120 BACTERIAL ORIGIN OF tJUMS OF A RABIN GROUP, 



acid. This was also shown by the decided formation of calomel 

 on boiling the distillate with mercuric chloride. 



The remaining solution of the volatile acids was evaporated to 

 dryness after the addition of an excess of calcium carbonate. 

 The dry residue was extracted with strong alcohol, and a portion 

 of the solution tested with zinc nitrate; no precipitate of zinc 

 valerate was formed. The remainder of the alcoholic solution 

 was evaporated to dryness and the small residue was found to be 

 insoluble in strong alcohol, and on the addition of dilute sulphuric 

 acidj evolved the odour of acetic acid. Thus the only volatile 

 acids that are formed by the bacteria are acetic and formic. 



The non-volatile acids which had been set aside to crystallise 

 produced colourless prisms that melted at 180°. They could be 

 sublimed and a neutral solution formed a pale buff precipitate 

 with ferric chloride. The cr3^stals, therefore, were succinic acid. 



Calcium acetate was added to the mother liquor and a slight 

 precipitate was deposited in twenty-four hours. The precipitate 

 consisted of microscopic octahedra of calcium oxalate. 



The filtered solution was warmed, then placed in the water- 

 bath, but no precipitate of calcium citrate could be obtained. 

 Half of the solution was neutralised with milk of lime and 

 returned to the remainder, but still no precipitation could be in- 

 duced. Evidently citric acid is not a b3^-product of the bacteria, 

 and in the preliminary experiments this acid must have been 

 derived from the potato extract. 



The solution was treated with an excess of milk of lime and 

 filtered. The filtrate, after evaporation to dryness, was extracted 

 with hot 70 % alcohol. The slight residue, insoluble in the alcohol, 

 consisted of carbonate and succinate of calcium. Mammillated 

 crystals of calcium lactate separated out from the alcohol on cool- 

 ing, and the quantity showed that lactic acid"^ was the chief 

 constituent of the non -volatile acids. The lactate was re- 

 crystallised from alcohol (calcium succinate being found as an 

 impurity) and an analy^sis made of the salt. 



0-4965 grm. gave 0-2245 grm. CaCO., = 18 09 % Ca. 

 Calcium lactate contains ... ... 18-35 % Ca. 



