Sxkv.—ÓOn a modification of the Mercuro-iodide Test. 555 
time with mercury, is decomposed, the organie base present being dissolved 
in a pure or nearly pure state by the alcohol, and the remainder of the com- 
pound precipitated in an iusoluble state. 
The mereuro-iodide of strychnia is, I observe, readily decomposed by 
cold concentrated sulphuric acid, and the addition of the proper oxidizing 
agents to this solution develope the chromatic reaction of strychnine. 
The mercuro-iodide of morphia, when recently formed, gives the morphia 
reaction with ferric chloride, that is, a blué colouration, and what is 
remarkable, this colour is not evanescent as is that which is got by operating 
with this test upon a solution of morphia, the colour being maintained for 
several days, but it is destroyed by bi-chloride of mercury; that it is 
destroyed in this way explains in part the reason why solutions of morphia 
so weak as to require the aid of mereurie chloride in conjunction with mer- 
curic iodide of potassium give a precipitate which does not colour blue in 
presence of ferric chloride. 
The mercuro-iodide of digitalin, which I believe I have produced, was 
especially sought for as an insoluble substance, because tannic acid is 
known to form an insoluble compound with this principle; this mercuro- 
salt has a great tendency to pass through filter paper ; it is easily and 
completely soluble in alcohol, also in ether and iodide of potassium, and 
manifests a distinct pink colouration when placed in contact with cold 
. strong sulphuric acid. 
Adverting to particulars in the case of the behaviour of potassic iodide 
with thealkaloids, [have to state that the strychnia and narcotina compounds 
with mereury and iodine are but feebly soluble in it. I should state that 
albuminous compounds of this nature are readily distinguished from alka- 
loidal ones by their insolubility in alcohol or ether, only the mercury and 
iodine dissolving, a viscid mass being left, as the albumen, etc. 
I have now to relate a few facts which, as being connected with the 
subject in hand, and arrived at collaterally with its prosecution, I think I 
am at liberty to do. 
The remarkable aptitude to form insoluble compounds with iodides of 
the alkaloids which mercuric iodide displayed to me during my pursuit of 
the subject of this paper, led me to seek substitutes for these organic iodides 
among our metallic ones, and this under the hope that the exact position of 
the alkaloids themselves, in regard to the metallic bases, might, in the case 
of success, be easier to define than it is now. In this I believe I have been 
successful ; at any rate, I find that the iodides of silver, thallium, and lead, 
combine with iodide of mercury. The thallium and lead compounds of this 
kind do not manifest any great or notable difference in colour from that of 
their simple iodides. A careful comparison however, of the salts side by 
