PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 761 



The filtered beet juice is next evaporated in vacuum pans, as is 

 the case in our refineries, with but this difference, that, Tvhile 

 here, after a single filtration, the liquor is at once boiled down to 

 the crystalizing point, beet juice, which contains more impurities, 

 is boiled doAvn only one-half, or to 25° B., and afterwards filtered 

 the second time over bone-black. The filters, before described, 

 are used, thick juice passing first through fresh bone-black, until 

 exhausted, then thin liquor is passed through the same black, 

 which still extracts impurities from this watery liquid. After the 

 exhaustion of the black, by this thin liquor, it is steamed and 

 removed for purification. The vacuum pan, one of the neatest 

 pieces of machineiy employed in manufacture, is used in Europe 

 with a view to more economy than in this country. Here single 

 pans are used, the vapors of which are condensed by water. In 

 Europe the heat of these vapors is used to evaporate juice in one 

 or two adjoining pans, where liquor is boiled under a still more 

 reduced pressure. The steam, after heating the second pan of 

 syrup, has lost a great deal of its heat, and requires two-thirds 

 less water for condensation, than that coming from a simple 

 apparatus. The difference in temperature, between the two or 

 three pans, during boiling, is about 30° F., the first being at 

 165° F., the second at 146° F., the third at 100° F., or even 

 below that. 



In order to preserve these boiling points, in accordance with 

 the density of the liquids, the pans communicate, so that into the 

 third pan fresh liquor is flowing, which, after some concentration, 

 rises into the second, and thence, again, after a lapse of time, into 

 the first pan, where it acquires the density of 25° B. In this 

 state it passes through a montejus upon the black filters, Avhencc 

 it comes, or should come, pure enough for final evaporation to 

 the crystallizing point. This, as well as the after treatment of the 

 sugar, is the same as that employed in our refineries, with but 

 this difference, that the yellow sugar or dark-colored syrup, gained 

 in claying of the sugar forms, is not brought iuto market in this 

 inferior state, but is worked over again, at the end of the beet 

 season, into white loaf-sugar or, though seldom, added as it is 

 produced, to fresh beet juice in the defecating pans. Where 

 these after-products are worked separately they again yield more 

 impure molasses, which is again worked over. In this manner 

 six different products are gained. The sugar, crystallizing at 

 first from such an after-product, is usually of an inferior quality, 



