OP ARTS AND SCIENCES. 355 



Trichlorpyromucic acid is readily soluble in alcohol or ether, quite 

 readily soluble in boiling benzol, and but sparingly soluble in cold 

 benzol. Hot water dissolves it but sparingly, and as the solution cools 

 most of the acid is deposited in microscopic needles which melt at 

 172-173°. This melting point was so much below that which we had 

 been led to expect from analogy to the known acid containing bromine 

 that we felt some doubt of its correctness, more especially since the 

 crude acid was so far from pure. A sample of the acid melting at 

 172-173° was therefore recrystallized twice from water and then three 

 times from benzol without perceptibly changing the melting point. 

 The acid was then converted into the calcium salt, and this separated 

 by crystallization into three successive fractions. The acid from 

 these three fractions melted simultaneously and sharply at 172-173°. 

 Finally, the ethyl ether was made, and the acid prepared from the 

 repeatedly recrystallized pure ether melted at the same point. 



The solubility of the acid in water at 19°. 5 was determined by boil- 

 ing with baric carbonate a weighed quantity of a solution of the acid 

 saturated at that temperature, and determining the barium dissolved as 

 sulphate. 



I. 49.1742 grm. solution saturated at 19°.5 gave 0.0344 grm. BaS0 4 . 

 II. 47.0228 grm. solution saturated at 19°.5 gave 0.0331 grm. BaSo 4 . 



The solution saturated at 19.5° therefore contained the following 

 percentages of acid : 



i. ii. 



0.13 0.13 



Baric Trichlorpyromucate, Ba(C 5 Cl.,0 3 ) 2 . 4 H 2 0. — The barium salt 

 was prepared by precipitating a dilute solution of the ammonium salt 

 with baric chloride, and recrystallizing the sparingly soluble salt thus 

 thrown down from hot water. The salt proved to be but sparingly 

 soluble even in hot water, and still less soluble in cold water. It sep- 

 arates from a hot concentrated solution in needles which apparently 

 contain four molecules of water. The salt is permanent in the air, 

 but loses three molecules of its crystal water over sulphuric acid. 

 When dried at 120°, it still retains a half-molecule of water which 

 cannot be expelled without essential decomposition. 



I. 0.6847 grm. air-dried salt gave 0.2511 grm. BaS0 4 . 



II. 0.6205 grm. air-dried salt gave 0.2273 grm. BaS0 4 . 



III. 0.5672 grm. air-dried salt gave 0.2076 grm. BaS< \. 



IV. 1.3625 grm. air-dried salt lost over II 2 S0 4 0.1148 grm. H.,0 and 



at 120° 0.1338 grm. II 2 0. 



