OXYTOLUIC ACIDS, ETC. 351 



dies, which are very slightly soluble in cold water. It 

 also unites with bases and acids. When a mixture of 

 tyrosin with nitric acid is evaporated at a slightly 

 elevated temperature, dinitrotyrosin, C 9 H 9 (!N"C) 2 ) 2 M) 3 , is 

 formed. This crystallizes in golden-yellow laminae. 

 Simultaneously with these two compounds, a red color- 

 ing matter (erythrosin) is produced by the action of 

 nitric acid on tyrosin. When heated with concen- 

 trated sulphuric acid, tyrosin yields several sulpho- 

 acids, the soluble salts of which are colored a beautiful 

 violet by iron chloride. 



2. Acids, C 8 H 8 3 . 



a. Oxytoluic Acids (Cresotic Acids). 



(OH 



C 6 H 3 \ CH 3 

 ( CO.OH. 



Three acids of this composition are known. They are 

 formed, like salicylic acid, by the simultaneous action 

 of sodium and carbonic anhydride on the three modifi- 

 cations of cresol (p. 298). 



a-Cresotic acid. From para-cresol. Long, colorless 

 needles ; fusing point, 147-150. 



0-Cresotic acid. From ortho-cresol. Long, color- 

 less needles ; fusing point, 114. 



y-Cresotic acid. From meta-cresol. Needles; 

 fusing point, 168-173.. 



The solutions of all three acids are colored violet by 

 iron chloride. 



b. Oxymethylphenylformic Acid. 



C6H4 CH 2 .OH 

 L CO.OH. 



When para-toluic acid is treated with bromine with 

 the aid of heat, an acid C 6 H 4 j ^Q QJJ is produced, 

 which as yet has not been prepared in a pure condition. 



