SANGER-RIEGEL. — PYROSULPH. CHLORIDE-CHLORSULPH. ACID. 681 



phuric acid and hydrochloric acid, according to Williams, ^^ the for- 

 mation of chlorsulphonic acid by their method must be due to the 

 concentration of the hydrochloric acid, i. e., 



H2S2O, + HCl ^ H2SO4 + SO3HCI. 



Though Miiller^s in 1873 had added phosphorus pentoxide to the 

 fuming acid, presumably to increase the yield, it is not clear that 

 he understood the action of the hydrochloric acid to be on the free 

 sulphur trioxide only. Beckurts and Otto could not substantiate the 

 result of A. Williamson,** furthur studied by Behrend ** and later 

 proved by Ruff,*^ that chlorsulphonic acid, heated to 170-180°, gives 

 sulphuric acid and sulphuryl chloride, for they considered that sulphur 

 dioxide and chlorine were the primary products ; sulphuryl chloride a 

 secondary one. 



Nothing new in regard to this method has apparently been published 

 in the past thirty years. We find further no specific statement of its 

 use in the preparation of material for investigation. Though it has un- 

 doubtedly been employed, yet most of the preparations of chlorsul- 

 phonic acid, so called, seem to have been made with non-metallic 

 chlorides.*® 



The contribution of Ruff *5 in 1901 to the knowledge of chlorsulpho- 

 nic acid is important, and throws light on the somewhat discordant 

 observations of former investigators. He does not state the method of 

 preparation, but this is of no importance to his paper. He studies the 

 decomposition to sulphuryl chloride and sulphuric acid by means of 

 catalysers, and bases on this study a valuable technical method for 

 the preparation of sulphuryl chloride. In Ruff's opinion, no chlorine 

 or sulphur dioxide is formed at the boiling point, nor between 170° and 

 180°, but only at higher temperatures. 



The Relation of Pyrosulphuryl Chloride and Chlorsulphonic Acid to 

 Each Other ; their Separation and Purification. 



The simultaneous formation of pyrosulphuryl chloride and chlorsul- 

 phonic acid by the action of chlorides on a hydrated sulphur trioxide, 

 though noted by some observers, does not receive serious consideration 

 until taken up by Konovaloff, who showed that the dehydration of 

 chlorsulphonic acid by phosphorus pentoxide was only partial,*'' but 



*' Quoted by R. Williamson (note 14, p. 676). 



** Rer., 8, 1004 (1875). 



" Ibid., 34, 3509 (1901). 



" E. g., Besson (note 48, p. 682). 



