G88 PROCEEDINGS OF THE AMERICAN ACADEMY. 



From the reaction 



(1) 2S08 + CCI4 = COCI2 + S2O6CI2 



we should have only pyrosulphuryl chloride when the sulphur trioxide 

 is absolutely anhydrous, as Konovalofif ^^ and others have shown. But 

 from the reaction 



(2) 2SO3 + H2O + CCI4 = COCI2 + 2SO3HCI, 

 (Reaction c of Table II.) 



the moisture conditions of which are fulfilled by ordinary fuming sul- 

 phuric acid, H2S2O7, we should theoretically get only chlorsulphonic 

 acid as the product. We may assume in this case that pyrosulphuryl 

 chloride would be at first formed according to (1) and then decom- 

 posed according to 



(3) S2O5CI2 + H2O = 2SO3HCI. 



If now we increase the hydration of the acid, we should expect the 

 chlorsulphonic acid to be decomposed according to 



(4) 2SO3HCI + 2H2O = 2H2SO4 + 2HC1. 



The limit of this decomposition is shown by combining equations (1), 

 (3), and (4): 



(5) 2SO8 + 3H2O + CCl, = COCI2 + 2H2SO4 + 2HC1 

 (Keaction a of Table II.) 



and we should expect no chlorsulphonic acid to be formed at a concen- 

 tration equivalent to 2S03"3H20. 



With a weaker acid, however, the greater concentration of the water 

 causes a greater proportional decomposition of the chlorsulphonic acid 

 and a larger amount of sulphuric acid ; in other words, less sulphur 

 trioxide is effective in attacking the carbon tetrachloride. Hence, as 

 the proportion of water in the acid increases, there is less than the 

 theory of chlorsulphonic acid found, more sulphuric acid left, and the 

 limit of the formation of chlorsulphonic acid is reached sooner. The 

 maximum effect (Preparation 8, p. 696) appears to be at a concentra- 

 tion of between 22 and 23 per cent of water. From 100 parts of the 

 monohydrate, SO3H2O (18.37 per cent water) we should get about 22 

 parts of chlorsulphonic acid instead of 59.4 parts (Preparation 9) 

 as would appear from Table II. From 100 parts of the hydration 

 3S03'2H20 (13.04 per cent water), there would be about 52 parts of 

 chlorsulphonic acid instead of 105.5 parts (Preparation 7). 



Now, as the concentration of the acid decreases to the hydration 

 2SO3 • H2O (10.11 per cent water) there is less and less tendency to de- 



