730 
COLOUR-TESTS FOR STRYCHNIA, ETC. 
It is evident, therefore, from these experiments, in which 
all the elements were equal, except the quantity of the colour- 
developing substance, that in order to ensure a successful 
and in every way characteristic result, we must operate with 
small quantities of the colour-developing reagents. We must 
use small fragments of the substance in question. If we think 
that we are dealing with such quantities of the alkaloid as 
the two-hundredth of a grain, we should use a fragment not 
exceeding the size of an ordinary pin’s head; and this quan¬ 
tity, small as it is, should be reduced if we have reason to 
believe that the quantity of the alkaloid falls short of this 
small amount. 
1 am now in a condition to give a distinct answer to the 
first of the four questions which I undertook to examine. 
The best mode of applying the colour-tests for strychnia is to 
dissolve the alkaloid in the acid, and then to apply the colour- 
developing substance; and the best form in which the two 
elements of the test—the sulphuric acid and the colour- 
developing reagent—can be used is the acid concentrated 
and the reagent in substance. This appears to be a fair 
inference from the experiments already detailed. But the 
experiments teach something more than this. They demon¬ 
strate the close dependence of the experiments, if they are to 
prove successful and characteristic, on the apportionment of 
the quantity and strength of the reagents. The injurious 
effect of even moderate dilution of the acid with distilled 
water shows that it should be applied as the strong acid, and 
affords a reason for its employment in the most concentrated 
form ; the failure, more or less complete, of a fragment of the 
colour-developing substance, when dissolved in a drop of 
water, contrasted with the perfect success of its counterpart 
when applied in the solid form, is conclusive as to the supe¬ 
riority of the solid to the liquid state; and the perfectly 
characteristic results obtained with the colour-developing 
reagents in small quantity, contrasted with the less character¬ 
istic results yielded by larger quantities, proves that the 
quantity of those reagents which we employ is by no means 
an unimportant element in the success of our experiments. 
But though the combination of a concentrated sulphuric 
acid with the colour-developing reagents in the solid state is 
that which promises the best results and is most likely to 
detect strychnia if present, it does not follow that either the 
moderate dilution of the acid or the use of the colour- 
developing reagents in solution may not give very character¬ 
istic results. Every one, indeed, who has been in the habit 
of showing the colour-tests for strychnia in the class-room 
