481 
Extracts from British and Foreign Journals. 
ON THE COLOUR-TESTS FOR STRYCHNIA, AND THE 
DIAGNOSIS OF THE ALKALOIDS. 
Being the. substance of part of the Croonian Lectures for 1861, 
delivered at the Royal College of Physicians , 
By William A. Guy, M.B. Cantab., Fellow of the College 
and Professor of Forensic Medicine, King’s College, London. 
(Continuedfrom p. 408.) 
Having shown that strychnia when treated with sulphuric 
acid undergoes no change of colour, and that the several 
tests (the peroxide of lead, the peroxide of manganese, the 
bichromate of potash, the ferricyanide of potassium, and the 
permanganate of potash) undergo either no change of colour, 
or such changes only as do not admit of being confounded 
with the strychnia colours, I proceed to consider in succession, 
1. The best way of applying the colour-tests; 2. The best 
order in which to use the reagents; and 3. The best form in 
which to apply the colour-developing test. 
1. The colour-tests are best shown on slabs of glass coated 
with white arsenical enamel by the process technically called 
“ flashing.”* But the lids of porcelain crucibles, or v 7 hite 
plates, or fragments of any white ware, will answer the purpose 
very well. If the enamelled glass is used, the tests should be 
applied to the glass-surface. In using the tests scrupulous 
cleanliness should be observed, and the sulphuric acid and 
colour-developing tests, if in solution, are best applied by the 
drop-bottle, as more delicate, and more secure from any soil, 
than the common glass-rod. For mixing the several sub¬ 
stances together a glass spatula is to be preferred to a glass 
rod. 
2. The order in which the sulphuric acid and the colour- 
developing tests should be applied is easily determined by one 
or two simple considerations. Good and characteristic re¬ 
sults may be obtained by mixing the sulphuric acid with the 
colour-developing tests, and then adding a crystal of strychnia. 
When so mixed with small quantities of the peroxide of 
manganese and lead, the acid solution has a neutral tint, which 
* I have been in the habit of using this enamelled glass for colour-tests 
for several years. Oblong slabs of the kind described in the text may be 
obtained at Powell’s Glass Works, Whitefriars. 
XXXIV. 
36 
