676 PROCEEDINGS OF THE AMERICAN ACADEMY. 



had known that this was a process of rectification, we might have had 

 pure pyrosulphuryl chloride at an earlier date. The further researches 

 of Rose ^2 do not throw any light on the preparation of either body. 



A. Williamson i* in 1854, by the action of phosphorus pentachloride 

 on "sulphuric acid" (strength not stated), obtained a liquid boiling 

 at 145°, decomposing violently with a small amount of water, quietly 

 with an excess. No method of purification is given, nor are there any 

 analyses of the product, but Williamson concludes that it was chlor- 

 sulphonic acid, and advances for the first time the theory of the suc- 

 cessive substitution of the hydroxyls in sulphuric acid by chlorine. He 

 makes a crude sodium salt, and considers the acid itself to be identical 

 with the preparation of E-ose,* for in his opinion that contained "the 

 elements of water." Williamson obtains a "similar" acid by the ac- 

 tion of hydrochloric acid on sulphur trioxide, which must be taken as 

 the first use of this reaction in the preparation of chlorsulphonic acid. 

 Though both of his products were impure, the first probably contained 

 some pyrosulphuryl chloride, the second none. 



R. Williamson i* in 1857 states that chlorsulphonic acid can be 

 made by the action of chloride of sulphur and chlorine on sulphuric 

 acid and by the combination of chlorine and sulphur dioxide in contact 

 with heated platinum black. The product of the first reaction is said 

 to have the same properties as that obtained by A. Williamson, but 

 details of purification, properties, and methods of analysis are lacking. 

 From information supplied by A. Williamson, it is stated that contin- 

 ued distillation of the body leads to its decomposition into sulphuric 

 acid and sulphuryl chloride. 



Schiff 1^ in 1857 shows that the supposed compound of phosphorus 

 pentachloride and sulphur trioxide obtained by Persoz and Bloch !• 

 was identical with the preparation of A. Williamson, and obtained by 

 the reaction a liquid boiling at 140-150°, which decomposed with water 

 into sulphuric and hydrochloric acids. 



Baumstark ^^ in 1866, using phosphorus pentachloride with fuming 

 sulphuric acid, obtained a liquid boiling from 145° to 156°, mainly at 

 150-152°, decomposing gradually with much water, violently with a 

 small amount. The agreement of the vapor density (4.10) with the 



" Pogg. Ann., 52, 57 (1841); 85, 510 (1852). 



" Proc. Roy. Soc, 7, 11 (1854); Phil. Mag. (4), 7, 365 (1854); Jour. Chem. 

 Soc, 7, 180 (1855); Jour, prakt. Chem., 62, 377 (1854); Ann., 92, 242 (1854). 

 " Jour. Chem. Soc, 10, 97 (1858); Jour, prakt. Chem., 73, 73 (1858). 

 « Ann., 102, 114 (1857). 

 " Compt. rend., 28, 86 (1849). 

 " Ann., 140, 75 (1866). 



