483 
COLOUR-TESTS FOR STRYCHNIA, ETC. 
the bichromate of potash, when brought into contact with 
the acid solution of strychnia, yields a blue colour at the 
point of contact, which colour quickly disappears on mixing 
the two liquids with each other. When, therefore, we make 
use of the colour-developing tests in substance, we obtain 
highly characteristic and lasting colours ; but when we use 
them in solution, one evanescent colour only. It is true that 
if to the mixture of the acid solution of strychnia with the 
watery solution of bichromate of potash we add a drop or 
two of strong sulphuric acid, we obtain a blue liquid, which 
undergoes the characteristic changes of colour ; but the im¬ 
portant fact remains that, other things being equal, solution 
in water greatly impairs the delicacy of the colour tests. If 
in this comparative experiment we substitute for the bichro¬ 
mate of potash the other soluble colour-developing substances 
—the ferricyanide of potassium and the permanganate of 
potash—we obtain the same results. 
The injurious effect of dilution with water upon the colour 
tests is differently shown in the following comparative expe¬ 
riment :—I placed on a porcelain slab four equal drops of 
the same solution of strychnia in strong sulphuric acid. To 
two of the four drops I added a drop of distilled water, and 
then to all the drops, diluted and undiluted, equal minute 
fragments of the bichromate of potash. The undiluted drops 
gave highly characteristic results—the usual succession of 
rich strychnia-colours; while the diluted spots gave no indi¬ 
cation of the presence of strychnia, but merely a yellow 
solution. The same comparative experiment gave the same 
results with the ferricyanide of potassium, the permanganate 
of potash, and the peroxides of manganese and lead. The 
ferricyanide gave a lemon-yellow T , and the permanganate of 
potash a pink, solution; while the peroxides of manganese 
and lead imparted a neutral tint. In multiplying this class of 
experiments I have now and then obtained a characteristic 
reaction, and occasionally an evanescent streak of blue ; but 
these were exceptional cases. 
The strength of the solution of strychnia in sulphuric acid 
used in both these series of experiments was one grain in 
200 drops ; and as the same pipette was used in preparing 
the solution and in the experiments, each drop contained the 
two-hundreth of a grain of strychnia. 
Now these experiments, though they cannot be taken to prove 
that the dilution with water of the acid solution of the alka¬ 
loid, or the application of the colour-developing substance in 
solution, must be fatal to the success of the colour-tests, 
whatever the quantity of the alkaloid or of the acid, they do 
