74 DR. EDWARD SCHUNCK ON SOME 



To this product I apply, for the sake of distinction, the 

 letter E. 



The acid liquid filtered from the mixture of substances 

 insoluble in water still contained in solution a product of 

 decomposition derived from the indigo-blue. It was evapo- 

 rated until crystals began to appear on its surface, and it 

 was then set aside and allowed to stand for some time, 

 when a large quantity of crystals was gradually deposited. 

 After separation from the mother liquor, these crystals 

 appeared of a brown colour ; but by recrystallization from 

 boiling water and decolorization with animal charcoal, they 

 were rendered white and pure. They were then found to 

 have the properties and composition of anthranilic acid, 

 the well-known product formed by the action of caustic 

 alkalies on indigo-blue. The mother liquor of the crystals 

 left, on evaporation, a thick brown syrup, which seemed to 

 be a compound of anthranilic acid and acetic acid. On 

 dissolving it in water, adding sulphuric acid to the solution 

 and evaporating, I obtained a quantity of crystals, which 

 were purified by crystallization, first from water and then 

 from boiling alcohol. They differed in appearance from 

 anthranilic acid, and consisted indeed of a compound of 

 the latter with sulphuric acid. The same compound is 

 obtained in place of uncombined anthranilic acid, if a great 

 excess of sulphuric acid beyond what is required to unite 

 with the free soda and that combined with acetic acid and 

 the various products yielded by the process has been em- 

 ployed in the first instance. The sulphate, being more 

 soluble in water than the free acid, does not crystallize so 

 easily from the brown syrup which the liquid always leaves 

 on evaporation, and hence it is advisable not to use an 

 excess of sulphuric acid in the process above described for 

 the separation of the anthranilic acid. 



As regards their properties, the products insoluble in 

 water present very little that is of interest. The body A 



