THE CONTROL OF THE FACTORY 555 



ratio of sugar in first-expressed juice to sugar in cane should be tabulated 

 as a part of the control records. 



Interpretation of the Mill Control Analyses. — In addition to obtaining 

 data to afford a record of the operations, the analyses should be used to 

 maintain the standard of work at its highest efhcienc5\ The criterion 

 usually used to judge the efficiency of the " crushing " is the water per cent, 

 in the bagasse. A number of \'ears ago 50 per cent, water in bagasse was 

 considered a standard of good work. With improved milling this figure has 

 been gradually reduced until at the present moment certain Hawaiian mills 

 report crop averages of less than 40 per cent, water. This reduction is largely 

 due to the adoption of drainage grooves in both front and back rollers. 

 Under equal conditions of milling, however, different varieties of cane will 

 behave in a different way. Generally a lower percentage of water will be 

 found with the harder canes, which contain both more fibre and a larger 

 proportion of rind tissue. The water as found by drjdng to constant weight 

 will also be affected by the constitutional water or water of hydration in the 

 fibre. Possibly this is less in the more fibrous canes, which contain a higher 

 proportion of rind tissue. The e.xceptionalh^ low percentages of water 

 reported from the Hawaiian Islands come from those mills operating almost 

 exclusively on Yellow Caledonia cane, which is of the nature referred to. 

 Conversely, the writer has observed that the cane known as Crj^stalina, 

 White Transparent, etc., tends to afford a bagasse retentive of water. 



The percentage of water is not altogether a rational basis of comparison, 

 since the water in a given volume of juice will vary \v4th the proportion of 

 dissolved solids. A more rational basis is the value of the expression :— 



Juice per cent, in bagasse ... , , ^ 



T^., — — — ^ ■ , T- — rz T^—- — which reduces to the form 



ribre per cent, m bagasse X density of juice, 



7 '- , where /"is the fibre and d is the densitv of the juice. 



f X d ■' . i 



It is usual to make the analysis of the bagasse on the material from the 

 last mill only. A complete control would demand the analysis from the 

 intermediate miUs since inferior work here is equally obnoxious. This 

 control is very seldom adopted. 



An oversight on the efficienc}' of the added water is very hard to obtain, 

 particularly with systems of compound maceration. The efficiency of the 

 added water will be most when the water mixes completely with the residual 

 juice after dry crushing, and consequently a comparison of the density of 

 the last mill juice with the computed density affords an oversight. 



A number of years ago it was the custom in Java to report a " coefficient 

 of admixture of added water," which was the value of the expression 

 Sugar per cent, in last mill juice. 

 Sugar per cent, in residual juice. 



This expression is liable to misinterpretation since a high coefficient must 

 necessarily be found with the use of little water, even if the admixture is 

 zero, and, further, the presence of constitutional or hj-dration water in the 

 fibre vitiates the value of the result. 



A third control may be obtained by comparison of the added water per 

 cent, cane and the dilution per cent, normal juice. As the weight of cane is 

 greater than the weight of normal juice at first sight, it appears that the water 



