23 



The mechanical difficulty is the same as that which attends all meth- 

 ods of diffusion in which the cane chips are moved instead of the diffu- 

 sion liquors. From a mechanical point of view, it is far easier and 

 more economical to move a liquid in a series of vessels than a mass of 

 chips. In the Hughes system the whole mass of chips undergoing 

 diffusion, together with adhering liquor, and baskets and suspending 

 apparatus, are lifted vertically a distance of several feet, varying with 

 the depth of the diffusion tanks every few minutes. The mechanical 

 energy required to do this work is enormous, and with large batteries 

 the process would prove almost impossible. 



The chemical defects of the system are shown in the exposure of so 

 large a surface to oxidation and the action of invertive ferments. It 

 is not surprising, therefore, to notice a distinct increase in the ratio of 

 glucose to sucrose in the data of Table No, 17, Diffusion in open ves- 

 sels was tried years ago with the sugar beet, and was abandoned as 

 being both unscientific and expensive. The degree of extraction in open 

 vessels is also less perfect than in closed diffusers where a considera- 

 ble pressure is exerted on the osmotic liquors. It is but just to say, 

 however, that the poor extraction obtained at Rio Grande is due more 

 to the low temperature at which the diffusion took place than to the 

 open diffusion vessels. I measured the temperature several times at 

 the beginning of the season and found it below GO C. 



By certain modifications made after the close of the season, Mr. 

 Hughes obtained a better extraction. (Bulletin 17, p. 67.) 



The composition of the diffusion juices is sufficiently shown in Table 

 Ko. 17. 



TABLE No. 18. Exhausted chip juice. 



