522 CHAPTER XXV 



and 75 c.c. of hydrogen peroxide lo per cent, by volume. The flask and its 

 contents are maintained at ioo° C. for 20 minutes. After cooHng and neu- 

 trahzing, clarification is effected with basic lead acetate and the reading 

 obtained, which is intended to afford that due to cane sugar alone. Actually, 

 however, it has been found that the optical inactivity of the reducing sugars 

 is not absolute, although it is reduced to a very small quantity. 



Midler's Routine.^^ — Muller obtains the optical inactivity of the reducing 

 sugars as under : — A solution of 25 grams Rochelle salts, 32 grams caustic 

 soda, and 11 grams bismuth subnitrate, is made up to 500 c.c. Fifteen c.c. 

 of this solution is heated with 20 grams of molasses at 100° C. for 15 minutes. 

 After making up to 300 c.c. with the addition of basic lead acetate, the solu- 

 tion is filtered and transferred to a flask graduated at loo-iio c.c. It is 

 acidified with acetic acid and treated, if necessary, with a little especially 

 prepared decolorizing carbon. The volume is completed to no c.c, and the 

 filtrate used for the observation. 



Errors due to Dark Colour after Inversion. — Very often the inverted 

 solution is so dark-coloured that it has to be observed in extreme dilution. 

 A decolorizing effect is obtained by the addition of a crystal of sodium 

 sulphite, by the use of sulphurous acid (Pellet's process supra), by the action 

 of nascent hydrogen following on the addition of zinc dust to the inverted 

 solution (Lindet^^), and, best of all, by the limited use of bone char. In 

 the strong acid solution the absorption, if any, of sugars by the small quantity 

 necessary is undetectable by ordinary means. Pellet's sulphurous acid 

 process also affords very light-coloured solutions. 



The Determination of Sucrose as Invert Sugar. — Since cane sugar is 

 quantitatively converted into equal quantities of glucose and fructose, 

 this reaction affords a process when properly conducted of accurately 

 estimating cane sugar. It may be carried out, for example, as under : — 

 Prepare a solution of the material, such that it contains not more than 2 

 grams total sugars per 100 c.c. Take 100 c.c. of this material, clarify with 

 basic lead acetate, and de-lead with potassium oxalate, and make up to 200 

 c.c. and filter. Determine the reducing sugars in this filtrate. Place 50 c.c. 

 of the filtrate in a 100 c.c. flask, invert by any of the processes given above, 

 neutralize, make up to 100 c.c, and determine the reducing sugars in the 

 inverted solution. An example of this method of calculation to be used 

 follows : — 20 grams of molasses were dissolved in 1,000 c.c Fifty c.c. of 

 the de-leaded filtrate in Munson and Walker's routine afforded 0-1510 gram 

 copper, equivalent to o • 0760 gram invert sugar (using column 4 of Munson 

 and Walker's table*). Fifty c.c. of the inverted solution gave 223 • 8 grams 

 copper, equivalent to 0-1174 gram invert sugar (using column 3 of Munson 

 and Walker's table). The invert sugar present in 50 c.c. of the inverted 



solution is then 0-1174 — ~ 0-0794 gram, which is equivalent to 



0-0794 X 0"95 = 0'0754 gram cane sugar, and the percentage of cane sugar 



. ^, . • 4000 100 ^ 



in the molasses is 0-0754 X ' X — = 30-16 per cent. 



^^^ 50 20 ^ 



In this example clarification is effected with basic acetate of lead, and, if 



the reducing sugars originally present in the molasses are required, this 



scheme must not be followed. Clarification in this case must be obtained 



* See Appendix. 



