674 PROCEEDINGS OF THE AMERICAN ACADEMY. 



During certain investigations in this laboratory it became necessary 

 to find better methods for the separation and purification of pyrosul- 

 phuryl chloride and chlorsulphonic acid than heretofore described, and 

 to determine with greater accuracy their more important physical con- 

 stants. It was very soon evident, not only that much of the literature 

 on the subject was valueless, since most observers had worked with a 

 mixture of the two substances or with impure material, but also that a 

 separation of the mixture into pure components or a complete purifi- 

 cation of either body could not be readily accomplished on the lines 

 laid down by these observers. We have succeeded, however, by uti- 

 lizing some of the facts already known and others which became evi- 

 dent in the course of our investigation, in preparing both of these 

 bodies in quantity and of great purity. ^ 



Historical. 



Action of MetalUc Chlorides on Sulphur Trioxide. 



The complete history of pyrosulphuryl chloride and chlorsulphonic acid 

 begins in 1822-1823 with the study of the reaction between sulphur 

 trioxide and sodic chloride at high temperature by Sertiirner,^ Doberei- 

 ner,3 and Gmelin.* Sertiirner had erroneously considered the products 

 to be hydrochloric acid and sodic sulphate ; Dobereiner thought that a 

 gaseous compound of chlorine and sulphur dioxide was formed, while 

 Gmelin showed, although only qualitatively, that the gaseous product 

 was a mixture of chlorine and sulphur dioxide. Rose ^ in 1836 investi- 

 gated the reaction at low temperature, using other metallic chlorides as 

 well. Fused sodic chloride absorbed anhydrous sulphur trioxide, forming 

 a solid, transparent mass, which, when heated, gave chlorine and sulphur 

 dioxide, similarly to Gmelin 's observation. Undoubtedly, as R. Wil- 

 liamson 1* also points out. Rose had in his hands the sodium salt of 

 chlorsulphonic acid. Rosenstiehl ^ in 1861 distils a mixture of fused 



* Acknowledgment is due to Mr. Laurence Haines Whitney for much assis- 

 tance in the beginning of this investigation, particularly in the separation of 

 pyrosulphuryl chloride and chlorsulphonic acid by crystallization and centrif- 

 ugal filtration at low temperature, and in the study of the use of phosphorus 

 pentoxide as a dehydrating agent, both in the preparation of the two bodies 

 and in the conversion of chlorsulphonic acid to pyrosulphuryl chloride. 



2 Gilbert's Ann., 72, 109 (1822). 



3 Ibid., 72, 331 (1822). 



4 Ibid., 73, 209 (1823). 



B Pogg. Ann., 38. 117 (1836). 



6 Compt. rend., 53, 658 (1861); Jahresb., 1861, 120; Rep. chim. pur., 4, 60 

 (1861). 



