444 MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
I. 0'3670 grm., dried at 100° C. and burnt with chromate of lead, gave 0‘3520 car- 
bonic acid and 0*0875 water. 
0*3360 grm. gave 0*2390 sulphate of lead. 
II. 0*4440 grm. of another preparation, burnt with chromate of lead, gave 0*4190 
carbonic acid and 0*1115 water. 
0*4320 grm. gave 0*3100 sulphate of lead. 
III. 0*4635 grm. of the same preparation as the last gave 0*4450 carbonic acid and 
0*1050 water. 
0*5405 grm. gave 0*3880 sulphate of lead. 
These numbers lead to the following composition ; — 
Carbon .... 
Eqs. 
. 56 
336 
Calculated. 
26*25 
I. 
26*15 
II. 
25*73 
III. 
26*18 
Hydrogen . . . 
. 34 
34 
2*65 
2*64 
2*87 
2*51 
Oxygen .... 
. 30 
240 
18*76 
18*89 
18*62 
18*51 
Oxide of lead . . 
6 
670 
52*34 
52*32 
52*78 
52*80 
1280 
100*00 
100*00 
100*00 
100*00 
Hence it appears that oxide of lead in combining with rubian does not replace any 
basic water, as is usually the case. 
It may easily be conceived that a body so readily decomposed as rubian gives a 
number of different products of decomposition. It is decomposed by acids, alkalies, 
chlorine, heat and ferments ; and I shall now proceed to describe the products of de- 
composition to which these various reagents give rise. 
Action of Sulphuric and Muriatic Acid on Rubian . — The action of these two acids 
is precisely the same ; but for the purpose of studying it, it is better to employ sul- 
phuric acid, as it is more easily removed again afterwards. On adding sulphuric acid 
in considerable quantity to a watery solution of rubian and boiling the liquid, no 
perceptible change takes place at first, except that the solution loses a little of its 
transparency and becomes slightly opalescent. If the solution was not very dilute, 
there begin to appear very soon a number of orange-coloured flocks. After boiling 
for some time and allowing to cool, these flocks are deposited in large quantities, and 
the liquid is now found to be much lighter in colour than before. After allowing to 
cool and filtering, the liquid, on being mixed with fresh acid and boiled again, often 
deposits on cooling a fresh quantity of these flocks. When after repeated boilings no 
more flocks separate on cooling, the process is completed. The last portions of 
rubian are usually more difficult to decompose than the first, and an additional quan- 
tity of acid is therefore necessary to effect their decomposition. The liquid retains 
to the last a light yellow colour. I shall return to it presently. The orange-coloured 
flocks are washed on the filter with cold water until all the acid is removed. They 
now consist of four different substances, three of which are bodies previously known, 
