MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 443 
III. 0*4755 grm. of the same preparation, burnt with oxide of copper, gave 0*8835 
carbonic acid and 0*2180 water. 
0*1690 grin., on being incinerated, left 0*0130 grm. of ash = 7*69 per cent. 
IV. 0*3910 grm. rubian, purified by means of acetate and basic acetate of lead, 
burnt with chromate of lead, gave 0*7455 carbonic acid and 0*1880 water. 
0*4050 grm. of this preparation left 0*0215 grm. of ash=5*30 per cent. 
V. 0*4235 grm. rubian, purified in the same way as I. and burnt with chromate of 
lead, gave 0*7890 carbonic acid and 0*2020 water. 
0*6400 grm. of this preparation left 0*0465 ash =7*26 per cent. 
VI. 0*4390 grm. rubian, purified in the same way as IV., burnt with chromate of 
lead, gave 0*8370 carbonic acid and 0*2120 water. 
0*8400 grm. of this preparation left 0*0440 ash=5*23 per cent. 
After making the necessary corrections for the ash, these numbers correspond in 
100 parts to — 
I. 
II. 
III. 
IV. 
V. 
VI. 
Carbon . . 
. . 54*89 
54*79 
54*89 
54*90 
54*78 
54*84 
Hydrogen . 
. . 5*41 
5*48 
5*51 
5*64 
5*71 
5*66 
Oxygen . . 
. . 39-70 
39*73 
39*60 
39*46 
39*51 
39*50 
Rubian contains no nitrogen. On burning it with oxide of copper and collecting 
the gas over mercury, I found the latter to be entirely absorbed by caustic alkali. 
When burnt with lime and soda, only a minute trace of chloride of platinum and 
ammonium was obtained. The statement contained in my former paper, which was 
made at a time when I had not obtained rubian in a state of absolute purity, that 
nitrogen is one of its constituents, must therefore be corrected. 
From the above analyses the following composition may be deduced : — 
Eqs. 
Calculated. 
Carbon . . . 
. . 56 
336 
55*08 
Hydrogen . . 
. . 34 
34 
5*57 
Oxvgen . . . 
y O 
. . 30 
240 
39*35 
610 
100-00 
The compound with oxide of lead, which was the only one that could be employed 
for the determination of the atomic weight, was prepared by dissolving rubian in 
alcohol, adding acetate of lead, precipitating with a little ammonia, taking care to 
leave an excess of rubian, and washing with alcohol. If it be prepared by precipitation 
from a watery solution by means of basic acetate of lead, great difficulties are expe- 
rienced in the course of filtration ; the liquid begins to run through slowly, the preci- 
pitate becomes somewhat mucilaginous and adheres to the paper, and sometimes even 
it seems to be decomposed and no longer gives unchanged rubian, but a dark brown 
viscid substance. Its analysis gave the following results : — 
