282 SOKGHUM. 



from the ordinary three-roll mill, by either hot or cold water or steam, 

 and then subjecting it to pressure again. For this purpose, the ba- 

 gasse is received upon a continuous carrier of wood or cloth, and, while 

 slowly passing to the second set of rolls, is exposed to a spray of water 

 or steam. The diluted juice obtained in this second pressure is gen- 

 erally used as sprinkling v.ater, to moisten fresh portions of bagasse, 

 until it attains, by repeated use, density sufficient for the sugar to be 

 extracted from it economically. 



In this process there is a very considerable saving of sugar, which 

 amounted, with sugar-cane, according to the data given in " Sugar Grow- 

 ing and Refining" (page 159), to 15.7 cents upon eacli 100 pounds of 

 cane used, or, estimating 10 tons of canes to every hogshead of sugar 

 produced, to a saving of $35.16 on each hogshead. 



But from this must be deducted the increased cost of the " plant," 



of labor, and of manufacture, owing to the greater amount of water 



necessary to be evaporated, so that the conclu^^ion given is as follows: 



" It would appear, from numerous statements, that the total extra cost 



of procuring the extra yield of sugar is about 50 percent of the value 



of the extra sugar." 



4. Diffusion. 



All the processes thus far mentioned for the extraction of the juice 

 froui sugar-cane and sorghum, depend, for their success, upon the rup- 

 ture of the cells of the plant, and the pressing out of the juice ; and, 

 in tlie process of maceration, the principle is mainly the washing oflf 

 of the juice remaining in the bagasse. In the process of which we 

 are now to speak, the extraction of the sugar depends upon an entirely 

 different imuciple, known in science as Diffusion, Dialysis and. Osmo- 

 sis ; and to fully understand the matter, it is necessary to again refer 

 to the physiological structure of the stalk of cane or sorghum. 



We have seen, p. 259, that the stalk is made up of an outer rind or 

 shell, firm and woody in its structure, coutaining within a soft, juicy 

 pith, and that this pith consists of numberless cells, composed of cellu- 

 lose similar to the woody'fiber of other plants, the juice being con- 

 tained in these cells, as is the juice of an orange in the larger cells 

 which make up the pulpy portion of that fruit. 



Now, it has been found that, if slices of cane, or of sorghum, or of 

 the sugar beet, are immersed in water, in a short time the water will 

 have become perceptibly sweet, and this sweetness will increase up to 

 a certain degree, after which it \vill remain ,,the same. If now we re- 

 place this sweet water with a fresh porticm of pure water, we may ex- 

 tract an additional amount of sugar, and by repeating this oi^eration a 

 few times, it will be found that the sugar has been entirely removed 



