CHEMICAL SCIENCE. 173 



the contrary, properties worthy of interest. Sulphurous acid, in ex- 

 cess, prevents all fermentation. The base which all these salts con- 

 tain neutralizes the sulphuric acid as fast as it is formed. It remains 

 to be seen if, by themselves, or by their excess of sulphurous acid, 

 they have or not the power to convert cane-sugar into grape-sugar. I 

 have heated, for several hours, small quantities of sugar-candy, dis- 

 solved in water, with a large quantity of bisulphite of lime. The 

 sugar was changed. It became uncrystallizable and deliquescent. 

 The syrup thus formed presented sometimes an appearance with 

 which manufacturers of sugar are well acquainted. Submitted to the 

 action of heat for evaporation, it remained motionless. There was, 

 therefore, the proper quantity to find out, and much care to be taken ; 

 but as it takes a great deal of the bisulphite of lime to destroy the 

 sugar, and a small quantity to destroy fermentation, I thought this 

 agent worthy of a closer examination. Sugar-candy in cold water, 

 charged with bisulphite of lime, even in excess, crystallizes without 

 loss and without change, by spontaneous evaporation, at a very slow 

 heat. It is, therefore, possible to manufacture sugar without artificial 

 heat. Perfectly white sugar candy being dissolved in ten times its 

 weight of water, I added half its weight of a solution of bisulphite of 

 lime, marking ten degrees of the areometer of Baume, and boiled it 

 for about an hour. It was then filtered, to clear it of the neutral sul- 

 phite, which was deposited. It was afterwards put into a plate, 

 where it crystallized entirely without a trace of molasses, leaving 

 precipitated, however, a small quantity of the tartrate of copper, 

 which had been dissolved in the potash. Straw-colored sugar-candy, 

 treated in the same way, gives the same result, only that the crystals 

 are lighter-colored than the candy itself. The same experiment with 

 all kinds of sugar produced the same results, whether the liquid, 

 when evaporated, was left acid, or had been carefully neutralized after 

 boiling. I found, also, that the crystallization was as perfect and rapid 

 when the liquid was left unfiltered, as when it was filtered before the 

 evaporation." 



POTATO-SUGAR. 



IT is not generally known to how great an extent the manufacture 

 of sugar from fecula, or starch, is carried on in France. The mode 

 of proceeding is to have large leaden boilers, in which is one ton of 

 water, heated to a boiling point, and to this twenty-two pounds of 

 sulphuric acid at 60, diluted with twice its weight of water, is added v 

 The vessel is provided with a wooden cover, coated with copper, which 

 has a small opening to allow the liquor to be stirred with a wooden 

 rod. After the liquor begins to boil, eight hundred-weight of starch 

 flour is gradually sifted into it, care being taken to prevent the forma- 

 tion of lumps and to have the boiling uniform. In some factories the 

 starch is first mixed with water, and placed in a vessel above the 

 water, and made to flow into the boiling acid in a uniform stream by 

 a tube. The boiling is continued about fifteen minutes after the 

 starch is put in, and then the fire is so regulated that the liquor ceases 



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