OF ARTS AND SCIENCES. 



309 



the polarizer remains unchanged. The apparent angles of the adjacent 

 edges, when the crystal lies upon its basal plane, are approximately 

 as follows : — 



Edge 100—001 upon edge 110—001 

 " 100—001 " " 1T0— 001 



« lio—ooi « " no— ooi 



141° 



147° 

 72° 



OO 1 



100 



The Potassium Salt, C 6 H 4 C1CH 2 S0. 3 K, was made by adding potas- 

 sic sulphate to the barium salt ; the filtrate from the baric sulphate 

 formed was evaporated to dryness, and the organic salt, dissolved out 

 from the excess of potassic sulphate with absolute alcohol, purified by 

 crystallization from water. 



1.1328 grs. of the salt dried in vacuo lost when heated to 160° 

 0.0075 gr., corresponding to 0.66 per cent. 



As one molecule of water corresponds to 6.85 per cent, it is evident 

 that this salt, like that of sodium, is free from water of crystallization. 



0.3000 gr. of the salt dried at 160° gave by the method of Carius 

 0.1760 gr. AgCl. 



0.3165 gr. gave by the same method 0.3025 gr. BaS0 4 . 

 0.3065 gr. gave, when heated with pure H 2 S0 4 , 0.1075 gr. of 

 K 2 S0 4 . 



Calculated for C 7 H S C1S0 3 K. Found. 



Chlorine 14.50 14.50 



Sulphur 13.08 13.13 



Potassium 15.98 15.75 



It resembles the sodium salt closely in appearance, but is much 

 more soluble in alcohol. As, therefore, the separation of this salt from 

 potassic bromide would be easier than that of the corresponding 

 sodium compounds, it is better in making a salt of the sulphoacid 

 from parachlorbenzylbromide to use potassic in place of sodic sulphite. 



To prepare the other salts of the parachlorbenzylsulphoacid the 

 mother-liquor of the sodium salt was treated with a small quantity 



