When eour eanea are aent to the buildings, the eugar is apt to get kicky in the pau, and occasionally to such a degree as to interfere with the formation of grain, and endanger the whole atrike of augar. If the stiekineas ia not very bad, 2-3 buckets of strong lime-water, taken into the pan through the acid-cock, will put things straight. Beeides this, the excess of acidity should be neutralized by lime-water, leaving the ayrup only elightly acid before drawing into the pan.
Molasses.—" First molaases " runs from masse-cuite which has had no melasses boiled intn it ; " 2nd molasses " drains from ma,se-cmte boiled with molaesee in it ; "3rd molasses " draius from vacuum-pan inolasaes-augar (not muscovado sugar). These are kept distinct. Third molasses ie so sticky and impure that it is sent to the rum distillery (see Alcoholic Liquors—Rum, p. 22S), as is &leo sometimes the eaae with 2nd molaeses, when low quotationa do not pay to convert it into sugar. Only let molasses should be used for mixing with syrup-sugar in the pan, and 2nd molassea for boiling molasses-augar ("3rd sugar "); 2nd mdlassea should never be used for boiling with pure syrup-sugar in lieu of lat molasaea. There ia a great difference of opinion about the boiling of molasses; but the plan now to be described ia the beat, provided arrangements permit the molaaaes to be boiled within 1-.2 hours of separation in the centrifugala.
Supposing that the pan has struck out 3 tons, been refilled and cut a second time, leaving it still half-full, for a third time fresh molasses tempered with lime-water, and reduced with water to 30° B., is drawn in. The coutents, struck out and " spun " in the centrifugal, ehould yield 2i-3 tone of 2nd sugar, i. ayrup-sugar with which molasses has been boiled, giving about 1.2 tone of sugar from molasaes, much improved in colour, in addition to the 2 tona obtained from the syrup, and upon which the molasaes was admitted. To make a very pale sugar, this procees will not answer, and the molasses muet be made into fine quality 3rd auger, or into rum.
For tempering molaimes, lime-water ahould be stirred in until most of the acidity is deatroyed, and only a faintly acid reaction is ahown on litmus-paper. For 2nd and 3rd syrups, or molaases which ia to he boiled for grain, the denaity muat be reduced to 30° B., either by blowing in live steam, or, if this be inadmissible, by the addition of condensed water. The boiling ia performed in an exactly aimilar way to lst ayrup, except that it is uaeless to try for large grain, as the impurities effectually prevent the grain from increasing beyond a certain size. It is not an unuaual custom to eonaidembly raise the temperature before striking, by dropping the vacuum 2-3 in.; thia ia
readily done by checking the supply of water to the condenser, and keeping the steam full on the coils and jacket. The temperature of the masse-cuite is then about 77° (170' F.), whereas it lias previously been about 68°-74° (155°-165° F.). The object of thie is to harden the grain, in order that it may be washed in the centrifugal. The masse-cuites from 2nd and 3rd syrups should alwaya be allowed to atand 2-3 days in coolers, to "grow " the crystals before eentrifugaling. Molassea from 3rd sugar of about 34°-36° B., are always "jellied " or " boiled emooth," and it is not then necessary to reduce the density. If very acid, they should be nearly neutralized, and boiled until a proof will draw out in a thread 1-1i in. long between the finger and thumb. At this stage, and before any sign of granulation has commenced, the contents of the pan are discharged into a cooler, and allowed to stand for 1-2 weeks, until the sugar has properly granulated, before eentrifugaling.
Multiple-effeete.—Figs.1371,1372 show an elevation and plan of a set of horizontal triple-effect apparatue by Fawcett, Preston, & Co.; and Figs. 1373, 1374, an elevation and plan of a set of vertical triple-effect apparatue by the same firm. Thie apparatus enables the planter to make use of all the exhaust-steam that can be collected in the augar-house, givea a syrup in good crystal lizable condition, and saves labour. It alao permita the use of a vacuurn-pan in many places, where with a double-effect or a simple evaporating-pan it would be imposaible, on account of scarcity of water. The exhaust-steam enters the heating-space of the pan C, and ia condensed by the juice contained iu the tubes. The first pan C is therefore a surface-condenser, and requires no injection-water ; and the condensed water runs away to a receptacle, to be used again in the boilers. The vapour from the juice in C passes into the interior of B, producing a aecond ebullition, and ia condensed here again by aurface-condensation. The condensed water from thia pan is water of vegetation, as it cornea from the cane-juice ; it is taken for washing the animal black. Finally, the vapour from B enters A, and the vapour formed in A is condeuaed by direct injection. As, therefore, injection-water is only used for condensing the vapour formed in the pan A, great economy is obtained. Triple-effects can be constructed either of vertical or of horizontal vacuum pans. Each system has ita advantages, but when equally well constructed and worked there ia little or no difference in their results. On the whole, it may be aaid that the horizontal system doea not require such expensive machinery and such good execution as the vertical.