COLOUR-TESTS FOR STRYCHNIA, ETC. 407 
Before I proceed to discuss these questions, I must premise 
that the most of the specimens of strychnia and of the other 
alkaloids on which 1 experimented were supplied to me by the 
Messrs Morson. The majority of them were presented to me 
by them as specimens of approved purity; the remainder were 
procured from them from time to time. For a few specimens 
I was indebted to my colleague, Professor Bentley. Several 
of the alkaloids in Mr. Morson’s series are crystals of large 
size and great beauty, and the remainder are evidently of the 
best quality. Of some of the more important alkaloids, such as 
strychnia, brucia, and aconitina, I have more than one speci¬ 
men. When the results which I obtained did not happen to 
agree with the descriptions of approved authorities, I made 
experiments with other specimens, and endeavoured to ascer¬ 
tain the reason of the discrepancy. I may add that the re¬ 
sults stated in these papers are based upon several hundreds 
of experiments carefully performed, and the reactions noted 
down at the time. In order to guard against any possible 
misapprehension, it may be well to state that the term “colour- 
testsis used throughout these communications in the sense 
of tests producing a series, or succession, of colours ; and that 
it is further restricted to the chemical colour-tests as dis¬ 
tinguished from the galvanic colour-test. 
1. Form and mode of application of the Colour-tests .—The 
chemical colour-tests for strychnia consist in the peculiar 
reactions of the alkaloid with sulphuric acid ,plus one or other 
of the following substances :—The bichromate of potash and 
the ferricyanide of potassium, and the peroxides of manganese 
and lead. To these may be added, as less generally recognised, 
the chromate of potash and chromic acid; and it may be well 
to state that the chromates of soda and ammonia yield 
characteristic reactions. 
To the four recognised colour-tests—the bichromate of 
potash, the ferricyanide of potassium, the peroxide of man¬ 
ganese, and the peroxide of lead—I propose to add the per¬ 
manganate of potash. 
In order fully to appreciate the action of these tests, it 
should be borne in mind— 
]. That sulphuric acid, of the strength and degree of purity 
commonly met with in the shops, when added to, and mixed 
with ordinary specimens of strychnia, does not produce in 
them any change of colour. 
2. That the acid does not occasion any change of colour in 
the peroxide of manganese or the peroxide of lead. 
3. That the acid, when mixed with a fragment of the 
