390 MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
which have a dark yellowish-brown tinge. On adding to this mass a small quantity 
of cold water, part of it dissolves with a deep yellow or reddish-yellow colour, while 
a yellow powder remains undissolved. The latter consists of a peculiar acid, to which 
I shall give the name of Rubianic Acid. After being collected on a filter and washed 
with cold water, it is purified by solution in boiling water, to which a little animal 
charcoal may be added. On filtering the solution boiling hot and allowing to cool, 
it crystallizes in beautiful lemon-yellow needles, which if the solution was at all con- 
centrated entirely fill the liquid. The substance dissolved by the cold water is left 
on evaporation in the shape of a reddish-yellow or brownish-yellow substance, resem- 
bling rubian itself in appearance and all its properties. As analysis shoM^ed it to be 
formed from rubian by the elimination of several equivalents of water, I shall call it 
Ruhidehydran. 
The liquid filtered from the red flocks, consisting of the baryta compounds of the 
two substances just named, has still a dark brownish-yellow colour, and contains a 
third organic substance in solution. In order to ascertain whether the whole quan- 
tity of the two former substances has been separated, and whether the solution still 
contains any unchanged rubian, it is well to add caustic baryta to the liquid, to 
supersaturate the latter with carbonic acid and to evaporate again. If no more red 
flocks separate on evaporation, but only a deposit of carbonate of baryta is formed, 
then the process is completed. On now adding to the filtered solution basic acetate 
of lead a red precipitate falls, while the liquid becomes colourless. The former being 
separated by filtration and washed with water, is to be decomposed with sulphuric 
acid in the cold, and the excess of acid having been removed with carbonate of lead, 
sulphuretted hydrogen is passed through the filtered liquid, and the latter, after 
being filtered again from the sulphuret of lead, is evaporated to dryness, when it 
leaves a dark brownish-yellow substance, resembling rubian in appearance, but dif- 
fering in being somewhat deliquescent. To this substance I will give the name of 
Ruhihydran. The liquid filtered from the lead compound of this substance some- 
times contains sugar, but this is entirely a secondary product of decomposition, formed 
at the cost of one or more of the primary products, and indicates the formation at the 
same time either of rubiadine or alizarine. 
The same products of decomposition may be obtained by adding to the solution of 
rubian a solution of bicarbonate of baryta made from chloride of barium and bicar- 
bonate of soda, and evaporating in contact with the air until red flocks begin to 
appear, or by adding caustic baryta to the solution, allowing the mixture to stand 
exposed to the air for some time and filtering, when the insoluble baiyta compound 
left on the filter will yield rubianic acid and rubidehydran, and the liquid ruhihydran. 
fl’he same process of decomposition takes place, if caustic soda, ammonia, or lime 
water be added to a watery solution of rubian, and the mixtures be allowed to stand 
exposed to the air for some time. On now adding chloride of barium to any one of 
them a dark red precipitate falls, which being collected on a filter, washed with water 
