REPORT OF THE CHEMIST. 



51 



tories. It is now apparent that this was a mistake. If a mill juice 



shows a density of 1.062, a diffusion juice should have one of not less 

 than 1.050. In fact the volume of the diffusion juice should represent 

 a weight not greater than that of the canes diffused. The average 

 ratio of the weight of the cane to that of the diffusion juice in the ex- 

 periments was not far from 100 : 125. It is true that in localities where 

 coal can be obtained for 820 a carload, a very dilute juice is not so ob- 

 jectionable, from a merely economical view. On the otherhand, if the 

 juice is first to be concentrated in open pans, its dilution becomes a very 

 serious matter. The liability to inversion on long boiling is too well 

 known to need any additional emphasis here. But there are many 

 localities where coal is dear and evaporating capacity limited. In such 

 places the production of a juice as dilute as that represented in the fore- 

 going tables would be a fatal objection to the process. 



It is difficult to see how such dense juices are obtained as those men- 

 tioned in the experiments in Guadaloupe. In quite a number of my ex- 

 periments the water was allowed to remain ten minutes in contact with 

 each cell of chips, or ninety minutes in all for the contents of each cell. 

 Yet the highest specific gravity obtained even by this method was 1.0173, 

 as shown in Analysis 141, Table I. 



There are three factors in the problem of the application of diffusion 

 to sorghum which demand a more careful study, viz., (a) time, (b) tem- 

 perature, and (c) pressure. 



(a) For nine cells two hours at a mean of 60° O. would not probably 

 be more than sufficient to secure the mean density desired. 



It is apparent now that the diffusion juices were not allowed to re- 

 main long enough in contact with, the chips. The chief objection to 

 allowing a longer time for diffusion is found in the tendency to fermen- 

 tation, which these dilute juices possess in the highest degree. This 

 objection would be fully met by the uniform practice of introducing 

 into each fresh charge of warm water some antiseptic like lime bisul- 

 phite or carbolic acid. Another objection is found in the increased 

 time required to complete the extraction. This, however, can be met 

 by increasing the size of the diffusers. 



(b) There is no doubt of the fact that osmosis in vegetable cells will 

 take place more rapidly as the temperature of the ambient fluid rises. 

 Thus a more rapid extraction of the sugar will take place if the temper- 

 ature be kept at a higher degree. On the other hand as water approaches 

 a boiling point it dissolves any starch granules which the cells may con- 

 tain, and transforms the insoluble pectose into soluble pectine, and 

 brings into solution any other difficult soluble bodies which the chips 

 may contain. It has been noticed, morever, at these high temperatures 

 that the outflowing juice is highly colored, and has a peculiar odor 

 whicli indicates the solution of some odoriferous bodies not dissolved by 

 a colder liquid. 



(e) This method works well and has none of the disadvantages which, 

 characterize the others. It has been noticed that, when by means of 

 a system of steam-pipes with which our battery was supplied, a pressure 

 of three or four atmospheres was produced for a few moments on each 

 cell, the degree of exhaustion was much greater than when only the 

 ordinary pressure of the water, amounting to less than two atmos- 

 pheres, was employed. The sorghum-cane is more compact than trop- 

 ical cane, and will require more care in diffusion.* Pressure appears 



*This is shown by the slow increase in density of the diffusion juices, and also by 

 some mill experiments, in which I found that Louisiana canes would yield about 4 per 

 cent, more juice than sorghum under the same conditions. 



