796 COLOUR-TESTS FOR STRYCHNIA, ETC. 
tinguished from esculine by giving a negative result, while 
esculine assumed a distinct yellow colour. In the same way 
narcotine was detached from its group of three, and naph¬ 
thaline from its group of two. Again, morphia was dis¬ 
tinguished by the rich orange hue given by the acid, together 
with the red fumes of nitrous acid; and brucia was effectually 
distinguished from strychnia by the intense red of the former 
contrasting with the faint tinge of red imparted to ordinary 
specimens of the latter. For the next eliminating test I have 
selected sulphuric acid followed by a solution of permanga¬ 
nate of potash, in the proportion of 10 grains of the salt to 
3 j of water. The effect of this test on strychnia was to 
develop its characteristic colours, strongly contrasted with 
the altogether different colours given with brucia, and still 
more with the brown colour imparted to morphia, followed 
by the bleaching of the liquid. This same test divided the 
somewhat unmanageable group of four at the top of the table 
(cantharadine and asparagine, and caffeine and cinchonine) 
into two small groups of two each. In the first two the 
immediate effect of the permanganate was a red-brown 
colour; in the second, a pink. Picrotoxia and santonine 
gave the same colour (pink), and remained undistinguished. 
The last and ultimate work of elimination was effected by 
means of heat applied to the active principle in its solid state. 
Cantharadine was found to be wholly dissipated by the 
heat of the spirit lamp, while asparagine gave a bulky 
carbonaceous deposit. And caffeine was found to present 
the same difference when compared with cinchonine. Lastly, 
picrotoxia was found to be distinguished from santonine by 
the bulky carbonaceous residue with the first and the scanty 
deposit of carbon with the second. 
Having by this succession of tests obtained a clue to the 
active principle with which we have been dealing, we should 
proceed to identify the substance indicated by the table 
through its own characteristic tests. 
In the second division of the one large table of elimination, 
or that which comprises active principles coloured by contact 
with cold sulphuric acid (Table II), the same succession of 
tests is employed. Cold, concentrated sulphuric acid at once 
separates this group of seventeen into eight smaller groups, 
of one, two, or six; and the subsequent warming and heating 
of the coloured acid solutions occasions such marked differ¬ 
ences of colour as to nearly complete the work of elimination. 
But I have added columns showing the effect of nitric acid, 
and of the solution of permanganate of potash. The appli¬ 
cation of heat to the alkaloids themselves did not prove 
necessary to the work of elimination. 
