SANGER-RIEGEL. — PYROSULPH. CHLORIDE-CHLORSULPH. ACID. 677 



calculated (4.03) and the analysis indicated a pure chlorsulphonic acid, 

 but there was probably enough pyrosulphuryl chloride present to raise 

 the low density which pure chlorsulphonic acid usually shows owing to 

 its dissociation. Similarly, Williams ^^ in 1869, repeating the Wil- 

 liamson reaction in the latter 's laboratory, is led by density (4.56) and 

 analyses to consider his product pure chlorsulphonic acid. The boiling • 

 point is not given. 



The first recorded use of carbon tetrachloride as a chlorinating agent 

 is by Schiitzenberger ^^ in 1869. On warming this with sulphur tri- 

 oxide until the phosgene was expelled, a product was obtained boiling 

 at 130°, reacting "at once" with water, and giving " figures leading 

 to the formula S2O5CI2." The sulphur trioxide was evidently hydrated 

 and the product contained much chlorsulphonic acid. In the next year 

 Armstrong 20 repeated the reaction and suggested its use as a source of 

 phosgene. His product boiled between 141° and 145°, was difficult to 

 purify, and did not decompose water easily. The analysis corresponded 

 more nearly to that of pyrosulphuryl chloride. Substituting chloro- 

 form for carbon tetrachloride, Armstrong obtains what he considers 

 from the analysis to be a mixture of the two bodies. He also investi- 

 gates the action of phosphorus trichloride on sulphur trioxide, but with 

 unsatisfactory results. 



Prudhomme ^i in 1870 tried the action of hexachlorethane on sul- 

 phur trioxide in a closed tube at 150°. The product boiled at 140° 

 and was considered to be pyrosulphuryl chloride. No analytical data 

 are given. 



The study of the question by Michaelis 22 in 1871 and succeeding 

 years is of interest. Using sulphur trioxide " free from hydrate " with 

 phosphorus pentachloride he obtains " pyrosulphuryl chloride " accord- 

 ing to the reaction : 



2SO8 + PCU = SaOeCU + POCI3. 



The product boiled at 143°, acted quietly with water, and had a 

 specific gravity of 1.819 at 18°. With sulphuric acid, the reaction was 

 considered to be 



3H2SO4 + PCle = SSOgHCl + HPOs + 2HCI 



" Jour. Chem. Soc, 22, 304 (1869); Zeitschr. f. Chcm., 12, 665 (1869). 

 " Compt. rend., 69, 352 (1869); Jahresb., 1869, 209; Ann., 154, 375. 

 20 .1. prakt. Chem., 109, 244 (1870); Ber., 2, 712 (1869) and 3, 7.30 (1870). 

 " Compt. rend., 70, 1137 (1870); Ann. Chem. Pharm., 156, 342 (1870). 

 " Jena Zeitschr., 6, 235 (1871); Zeitschr. f. Chem. (2), 7, 149 (1871). 



