VARIETIES OF SUGAR.. 259 



to light. It is well known that some kinds of sugar crystallise with ease, 

 whilst others cannot be crystallised at all. Analysis has detected a slight 

 difference in their atomic constitution, which would account for this 

 singular disagreement in their crystallising power. Of the crystallisable 

 class are the cane, maize, beet, and maple sugar. Uncrystallisable sugar is 

 frequently termed grape-sugar, as it exists ready formed in the juice of 

 ripe grapes : of this class are sugars made from starch, whether by the 

 action of diastase or sulphuric acid, and sugar from linen rags or saw-dust 

 and gluten. The formation of sugar from the action of diastase upon starch 

 presents a curious phenomenon, but cannot be considered of practical value, 

 although this idea has been entertained by some. 



Diastase is extracted by water from malt, and possesses the remarkable 

 property of converting starch into sugar in a few hours, and in some cases in 

 a few minutes : 100 parts of starch, made into a paste with 39 times their 

 weight of water, mixed with 6 parts of diastase, dissolved in 40 parts of 

 water, and kept for one hour between 140 and 149 deg. Fahr., afford 80 parts 

 of sugar. 



That sugar might be obtained from the potato, was a discovery which 

 before the days of chemical knowledge might justly have been considered as 

 wonderful as the conversion of lead into gold, promised by alchymists. 



The discovery, by chemical analysis, that the potato, though far different 

 in form, taste, and all external qualities, was perfectly similar in com- 

 ponent parts to the different kinds of grain used for the food of man, 

 led naturally to inquiries, whether the products derived from these grains, 

 by submitting them to different chemical operations, might not be procured 

 also from this root. Complete success was the consequence. It was found, 

 among other things, that a substance possessing all the properties of sugar, 

 though differing a little from that of the sugar-cane, could be procured by a 

 simple operation from the potato. Until 1830, however, the discovery was 

 considered only as a matter of curiosity, and was mentioned only among 

 men of science. In 1832, experiments were tried, on an extensive scale, in 

 the United States of America, to ascertain whether, in districts where the 

 potato grows abundantly, this sugar might not be made advantageously to the 

 population of the district, and to the manufacturer himself. An account of 

 the process and the results is interesting. The potatoes were ground by a very 

 ingenious and simple method, by exposing them through a box or hopper to 

 the action of a wooden cylinder, having nailed upon it long strips of iron 

 punched full of holes, to give them a rough, grating surface. This cylinder 

 was driven by a band of leather attached to the drum of a water-wheel. On 

 filling the hopper with potatoes, and giving the grater the necessary motion, 

 the potatoes were reduced with surprising rapidity to a fine pulp, from 

 which, by the aid of a sieve and water, the starch in great purity was 

 readily obtained. This apparatus ground 3,500 bushels of potatoes without 

 the least repair. The starch thus obtained was then dissolved completely 

 in water, heated by steam let into it. A certain quantity of sulphuric acid 

 or vitriol was then mixed with it, and heat being applied, the whole of the 



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