238 COLOUR-TESTS FOR STRYCHNIA, ETC. 
later coated with a fine, black, pulverent deposit of metallic 
antimony. Arsenic is not thus deposited, or there is only a 
- slight discoloration of the tin, after some days. In the absence 
of antimony, the surface of the tin, after several days, presents 
merely a crystalline appearance. 
The process above described is sufficiently delicate for all 
practical purposes. As a proof of this, I may mention that it 
enabled Dr. Miller, Dr. Edwards, of Liverpool, and myself, to 
procure good evidence of antimony in a liver containing not 
more than ]-l60th of a grain in two ounces of its substance. 
We also employed the process successfully for the detection of 
free and absorbed antimony, when existing in very small 
quantity, in sixteen separate analyses of the viscera. Three of 
the bodies, from which the viscera were taken, had been 
buried for a period of from six to nine months. 
ON THE COLOUR-TESTS EOR STRYCHNIA, AND THE 
DIAGNOSIS OF THE ALKALOIDS. 
Being the substance of part of the Croonian Lectures for 1861, 
delivered at the Boyal College of Physicians. 
By William A. Guy, M.B. Cantab., Fellow of the College, 
and Professor of Forensic Medicine, King’s College, London. 
(Continued from vol. xxxiv, p. 732.) 
In the first series of experiments I placed side by side two 
rows of porcelain slabs, twenty in each row; on each slab of 
the one row, a drop of the acid solution, and a fragment of 
the peroxide of manganese; and on each slab of the other 
row, an equal drop of the same solution, and an equal frag¬ 
ment of the peroxide of lead. I stirred the several fragments 
into the several drops of acid in the same way, and obtained 
highly characteristic results with the peroxide of lead in every 
instance ; but with the peroxide of manganese there were 
three instances in which the first colour was imperfectly 
developed. In the other cases the first colour was very dis¬ 
tinctly produced. But the action of the peroxide of lead was 
certainly more speedy and more delicate, as well as more 
constant, than that of the peroxide of manganese. The solitary 
advantage possessed by the peroxide of manganese consisted 
in the greater permanence of the third colour. But as this 
advantage is very small, as compared with the quickness, 
delicacy, and certainty of the action of the peroxide of lead, 
in developing the first and most characteristic of the strychnia- 
