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it the impurities of the juices. The diffusion juice as it comes from the diffusion battery is usually almost as black as ink. After carbonatation, as the process above is called, it is of a clear, light amber tint. To separate the liquid from the solid matter the whole is passed through a filter press from which the juice emerges bright and clear and the carbonate of lime with its adhering impurities remains in the filter press as hard cakes. This process is repeated in order to secure as great a purity as possible in the juice.

Fig. 73.—Multiple-effect Evaporating Apparatus.—(Farmers' Bulletin 52.)

Evaporation.—The purified juice is conducted into multiple-effect vacuum pans, Fig. 73, from which the air is partially exhausted by a pump, the vacuum rising in the series. There are usually three or four of these pans connected together,—the first one having the least air exhausted from it and the last one the most, that is, having the highest vacuum. The vapor which arises from the first pan is conducted through the copper coils to the second and serves as the heating agent while the vapor from the second pan passes through the copper coils to the third and so on to the fourth. Thus the steam used for evaporating is turned only on the first pan and by this means a great economy in the use of fuel is secured. In this way the juice is evaporated to a sirup. This is usually somewhat colored and if white sugar is made it is bleached by passing through bone-black or by the application of sulfur fumes. When sulfur is used it is often applied first to the unevaporated juice as well as to the sirup.