416 Dr. Schunck on Rubian and its Products of Decomposition, 



The ulmic acid of Mulder, obtained by the action of muri- 

 atic acid on cane-sugar, contains, according to that chemist 

 (C=611),~ 



Carbon 68*95 



Hydrogen 4*23 



Oxygen 26-82 



The formula given by Mulder for ulmic acid, viz. C*^ H**0^*, 

 requires in 100 parts — 



Carbon 68-57 



Hydrogen 4*00 



Oxygen 27*43 



The identity in composition and properties of this acid, and 

 the substance formed by the action of alkalies on rubian, leave 

 no doubt of their being the same. 



Rubiadine, — This substance, which has not hitherto been ob- 

 served among the products derived from madder, bears a close 

 resemblance in its appearance and many of its properties to 

 rubianine, the place of which it in fact occupies in the series of 

 substances produced by the action of alkalies on rubian. Besides 

 its composition, however, there are several properties belonging 

 to it so characteristic, that it cannot be confounded with rubianine 

 or any of the substances previously described. When crystallized 

 from alcohol, it is obtained in the shape of small yellow or orange- 

 coloured needles. A very minute degree of impurity, however, 

 seems to prevent its assuming a crystalline form, in which case 

 it is obtained in small granular masses, or as a yellow amor- 

 phous powder. It may be purified by dissolving it in a small 

 quantity of boiling alcohol, and adding to the boiling solution 

 either hydrated oxide of lead, or protoxide of tin. On filtering 

 boiling hot and allowing to cool, it crystallizes out. When 

 heated on platinum foil, it melts and burns with flame. When 

 cautiously heated between two watch-glasses, it may be almost 

 entirely volatilized. On the lower glass a very slight carbona- 

 ceous residue is left, while the upper glass is covered with a 

 ■quantity of partly yellow, partly orange- coloured micaceous 

 Scales, endowed with considerable lustre. These scales possess 

 all the properties of rubiadine itself. Rubiadine is insoluble in 

 water. It communicates hardly any colour to boiling water, and 

 the filtered liquid deposits nothing on cooling. It is more solu- 

 ble in alcohol than rubianine. It dissolves in concentrated sul- 

 phuric acid with a dark yellow colour, and is reprecipitated by 

 water in yellow flocks. If the solution in sulphuric acid be 

 boiled, the colour changes to a dark yellowish-brown, a little 

 sulphurous acid is disengaged, and the addition of water now 

 causes a yellowish-brown precipitate. On treating rubiadine 



