500 



CHAPTER XXV 



and repeat until consecutive weights do not vary. Vacuum drying is ad- 

 missible, but unnecessary. Where results of less exactitude are required for 

 immediate use, the drying may be carried out at iio° C. 



Sugars of Lower Grade. — As for higher grade sugars, with the obligatory 

 use of vacuum drying at low temperatures. 



Massecuite, Molasses, Juices. — In a flat shallow container, place about 

 10 grams of some absorbent material, such as pumice stone, quartz sand, 

 or filter-paper, then obtain the weight of the container, absorbent material, 

 and stirrer. Weigh into the container the massecuite, molasses or juice. 

 With the first two materials, add sufficient distilled water to dissolve and to 

 distribute over the absorbent material. Dry at a low temperature to 

 constant weight. 



The necessity for the use of a low temperature is most pronounced 

 with molasses where the proportion of reducing sugars is greatest. Resiilts 

 of reasonable exactitude may be obtained with juices at atmospheric pressure. 



Alternatively, the following scheme may be adopted : — Fold and crimp 

 a strip of filter paper. Insert this in a stoppered tube, through the stopper 



"^ 



Fig. 332 



Fig. 333 



HBtzD 



of which are led two tubes. Dry and weigh the tube and its contents. 

 Weigh and dissolve, if necessary, the material to be dried. Distribute it 

 over the crimped paper. Insert the tube in a bath of boiling water and draw 

 through the tube a current of dry air, until constant weight is obtained. 



Bagasse. — As shown by Norris^, bagasse may be dried at a temperature 

 of 130° C. with so small a decomposition as not to affect the value of the 

 results. At this temperature desiccation is complete within two hours, as 

 compared with at least six hours at 100° C. Two very different routines 

 obtain. The method followed in Java and Hawaii entails the use of flat 

 containers in which the bagasse is placed in a shallow laj^er. These con- 

 tainers, which are from one half to one inch high, and about 20 square inches 

 in area, hold from 20 grams to 50 grams of material. In order to obtain a 

 representative sample in so small a quantity, the original sample must be 

 brought to a fine state of division in a chopping machine. A change in 

 composition during the process of subdividing is inevitable. 



The other routine is that recommended by Spencer', and with him the 

 writer is in complete agreement. In this method much larger quantities of 

 material are used, and the analysis is made on the bagasse without any 

 subdivision. The apparatus designed by the writer for the purpose, and 



