238 DR. EDWARD SCHUNCK ON 



first with hot water to remove the iodide of potassium, and 

 then with a little cold alcohol. The alcohol (which dis- 

 solved out a brown resinous substance) having been filtered 

 off, the residue was treated with dilute caustic potash lye, 

 in which the alizarine not acted on dissolved with a violet 

 colour. The liquid was filtered, and the residue, which 

 consisted of the potassium compound of methyl- alizarine, 

 a compound very little soluble in cold water, was washed 

 until the percolating liquid began to be of a cherry-red 

 colour. It was then treated with hydrochloric acid ; and 

 the orange-coloured flocks left undissolved were filtered 

 off, washed, and dissolved in boiling alcohol. The alco- 

 hol, on cooling, deposited crystalline needles of methyl- 

 alizarine. 



Methyl- alizarine as thus prepared has the following 

 properties : — When crystallized from boiling alcohol it 

 appears in long yellow needles which resemble crystallized 

 alizarine, though devoid of the semimetallic lustre pecu- 

 liar to the latter. When heated it melts, and is then 

 entirely volatilized, yielding a sublimate of yellow lustrous 

 scales and needles. It is very little soluble in boiling 

 water, but dissolves easily in concentrated sulphuric acid, 

 even in the cold, giving a dark red solution. It does not 

 dissolve perceptibly in caustic potash lye in the cold ; but 

 on boiling, a bright cherry-red solution is obtained, which 

 on cooling deposits dark red crystalline masses. The 

 solution shows no trace of absorption bands, but only a 

 general obscuration of the green part of the spectrum, and 

 in this respect differs widely from the alkaline solutions of 

 alizarine, which exhibit such very characteristic absorption 

 bands. The solution in concentrated sulphuric acid, how- 

 ever, does show an absorption band on the border of the 

 green and blue of the spectrum, just like a solution of 

 anthraflavic acid in the same menstruum, but far less 

 distinctly than the latter, on account of the much greater 



