Dr. Inglis’s Extracts from his Prize Essay on Iodine. 191 
hand, it will retain some part of that heat for a minute or 
more; but in this experiment the heat vanishes in a mo- 
ment. It is not, therefore, heated glass which we feel, but 
heat which has come through the glass, in a free or radiant 
state. 
XXXVII. Extracts from a Prize Essay on Iodine. By James 
7 Ineuis, M.D. 
[Continued from p. 20, and concluded. ] 
I MENTIONED before that Serullas had proposed iodic 
acid as a test for the vegetable alkalies. I find that hydriodic 
acid may be used as such also. To the sulphate of quinine 
I added in solution a few drops of sulphuric acid, so that the 
sulphate might be soluble in water. I next added a solution 
of hydriodate of potassa; instantly there was a yellow preci- 
pitation, which became gradually ofa greenish colour. I added 
more hydriodate, and the precipitation of yellow iodide of 
quinine still took place, which finally became of a reddish 
brown colour. I have not examined this compound, but call it 
iodide of quinine, the hydriodates being all soluble; and I do 
not see how it could be an iodate. 
I find also that the hydriodate of potassa throws down a 
white precipitate with tincture of capsicum. I cannot deci- 
dedly say that this acid is as good a general test as the io- 
di * * * * 
I wished to obtain a compound of cyanogen with iodine, 
and for this purpose made a solution of bicyanuret of mer- 
cury in water, which I added to an alcoholic solution of io- 
dine; immediately the red biniodide of mercury fell, and the 
action I thought to be this: 
L atom of ‘) Cyanogen. Bicyanuret 
bicyanuret | Cyanope eae of iodine. 
of mercury. | Mercury. 
\ ‘ 
3 atoms Iodine. . 
of Iodine. . Biniodide 
iodine. J  Iodine.. of mercury. 
If too much cyanuret of mercury be added, then all the 
precipitation is red. But if there be only sufficient, then a 
lightish brown powder in crystals falls. I boiled and strained 
off the supernatant liquor from the biniodide of mercury, and 
Jaid it aside to crystallize; but this could not be effected. 
The liquid is exceedingly pungent, and exhales a vapour 
