ANHYDRIDES OF ORGANIC ACIDS 239 



salts. Thus if silver succinimide (2 mols.) is shaken for some 

 time with sulphur chloride (1 mol.) in presence of dry benzene, 

 there is obtained, after filtration and evaporation of the 

 benzene in vacuo, a quantitative yield of sulphur succinimide 

 as a white crystalline powder which is stable when dry but 

 decomposes fairly readily when in solution in such solvents 

 as acetone. It is at once decomposed by sodium hydroxide 

 solution. The molecular weight of this compound, as deter- 

 mined experimentally, points to the formula [C 2 H 4 (CO) 2 .N] 2 S 2 . 

 Silver phthalimide does not react smoothly with sulphur 

 chloride, but, from potassium phthalimide, the sulphur 

 derivative can be obtained though the yield is not very good. 

 It is remarkable that the values found for the molecular 

 weight of sulphur phthalimide agree with the simple formula 

 C 6 H 4 .(CO) 2 NS, a fact which, taken in conjunction with the 

 quantitative yield of the bimolecular succinimide derivative, 

 points to the unsymmetrical formula for sulphur chloride, as 

 is indicated by the formulae : 



>N-S >N\ i 



>N-S 



a consideration of which shows that a theoretical yield of the 

 monomolecular substance might be obtained by the breaking 

 down of the double molecules of symmetrical structure, but 

 less probably by the breaking down of those of unsymmetrical 

 structure. 



Sulphur phthalimide can be prepared in good yield by 

 acting on phthalimide with excess of sulphur chloride and 

 pyridine in presence of an indifferent solvent. It is a stable 

 substance which crystallises from chloroform in colourless 

 crystals which contain chloroform of crystallisation. Like 

 the succinimide compound, it is at once decomposed by 

 sodium hydroxide solution. 



Thionyl chloride and silver succinimide when shaken 

 together in presence of benzene appear to give the thionyl 



