490 M. Carey Lea — Allotropic Forms of Silver. 



low product, however, is only an allotropic form of silver, but 

 it lias all the color and brilliancy of gold, a fact which was 

 apparent even in the minute specks hitherto obtained. 



By the means presently to be described, silver can be con- 

 verted wholly into this form. It is a little curious that its 

 permanency seems to depend entirely on details in the mode 

 of formation. I found many ways of obtaining it, but in a few 

 months the specimens preserved changed spontaneously to 

 normal silver. This happened even in well closed tubes. The 

 normal silver produced iu this way is exquisitely beautiful. 

 It has a pure and perfect white color like the finest frosted 

 jewelers' silver, almost in fact exceeding the jeweler's best 

 products. I found, however, one process by which a quite 

 permanent result could be obtained. Specimens made by it in 

 November of 1886 are now, at the end of thirty months, un- 

 changed. 



In forming the blue product which I have called A, very 

 concentrated solutions were necessary. C on the contrary is 

 best obtained from very dilute ones. The following propor- 

 tions give good results. 



Two mixtures are to be prepared : No. 1, containing 200 c. c. 

 of a ten per cent solution of silver nitrate, 200 c. c. of twenty 

 per cent solution of Rochelle salt and 800 c. c. of distilled 

 water. No. 2, containing 107 c. c. of a thirty per cent solution 

 of ferrous sulphate, 200 of a twenty per cent solution of Ro- 

 chelle salt and 800 of distilled water. The second solution 

 (which must be mixed immediately before using only) is poured 

 into the first with constant stirring. A powder, at first glitter- 

 ing red, then changing to black, falls, which on the filter has a 

 beautiful bronze appearance. After washing it should be 

 removed whilst in a pasty condition and spread over watch 

 glasses or flat basins and allowed to dry spontaneously. It 

 will be seen that this is a reduction of silver tartrate by 

 ferrous tartrate. The' metallic silver formed by reduction 

 with ferrous citrate and ferrous tartrate is in an allotropic 

 condition ; with ferrous oxalate this result does not seem to be 

 produced. 



Although the gold-colored silver (into which the nitrate used 

 is wholly converted) is very permanent when dry, it is less so 

 when wet. In washing, the filter must be kept always full of 

 water : this is essential. It dries into lumps exactly resembling 

 highly polished gold, especially the surfaces that have dried in 

 contact with glass or porcelain. For this substance has in a 



which he presented to the French Academy with one of his papers. To his great 

 disappointment he did not succeed in repeating these experiments in Paris, with 

 more than an infinitesimal result. All gold in his opinion had been originally 

 silver, and this belief, he affirms, is universal amongst Mexican miners. The 

 book has for title " Les Metaux sont des Corps composes." 



