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CANE SUGAR.i.e., 91 91 per cent. of that required with conventional triple effectevaporation. Results of similar calculations are tabulated below :—In addition combinations of the pre-evaporator with extra steam fromthe multiple can be devised.The Picard System.—This method has never, the writer believes,been applied in any sugar factory, although it has been working in othermanufacturing processes since 1878. In this scheme part of the vapours givenoff from the first vessel are drawn off into a compressor and raised to a highpressure; their temperature is thereby increased, and on again being introducedinto the calandria of the effect are capable of evaporating a further quantity ofwater. This scheme can of course be worked to its best advantage wherepower, as from a fall of water, is available to drive the compressor. Thismethod was described in 1880 by P. 0. Whitehead, 11 and its mathematicshave been discussed in detail by Svorcik, 12 who as a final result lays down thatin a triple with this scheme one part of steam will evaporate altogether 4.248parts of water. His idea of the regeneration of vapours has been madepractical by Selwig and Lange, who have put into practice the scheme ofwithdrawing part of the vapour from the penultimate vessel of a multiple by -the use of live steam injectors, and returning them either to an earlier vesselor utilizing them in heating or in the pans.Calculation of Heating Surfaces.—When the amount of heatnecessary to be transmitted, the difference of temperature between the juiceto be heated or juice to be evaporated, and heating steam are known, therequisite surface can be calculated by moans of the coefficients of transmissionalready quoted.320