OP ARTS AND SCIENCES. 189 



time the formation of the sulphonic acid is complete. We have usually 

 taken three parts of sulphuric acid to one of pyromucic, and have 

 allowed the viscous solution to stand for twenty-four hours before 

 diluting and neutralizing with baric carbonate. The aqueous solution 

 filtered from the baric sulphate and concentrated by evaporation de- 

 posits on cooling globular aggregations of minute crystals, which are 

 readily purified by recrystallization from hot water. The acid pre- 

 pared by exact precipitation with sulphuric acid is extremely soluble 

 in water, but may be obtained by concentration in large transparent 

 prisms which deliquesce in moist air. 



Baric b-Sulphojyyromucate, BaC-H 2 SO . 4 H 2 0. — This salt crys- 

 tallizes in thin flat prisms, which are usually closely aggregated in 

 hemispherical masses. It is readily soluble in hot water, more spar- 

 ingly soluble in cold water, and its aqueous solution is precipitated by 

 the addition of alcohol. When dried by exposure to the air it contains 

 four molecules of water, a part of which it slowly loses over sulphuric 

 acid or at 100°, the rest at 160°. 



I. 2.1205 grm. of the air-dried salt lost, at 162°, 0.3827 grin. H 2 0. 

 II. 2.5754 grm. of the air-dried salt lost, at 160°, 0.4605 grm. H„0. 



H 2 



I. 0.7695 grm. of the salt dried at 160° gave 0.5480 grm. BaS0 4 . 

 II. 0.7010 grm. of the salt dried at 160° gave 0.4990 grm. BaS0 4 . 



Ba 



The solubility of the salt in cold water we have determined accord- 

 ing to the method of V. Meyer. 



I. 15.1350 grm. of a solution saturated at 21° gave 0.3672 grm. 



BaSO r 

 II. 13.9856 grm. of a solution saturated at 21° gave 0.3384 grm. 

 BaS0 4 . 



The aqueous solution saturated at 21° therefore contained the fol- 

 lowing percentages of the anhydrous salt : — 



I. ii 



3.40 3.39 



