718 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Pyrosulphuryl chloride is obtained in a perfectly pure state and its 

 chief constants determined. A rapid method is devised for finding 

 melting points at low temperatures. 



Chlorsulphonic acid is shown to be unstable when subjected to dis- 

 tillation, but it is purified by crystallization and its chief constants are 

 determined. 



It is confirmed that the Schiitzenberger reaction of sulphur trioxide 

 upon carbon tetrachloride, which is best adapted to the preparation of 

 pyrosulphuryl chloride, gives also chlorsulphonic acid when the sul- 

 phur trioxide is in the form of oleum, and it is shown that the propor- 

 tion of the two bodies in the product depends roughiy upon the 

 hydration of the oleum (Table II). It is also shown that, with a 

 hydration corresponding to that of pyrosulphuric acid, 2S03' HoO, or 

 greater, only chlorsulphonic acid is formed, and that, while the limit 

 of the formation of chlorsulphonic acid is theoretically at the hydra- 

 tion corresponding to the formula 2S03' 3H2O, yet the increasing 

 concentration of the water up to the latter point results in a more 

 rapid decomposition of the chlorsulphonic acid than the theory 

 demands. 



A method of separation of the products of the Schiitzenberger reac- 

 tion is described, by which the pyrosulphuryl chloride may be com- 

 pletely freed from chlorsulphonic acid, and the latter may also be 

 recovered. 



The conditions under which pure chlorsulphonic acid is best pre- 

 pared by the Williamson method are studied, and it is confirmed that 

 the action of the hydrochloric acid is only upon the sulphur trioxide 

 in the oleum in excess of that corresponding to the formula SOs" H2O. 



The dissociation of chlorsulphonic acid is studied and discussed. 



Properties of mixtures of pyrosulphuryl chloride and chlorsulphonic 

 acid are given (Table III). 



The action of water upon pyrosulphuryl chloride is studied. 



In conclusion, we desire to express our indebtedness to the C. M. 

 Warren Fund of Harvard University for assistance in defraying the 

 expense of the liquid air used in this investigation. 



Hakvakd University, Cambridge, Mass., 

 December, 1911. 



