Vol. IX. No. 210. 



THE AGRICULTURAL XEWS. 



147 



SUGAR INDUSTRY. 



THE INFLUENCE OP THE STRUCTURE 

 OF SUGAR-CANE ON MILL WORK. 



The Exiieriment .Station of the Hawaiian Sugar Planters' 

 Association has recently issued its thirtieth bulletin under the 

 title of The Iiijfuenre of the Stiuctuie of the Cane on Mill 

 Work in Swjar Faetories, by Noel Deerr. As is stated in the 

 introduction, this is divided into three parts: a discussion of 

 the intiueiice of the dirt'ereut juices contained in the cane on 

 control wor]%-; an account of some experiments made with the 

 object of determining the etfert of ditierent methods of 

 extraction; and a consideration of the cane as being compet- 

 ed of pith and rind, ?o that these are regarded as separa'e 

 entities wlien dealing with the results of milling operation.-. 



The tir.st part commences with the "consideration of the 

 inferential method of controlling the weight of cane entering 

 the factory which is due to Geerligs, namely that the 

 percentage of sucrose in the cane, divided by the percentage 

 of sucrose in the first mill juice, gives the constant quotient 

 S.5, under certain fixed conditions. As the author points 

 out, it is evident that this can only hold under constant 

 circumstances of mill pressure and fibre content of the cane: 

 as the proportion of juice obtained from the cane increases, 

 and at the .same timeap|)roa(hes more nearly the coni[>ositi<in 

 of all the juice contained in the cane, the value tends to 

 increase; its value will become smaller, on the contrary, with 

 an increase in the fibre content of the cane. This was 

 recognized by Geerligs, and attention is drawn to a table 

 which was constructed by him for the purpose of giving the 

 various values of this quotient with different mill pressures 

 and fibre contents, in the case of the Cheribon cane. 

 Other investigators found different values for the various 

 canes that were used under the conditions with which they 

 had tc deal, and this led the author to determine those for 

 the chief canes employed for sugar-making in Hawaii: the.se 

 are given in the bulletin, and it is shown that the quotients 

 for Hawaiian canes are very similar to those for the Cheribon 

 cane. The practical use of the figures oVitainid is to indicate 

 that, in factories where the sucrose content of cane is deter- 

 mined by working back from the sucrose in mixed juice and 

 that in megass, a low value will show that either the weight 

 of cane recorded is too high, or that the measurement of the 

 amount of juice is inaccurate. 



In employing his experiments to find the values of the 

 i|Uotient of which mention has just been made, the author 

 worked out the ratio between the .solids in what he terms the 

 ' absolute ' juice of the cane and those in the expressed juice, 

 liy the absolute juice, he means 'everything which is not left 

 behind on extraction with water', so that this term includes 

 protoplasm, together with the ' colloid water' of Geerligs, and 

 the ' water other than juice', as it is described by Dr. Franci.- 

 AVatts (see West Indinn livUetin, Vol. IX, p. S.")); that is to 

 say, absolute juice comprises the sugar-bearing juice of the 

 cane, as such, protoplasm, and what is usually understood 

 by ' imbibition water', in a botanical sense. IJeturning 

 to the relation just referred to -that between the 

 solids in the absolute juice, as defined, and those in 

 the expressed juice — it was found that this was far 

 more con.stanl than the quotient which was first under 

 consideration, namely, that obtained by dividing the per- 

 centage of .sucrose in the cane by that in the first mill 

 .luice. This is shown by the fact that, for at least three 

 varieties of cane, with a fibre content varying from 10 per 

 cent, to 14 per cent., it was found to lit- between the values 

 0-'J7 and 0-98. The practical development of this is that, if 



the density of the absolute juice of the cane is known, then, 

 with the usual results of analysis alone, all the essential 

 measurenr.ents relating to mill control can be expressed in 

 terms of cane: and il eitlier the weight of cane, of megass, of 

 mixed juice or of added water has been determined, all the 

 other quantities can be found. It is not suggested that the 

 making of direct measurements should be discarded in favour 

 of an inferential method: but that the latter should form 

 a means of checking such measurements, and the author pro- 

 poses, in the light of the determinations made by him, that the 

 value of the ratio employed for the purpose should be 0'977, 

 laying stress at the .same time on the necessity for accurac)' 

 in the determination of the total .solids in the megass, before 

 reliable results can be obtained. 



As has been stated, the second part of the bulletin deals 

 with the effect of difi'erent methods of extracting juice: the 

 difference of the.se methods consisted in using nine and twelve- 

 roller milks, maceration with hot and cold water at different 

 stages in the milling, returning or not returning the dilute juice, 

 and the application of increasing extractions. It was found 

 that the highest extraction was obtained when the water was 

 added in divided quantities; the result was lowest when its 

 additiiin took place before the last mill, and was intermediate 

 when it was divided before the .second and third mills. There 

 was little difference found, whether the water was hot or cold; 

 a slight advantage obtaining when it was hot was probably 

 due to the slightly greater dilution. The comparison of the 

 Work of a nine-roller and a twelve-roller mill led to the 

 conclusion that, making allowance for difference in fibre 

 content, the latter ettects extraction from 50 tons of cane per 

 hour as well as a nine-roller mill dealing with 35 tons in the 

 same time, w itli a dilution in the case of the larger mill, of 

 1 '1 per cent, instead of 34 per cent. It is the author's opinion 

 that the matter of chief inqiortance in these trials is the econ- 

 omy effected in the case of the twelve-roller mill, as a result 

 of the greater quantity of cane dealt with and the smaller 

 amount of liquid to be treated, on account cf the lessened 

 dilution. In the last connexion, it was not found that any 

 approach to equalitj' of final efficiency of work in the two cases 

 could be obtaiiied by using less water: the ett'ect was rather 

 to gain very inferior results with the smaller mill. 



The object of further work was to ascertain the influence 

 of high extraction on the purity of the juice: in other words, 

 to find the effect of expressing increasing quantities of juice 

 from the cane on the amount of sugar that could be obtained. 

 The average results of experiments showed that an extraction 

 of 930 may be considered to correspond with a purity of 

 890, and an extraction of 87 with one of 906. I5y inter- 

 polating values and extending the extraction numbers to 95"0, 

 a table is obtained in which, while the latter increase by 

 unity, those representing the purity decrease by 02 in the 

 first, fourth and seventh steps, and by 03 in the others. 

 Thus extractions of 90 and 950 correspond, respectively, to 

 purities of 89-8 and S8'5, so that increasing the extraction 

 from 90 to 95 does not increase the amount of sugar that can 

 be obtained in the ratio of 95 to 90, but in that ratio 

 multiplied by the quotient obtained by dividing 88 5 by 89-8. 

 In other words, the increase in available sugar, calculated 

 from the extraction alone, would be 56 per cent.: it is 

 actually 4 per cent. The subject is developed by the author, 

 who, however, in view of the conditions peculiar to any 

 given factory, does not deal with the financial aspect of high 

 extraction, but leaves the data brought forward by him to 

 be worked out on the basis of uioney units in any special case. 



The third part of the bulletin, namely that which treats 

 of the eti'ect of the structure of the cane on mill work, will be 

 dealt with in the next number of the Aiirimltund Keius. 



