THE ASSAY OF SUGAR HOUSE PRODUCTS. 



Analysis of Filter -Press Cake. Water. Dry to constant 

 weight at a temperature of 105C. The use of a vacuum oven, though 

 permissible, is not so necessary as in the case of juices and molasses, &c. 



Sugar. The amount of insoluble matter in filter-press cake is so con- 

 siderable that error is introduced if the volume is not allowed for. Well- 

 pressed cake contains on an average 40 per cent, of insoluble matter, which 

 occupies about 20 c.c. per 100 grms. ; the volume occupied by the insoluble 

 matter in 25 grms. is then about 5 c.c., and if this quantity be weighed out 

 and made up to 100 c.c. after addition of lead acetate, the polariscope reading 

 will indicate at once the apparent percentage of sugar ; or instead, the normal 

 weight may be weighed out and polarized after making up to 105 c.c. 



In factories using the carbonation process, saccharates of lime may occur 

 in the press cake. Before polarization these must be decomposed ; the decom- 

 position can be effected by the passage of a current of carbon dioxide, or more 

 conveniently by the addition of a few drops of acetic acid. 



Analysis of Sugars. Polarisation.. The routine of a polariscope 

 test of sugar is as follows : 



The normal weight of sugar is weighed out in a suitable vessel, transferred 

 to a 100 c.c. flask, and dissolved in water; if necessary the sugar solution is 

 clarified with lead acetate, then made up to 100 c.c., filtered, and the polariscope 

 reading of the solution obtained ; the result is the polarization, and on this 

 test sugars are bought and sold. It cannot be too strongly insisted on that the 

 polarization and the percentage of sugar as determined by the methods given 

 already, in which the manifold sources of error are eliminated, are two entirely 

 distinct terms. 



In the determination of the polarization a minimum of lead acetate is 

 to be used, and a correction for volume of lead precipitate is not applied. 



The water, ash, &c., are determined by the methods already given. 



The Detection and Estimation of small Quantities of 

 Sugar. Molisch's Reaction depending on the production of a red coloura- 

 tion by small quantities of sugar in the presence of sulphuric acid, is thus 

 carried out. 5 c.c. of concentrated sulphuric acid are placed in a test tube, 

 into which is then run 2 c.c. of the water supposed to contain sugar, followed 

 by the addition of two or three drops of a 5 per cent, alcoholic solution of 

 a-naphthol ; the contents of the test tube are shaken, and the colour produced 

 compared with that obtained with known quantities of sugar ; as little as one 

 part of sugar in 1,000,000 can be detected. If the sulphuric acid alone 

 produces the reaction it should be boiled to destroy organic matter before use. 



PinoflTs Ammonium Molybdate reaction was originally given 

 as a test for 'glucose,' and is applied by Pinoff 17 to levulose : 'I grin, of 



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