228 THE PREPARATION OF 



Consideration of the above reactions suggests at once the 

 possibility of preparing organic anhydrides by formation and 

 subsequent decomposition of mixed anhydrides of organic 

 and inorganic acids ; such mixed anhydrides are known, and, 

 like those which contain organic radicals only, they are unstable 

 and readily undergo a similar decomposition. Thus Pictet 

 and his colleagues (Abstr., 1903, i. 309, 456, 675 ; 1906, i. 3) have 

 prepared mixed anhydrides of acetic acid with boric, arsenious, 

 phosphoric, sulphuric, and nitric acids respectively by the 

 interaction of glacial acetic acid or of acetic anhydride with 

 the inorganic anhydride, while Francis (Ber., 1906, 39, 3798) 

 has prepared benzoyl nitrate from benzoyl chloride and 

 silver nitrate, and Francesconi and Cialdea (Abstr., 1903, 

 i. 788 ; 1904, i. 707) have made mixed anhydrides of nitrous 

 acid and organic acids by the interaction of nitrosyl chloride 

 and silver salts of organic acids. 



In the methods already described, in which sulphur 

 dichloride is used, the reactions are carried out in absence 

 of solvent, and the primary product is the acid chloride; 

 while Carius, using equimolecular proportions of sulphur 

 monochloride and sodium benzoate in equimolecular pro- 

 portions, obtained benzoyl chloride even when he used carbon 

 disulphide as solvent. By a modification of the conditions 

 under which Carius worked, the writer has succeeded in pre- 

 paring a series of acyl derivatives of the unknown acid, thio- 

 sulphurous S 2 (OH) 2 , of which sulphur monochloride may be 

 regarded as the chloride. Thus, if dry sodium benzoate 

 (2 mols.) and sulphur monochloride (1 mol.) are boiled 

 together in presence of carefully dried ether or other indifferent 

 solvent, the yellow colour of the sulphur chloride quickly 

 disappears, and, after filtration from the sodium chloride 

 formed in the reaction and concentration, the solution deposits 

 crystals of benzoyl thiosulphite. The reaction is represented 

 by the equation : 



2C 6 H 6 . COONa+S 2 Cl 2 = (C 6 H 5 .COO) 2 S 2 +2NaCl. 



