IIG BACTERIAL ORIGIN OF GUMS OF ARABIN GROUP, 



coiifiriii the method of precipitation and microscopical exami- 

 nation. 



The riltrate from the calcium citrate was treated with an 

 excess of milk of lime and filtered. The residue obtained on 

 evaporating the filtrate to dr3^ness was extracted with hot 70 % 

 alcohol and filtered. The filtrate, after standing overnight, had 

 deposited mammillated crusts of what appeared to be calcium 

 lactate. These were washed with cold alcohol and ether and 

 finally dried at 100°. In the dry crystals the calcium was 

 estimated : — 



0-2740 grm. gave 0-1284 grm. CaCO. = 18-75 % Ca. 

 Calcium lactate contains ... ... 18-27 % Ca. 



Another portion of the fixed acids, after separating the 

 crystals of succinic acid, was boiled with an excess of baryta, 

 water, and neutralised with sulphuric acid. The barium sulphate 

 was removed, and the clear filtrate treated with ammonia and 

 three volumes of alcohol. The precipitate, when dried at 140°,* 



* The barium salt was dried at 100° until it ceased to lose weight. On 

 increasing the temperature to 140*^ a further loss of weight occurred. As the 

 drying temperature would influence the analysis of the salt, a small quantity 

 of succinic acid, which was one of the acids present in the solution, was 

 neutralised with baryta water, and precipitated with alcohol, filtered, and 

 dried at 100° and 140®. The following results were obtained : — 



0-1 grm. succinic acid gave 0-2102 grm. barium succinate dried 



at 100°, and 0-206 2grm. dried at 140°. 

 The barium sulphate therefrom weighed 0*1874 grm. 

 Ba % at 100° -= 52-43; at 140° = 53 '44. 

 Ba in BaC^H^O^ (theoretical) 54-16 %. 

 98*04 % of the succinic acid was recovered. 

 Citric acid was converted into the barium salt, and the following numbers 

 were obtained : — 



0-1 grm. crystallised citric acid gave 0-1840 grm. barium citrate 



at 100°, and 0-1740 grm. at 140°. 

 The barium sulphate therefrom weighed 0*1523 grm. 

 Ba % at 100° = 48-67; at 140° - 51*47. 

 Ba in BaalCeH.O^).^ = 52*11 %. 

 98*53 % ot the citric acid was recovered. 

 From these results it is evident that the barium salts must be dried at 

 a temperature over 100°. 



