Dr. Schunck on Rubian and its Products of Decomposition, 217 



0'2500 grm. of the crystallized substance lost, on being 

 heated in the water-bath, 0'0460 water =18'40 per cent. 



0-2800 grm. of the dry substance gave 0*7110 carbonic acid 

 and O'lOSO water, corresponding in 100 parts to — 



Carbon . . . 6925 



Hydrogen . . 4'08 



Oxygen . . . 26*67 

 Ruhihydran. — This substance, like rubidehydran, bears a great 

 resemblance to rubian, the body from which it is derived. It is 

 obtained on evaporation of its solutions as an uncrystalline, 

 transparent mass like gum, having a dark brownish-yellow colour 

 and a bitter taste. When quite dry it is brittle and may be easily 

 pulverized, but on exposure to the atmosphere at the ordinary 

 temperature it rapidly attracts moisture and becomes soft, a pro- 

 perty by which it may be distinguished from rubian and rubide- 

 hydran. On being heated in a tube it gives less crystalline 

 sublimate than rubian does. Its watery solution, on being boiled 

 with the addition of sulphuric or muriatic acid, becomes muddy, 

 and slowly deposits a quantity of yellow flocks mixed with some 

 brown resinous drops. The liquid must be boiled for a consider- 

 able time in order to effect the entire decomposition of the ru- 

 hihydran contained in it and make it appear colourless. The 

 flocks on being collected on a filter are found to consist chiefly 

 of rubiretine, verantine, and rubiadine, with only a very small 

 quantity of alizarine, while the filtered liquid contains sugar. 

 The products of decomposition with acids are therefore the same 

 as those of rubidehydran, the only difference being in the rela- 

 tive proportions of the products formed. It is not decomposed, 

 when treated with boiling phosphoric, oxalic, tartaric or acetic 

 acids. If a watery solution of ruhihydran be boiled with caustic 

 potash or soda, the colour of the solution, which was red on the 

 first addition of alkali, changes to reddish- or yellowish-brown, 

 but only a few purple flocks are deposited. This circumstance 

 also serves to distinguish this substance from rubian and rubi- 

 dehydran, the watery solutions of which, when mixed with caustic 

 alkali and boiled, deposit an abundance of the purple compound 

 of alizarine and alkali. Nevertheless the ruhihydran is completely 

 decomposed by the caustic alkali, for on adding an excess of acid 

 to the liquid a quantity of yellow or light brown flocks are pre- 

 cipitated like those produced by the action of acids, while the 

 liquid becomes almost colourless. When chlorine gas is passed 

 through the watery solution, it produces exactly the same effects as 

 in watery solutions of rubian or rubidehydran. It is the behaviour 

 to chlorine, which more than any other reaction proves that these 

 substances have a similar composition, and forms perhaps the most 



