288 DR. KANE ON THE CHEMICAL HISTORY OF ARCHIL AND LITMUS. 
A specimen of azoerythrine, which I had every reason to look upon as being com- 
pletely pure, was analysed. 
0300 gramme of substance dried at 212° gave 0-421 gramme of carbonic acid, and 
0-154 of water. 
To determine the quantity of nitrogen, the method of estimating the relative vo- 
lumes of the carbonic acid and the nitrogen gases was adopted, in preference to the 
method of absolute determination, because I was perfectly certain of the relative ac- 
curacy of graduation of the tubes which I employed, but I could not be so certain of 
their absolute exactness. The following numbers express the result of an experiment 
of this kind, made with every precaution for avoiding error. 
Tube. 
C 0 2 + N. 
N. C 0 2 . 
N : CO,. 
A. 
464 gave 
21 and 443. .-. 
1 : 21*1 
B. 
205 gave 
9 and 196. .-. 
1 : 21-8 
C. 
242 gave 
1 1 and 231. .*. 
1 : 20-0 
D. 
359 gave 17 and 342. .-. 
1 : 20-1 
In an experiment of this kind all sources of error tend to increase the quantity of 
nitrogen in relation to the carbon, and hence I consider the numbers above given as 
rendering it highly probable that the true proportion is one of nitrogen to twenty-two 
of carbon, and on this idea the analysis leads to the formula C 22 H 19 N 0 22 , giving 
Theory. 
Experiment. 
22 Carbon 
. 134-2 
3909 
38-80 
19 Hydrogen . 
19-0 
5-53 
5-70 
22 Oxygen. . 
. 176-0 
51-271 
55-50 
1 Nitrogen . 
14-1 
4-1 1 j 
343-3 
100-00 
100-00 
A portion of a brownish red compound of azoerythrine with oxide of lead, prepared 
by mixing a solution of azoerythrine in potash water, rendered very nearly exactly 
neutral by acetic acid, with a solution of tribasic acetate of lead, was analysed as 
follows, having been previously dried at a temperature of 180°. 
0-657 gramme gave 0-456 of carbonic acid, and 01 77 of water. 
0*746 gramme gave 0112 of metallic lead, and 0’251 of oxide of lead. 
These results are expressed by the formula C 22 H 19 N 0 22 + 3 Pb O, by which is 
obtained 
Theory. 
Experiment. 
22 Carbon . . 
= 134-2 
1979 
1933 
19 Hydrogen . 
= 19-0 
2-80 
300 
22 Oxygen . . 
= 176-01 
28-03 
27-88 
1 Nitrogen . . 
= 14*1 J 
3 Oxide of lead 
= 334-8 
49-38 
49-79 
678-1 
100-00 
100-00 
