266 CHAPTER XIII 



In the presence of larger quantities of alkalies, the reducing sugars are 

 actually destroyed. The products of decomposition are dependent on 

 the temperature. At temperatures below 60 C. the chief products are 

 saccharic and lactic acids, with only small quantities of glucinic acid. Above 

 this temperature glucinic acid is formed in large quantity. This body 

 forms a basic glucinate with lime, which is insoluble in alkaline solution 

 and is of a dark brown colour. At temperatures near the boiling 

 point, the whole of the reducing sugars are rapidly destroyed as well as 

 these dark-coloured bodies, but the action has not been completely 

 examined. 



Action of Lime on Cane Juice. If lime either in a thin suspension or as 

 saccharate be added to a cane juice, the first effect is the neutralization 

 of any free acid present. The continued addition causes the appearance 

 of a precipitate consisting in part of those bodies referred to in a previous 

 chapter as colloids. There is also precipitated the phosphoric acid which 

 is always present and some small quantity of aluminium and ferric oxides. 

 In the precipitate is contained most of the nitrogen that is present in the 

 albuminoid form, the chlorophyll, cane wax and some of the colouring matter. 

 The actual weight of the precipitate due to the action of different quantities 

 of lime was found to be as follows : 



To a juice which had an acidity of 3-2 c.c, normal per 100 c.c. with 

 reference to phenolphthalein, lime in the quantities indicated below was 

 added, and the weight of the precipitate determined. 



Acidity of juice Lime used as Weight of pre- Weight ot 



in normal c.c. CaO ; grams per cipitate per ash in 



per 100 c.c. 100 c.c. 100 c.c. precipitate. 



3-2 o 0*242 0-012 



2-7 0-013 0-248 0-014 



2-3 0-026 0-264 0-024 



1-8 0-039 0-288 0-030 



1-4 0-052 0-320 0-044 



0-9 0-065 '34 " 0-070 



0-5 0-079 0-370 0-088 



o 0-092 0-408 0-104 



0-5 (alkaline) 0-104 0-406 0-112 



The maximum quantity of precipitation is seen to be reached as soon as 

 the juice becomes alkaline towards phenolphthalein. As explained in the 

 previous chapter, heat or filtration alone removes the colloids from solution, 

 so that the action of lime and these agencies overlaps. The peculiarly 

 specific action of the lime is the precipitation of the phosphoric acid. The 

 figures given above refer to a juice which had been freed from the grosser 

 particles of suspended matter by filtration through glass wool. 



The Fate of the Lime in Contact with Cane Juice. A portion of the lime 

 which is added to cane juice remains in solution, and a portion is found in 

 the precipitate as shown in the following experiment : To 100 c.c. of cane 

 juice which contained 0-045 gram lime as CaO per 100 c.c., successive 

 quantities of lime were added, and the quantity of lime remaining in solution 

 determined, with the results shown below. 



