DR. E. SCHUNCK ON ANTHRAFLAVIC ACID. 231 



ammonia. These crystals, however, after a short exposure 

 to the air, lose the whole of their ammonia, leaving a yel- 

 low residue of uncombined acid. This inability to retain 

 ammonia, even at the ordinary temperature, is a proof of 

 the feeble nature of the acid. The potassium and sodium 

 salts are also rather unstable compounds; for if it be 

 attempted to recrystallize either of them from boiling 

 water, a portion of the acid separates, the solubility of the 

 base in water being sufficient to overcome its affinity for 

 the acid. Anthraflavate of barium may be obtained by 

 dissolving the acid in boiling baryta-water, or by adding 

 chloride of barium to a solution of the substance in caustic 

 alkali. The salt may be dissolved in boiling water without 

 decomposition, and is deposited from the solution, on cool- 

 ing, in small shining crystalline plates of a brownish-red 

 colour, which, when examined under the microscope, are 

 found to be very regular in form. The strontium salt is 

 very similar, being soluble in boiling water, and crystal- 

 lizing in long needles. The calcium salt, however, is 

 insoluble in water, and is precipitated, in orange -coloured 

 flocks, on the addition of chloride of calcium to a solution 

 of the acid in ammonia. On adding sulphate of magne- 

 sium to an ammoniacal solution of the acid, no precipitate 

 is produced; but, on standing some time, the magnesium 

 salt is deposited in dark yellow crystalline plates and 

 needles, arranged in star-shaped clusters, and possessed of 

 much lustre. The aluminium compound, prepared in a 

 similar manner, appears as a yellow deposit, consisting of 

 microscopic crystals. The ammoniacal solution gives 

 with acetate of lead a voluminous orange-coloured preci- 

 pitate, with acetate of copper a light brown, and with 

 nitrate of silver a reddish-brown precipitate. 



All the compounds of the acid which are soluble in 

 water yield yellow solutions. It is chiefly the presence of 

 this acid in crude alizarine which affects the colour of the 



