380 
amount of the bisulphide may he large in comparison with 
that of the oils, since the presence of much oil causes the 
bands to lie nearer the blue end, and thus interferes with the 
production of the characteristic spectrum. 
Butter. 
Treating yellow butter in a sometvhat similar manner, I 
obtained the spectrum 6 This differs entirely from that 
in the case of cheese, and corresponds with the spectrum of 
the colour of the exterior orange portion of carrots ; but I am 
not quite certain whether this might not be derived from 
carrots eaten by the cows, though I am more strongly inclined 
to believe that it had been artificially introduced to increase 
the colour of the butter. 
The difference between the spectra of the above-named 
colours and of various others closely allied to them will be 
better understood from the following table. In all cases they 
are those of the solutions in pure bisulphide of carbon : 
Red annatto 5| 
Exterior of carrot and the shins of several kinds of fruit 6 7 A 
Xanthopkyll of many yellow leaves and flowers, and of 
the interior of carrots ...... 6§ 8 
Colour of the petals of Brassica, and of many other 
yellow flowers ....... 8-| 
Orange-yellow colour of turnip roots, and of the flowers 
of Eryssimum Perofskianum . . . ’ . 5^ 8f 
It will thus be seen that these spectra differ from one 
another so much as clearly to show that they are due to 
different substances, which are often further distinguished 
by their different behaviour with bisulphide of carbon and 
alcohol, some being almost entirely, and others only very 
partially removed from the alcoholic solution by that reagent, 
so that they may be separated when two occur mixed, as is 
not uncommon in some leaves and flowers. By first agitating 
the alcoholic solution with a little bisulphide, and washing 
this with alcohol, one may be procured nearly pure ; and then, 
after agitating with a second small quantity of bisulphide and 
removing it, the other colour may be obtained nearly pure by 
evaporating the alcoholic solution to dryness, and dissolving 
the residue in bisulphide, which leaves indissoluble any of 
those numerous colours soluble in water which so commonly 
occur in leaves, flowers, and fruits. It is now nearly two 
years since I determined the existence of a considerable 
number of distinct substances, of which at least eight have 
