526 



CHAPTER XXV 



Determination of Gums. — By gums are meant those bodies insoluble in 

 alcohol ; loo c.c. of juice are concentrated to a volume of about 20 c.c, and 

 poured into 100 c.c. of 90 per cent, alcohol containing i c.c. hydrochloric 

 acid. The precipitate is allowed to settle and washed by decantation with 

 strong alcohol, collected on a tared filter paper, or, better, in a Gooch crucible, 

 and dried to constant weight. The increase in weight gives gums and ash ; 

 the weight of ash is determined, and being deducted from the weight of gum 

 and ash gives the weight of gum. 



Acidity and Alkalinity. — 100 c.c. of the juice are titrated from a burette 

 with decinormal alkali ; to the juice a few drops of phenolphthalein solution 



»g— 



" rA,s is made of /2 Pangt^ 



Fig. 341 



Fig. 342 



are added, the neutralization of the excess of acid being shown by the appear- 

 ance of a pink coloration. The juice may be conveniently contained in a 

 white porcelain basin. In this method the juice is alkaline to litmus before 

 the appearance of the pink colour. A variation of this procedure is given 

 in Chapter XIII. 



Carbonated Juice. — The carbonation process, which is but sparingly used 

 in cane sugar factories, requires special methods for its control ; an abstract 

 of the methods employed in beet sugar factories may be given here. 



It is customary to determine the alkalinity of the juice of the first and 

 second saturation in terms of lime as CaO ; as this determination has to be 

 done rapidly, special methods of moderate accuracy are employed. One 

 of the simplest and most convenient is Vivien's. A standard acid containing 

 0-875 grm. H2SO4 per 1,000 c.c. is prepared: the acid is standardized 



