MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 407 
Action of Chlorine on Riihian . — If a current of chlorine gas be passed through a 
watery solution of ruhian, the latter begins immediately to deposit flocks of a lemon- 
yellow or orange colour. These flocks continue to be formed as long as the solution 
retains any portion of its yellow colour. When the action is completed the liquid 
appears colourless. The flocks, the quantity of which is considerable compared with 
that of the rubian employed, consist almost entirely of one substance, which 1 shall 
call though this name is not perfectly appropriate, since it is not formed 
from rubian simply by the substitution of hydrogen by chlorine. If these flocks, after 
being collected on a filter and washed until all the acid and chlorine are removed, 
be treated with a little cold alcohol, the latter dissolves a small quantity of a sub- 
stance, which after the evaporation of the alcohol is left as a yellow or yellowish- 
brown resinous residue. This substance melts at the temperature of boiling water; 
it contains chlorine, and dissolves in caustic alkalies with a dirty purple colour. Idie 
chlororubian may be purified by simply dissolving it in boiling alcohol. It crystal- 
lizes on the solution cooling in small orange-coloured needles, which increase very 
much in quantity after standing for several hours. The acid liquid, filtered from the 
yellow flocks formed by the action of chlorine, contains sugar, which may be 
obtained by neutralizing the acid with carbonate of lead, filtering, evaporating the 
liquid to a small volume, decolorizing with animal charcoal, filtering, evaporating 
to dryness, and treating the residue with alcohol. The alcohol after filtration and 
evaporation leaves a yellow syrup having all the properties of sugar, as usually 
obtained by the decomposition of rubian. Chlororubian may be prepared as well 
from impure as from pure rubian. It is only necessary to extract madder with boil- 
ing water, add sugar of lead to the extract, add ammonia to the liquid filtered from 
the precipitate, decompose the red precipitate produced by ammonia with sulphuric 
acid, and pass chlorine gas through the filtered liquid. The first portions of chlorine 
generally produce a dirty yellow flocculent precipitate, which, being separated by 
filtration, is found to consist of the resinous easily fusible substance just mentioned. 
On passing chlorine through the filtered liquid, pure yellow flocks of chlororu- 
bian are precipitated, which are purified as before by crystallization from boiling 
alcohol. 
Chlororubian has the following properties. After crystallization from alcohol and 
drying, it forms a mass of a light orange colour, consisting of small crystalline 
needles. It has no perceptible taste at first, but on chewing it for some time it pro- 
duces a slightly bitter taste. When heated on platinum it melts and burns with a 
smoky flame slightly tinged with green, and leaves a considerable quantity of char- 
coal. On being heated in a tube it melts to a brown liquid, and gives fumes which 
condense on the colder parts of the tube to a white crystalline sublimate, consisting 
of star-shaped masses, while much carbonaceous residue is left. On being treated 
with boiling water chlororubian dissolves in considerable quantity, forming a yellow 
solution, which on cooling deposits a great part of the substance, not in crystals, but 
MDCCCLV. 3 I 
