438 CHAPTER XXI 



and all tliese methods descend from the process proposed by Pay en in 1846. 

 A summary of these methods is appended. 



Payen's Method}'^ — The raw sugar is washed free from the adhering 

 molasses with a saturated solution of sugar in 88 per cent, alcohol, con- 

 taining also 50 c.c. acetic acid per litre. After the removal of the molasses, 

 the remaining crystals are dried, the loss in weight giving data to calculate 

 the quantity of adhering wash liquor, after which the weight of crystals 

 can be calculated. 



Scheihler's Method. ^^ — Four solutions are used, (i) 85 per cent, alcohol 

 saturated with sugar and containing 50 c.c. of acetic acid per litre. (2) 92 per 

 cent, alcohol as in (i). (3) 96 per cent, alcohol as in (i). (4) Two volmnes 

 of absolute alcohol and i volume of ether. The raw sugar is washed with 

 solutions 4, 3, 2, I, in the order named, the washing with (i) being continued 

 until the washings are colourless. The process is then reversed, and the 

 purified crystals are washed with solutions 2, 3, 4, in the order named, so as 

 to remove the adhering wash liquor. Finally, the residue of pure crystals 

 is brought into solution and polarized. 



Koydl's Method.'^^ — Five solutions are used, (i) 82 per cent, alcohol 

 with 50 c.c. acetic acid per litre. (2) 85 per cent, alcohol with 25 c.c. acetic 

 acid per litre. (3) 91 per cent, alcohol. (4) 96 per cent, alcohol. (5) Abso- 

 lute alcohol. Solutions i to 4 are saturated with sugar. In making the 

 determination 50 grams of the sugar are washed on a weighed filter paper 

 with 250 c.c. of solution (i), followed by washings with 50 c.c. each of solu- 

 tions 2, 3, and 4, and finally by 100 c.c. of 5. The residue of crystals is 

 then dried to constant weight. 



Herzfeld-ZimmeymannMethodV — In this process the raw sugar is washed 

 with a solution of sugar saturated at the temperature of observation. After 

 removal of the adhering molasses, the major portion of the wash liquor is 

 removed by centrifugalling, the residue is weighed and finally dried to con- 

 stant weight, whence is calculated the weight of crystals when the proportion 

 of sugar to water in the wash liquor is known. 



All these methods assume that the crystals in a raw sugar represent the 

 refined sugar capable of extraction. If the adhering molasses is not ex- 

 hausted, some sugar is capable of being obtained therefrom ; and, accordingly, 

 sugars of the same crystal content need not necessarily have the same re- 

 fining value. The methods would also be inapplicable to sugars boiled on 

 seed grain. 



The Refiner and the Producer. — In the following section is given an 

 algebraical representation of the relations between refiner and producer, 

 considered from the financial standpoint. 



The A mount of Raw Sugar obtainable from a Given Juice as determined 

 by its Composition. — If s, j, and m have the significance given to them in 

 Chapter XXVII, then, per unit of sucrose in the raw juice, the sucrose in a 

 raw sugar of purity s obtained from a juice of purity j, affording waste 



s (J — m) 

 molasses of purity m, is given by the expression 



If s changes to s^ the sucrose obtained is 



J {s — m) 

 Si (;■ - wi) 



j (Si - m) 

 Whence it follows that : — 



