I OP ARTS AND SCIENCES. 101 



It will be seen by inspection of the forms of dibromiodacrylic and 

 chlorbromiodacrylic acids that these substances present a striking in- 

 stance of isomorphism. In fact the only form not common to both is 

 that of {201}, which was not observed on the crystals of dibromioda- 

 crylic acid. This similarity in form, which extends also to tribroma- 

 crylic acid, is rendered more prominent by a comparison of the observed 

 angles. The measurements of tribromacrylic acid show a greater 

 variation in the observed angles except in the case of the angle which 

 the prism {110} makes with the piuacoid {010}. 



Dibromiod- Chlorbromiod- Tribrom- 



acrylic acid. acrylic acid. acrylic acid. 



110 and 010 64° 65° 3' 65°33 



110 " TIG 128° 130° 6' 



110 " 001 123° 26' 123° 26' 



111 " 010 62° 11' 62° 43' 

 111 " 110 59° 141' 58° 23' 

 121 « 010 42° 59' 43° 48' 

 121 « 110 55° 59' 55° 45' 



The elements of the crystals also proved to be nearly identical. 



Dibromiod- Chlorbromiod- 



acrylic acid. acrylic acid. 



Clinodiagonal a 0.617 0.594 



Orthodiagonal 5 1. 1. 



Vertical axis c 0.581 0.572 



Angle of axes XZ 52° ll'i 52° 47' 



A study was made of some of the more important salts of chlorbrom- 

 iodacrylic acid. 



Baric chlorhromiodacrylate Ba(C3ClBrI02)2 • SJHjO. 



A solution of the acid was saturated with baric carbonate, filtered, 

 and concentrated on the water bath. The salt separated on cooling 

 in rectangular prisms, which when dried by exposure to the air con- 

 tained three and a half molecules of crystal water. It is quite soluble 

 in cold, and very soluble in hot water. 



I. 0.8250 grm. of the air-dried salt lost when heated to 80° 0.0636 



grm. HgO. 

 II. 0.7273 grm. of the air-dried salt lost at 80° 0.0540 grm. HgO. 



III. 0.5401 grm. of the air-dried salt lost at 80° 0.0384 grm. H^O. 



IV. 0.5502 grm. of the air-dried salt lost at 80° 0.0438 grm. H^O. 



