Dr. Schunck on Rubian and its Products of Decomposition, 215 



salt, with the exception of basic acetate of lead, which produces 

 a red precipitate, while the liquid becomes colourless. The 

 alcohol 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 principally of alizarine, with some rubiadiue and a little 

 verantine and rubiretine, but not a trace of rubiauine, 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 there- 

 fore 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 igni- 

 tion, and then made the corrections accordingly. 



I. 0'4360 grm. rubidehydran, formed by the action of bicar- 

 bonate of baryta on rubian, dried at 100° C. and burnt with 

 chromate of lead, gave 0*8005 carbonic acid and 0'2130 

 water. 



0-2790 grm., on being incinerated, left 0-0150 grm. ash, 

 which after being treated with sulphuric acid and heated again, 

 weighed 0*0325 grm. =11*64 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. 



1*0785 grm. left 0*0245 grm. ash, which after treatment with 

 sulphuric acid, weighed 0*0455 grm. =4*21 per cent. 



IV. 0*4990 grm., obtained by means of ammonia, gave 0*9780 

 carbonic acid and 0*2320 water. 



0*7385 grm. left 0*0155 grm. ash, which after treatment with 

 sulphuric acid, weighed 0*0395 grm. = 5*34 per cent. 



