3 77 
cence, with no special (lark or bright bands. Half an ounce 
of the suspected beer should be evaporated to so small a bulk 
that it may occupy only about half an inch in the depth of 
a test tube half an inch in diameter, and an equal amount of 
benzol added to it, with about an equal quantity of alcohol ; 
since without this last the globules of benzol collect together 
with extreme slowness. After well agitating the whole, the 
tube should be set aside until the benzol has collected at the 
top, as a clear solution, which must then be introduced into 
one of the cells just described, by means of a pipette. In 
the case of pure beer, this solution is of a faint yellow colour, 
but is scarcely at all fluorescent. If no more than one grain 
of turmeric has been added to a gallon of beer, the fluores- 
cence is so strong that it could not be seen to greater 
advantage, and even as little as one tenth of a grain per 
gallon may be detected with confidence. 
It will thus be seen that the spectrum method of study 
serves to throw considerable light on some of the changes 
that take place in the process of brewing, and rvould also 
enable us to detect the presence of some adulterations ; but, 
at the same time, it would always be requisite to bear in 
mind that it is possible that some of th£ colouring matters I 
have described may themselves become altered when kept in 
solution for a considerable time. 
Adulteration in Drugs, fyc. — Mustard. 
I now proceed to describe the detection of adulteration in 
a variety of substances. Having just explained the method 
to be employed when the presence of turmeric is suspected, it 
may perhaps be well to mention now all that need be said on 
that substance. Its presence may easily be detected in nearly 
all the ground mustard sold in the shops ; and, as far as I 
am able to judge from the intensity of the fluorescence, the 
amount varies from about one third to one half per cent. 
The natural seeds contain a yellow colour soluble in water, 
which is the same as that found in many yellow leaves ; 
another yellow colour, insoluble in water, but soluble in 
alcohol, which corresponds with the xanthophyll of yellow 
leaves ; and there is also often present a small quantity of 
chlorophyll, in the imperfectly ripe seeds. The powdered 
mustard should be digested in alcohol, about an equal quantity 
of water added, and the solution filtered. On agitating with 
benzol this rises to the top, with the colour of the turmeric 
in solution, which can be easily detected by its strong green 
fluorescence. Chlorophyll, if present, would give a red fluor- 
escence, and by transmitted light a spectrum with •well- 
marked absorption bands. 
