376 
the water, and on evaporating to dryness more or less of a 
clear bright yellow is obtained. If as little as a grain per 
gallon were present, when dissolved in water with a drop of 
alcohol a clear bright yellow solution would he obtained, 
giving the spectrum 8 . . . made much paler by the addition 
of sulphuric acid, which decolorizes the picric acid, and 
merely shows the colour of the beer itself, which, if one ounce 
had been used, and all the product introduced into the expe- 
riment cell, would not be deeper than 9 . . 10 - - 11 — , or very 
decidedly paler than what would be seen before the addition 
of sulphuric acid, if even less picrid acic than one grain per 
gallon had been present in the beer. 
I have not been able to discover any essential difference 
between the colouring matter of Cocculus Indicus and that 
of liquorice ; and though it would be difficult to prove it in a 
positive manner, yet I think it very probable that a small 
quantity of this colouring matter is the cause of the brown 
colour of chiretta, and of the slightly brown tinge in hops. 
It would, therefore, be impossible to detect Cocculus Indicus 
in porter by means of its colouring matter, even if present in 
far larger amount than is ever likely to be the case. 
Though the detection of turmeric in beer does not neces- 
sarily depend upon the spectrum microscope, yet the method 
employed is so closely related to our present subject that it 
may be well to describe it. The best test for its presence is 
the very strongly fluorescent character of the solution in 
benzol. The alcoholic solution is much less fluorescent. In 
order to be able to detect fluorescence and examine the spec- 
trum of the dispersed light, I have found it very convenient 
to make use of cells about three quarters of an inch deep, 
made out of moderately thick barometer tube, having an 
internal diameter of about one sixth of an inch, cut square 
and polished at one end, and melted up at the other, which 
is fixed into a small brass foot by means of black sealing- 
wax. On introducing a clear solution, covering it with a 
small piece of thin glass, illuminating the tube at the side by 
strong daylight, and looking down the axis, the liquid appears 
quite black, if it be not at all fluorescent, for no light is 
reflected from either the apparatus or the liquid ; whereas, if 
fluorescent, it looks more or less opaque and of a colour 
depending on the nature of the substance. Such tubes can 
easily be placed on the stage of the microscope, and the 
spectrum observed, which in some instances is remarkable in 
showing one or more narrow bright bands. 
In the case of turmeric, a very minute quantity dissolved 
in benzol gives a beautiful more or less blue-green fluores- 
