792 
COLOUR-TESTS FOR STRYCHNIA, ETC. 
To this cold acid solution of the alkaloid we add a minute 
fragment of bichromate of potash, ferricyanide of potassium, 
permanganate of potash, peroxide of lead, or peroxide of 
manganese. The result is the remarkable development of 
successive transient, or short-lived, colours already described. 
The negative reaction of strong cold sulphuric acid on 
strychnia, followed by the effect of heat on the acid mix¬ 
ture, and this by the peculiar colours produced by the 
application of the colour-developing substances to the cold 
acid mixture, constitute a series of phenomena which afford 
fair promise of proving the means of a successful diagnosis 
of the alkaloids. 
To this work of distinction I now address myself, and in 
order to prepare the way more completely for the work of 
tabular analysis towards which the details given in my 
former communications have been tending, I must again 
revert to the question whether the action of the colour-tests 
on strychnia is, or is not, characteristic, and therefore 
diagnostic. 
This is a question which must have suggested itself to 
every chemist engaged in medico-legal inquiries as of the 
utmost practical importance, and one chemist (Mr. Thomas 
E. Jenkins), having been employed to investigate a case of 
suspected poisoning in which the colour-tests gave indica¬ 
tions of the presence of strychnia, very properly put the 
question to the test of experiment, by applying to a variety 
of active principles, including most of the alkaloids, first, 
colourless concentrated sulphuric acid, and then a fragment 
of a crystal of bichromate of potash. The experiments, 
which were carefully performed, and appear to have been 
strictly comparable one with another, embraced no less than 
fifty alkaloids and active principles, derived from the animal 
as well as the vegetable kingdom, and among them urea and 
uric acid, and cantharidine. More than half of these sub¬ 
stances differed from strychnia in yielding colour when 
treated with sulphuric acid. The smaller half resembled 
strychnia in this respect. But not one of the whole fifty 
gave with the bichromate of potash the characteristic coloured 
reactions of strychnia. Feeling that my time would not be 
w r asted in repeating his experiments, and, if possible, extend¬ 
ing them to substances not included in his list, I possessed 
myself (partly by the kind assistance of Mr. Morson) of all 
the alkaloids and similar active principles which could be 
obtained, and tested them in the same way. To Mr. 
Jenkins's list, some of which I was not able to procure, 1 
succeeded in adding as many as sixteen new substances. 
None of these gave the characteristic coloured reactions ol 
