428 MONTHLY JOURNAL OF AGRICULTURE. 



tried and saccossively abandoned ; until, at last, opinion has settled down in 

 favor of the double-effect vacuum system. 



We say tiiat opinion has sealed down in favor of our system, although our 

 apparatus is far from having been introduced into all manufacturing establish- 

 ments ; but its superiority is acknowledged, as well by those who do not, as by 

 those who do, make use of it; and, were it not for the uncertainty that hangs 

 over the sugar-making interest, it would be universally adopted, because it is 

 established by the experience of the great manufacturers that without it com- 

 petition is impossible. 



It is now fully recognized by chemists, and admitted by all manfacturers, that 

 ebullition at a high temperature is injurious to syrup ; that under the influence 

 of that temperature the greater part of the sugar in solution becomes uncrys- 

 talizable, and is converted into molasses. Hence the importance of rapid evap- 

 oration, by withdrawing more quickly the saccharine solution from the influence 

 of high temperature. 



It is admitted by the last chemists who have analyzed the juice of the sugar 

 cane, that molasses is not preexisting in it, but that it is wholly formed during 

 the process of evaporation. Our Derosne, while in Havana, concreted, by solar 

 heat, cane juice that had undergone no previous preparation ; and he obtained 

 a completely dry and crystalized substance, without any indication in it of the 

 presence of molasses. 



These principles, now undisputed, should therefore direct attention to that 

 system of evaporation which secures most completely the fulfillment of all the 

 requisite conditions. 



We may class the systems of evaporation that have been successively tried in 

 three categories : 



1. Apparatus by naked fire ; 



2. Apparatus by steam in free air [under atmospheric pressure] ; 



3. Apparatus in vacuo, operating at a low temperature. 



We will examine successively each of these divisions, in order to bring to 

 view the advantages and disadvantages incident to each. 

 Apparatus hy Naked Fire. 



The apparatuses by naked fire were the first to be tried, being those which 

 naturally were the first suggested. In those apparatuses, ebullition, that causes 

 the evaporation of the juice, begins at 100°,* and terminates when the syrup has 

 acquired the density of the strike, or cooked syrup, at llo^^.f This last temper- 

 ature especially is highly injurious. Attempts were made in France to temper 

 the action of this last degree of heat, by diminishing, as much as possible, the 

 time during which the concentrated syrup was exposed to it. With this view 

 the bascule kettles were constructed, by means of which a small quantity of 

 syrup could be cooked at one time, and, when cooked, could be quickly emptied 

 out. This contrivance did not, however, prevent the syrup from being exposed 

 to the hurtful temperature of a blazing furnace, and from experiencing a very 

 disadvantageous modification. 



JMaked fire was therefore abandoned in France, after a few years' trial, in beet- 

 root establishments, for the apparatus by steam in free air. 



In the Colonies, the mode of heating by naked fire was persisted in, and exists 

 at this day in conditions much more unfavorable than those to wiiich the beet- 

 root manufacturers Avere subjected from the beginning. The kettles, in most 

 cases of cast-iron, exposed to the heat of a furnace, are emptied one into an- 

 other by means of ladles and buckets. During the time of emptying, the lire in 

 the furnace continues to act, and the level of the syrup falling continually, that 

 portion which is exposed on the sides of the kettles is burnt ; hence the caramel- 

 ization of a portion of the saccharine matter, which, mixed with the syrup, forms 

 a leaven that decomposes a portion of the sugar. The cooked syrups thus ob- 

 tained yield but from 45 to 50^ per cent, of crystalizable susar. 



Kettfes iieated by naked fire, called jumellcs, were tried in the Colonies, as 

 well as bascule kettles ; but it was found that the advantage resulting therefrom 

 cost more than it was worth — the temperature of cooking experiencing- no dimi- 

 nution. 



* Centi},'rn(le— C(mnl to '21-J F. t OHO'' Fahrenheit. 



X Note bv Tbanslatok. — A uiisidkc. They yield, even in Louieiana, about 65 per cent, of sugar. 

 (860) 



