CAN?; SUGAR. 



a uniform gelatinous mass that can be measured with a pipette. Determine 

 the amount of copper hydroxide per c.c. of this mixture. 



Determination of Gums. By gums are meant those bodies 

 insoluble in alcohol ; 100 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 1 c.c. 

 hydrochloric acid. The precipitate is allowed to settle and washed by decan- 

 tation 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. 1. 100 c.c. of the juice are titrated 

 from a burette with decinorrnal alkali ; to the juice a few drops of phenol - 

 phthalein solution are added, the neutralization of the excess of acid being 

 shown by the appearance of a pink colouration. 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. 



2. To 50 c.c. of the juice an excess of alkali is added and the volume 

 completed to 100 c.c. To successive further quantities of 50 c.c. varying 

 quantities of decinormal alkali are added and the volume completed to 100 c.c. 

 The minimum quantity of alkali that gives a juice of the same tint as that 

 to which an excess of alkali was added is a measure of the acidity of the 

 juice. The tint may be observed in small test tubes of about half-an-inch 

 diameter. 



The point of exact neutrality in cane juice is hard to determine, the 

 change not being sharp, but a dirty olive-green colour obtaining over as many 

 as 4 to 5 c.c. of decinormal alkali ; and when indicators are used the change is 

 masked by the colour of the juice. 



Carbonated Juices. 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 Yivien's. A standard acid containing 

 875 gnn. H 2 S0 4 per 1000 c.c. is prepared; the acid is standardized against 

 decinormal alkali; 10 c.c. of the latter are equivalent to 56 c.c. of the acid 

 which, when exactly made up, neutralizes volume for volume a solution 

 containing -05 grm. lime per 1000 c.c. ; the indicator employed is phenolph- 

 thalein, which is placed in the stock of standard acid. The tube, Fig. 264, 

 is filled to the zero mark, and the standard acid added; as long as lime is- 



482 



