Dr. Schunck on Ruhian and its Products of Decomposition. 301 



with boiling water, after which it generally retains only a slight 

 pink tinge. The filtered solution deposits on evaporation a 

 quantity of yellow crystalline needles. After evaporating to 

 dryness there is left a yellow mass, the surface and edges of 

 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 Ruhianic Acid. After being col- 

 lected 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 concentrated, 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, re- 

 sembling rubian itself in appearance and all its properties. As 

 analysis showed 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 quantity 

 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 

 be 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 sepa- 

 rated 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 dry- 

 ness, when it leaves a dark brownish-yellow substance, resem- 

 bling rubian in appearance, but difi'ering in being somewhat 

 deliquescent. To this substance I will give the name of Rubi- 

 hydran. The liquid filtered from the lead compound of this 

 substance sometimes contains sugar, but this is entirely a se- 

 condary 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 



