137 
PHYSICAL AND MATHEMATICAL SECTION. 
April 22nd, 1879. 
E. W. Binney, F.R.S., F.G.S., President of the Section, in 
the Chair. 
“ Colorimetric Experiments, Part II.,” by James Bottom- 
ley, B.A., D.Sc., F.C.S. 
In a short note which I read before this Society (Vol. XV., 
p. 63) I proposed to measure quantities of colouring matter 
in solution, using the formula qt=qt' in the calculation, 
^ and g denoting quantities of colouring matter, and t } t' 
lengths of columns of coloured fluid \ the colouring matters 
being dissolved in equal volumes of water. Last session I 
gave the results of some experiments which I had obtained 
two years previously. Lately I have made some further 
experiments, which I give in this paper, along with some 
additional remarks on colorimetry. In my last paper I took 
0001 grams as the unit of measurement. For comparison 
I have retained it in this, although the quantities used can 
can no longer be considered as traces. The colouring mat- 
tei used was ammonio-sulphate of copper. A solution was 
made by dissolving 10 grams of crystallized sulphate of cop- 
per in a mixture of 200 cubic c. of water and 50 cubic c. of 
ammonia. Mixtures of various degrees of intensity were 
made by taking portions of this solution and mixing with 
water so as to make up 500 cubic c. As in my last paper, 
A denotes the amount of the colouring salt present, B the 
length of the column of fluid, and C the amount of the 
colouring salt thence derived by calculation. 
Standard solution 4000 in 500 cub. g. of water (depth of 
disc 8’3) 
ABC 
6000 4*3 7721 
