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XXXV. On Rubian and its Products of Decomposition. 

 By Edward Schunck, F.R.S. 

 [Concluded from p. 220.] 



ACTION of Chlorine on Rubian, — If a current of chlorine gas be 

 passed through a watery solution of rubian, the latter begins 

 immediately to deposit flocks of a lemon-yellow or orange co- 

 lour. These flocks continue to be formed as long as the solu- 

 tion retains any portion of its yellow colour. When the action 

 is completed the liquid appears colourless. The flocks, the 

 quantity of which is considerable compared with that of the 

 rubian employed, consist almost entirely of one substance, which 

 I shall call Chlororubian, though this name is not perfectly ap- 

 propiate, since it is not formed from rubian simply by the sub- 

 stitution of hydrogen by chlorine. If these flocks, after being 

 collected on a filter and washed until all the acid and chlorine 

 are removed, be treated with a little cold alcohol, the latter 

 dissolves a small quantity of a substance, which after the eva- 

 poration of the alcohol is left as a yellow or yellowish-brown 

 resinous residue. This substance melts at the temperature of 

 boiling water ; it contains chlorine, and dissolves in caustic 

 alkalies with a dirty purple colour. The chlororubian may be 

 purified by simply dissolving it in boiling alcohol. It crystal- 

 lizes on the solution cooling in small orange-coloured needles, 

 which increase very much in quantity after standing for several 

 hours. The acid liquid, filtered from the yellow flocks formed 

 by the action of chlorine, contains sugar, which may be obtained 

 by neutralizing the acid with carbonate of lead, filtering, evapo- 

 rating the liquid to a small volume, decolorizing with animal 

 charcoal, filtering, evaporating to dryness, and treating the 

 residue with alcohol. The alcohol after filtration and evapo- 

 ration leaves a yellow syrup having all the properties of sugar, 

 as usually obtained by the decomposition of rubian. Chlo- 

 rorubian may be prepared as well from impure as from pure 

 rubian. It is only necessary to extract madder with boiling 

 water, add sugar of lead to the extract, add ammonia to the 

 liquid filtered from the precipitate, decompose the red precipi- 

 tate produced by ammonia with sulphuric acid, and pass chlorine 

 gas through the filtered liquid. The first portions of chlorine 

 generally produce a dirty yellow flocculent precipitate, which, 

 being separated by filtration, is found to consist of the resinous 

 easily fusible substance just mentioned. On passing chlorine 

 through the filtered liquid, pure yellow flocks of chlororubian 

 are precipitated, which are purified as before by crystallization 

 from boiling alcohol. V ' " 



Chlororubian has the following properties. After crystalliza- 

 tion from alcohol and drying, it forms a mass of a light orange 



