ON A NEW TEST FOR BILE AND SUGAR. Il5 
water are now added and the mixture shaken. If choleic 
acid be present, the violet-red colour will appear more or 
less distinctly according to the quantity present. The fol- 
lowing precautions are however requisite to be attended to : 
1st, the temperature must not exceed that mentioned to any 
extent, otherwise the colour, although formed, will be again 
destroyed ; 2nd, the quantity of sugar must not be too large, 
because the colour of the sulphuric solution will become 
dark brown, and sulphurous acid will be formed whereby the 
violet-red colour may be concealed or destroyed ; 3rd, the 
sulphuric acid must be free from sulphurous acid; 4th, if 
the fluid contain albumen, it is best to coagulate this previ- 
ously, since albuminous solutions, although only when very 
concentrated and when heated with sugar and sulphuric 
acid, produce a similar colour. It could not be produced 
with mucous, nor with dilute albuminous solutions, which 
were always altered to a brown colour ; 5th a great excess 
of chlorides, although such is rarely found in animal bodies, 
converted the colour to a brownish red; 6th, if the bile be 
in very small quantity, the fluid should be carefully concen- 
trated on the water-bath, extracted with alcohol, this also 
evaporated to a small volume, and the test applied to the 
cold solution. Sometimes an interval of several minutes is 
required for the production of the colour, especially when 
the sulphuric acid is added very slowly, and conseqently a 
lower temperature is generated. In liquids, where the bile 
is in very small quantity, as in urine, secretions, &c, the au- 
thor has found it requisite to make a spirituous extract, to 
evaporate this nearly to dryness on the water-bath, and 
then to transfer the moist residue into a watch-glass. When 
quite cold, sulphuric acid and a very small quantity of 
syrup are added, so that the temperature of the solution re- 
mains low. In the course of a few minutes, if the most mi- 
nute trace of bile is present, the colour is produced. In this 
reaction, the grape-sugar starch, or in fact any substance 
which is convertible into grape-sngar by sulphuric acid, 
