220 Dr. Schuuck on Rubian and its Products of Decomposition. 



In employing sulphuret of tin, which is the only one that at all 

 approaches it in efficiency, much time is consumed in the pro- 

 cess of nitration and washing. Besides this, I found that on 

 operating with it on a large scale, the rubian obtained was in 

 great part decomposed on evaporating the alcoholic solution, 

 just as if it contained a quantity of acid ; and even on treating 

 a portion of the solution with carbonate of lime, for the purpose 

 of neutralizing any free acid that might be present, and evapo- 

 rating over sulphuric acid at the ordinary temperature, there 

 was obtained a deliquescent mass, which as further experiments 

 showed, could not be considered as pure rubian. After many 

 trials I at length adopted the following method of preparation, 

 which surpasses all others in facility and certainty of execution. 

 A weighed quantity of madder* being placed on a piece of 

 calico or tine canvas stretched on a wooden frame, boiling water, 

 which is preferable to cold water, as all decomposition of the 

 rubian by means of fermentation is thereby arrested, is poured 

 on it, four quarts of the latter being sufficient for every pound 

 of madder. A dark yellowish-brown liquor is obtained, to which 

 there is added, while hot, for every pound of madder taken 1 

 ounce of animal charcoal, prepared in the usual way from bones. 

 This proportion of charcoal should not be exceeded, for if an ex- 

 cess of it be taken, as for instance li ounce for every pound of 

 madder, the whole of the rubian is certainly removed from the 

 solution ; but on afterwards treating the charcoal with alcohol 

 very little rubian is dissolved, from which it appears that the sol- 

 vent power of the alcohol only overcomes the attraction of the 

 charcoal for rubian in part. In using the first proportion, part 

 of the bitter taste of the extract remains, showing that the rubian 

 is in excess. The liquid being well stirred with the charcoal, the 

 latter is allowed to settle, which it does in a very short time, and 

 the liquid, which still retains a brown colour, is decanted. The 

 charcoal is then placed on a piece of calico or on a paper filter 

 and washed with cold water, until the percolating liquid, when 

 mixed with muriatic acid and boiled, no longer acquires a green 

 colour, which is a sign that the chlorogenine is removed. These 

 operations occupy a very short time, in consequence of the rapidity 

 with which the animal charcoal may be washed. The animal char- 

 coal is now treated with boiling alcohol, which is filtered boiling 

 hot, and the treatment is repeated until it no longer communi- 

 cates to the alcohol any yellow colour. The rubian obtained by 

 evaporating the alcoholic liquid is however impure ; it contains a 

 considerable quantity of chlorogenine, however carefully the char- 

 coal may have been washed with water, and consequently gives a 

 green powder when treated with boiling sulphuric or muriatic acid. 

 * Avignon madder, of the variety called Rosa, was the kind used. 



