SANGER-RIEGEL. — PYROSULPH. CHLORIDE-CHLORSULPH. ACID. 689 



composition of the chlorsulphonic acid, and the latter approaches 

 closely to its theoretical maximum at this point, as shown by Prepara- 

 tion 2, p. 695. This is indicated also in Preparations 1 and 2 by the 

 small amount of sulphuric acid left in the reaction. 



In view of the fact that chlorsulphonic acid has a greater avidity 

 for water than pyrosulphuryl chloride (p. 714), reaction (3) may not 

 be entirely completed before its product is acted upon according 

 to reaction (4). Hence the limit of the formation of pyrosulphuryl 

 chloride may not be exactly at the hydration 2S08 • H2O (reaction c of 

 Table II), but at a somewhat greater concentration of water. This 

 is indicated by the yield of pyrosulphuryl chloride in Preparations 1 

 and 2, which is higher than would be expected. Conversely, the yield 

 of chlorsulphonic acid would be less at this concentration. The 

 amount of sulphuric acid would be greater, which is borne out also by 

 these preparations. 



The hydration of the sulphur trioxide will similarly influence the 

 chlorination by sulphur monochloride according to the reactions : — 



(1) 5SO3 + S2CI2 = 5SO2 + S2O5CI2 



(2) 5SO3 + S2CI2 + H2O = 5SO2 + 2SO3HCI. 



Here, while the reaction is complete, the boiling point of the sulphur 

 monochloride is so near to that of each of the two bodies as to make 

 purification by distillation practically impossible. With the chlorides 

 of phosphorus, the reactions not only do not run to completion, but 

 the purification of the product is complicated by the presence of phos- 

 phorus bodies. The use, therefore, of the chlorides of sulphur and 

 phosphorus is of no value, especially as carbon tetrachloride is now so 

 cheaply obtained. 



We have found that the separation of the pjn-osulphuryl chloride 

 and chlorsulphonic acid formed in the Schiitzenberger reaction is com- 

 pletely accomplished by the addition of fused sodic chloride in excess 

 and subsequent distillation under diminished pressure. The pyrosul- 

 phuryl chloride is unaffected by the sodic chloride and is distilled off. 

 The chlorsulphonic acid is converted to its sodium salt, remains in the 

 distillation residue, and may even be regenerated from this by distilla- 

 tion with fuming sulphuric acid. The recovery is not advantageous, 

 however, owing to the difficulty of purifying the product. We have 

 also found that pyrosulphuryl chloride may be separated in a mixture 

 of the two bodies by crystallization. When the mixture is cooled and 

 centrifu gaily filtered below the melting point of p)a'Osulphuryl chloride 

 (ca.— 37°), a very pure product is obtained, — the chlorsulphonic acid, 

 with some pyrosulphuryl chloride, remaining entirely in the filtrate. 



VOL. XLVII. — 44 



