Mr. Wilson's process differed also in othell re spects from the common one. For every cwt. of sugar a solution of sulphate of zinc, in as small a quantity of water as possible, is added to the melt ed sugar in the pan. The oxide of zinc combines with the extractive matter, tannin and gallic acid, and renders them insoluble, while the sulphuric acid combined with the lime is insoluble also. When a strong grain is required, and the raw sugar contains much acid, a mixture of lime, consisting of an oz. of powdered lime in water is added about five minutes after the sulphate of zinc solution has been added. This method is used along with the patent filtering apparatus invented by Mr. J. Sutherland.
It is well known that sugar can he obtained from many vegetable substances, but particularly from the root of White Beet. In consequence of the de struction of the sugar plantations of St. Domingo, and the resolution of Bonaparte to exclude the col onial produce of Great Britain from the continent, he exerted all his means to supply the place of col onial produce hy articles of indigenous growth.
Chaptal, Dombasle and others, seconded his views; the Institute reported on the subject in 1800, 1810; and in 1812, the manufacture was extending rapid ly. The events of the war put an end to such opera tions, hut in 1819 they were again in considerable activity, and in 1825, there were 100 manufacturers who furnished altogether about 4 or 5 millions of lbs. of raw sugar (from 2000 to 2500 tons), which was not the twentieth part of the consumption of the kingdom.
The following table from M. Duhrunfaut shows the expense of growing the beet in ten different estates in France and Flanders, and the quantity produced in each for every hectare (21 acres). The expense in the last column includes that of labour, &c Hence the abstraction of a little hydrogen and carbon would convert starch into sugar.
The most remarkable discovery, however, re lative to sugar, is that made by M. Braconnot relative to the formation of sugar from the sawings of wood, old rags, and paper, of which a brief account will be found in our article SCIENCE, Amusements in, Vol. XVI. p. 610.