392 MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
from these flocks contains chlorogenine as well as riibihydran, and the separation of 
the latter becomes therefore rather more difficult. This may however be effected by 
precipitating it with basic acetate of lead, filtering, washing the precipitate with 
water, then redissolving it in warm acetic acid, and again precipitating by means of a 
little ammonia. The last precipitate contains hardly any chlorogenine, and after 
being put on a filter and washed, is decomposed with sulphuric acid in the cold. 
The excess of acid is removed by carbonate of lead, the liquid is filtered, sulphuretted 
hydrogen is passed through it. it is again filtered from the sulphuret of lead, and on 
being evaporated leaves the rubihydran free from chlorogenine. Should it still con- 
tain a little of the latter substance, in which case its watery solution turns green on 
being boiled with muriatic or sulphuric acid, the precipitation with basic acetate of 
lead must be repeated. It frequently happens, that besides the usual products of 
decomposition, a quantity of rubiadine is also formed. In this case the red flocks 
deposited on evaporating the barytic solution yield, on beihg decomposed with 
sulphuric acid, besides the substances soluble in water, a yellow powder, which is 
insoluble both in cold and boiling water, and which consists of impure rubiadine; 
but this, like the sugar, which is also sometimes formed during the process, is without 
doubt a secondary product of decomposition. Indeed the formation of the one is 
most probably dependent on that of the other. 
The process of decomposition just described is always accompanied by an absorp- 
tion of oxygen. In order to ascertain the quantity of the latter which an alkaline 
solution of rubian was capable of absorbing, I took 4*2280 grins, of rubian, which 
after deducting the inorganic matter with which it was contaminated, was equivalent 
to 4*1049 grms. of the pure substance, dissolved it in hot water, poured the solution 
into a graduated tube, added to it a solution of about 6 grms. hydrate of baryta, 
filled the rest of the tube with mercury, and then inverted it over mercury. Oxygen 
gas was then introduced, and the liquid was from time to time agitated with the gas, 
in order to bring every portion, and especially the red flocculent precipitate’produced 
by the baryta, and which sank to the bottom of the solution, into frequent contact 
with it. After 143 days I found that 147 cubic centimetres of gas had been absorbed. 
The contents of the tube were then removed and filtered. There remained on the filter 
a red baryta compound, which, on being treated as usual, yielded rubianic acid and 
rubidehydran, as well as a small quantity of alizarine. To the red liquid sulphuric 
acid was added ; the excess of acid was removed with carbonate of lead, and sulphu- 
retted hydrogen having been passed through the filtered liquid, the latter, after being 
filtered again from the sulphuret of lead, was submitted to distillation. The distillate 
was acid, and after being neutralized with carbonate of soda and evaporated, left a 
saline residue having all the characters of acetate of soda. Acetic acid is therefore 
another product formed in this process, but whether this acid is an essential product 
of decomposition or not, still remains doubtful. The residue of the distillation con- 
tained rubihydran, which was separated by precipitation with basic acetate of lead, as 
