During the 

 past month your valuable articles, from some of our 

 most esteemed photographists, show that your pages 

 are the agreeable medium of publishing their re- 

 searches. 1 would therefore respectfully suggest that 

 you should yourself offer a prize for the best mode of 

 making a good useful collodion, and that that prize 

 should be a complete set of your valuable journal, 

 which now, I believe, is progressing with its ninth 

 volume. You might associate two independent names 

 with your own, in testing the merits of any sample 

 supplied to you, and a condition should be that the 

 formula should be published in " N. & Q." Your ob- 

 servations upon the manufacturers of paper, respecting 

 the intrinsic value of a premium, are equally applicable 

 to this proposition, because, should the collodion pre- 

 pared by any of the various dealers who at present ad- 

 vertise in your columns be deemed to be the most satis- 

 factory, your sanction and that of your friends alone 

 would be an ample recompense. I would also suggest 

 that samples sent to you should be labelled with a 

 motto, and a corresponding motto, sealed, should con- 

 tain the name and address, the name and address of the 

 successful sample alone to be opened : this would effec- 

 tually preclude all preconceived notions entertained by 

 the testing manipulators who are to decide on the 

 merits of what is submitted to them. 



A Reader of " N. & Q." and a Photographer. 



[We are obliged to our correspondent not only for 

 the compliment he has paid to our services to photo- 

 graphy, but also for his suggestion. There are many 

 reasons, and some sufficiently obvious, why we should 

 not undertake the task proposed ; and there are as ob- 

 vious reasons why it should be undertaken by the 

 Photographic Society. That body has not only the 

 means of securing the best judges of such matters, 

 but an invitation from such a body would probably 

 call into the field of competition all the best photo- 

 graphers, whether professional or amateur.] 



Double Iodide of Silver and Potassium. — I shall feel 

 greatly indebted to you, or to any correspondent of 

 " N. & Q.," for information as to the proportion of 

 iodide of silver to the ounce of water, to be afterwards 

 taken up by a saturated solution of iodide of potassium, 

 and converted into the double iodide of silver and 

 potassium. 



I generally pour all waste solution of silver into a 

 jar of iodide of potassium solution ; and last year, 

 having washed some of the precipitated iodide of silver, 

 I redissolved it in a solution of iodide of potassium of an 

 unknown strength. Paper prepared with this solution 

 answered very satisfactorily, kept well after excitation, 

 and was very clear and intense; but this was purely 

 accidental : and if you can tell me how to insure like 

 success this summer, without a series of experiments, 



for which I have but little time just now, the inform- 

 ation will be very acceptable to me, and probably to 

 many others. 



I excite my paper with equal proportions of satu- 

 rated solution of gallic acid and aceto-nitrate of silver, 

 one or two drops of each to the drachm of distilled 

 water. I always plunge the bottle of gallic acid solu- 

 tion into hot water when first made, which enables it 

 to take up more of the acid ; on cooling, the excess 

 crystallises at the bottom. This ensures an even 

 strength of solution : it will keep any length of time, 

 if a small piece of camphor be allowed to float in it. 



J. W. Walrond. 



Wellington. 



[The resultant iodide from fifteen grains of nitrate 

 of silver, precipitated by means of the iodide of potas- 

 sium, will give the requisite quantity of iodide for 

 every ounce of water ; or about twenty-seven grains 

 of the dried iodide will produce the same effect. It 

 is however far preferable, and more economical, to 

 convert all waste into chloride of silver, from which 

 the pure metal may be again so readily obtained. 

 Iodide of silver, collected in the manner described by 

 our correspondent, is very likely to lead to disappoint- 

 ment.] 



Albumenized Paper. — I have by careful observation 

 found that the cause of the albumen settling and dry- 

 ing in waving lines and blotches on my paper, arose 

 from some parts of the paper being more absorbent 

 than others, the gelatinous-like nature of the albumen 

 assisting to retard its ready ingress into the unequal 

 parts, and, consequently, that those places becoming 

 the first dried, prevented the albumen, still slowly 

 dripping over the now more wetted parts, from running 

 down equally and smoothly, thereby causing a check 

 to its progress ; and as at last these became also dry, 

 thicker and irregular patches of albumen were de- 

 posited, forming the mischief in question. 



The discovery of the cause suggested to me the 

 propriety of either giving each sheet a prolonged float- 

 ing of from ten to fifteen minutes on the salted albu- 

 men, or until every part had become fully and equally 

 saturated ; or, as a preliminary to the floating and 

 hanging up by one corner on a line, of putting over- 

 night between each sheet a damped piece of bibulous 

 paper, and placing the whole between two smooth 

 plates of stone, or other non-absorbent material. 



Either method produces equally good results ; but 

 I now always use the latter, thereby avoiding the 

 necessity of otherwise having several dishes of albu- 

 men at work at once. Henrv H. Hele. 



Cyanide of Potassium (Vol. ix., p. 230.) I have 



for a long time been in the habit of using a solution of 

 the above-named substance for fixing collodion positives, 

 because the reduced silver has a much whiter appear- 

 ance when thus fixed, than when the hyposulphite of 

 soda is used for the same purpose ; but I cannot quite 

 agree with Mr. Hockin that it is equally applicable to 

 negatives, though in many cases it will do very well. I 

 find the reduced metal is more pervious to light when 

 fixed with the cyanide solution, particularly in weak 

 negatives. Lastly, I find that a small quantity of the 



