Dr. Schunck on Rubian and its Products of Decomposition. 303 



posed by Kuhlmann, Berzelius, Eunge and Higgin, as well as 

 the ruberythric acid of Rochleder, the use either of alkaline 

 earths or basic acetate of lead being prescribed by all these 

 chemists^ products of the decomposition of rubian must in every 

 case be formed. 



For the purpose of preparing the three bodies which result 

 from this process of decomposition, it is not necessary to employ 

 pure rubian. If madder be extracted with boiling water, and 

 sugar of lead be added to the extract, a purple precipitate is 

 produced, and ammonia being added to the filtered liquid, the 

 whole of the rubian is precipitated together with some chloroge- 

 nine in combination with oxide of lead. The precipitate is de- 

 composed with sulphuric acid in the cold, and the excess of the acid 

 is removed by means of carbonate of lead. To the filtered solu- 

 tion a quantity of baryta water is to be added, and the baryta is 

 then converted into bicarbonate of baryta by a stream of car- 

 bonic acid gas. The solution is left exposed to the air for 

 some time and then slowly evaporated. The red flocks which 

 are deposited are collected on a filter as they form, and after 

 being treated in the same way as the flocks from pure rubian, 

 yield rubianic acid and rubidehydran. The liquid filtered from 

 these flocks contains chlorogenine as well as rubihydran, and 

 the separation of the latter becomes therefore rather more diffi- 

 cult. This may however be effected by precipitating it with 

 basic acetate of lead, filtering, washing the precipitate with water, 

 then redissolving it in warm acetic acid, and again precipitating 

 by means of a little ammonia. The last precipitate contains 

 hardly any chlorogenine, and after being put on a filter and 

 washed, is decomposed with sulphuric acid in the cold. The 

 excess of acid is removed by carbonate of lead, the liquid is fil- 

 tered, sulphuretted hydrogen is passed through it, it is again 

 filtered from the sulphuret of lead, and on being evaporated 

 leaves the rubihydran free from chlorogenine. Should it still 

 contain a little of the latter substance, in which case its watery 

 solution turns green on being boiled with muriatic or sulphuric 

 acid, the precipitation with basic acetate of lead must be re- 

 peated. It frequently happens, that besides the usual products 

 of decomposition, a quantity of rubiadine is also formed. In 

 this case the red flocks deposited on evaporating the barytic 

 solution yield, on being decomposed with sulphuric acid, besides 

 the substances soluble in water, a yellow powder, which is inso- 

 luble both in cold and boiling water, and which consists of im- 

 pure rubiadine ; but this, like the sugar, which is also sometimes 

 formed during the process, is without doubt a secondary product 

 of decomposition. Indeed the formation of the one is most pro- 

 bably dependent on that of the other. 



