7 1 Intelligence and Miscellaneous Articles. 



operation it passes from violet-black to dark brown), and may then 

 be exposed bo light either under liquid ammonia or under pure 

 water: in either ease the bleaching takes place, though in the latter 

 ease more slowly. 



If the experiment be performed in a test-tube, the bleaching 

 under ammonia requires several hours, under water from one to 

 three days. But if the iodide be formed upon paper, and this 

 paper be exposed to light, washing it constantly with liquid 

 ammonia, the darkening followed by the bleaching requires little 

 more than a minute. In this case, however, the bleaching is not 

 so complete, perhaps because of the influence of the organic matter 

 present. The bleaching appears to depend upon the escape of 

 ammonia ; for if the darkened ammonia iodide is covered with strong 

 liquid ammonia and the test-tube well corked, the bleaching does 

 not take place. 



It became a matter of interest to know whether the darkening 

 under ammonia was accompanied by any decomposition — whether 

 the ammonia took up iodine from the silver salt under the action 

 of light. For this purpose Agl was precipitated with excess of 

 KI, and subjected to a long and thorough washing; it was then 

 exposed for several days to light under strong liquid ammonia. 

 As Agl is not wholly insoluble in ammonia, the mother- water was 

 first evaporated to dryness at a heat but little over ordinary tem- 

 peratures. The traces of residue were washed with water ; and 

 this water gave distinct indications of iodine. The iodine present 

 is in so small a quantity that it may easily be overlooked ; but it is 

 certainly there. The washing given to the Agl was so thorough 

 that it seemed impossible to admit that traces of KI remained at- 

 tached to the Agl ; but in order to leave no room for doubt, the 

 experiment was repeated, using an excess of silver nitrate in 

 making the precipitation, followed by thorough washing. Iodine 

 was still found in combination with ammonia ; and under these 

 conditions there could be no doubt that Agl had been decom- 

 posed. 



When Agl is blackened under ammonia in a test-tube, and the 

 uncorked test-tube is set aside in the dark for a day or two, the 

 Agl assumes a singular pinkish shade. It thus appears that Agl 

 under the influence of ammonia and of light gives indications of 

 most of the colours of the spectrum. Starting with white, it 

 passes under the influence of light to violet, and thence nearly to 

 black : this violet-black substance washed with water passes to 

 brown. The brown substance covered with ammonia and left to 

 itself in an open test-tube becomes pinkish in the dark, yellow in 

 sunlight. These curious relations to colour which we see in the 

 silver haloids, from time to time exhibiting themselves in new ways, 

 seem to give hope of the eventual discovery of some complete 

 method of heliochromy. — Silliinan's American Journal, May 1878. 



Philadelphia, March 25, 1878. 



