ON COLOURING MATTER OF BONELLIA VIRIDIS, VE 
Red end. Blue end. 
700 600 500 400 
i Alkaline 
| | or 
neutral. 
ly 
| | Slightly 
‘a | acid. 
iE 
Nig ll 
| Strongly 
| ih acid. 
l 
Spectra of Bonelleine in Alcohol. 
The numbers given on the upper side represent the wave- 
lengths of those parts of the spectrum in millionths of 
millimétres, and the scale on which it is drawn is 1 inch to 
100 millionths, which appears to me to be a very conve- 
nient and suitable size. 
A glance at the figure will at once show how some of the 
bands are common to both the alkaline or neutral and the 
slightly acid solution, whilst some are diminished in 
intensity or disappear, and others are made much more 
intense or are only developed when the solution is slightly 
acid. It will also be seen that the addition of more acid 
still further modifies the spectrum in a similar manner, and 
that the two principal bands represent two which are com- 
paratively very feeble in the neutral solution, whilst the two 
principal bands in this latter have entirely disappeared. It 
will also be noticed that the addition of a strong acid lowers 
the bands at the red end somewhat towards the red and 
raises that at the blue end towards the blue, whilst the cen- 
tral band remains in the same position as when the solution 
is neutral. 
It will thus be seen that, though the spectra of bonelleine 
are of an unusually complex character, they agree in a 
remarkable manner with the general principles which I have 
briefly explained, and furnish us with an admirable illustra- 
tion of the peculiar laws connecting together the wave- 
lengths of the bands, and of the influence of solvents and of 
such foreign substances as weak or stronger acids. I cannot 
but think that the further application of this method of 
VOL, XV.—NEW SER. M 
