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Page:Popular Science Monthly Volume 35.djvu/225

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double, triple, or quadruple, and provided with a system of heating pipes. The steam which proceeds from the boiling juice of the first vessel serves to heat the second vessel, and so on through the entire series. The evacuation of the heating system on the evaporator is effected by means of small tubes leading from one vessel to the other and connected with a condenser.

When the sirup has attained to a certain degree of concentration, it is drawn off by means of pneumatic suction direct into the vacuum boiler. The vacuum boiler. Fig. 8, consists of a vertical, cylindrical, or ball-shaped vessel, with a conical base, containing heating worm tubes. The mass obtained from the vacuum boiler is first of all placed in a refrigerator, which consists of a trough provided with a stirrer and a refrigerator jacket. The mass of sugar crystals must now be separated from the sirup, so that raw sugar may be obtained, and hence it is sent forward from the refrigerator to the centrifugal machines.

A centrifugal machine. Fig. 9, consists of a cylindrical drum, over which is a finely perforated sieve, and which rotates with great rapidity on its own axis. The mass placed in the drum is pressed against the sieve by the action of centrifugal force, and the fluid escapes through the small apertures. The sirup having been disposed of, the yellow sugar obtained is called the first product, and this, having been emptied from the drum, is transferred to another sieve, where it is freed from the lumps which it may contain, and the raw sugar is finally emptied into sacks on the lower floor, when it is ready for the refinery. The process of refining raw sugar into the block sugar of commerce is an independent industry.



VERY recently it was announced by Proust that the bicarbonate of soda used as a preservative of milk formed a compound particularly injurious to children—i. e., the lactate of soda. There appears to be great danger, in the newly aroused fear of fermentative changes in food and of the baneful products of the busy bacilli, that any vaunted preservative or germicide may be greedily seized upon at once, without thought as to the innocence of its chemical activity. This easy credence in antiseptics seems to be characteristic of the minds that shrink with most unreasoning fear from every advance in bacteriological research. Not long since, a novelist, more imaginative than scientific, arraigned Science because "the idea of the comma bacillus is more dreadful than that of the cholera." This, as an outburst of ignorance, would be