610 THE GUM FEUMENTATIOX OF SUGAR CANE JUICE, 



With regard to" the relative amounts of acids formed in 

 saccharose solutions, a determination was made as follows. The 

 acids separated from a fourteen days' chalk culture measured 

 about 20 c.c. This was diluted with an equal volume of water, 

 and distilled in a current of steam. When 141 c.c. had passed 

 over the distillation was stopped, and a 10 c.c. portion was found 

 to contain a quantiy of acid equivalent to 0-35 c.c. ^/^ acid which 

 for the whole 141 c.c. equals 4*9 c.c. The remaining 131 c.c. were 

 evaporated down with chalk to dryness, and extracted with hot 

 absolute alcohol. The calcium salt which dissolved weighed -054 

 grm., and on the assumption that this consisted entirely of 

 calcium butyrate, is equivalent to 0*048 grm. butyric acid in the 

 whole distillate. The remaining acids ( = 2'2 c.c. ^Z^), if taken as 

 a mixture of equal parts of formic and acetic, would weigh 0*023 

 grm. This gives a total of 0*071 grm. of acids in the distillate. 

 It must be borne in mind that lactic acid occurs in the distillate, 

 and is calculated with the other acids, so that for this reason 

 alone these figures must not be considered too narrowly. The 

 main object in quoting them is to show how small is the quantity 

 of the volatile acids when compared with the lactic acid. The 

 residual fluid in the distilling flask was made up to 50 c.c, and 

 10 c.c. was boiled with zinc oxide and filtered. The filtrate, 

 when evaporated and dried at 160°, yielded 1*076 grms. of a zinc 

 salt. Another 10 c.c. was titrated with standard alkali by 

 Kunz's method.* It contained — 



Lactic acid ... ... ... 0*673 grm. 



Dilactic acid as lactic acid ... 0139 grm. 



Total lactic acid ... ... 0*812 grm. 



The zinc salts of these acids would have yielded 1*0745 grms., 

 which agrees closely with 1*076 grms. found. In the total 

 residual liquor there were, therefore, present 08 12 x 5 = 4*06 

 grms. lactic acid. Comparing this with the volatile acids, there 



* Kunz, JoLirn. Chem, Soc, 1901, Abs. ii., 428. 



