THE DETERMINATION OF CANE SUGAR 525 



This method may be used with cane after extracting most of the juice 

 in a hand-mill and determining the soluble solids in the expressed juice. 

 Error is introduced since the composition of the juice remaining is not the 

 same as that expressed. If the cane is comminuted with a Hyatt shredder 

 the juice expressed and retained is of uniform composition due to the rupture 

 of all the cells. In the case of bagasse taken from mills, it is often custo- 

 mary to accept the last mill juice or last roll juice as being the same as 

 that of the juice retained in the bagasse. 



In the routine of control of bagasse analyses, one portion of the sample 

 is usually used for water determination and one for sugar. The soluble 

 solids may be estimated directly in the sugary extract obtained, and if the 

 analysis, as is convenient, is made with constant quantities of bagasse and 

 water an exact mechanical average of a day's run can be obtained in one 

 analysis by combining equal quantities from each sugar determination. 

 In a series of tests made by the writer^^ it was found that, due to a compensa- 

 tion of errors, the use of the polarization gravity purit}' of the last mill juice 

 to calculate the soluble solids in the bagasse {cf. Chapter XXVII) gave 

 results almost exactly the same as the use of the dry substance in the extract. 



2. Direct Methods. — Extract the finely divided sample in a Soxhlet 

 apparatus using water as the solvent, dry and weigh. This method demands 

 the use of very smaU quantities of material. It is objectionable, since pro- 

 longed exposure to hot water does not obtain in the process of milling, and 

 the object of the analysis is to control this process and not to determine matter 

 insoluble in hot water. A similar objection lies against the use of alcohol as 

 a solvent. The most rational method is the use of cold water. One way of 

 application is to immerse the material for a long period in a linen bag in a 

 stream of water, followed by subsequent pressure and drying. The time 

 required may be much shortened by the use of a hydraulic or powerful 

 screw press. The type shown in Fig. 341 is useful and can be readily con- 

 structed in the plantation workshop. After each pressing the wad of bagasse 

 is loosened, additional water placed in the pot and pressure again applied 

 until extraction is complete. 



Determination of Ash. — Weigh out from five to ten grams of material 

 in a dish, preferably of platinum. Heat gently till gases no longer escape, 

 and finally at a low red heat. Moisten with a solution of ammonium car- 

 bonate, expel the excess at a moderate heat and weigh. The result is 

 returned as carbonate ash. 



In place of returning carbonate ash, the sulphate ash is often returned. 

 In this process the preliminary carbonization is effected by sulphuric acid. 

 It is attempted to reduce the results to carbonate ash by a deduction of 

 10 per cent. A whole series of investigations, dating from Violette^^ in 

 1873 to Ogilvie and Lindfield^' in 1918, have demonstrated that this correc- 

 tion is generally much too small. The average of the last-named chemists* 

 results indicate an average correction of the order rather over 15 per cent., 

 with, however, very irregular results, the correction varying from 6 per cent, 

 to 26 per cent., with only four results out of thirty-six giving a value of 10 

 per cent, or under. 



The continued use of the 10 per cent, deduction is an instance of the per- 

 sistence of a once accepted error in spite of numerous protests. 



