Dr. Schunck on Buhian and its Products of Decomposition. 413 



of a purple powder, while the liquor still retains a red colour. 

 The purple powder is placed on a filter and slightly washed with 

 cold water. On passing carbonic acid through the filtered liquid, 

 the latter loses its red colour, and a yellow flocculent substance 

 is precipitated together with carbonate of baryta. The liquid, 

 after being boiled in order to decompose the bicarbonate of 

 baryta, and then filtered, is evaporated over sulphuric acid at 

 the ordinary temperature, when it leaves a substance of a light 

 brown colour, which resembles the sugar produced by the action 

 of acids on rubian, but is not quite so deliquescent. This sub- 

 stance, as I shall presently show, is in fact a baryta compound 

 of sugar. The mixture of yellow flocks and carbonate of baryta 

 is now added to the purple powder before mentioned, and the 

 whole is treated with muriatic acid in order to extract the baryta. 

 The acid leaves undissolved a quantity of orange-coloured flocks, 

 which consist, as before, of alizarine, rubiretine, verantine, and 

 rubiadine, as well as of some of the dark brown flocculent sub- 

 stance, insoluble in boiling alcohol, and are separated from one 

 another in the manner just described. If sulphuric acid be em- 

 ployed instead of carbonic acid for separating the baryta from 

 the red liquid, and the excess of acid be neutralized with carbo- 

 nate of baryta, the liquid on evaporation gives a substance exactly 

 similar to that obtained in the other case, being also a compound 

 of sugar and baryta, but differing from the latter in containing 

 only half the quantity of baryta. The identity of the alizarine 

 and rubiretine obtained by the action of alkalies, with those pro- 

 duced by the action of acids on rubian, is proved by the following 

 analyses. 



0'2255 grm. crystallized alizarine obtained by means of caustic 

 soda, lost on being heated in the water-bath, 0*0405 water 

 = 17-96 per cent. 



0'1820 grm. of the dry substance, burnt with chromate of 

 lead*, gave 0*4610 carbonic acid and 0*0770 water. 



These numbers correspond in 100 parts to — 



Carbon 69*07 



Hydrogen 4*70 



Oxygen ...... 26*23 



I. 0*2610 grm. rubiretine, prepared by means of caustic soda, 

 and dried at 100° C, gave 0*6565 carbonic acid and 0*1250 

 water. 



II. 0*3630 grm. rubiretine, prepared by means of caustic 

 baryta, gave 0*9130 carbonic acid and 0*1715 water. 



* In order to avoid repetition, I may state that all the organic analyses 

 given in this paper, in which the material used for combustion is not espe- 

 cially mentioned, were performed with chromate of lead. 



