192 Dr. Inglis’s Extracts from his Prize Essay on Iodine. 
painful to the eyes. When added to water a copious yellow 
precipitation takes place. It contains about two thirds of al- 
cohol; is, when pure, of a clear amber colour; when placed on 
the skin it causes a painful sensation, and excites an inflam- 
matory blush. It, after being boiled, deposits acicular red 
crystals, interspersed with yellow ones of a similar shape. 
Even when much diluted with either water or alcohol, the 
odour and taste of this new cyanide are very pungent. * * * 
I next wished to obtain an iodide of chromium, and this 
I endeavoured to do in the same manner as the chloride is 
got. I mixed adrachm of the hydriodate of potassa with 
half a drachm of the bichromate of potassa, and adding 
fuming sulphuric acid, I distilled; but could not succeed in 
procuring it. In the Lond. and Edinb. Phil. Mag. and Jour- 
nal of Science, (No. 15. September, 1833, vol. iii. p. 235,) 
I observed that M. Peligot describes a compound of chromic 
acid with metallic chlorides. I thought that some analogous 
compound might be formed with the metallic iodides. 
To the bichromate of potassa in solution, and when boiling, 
I added concentrated hydriodic acid in excess. A consider- 
able portion of iodine is evolved, and a thick black compound 
formed, having iodine in excess.. I put a portion of this into 
water, and having boiled it, laid it aside to cool. No crystal- 
lization took place, but the solution was of a decided green 
colour. 
The black compound when dried and broken into pieces 
resembles kino; it is of a dark green colour, with considerable 
lustre, and is friable. The liquid that drained from it gave 
crystals of hydriodate of potash. ‘The action I suppose to be 
as follows : 
Chromic acid. 
Chromic acid. 
Potassium. ... 
Chromate of potassa. 
Oxygen. ...... Water. 
Hydrogen. 
Todine...... Chromate of the iodide 
Potassa..... of potassium. 
I thought that hydrocyanic acid, being of easy decomposi- 
tion, would, when combined with tincture of iodine, give hy- 
driodic acid and a cyanuret of iodine. I allowed them to react 
on each other for some weeks; no deposition was observed, 
but on testing the fluid, hydriodic acid is readily detected. I 
consider this solution as a hydriodate of the iodide of cyano- 
gen.” a eae Oe ae ae 
