CHEMISTRY AND USES OF THE POTATOE. 25 



(89.) The refuse of potatoe from starch making is em- 

 ployed, according to Loudon, for cleansing woollen clothes 

 without injuring their color; and the liquor decanted from 

 the starch is excellent for cleaning silk without doing the 

 smallest injury to the color. 



(90.) Potatoe starch may be converted into dextrine, or 

 British gum, by merely heating ft. This substance is now 

 largely used as a substitute for gum-arabic, and a familiar 

 example of this is furnished by the postage-stamps, which 

 are said to be gummed with potatoe dextrine. Dextrine is 

 composed, according to Marcet, of carbon 35-7, hydrogen 

 6-2, oxygen 58-1. 



(91.) Potatoe starch is converted into sugar by means 

 of acid. To effect this, a pound of starch may be digested 

 in six or eight parts of distilled water, rendered slightly 

 acid by two or three drachms of sulphuric acid. The 

 mixture should be simmered for a few days, fresh portions 

 of water being occasionally added to compensate for the 

 loss by evaporation. After this process the acid is to be 

 saturated with a proper proportion of chalk, and the mixture 

 filtered and evaporated to the consistence of syrup : its taste 

 is sweet, and by purification in the usual way it affords 

 granular sugar. 



(92.) This sugar is manufactured at Bow, but it con- 

 tains sulphate of lime, which gives it an offensive bitter 

 taste. It is employed to adulterate the sugars sold by 

 grocers at a very cheap rate. 



(93.) Potatoes may be employed for the preparation of 

 alcohol, and Donovan states that there are large manu- 

 factures for that purpose in France ; and Cadet states that 

 100 Ibs. of potatoes will afford 30 Ibs. of spirit. The 

 alcohol may be obtained either by fermenting the potatoes 



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