COLOUR-TESTS EOR STRYCHNIA, ETC. 
431 
change of colour when treated with sulphuric acid. The 
statement made by Dr. Taylor that in giving a blood-red 
colour with strong nitric acid and a rich carmine tint with 
sulphuric acid, curarina resembles brucia, is evidently founded 
in error. The reaction of brucia with nitric acid is correctly 
stated, but brucia certainly does not yield a carmine tint with 
sulphuric acid. It is one of the list of substances grouped 
together in my tables as characterised by a negative action 
with sulphuric acid; and Mr. Jenkins, in the table which I 
sent round in my last lecture, attributes to it a negative 
reaction with sulphuric acid (see Chemical News , Oct. 6, 18(30); 
and here I may observe that it is one of the obvious advan¬ 
tages of tables such as these, that they place before us the 
common and familiar reactions of the substances which they 
comprise, in such an orderly and methodical way as greatly 
to assist the memory, and to guard against such inadvertent 
statements as this of Dr. Taylor’s respecting brucia.* 
On referring to the tests for brucia itself, as given at page 
801 of Dr. Taylor’s work on Poisons from which I have been 
quoting, I find it stated that “ strong sulphuric acid colours 
brucia of a rich rose-pink colour.” This colour differs widely 
from the rich carmine (belle teinte carminee) of Bernard, said by 
Dr. Taylor to be characteristic of the same reaction, and 
I think that I may venture to state of it that it is not the 
reaction of pure brucia with pure sulphuric acid. Indeed, it 
is not the reaction of specimens of brucia of ordinary purity 
with specimens of sulphuric acid of similar purity. To obtain 
a rich rose-pink with brucia, we must use a specimen of 
sulphuric acid containing an unusual quantity of nitric acid, 
and I have no doubt that the unintentional use of such an 
acid gave rise to this misapprehension. I may add, that to 
specimens of brucia of fair average quality, sulphuric acid 
will impart a very slight tint (rose-colour or buff), and a still 
slighter tint to the solution of the alkaloid in the acid. But 
a rich rose-pink colour is an evidence of the presence of 
nitric acid, and is readily developed in the solution of the 
alkaloid in sulphuric acid by a short exposure to the vapour 
of nitric acid. 
I could not have accomplished the object I have in view 7 of 
vindicating the colour-tests for strychnia from unfounded 
objections, without tracing this particular objection to its 
true source. It was necessary to show that the reactions of 
the rare alkaloid, curarina, differ essentially from those of 
strychnia, and of brucia, w hich is associated with strychnine 
in more than one of the plants that yield it; and I could not 
* These tables will be referred to more particularly in my next paper. 
