686 PROCEEDINGS OF THE AMERICAN ACADEMY. 



ing properties obtained by this long list of observers renders a revision 

 of the constants desirable. 



In deciding upon the purity of the products too much reliance has 

 been placed by most investigators on the analysis. The difference be- 

 tween the two molecular weights, 233 and 215, is so small that even a 

 very careful analysis might not detect a sufficient admixture of one 

 body to influence the properties of the other (v. Table III, p. 713), nor 

 show contamination by a slight amount of the products into which 

 each body is easily decomposed. 



In the separation and purification we have found most suggestive 

 the early statements of Rose concerning the action of fused sodic 

 chloride, the distillation under diminished pressure and the determi- 

 nation of the solidifying points as suggested by Besson. As a test of 

 purity we have paid little attention to the analysis, but have relied 

 upon the wide difference in melting points, the specific gravity, the 

 action with water, the characteristic appearance of the two bodies in 

 the solid state, and the color reactions with tellurium and selenium as 

 given by Prandtl and Borinski. 



General Methods for the Preparation of Pyrosulphuryl Chloride 

 and Chlorsulphonic Acid. 



The reaction of Schiitzenberger,!* in which sulphur trioxide is acted 

 upon by excess of carbon tetrachloride, is the one best adapted to the 

 preparation of pyrosulphuryl chloride, since the reaction runs more 

 nearly to completion, and excess of reagent is easily removed. While 

 the presence of chlorsulphonic acid has been suspected or shown by other 

 investigators in the crude product, yet it has not been definitely 

 pointed out that the hydration of the sulphur trioxide would deter- 

 mine the proportion of each body in the mixture, at least roughly, and 

 that by varying the strength of the sulphur trioxide a preponderance 

 of either body may be secured. This we have found to be true, and 

 we can therefore say, in general, that either pyrosulphuryl chloride 

 or chlorsulphonic acid may be made by the Schiitzenberger method. 

 The proportions of each body theoretically formed in the reaction by 

 using different concentrations of sulphur trioxide are given in the fol- 

 lowing table, though it will be shown that these proportions do not 

 hold good when the concentration of the sulphur trioxide is less than 

 89 per cent. 



