OF ARTS AND SCIENCES. 143 



Calcic Tetrabrompropionafe, Ca(C.;IIBr^0^)2. The calcium salt, 

 made by neutralizing an aqueous solution of the acid with calcic car- 

 bonate and allowing the solution to evaporate spontaneously, crys- 

 tallized in needles which proved to be anhydrous. The salt freed 

 from moisture by pressure did not materially lose in weight when 

 exposed to the air, and when air-dried lost nothing over sulphuric 

 acid. 



I. 0.5065 grm. of the salt dried over IlaSO^ gave on ignition with 

 IT^SO, 0.0888 grm. CaSO^. 

 II. 1.088G grm. of the salt dried over H.SO^ gave 0.1850 grm. 

 CaSO, . 



Calculated for Ca(C3H.,Br40.,)2. Found. 



I. II. 



Ca 4.89 5.1G 5.00 



When a solution of baric tetrabrompropionate was heated baric 

 bromide was formed, carbonate dioxide escaped, and at the same time 

 the liquid became turbid through the separation of a colorless oil.* 

 On distilling the liquid the oil passed readily over with steam, and 

 since from the method of its formation there could be little doubt that 

 it was tribromethylen, for identification it was immediately converted 

 into its dibromide by the addition of bromine. The crystalline addi- 

 tion product which was thus obtained when purified by recrystallization 

 melted at 53° and gave on analysis a percentage of bromine which 

 showed it to be pentabromethan. 



0.1696 grm. substance gave 0.3766 grm. AgBr. 



Calculated for C^llBr^ . Found. 



94.12 94.48 



This decomposition may therefore be expressed by the equation : 



Ba(C3HBr,0.,)2 = BaBr., + 2 CO., + 2 CaHBrg. 



By the action of an alcoholic solution of potassic hydrate upon tetra- 

 brompropionic acid a molecule of hydrobromic acid is removed, and 

 there results the tribromacrylic acid melting at 118° which we have 



* Mauthner and Suida assert tliat this decomposition also takes place on long 

 standing at ordinary temperatures. They were therefore able to isolate no 

 salts. We have never observed any decomposition in the cold. Loc. cit. 

 p. 284. 



