402 MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
to purify it any further, for fear of inducing’ a change in its composition. Rubide- 
hydran resembles rubian exactly in most of its properties. It is not in the least deli- 
quescent. If it shows any tendency to deliquesce on exposure to the air, this must 
be attributed to its containing some impurity. It has a strongly bitter taste. The 
watery solution is yellow, and when boiled, with the addition of sulphuric or muriatic 
acid, deposits yellow flocks, and after cooling appears almost colourless. Like rubian, 
is also decomposed on boiling the watery solution with the addition of caustic potash 
or soda, the solution becoming purple and depositing yellow flocks on supersaturating 
the alkali with acid. It is not precipitated from its aqueous solution by any earthy 
or metallic salt, with the exception of basic acetate of lead, which produces a red 
precipitate, while the liquid becomes colourless. The alcoholic solution, however, 
gives, with an alcoholic solution of neutral acetate of lead, a red precipitate, similar 
to the last, which is soluble in water. When exposed in a dry state to the action of 
heat, and to that of chlorine in its watery solution, rubidehydran behaves exactly like 
rubian. It may, however, be distinguished from rubian by its not yielding a trace of 
rubianic acid, when its watery solution is mixed with caustic soda or baryta and left 
exposed to the atmosphere for some time. Its products of decomposition with acids 
differ also from those of rubian. If a solution of the substance in water be boiled 
with the addition of sulphuric acid, yellow flocks are deposited, which consist prin- 
cipally of alizarine, with some rubiadine and a little verantine and rubiretine, but not 
a trace of rubianine, while the filtered liquid contains sugar. Rubidehydran yields 
therefore the same products with acids as rubian does with alkalies, which makes it 
very probable that rubian, when acted on by alkalies, is first changed, in part at least, 
into rubidehydran. 
In calculating the composition of this substance from the analysis, I took it for 
granted that the lime and magnesia found in the ash are contained originally in it as 
sulphates, and therefore always treated the ash obtained in the first instance with 
sulphuric acid, in order to replace that portion of the sulphuric acid which might 
have been reduced during the process of ignition, and then made the corrections 
accordingly. 
I. 0’4360grra. rubidehydran, formed by the action of bicarbonate of baryta on 
rubian, dried at 100° C. and burnt with chromate of lead, gave 0’8005 carbonic acid 
and 0’2130 water. 
0’2790grm., on being incinerated, left O’OlfiOgrm. ash, which after being treated 
with sulphuric acid and heated again, weighed 0’032,5 grm. =1T64 per cent. 
II. 0’4950 grm., formed by the action of lime-water on rubian, gave 0'9750 carbonic 
acid and 0’2320 water. 
0’6220 grm. left 0’0200 grm. ash, which after treatment with sulphuric acid weighed 
0’0340 grm. =5’46 per cent. 
III. 0’4795 grm., obtained by means of caustic baryta, gave 0’9540 carbonic acid 
and 0’2320 water. 
