678 DETERTORATION OF SUGAR CRYSTALS IN BULK, 



precipitable by alcohol becomes less, and at the same time the invert 

 sugar increases. This is proved by the analysis of a 50 da3^s' 

 culture which in the following table is compared with the analysis 

 during the height of the fermentation. As in the previous paper, 

 the figures are expressed in parts (grms.) from 100 of the original 

 saccharose. 



Gum and Reducing Sugars in Old Cultures. 



12 days. 50 days. 



Mixed reducing sugars ... 62 .. 71 



Crude gum ... ... 31 . 22 



The slow hydrolysis of the gum is probably the result of the 

 action of the acids secreted by the organism and contained in the 

 culture fluid. In a previous paper {aritea, p. 595) the solvent action 

 of the acid upon the gum was noted, and it was seen that when the 

 acidity of the culture was not neutralised the gum was incom- 

 pletely precipitated, and during the process of eliminating the 

 alcohol it was partly (or entirely) converted into reducing sugar. 

 But to place the hydrolytic action of the acid, which is chiefly 

 lactic, beyond doubt, the following test was made. A fragment 

 of pure gum was dissolved in water and a portion of the solution 

 tested with Fehling's solution. There was no reduction of the 

 copper hydrate. Another portion was boiled for 30 seconds with 

 an equal volume of normal lactic acid, neutralised and tested, 

 when a copious precipitate of the red suboxide was obtained. 

 This test places the action of the acid beyond doubt. 



The action was also tested quantitatively. The acidity of the 

 50 days' culture was first tested and found to be equal to 9 c.c. 

 normal lactic acid in every 100 c.c. of culture fluid. Then 1-388 

 grms. of gum, free from reducing sugars and dried at 100° C. for 

 several days, were dissolved in 100 c.c. of water to which 0*9 c.c. 

 normal lactic acid was added. The solution was heated at 80° C. 

 for three hours, and after being cooled was made up to volume. 

 The sugar was estimated and found to be equal to 1*21 grms. of 

 reducing sugar. Assuming the gum to have been 96 % pure and 

 to have the formula C^HjyO-, the determination showed that 



