SUGAR, the name of a well known vegetable pro duct, of the general and chemical nature of which we have given a pretty full account in our article CHEMISTRY, Vol. V. p. 747.
The art of refining sugar, however, which is not described in that article, arid which has been brought in this country to great perfection, still, re mains to be considered.
In the common method of refining sugar, the or dinary Muscovado sugar is boiled with fresh bul locks' blood and lime water, and the scum or impu rities produced by the successive additions of the bullocks' blood, is continually removed, till the sugar casts up only a clean milky froth, which indi cates the removal of impurities. In order to heighten the whiteness, a little of the finest indigo is added. In this operation the heat of the fire is applied directly to the pan containing the sugar.
The next process is that of evaporating the pure saccharine solution: This is effected by a moderate fire, and the boiling is continued till the sugar has the proper degree of viscidity or ropiness, which•s easily ascertained by what is called the proof stick.
When the evaporation is completed, the hot sugar liquor is removed out of the pans into coolers, and it is here gently stirred to prevent the formation of a crust. It is then granulated by an oar, the violent motion of which continued for several minutes, destroys the viscousness of the sugar, and completes the granulation. The beauty of the sugar depends on the perfection of this process.
The next step is to fill the moulds, which are earthen vessels like inverted cones, the apex of which is undermost. The clarified concentrated juice is then poured in by three different pourings. In order to prevent adhesion to the moulds, and to lay the grain of the mass even and regular through out, the sugar is scraped from the sides of the cone by a wainscoat knife, the fluid is allowed to rest a few minutes till it has got some firmness. The moulds are then stirred round three or four times, and the process is finished.
The above is the process for single loaves, or sugar once refined. The double loaves, or those
doubly refined, are made by a process in which the clarification is effected by the whites of about 200 eggs for each pan, and with fresh water in place of lime water.
The scums taken off during these processes are employed to yield an inferior sugar by methods of purification, which are not interesting to the general reader.
We had left the sugar in the conical moulds. These moulds are now placed above pots, and the stopper or rag at the bottom or apex of the moulds having been previously taken out, and a punch made with an awl, there will exude from this aperture a syrup or molasses, which in twenty four hours will fill one half of the pot. This syrup is then removed, and the pot replaced under the apexes of the moulds. A small ladleful of wet clay is then poured on the face or base of each loaf or cone of sugar, which, after drying into a cake, in five or six days is removed and laid by for future use. On the clay following the loaves are clayed a second time, and the cake when dry, is removed like the first. Each loaf is now drawn out of its mould, and irregularities and impurities brushed off. They are next left some days in the moulds to acquire hardness of surface. They arc then turned out upon paper, freed from all little specks, and then dried on a stove for five, six, or seven days, when they are fit for sale.
In the preceding method of refining sugar, be tween twenty and thirty-five per cent. of molasses are found in the pots, and it is supposed that about two-thirds of this are produced by the intensity of the heat employed for concentrating the syrup. To remedy this evil various ingenious methods have been devised and successfully put in exe cution.
The first of these was invented by Edward Charles Howard, Esq. and was secured by patent in 1812. He brings the sugar liquor to a temperature of from to of Fahrenheit, by surrounding the pan with boiling water or steam, under the common pressure of the atmosphere.