330 CHYMISTRY APPLIED TO AGRICULTURF, 



ARTICLE V. 



On the ConcentratiGTi or Evaporation of the Purified 

 Juice. 



As soon as the bottom of the evaporating vessel is covered 

 with juice, the fire is kindled, and ebullition is produced as 

 speedily as possible, — the juice which continues to flow 

 from the clarifying boiler supplying the loss occasioned by 

 evaporation. 



When the boiling juice marks 5° or 6° (= 1.036 to 1.044) 

 of concentration, a portion of animal charcoal is thrown in,, 

 and this is continued, the quantity being gradually increas- 

 ed, till the juice is concentrated to 20^, (■=. 1.161.) Sixty 

 pounds of charcoal are used in this manner, for a quantity 

 of juice equal to from 422 to 475 gallons. 



After having brought the liquor to the twentieth de- 

 gree of concentration, the boiling is continued till the 

 sirup marks 27° or 28° of the hydrometer, (= specific 

 gravity of 1.231 to 1.242.) The sirup, being mixed with 

 animal charcoal, requires to be filtrated. This operation ^ 

 as it is usually performed, is very tedious, and sometimes 

 becomes impracticable ; the consistency of the sirup is in- 

 creased two or three degrees by cooling, and the pores of 

 the filter becoming, in a short time, obstructed by the 

 finely divided charcoal, the thickened liquor can no longer 

 pass through them. 



To obviate these inconveniences I place a large willow 

 basket over a boiler ; into the basket I put a coarse bag of 

 the same diameter, but about two feet deeper. I pour 

 the thickened sirup into the bag ; for some minutes filtra- 

 tion goes on very well, but as the liquor grows thick in 

 consequence of its cooling, filtration slackens and at 

 length stops ; as soon as 1 perceive this, I turn the borders 

 of the sack into the basket, and upon them place a wooden 

 trencher, which I gradually load with cast-iron weights 

 till the necessary pressure is produced ; filtration is by this 

 means completed in two or three hours. 



The charcoal contained in the sack is leached with 

 warm water, and afterwards submitted to the lever press, to 

 force from it all the sirup contained in it. The waters 

 used for these leachings during one day, are the next day 

 mixed in the clarifying boiler with the juices that are then 

 prepared. 



