MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 441 
Acetate of alumina, alum, protacetate and peracetate of iron, acetate of zinc, neutral 
and basic acetate of copper, acetate of lead, nitrate of silver, perchloride of tin, pro- 
tonitrate of mercury, perchloride of mercury and chloride of gold produce no preci- 
pitate whatever in a watery solution of pure rubian, nor does any reaction take place, 
except a darkening of the solution in the case of some of these salts. If the rubian be 
impure, which is always the case when the solution has been incautiously evaporated 
and the rubian has been exposed to too great a heat after evaporation, then its solu- 
tion, though it does not differ in appearance from one of pure rubian, when mixed 
with any mineral or organic acid, even acetic acid, or the salts of the alkalies or alka- 
line earths, is rendered milky, and a quantity of dark brown transparent resinous 
drops, mixed with yellow flocks, are deposited. These drops, in the case of the salts, 
consist merely of a substance insoluble in saline liquids, which dissolves again in pure 
water ; hut in the case of acids, they are, though similar in appearance, a product of 
decomposition of the latter substance, and do not redissolve in pure water. Sugar 
of lead gives, in a solution of impure rubian, a dark reddish-brown precipitate. Most 
metallic salts also give precipitates, consisting either of the substance itself which 
accompanies the rubian, or of compounds of this substance, with the respective me- 
tallic oxides. I shall return to these reactions when I come to treat of the action of 
heat on rubian. Basic acetate of lead gives a copious light red precipitate in a solu- 
tion of pure rubian, the solution becoming colourless. This is the only definite com- 
pound of rubian with a base that I am acquainted with. Concentrated sulphuric acid 
dissolves rubian with a blood-red colour ; on boiling the solution it becomes black 
and disengages sulphurous acid gas in abundance, after which water precipitates a 
black carbonaceous mass. If sulphuric acid be added to a watery solution of rubian, 
and the mixture be boiled, the solution, if dilute, becomes opalescent, and on cooling a 
quantity of light yellow flocks are deposited; and if the solution was concentrated, 
these are formed in such abundance on cooling as to render the liquid thick. If these 
flocks exhibit the least tinge of green, the presence of chlorogenine is indicated. Mu- 
riatic acid acts in precisely the same manner. Nitric acid produces in the cold no 
effect in a solution of rubian, but on boiling a disengagement of nitrous acid takes 
place, the liquid becomes light yellow, and now contains the acid which I called in 
my former papers alizaric acid, and which Laurent and Gerhardt consider as iden- 
tical with naphthalic acid. Phosphoric, oxalic, tartaric and acetic acids produce no 
effect on the solution, even on boiling for some time. When a stream of chlorine gas 
is passed through a watery solution of rubian, the solution immediately becomes milky 
and begins to deposit a lemon-yellow powder, into which, on continuing the action, 
the whole of the rubian is converted, the liquid becoming colourless. Caustic soda 
turns the colour of the solution from yellow to blood-red, and on neutralizing the 
alkali with acid, a clear yellow solution is again obtained. By boiling the solution to 
which the soda has been added, the colour changes from blood-red to purple ; and on 
now supersaturating the alkali with acid, a reddish yellow precipitate falls, while the 
