38.2 
are in distinctly different positions. The production of the 
fluorescent colour is apparently due in both cases to deoxidi- 
zation, for even proto-sulphate of iron has the same effect as 
sulphite or hyposulphite of soda. If too much bromine be 
added, this change does not take place ; but by a little care 
a small amount of the petals of the yellow crocus could be 
detected in a considerable quantity of saffron. The presence 
of safflower might be recognised by a similar process, but not 
so decidedly. After adding bromine and ammonia it remains 
distinctly yellow, but gives no absorption-band; whereas pure 
saffron is thereby quite decolorised. 
Aloes. 
I have tried a number of experiments in order to ascertain 
whether it would be possible to detect the adulteration of the 
soccotrine aloes with the hsepatic, but have not yet succeeded 
in discovering any satisfactory method. It appears as if both 
contain the same general colouring matter, but the soccotrine 
a second in addition. When ammonia is added to the alco- 
holic solutions, the soccotrine gives a more orange colour than 
the hsepatic, and the green part of the spectrum is more 
absorbed, so that when compared side by side the spectra 
are — 
Soccotrine . . . 4 6§ — 
Haepatic . . . . 6^ — 
It would, therefore, be possible to distinguish them from one 
another, or to detect the soccotrine in the haepatic, which is, 
however, the reverse of what would be likely to occur, since 
inferior things are not often adulterated with better. 
Adulterations by means of Cochineal and Magenta. 
Cochineal may be best detected in the tincture of roses by 
adding to the aqueous solution bicarbonate of ammonia and 
sulphite of soda. This changes the colour of the pure tinc- 
ture to a very pale yellow, but that adulterated with cochineal 
to a light red. The spectra are somewhat thus : 
Pure tincture . . . 8 •• 9 — 10 — 
Adulterated with cochineal 3J •• 7 — 9 — 
The presence of magenta might be recognised by the spec- 
trum of the solution in its natural state. The pure tincture 
shows no narrow absorption band in the green, whereas 
magenta gives a very distinct one, situated at 5 of my scale. 
In the case of the syrup of damsons and similar fruits, 
magenta may be detected, when in very small quantity, by 
