STARCH. 41 



remains in the form of a grey tenacious substance. Arum roots, acorns, 

 horse chestnuts, &e., may be, and are used in Europe for making 

 starch. These, with the potato, are grated into a hair seive and the 

 starch washed through. Oily seeds require the oil to be pressed out 

 before the farina is extracted. Water, a little acidulated, is mixed 

 with the flour to regulate the fermentation and prevent the mixture 

 from becoming putrid. It is then left ten days in summer and fifteen 

 days in winter, when the water is skimmed, poured off, and the starch 

 washed from the bran and dried in the air or in an oven. 



Potato starch, when roasted at a low heat in an oven, forms a gum 

 much used by calico printers. Starch is otherwise in great use for do- 

 mestic purposes, in manufactures, and occasionally as a medicine. Po- 

 tato starch differs from that of wheat ; it is more friable, the grains 

 are larger and it decomposes less readily by fermentation. It is sold 

 under the name of English arrow root and potato sago, in parts of 

 France, and nearly resembles the starch of these plants, which are 

 composed mostly of starch. A sympathetic ink is made by writing with 

 starch-water on paper, and then, at any time afterwards, washing it 

 with Iodine in alcohol, when the writing appears of a deep blue color. 

 When triturated with iodine, various and fine colors are produced ; 

 hence each is a test for the other. 



The ultimate elements of starch are carbon 43.48, oxygen 49.45, 

 and hydrogen 7. These differ little from those of sugar, but starch 

 is much better calculated for human food, as it does not undergo the 

 changes in the stomach which sugar does, producing, frequently, flatu- 

 lency, &-C. 



To change starch into sugar, 2.000 parts are diffused in 8.000 of 

 water containing 40 parts of sulphuric acid. The mixture is boiled 36 

 hours in silver or leaden vessels, and stirred during the first hour, and 

 occasionally afterwards ; and the water is replaced as it evaporates. 

 Chalk and animal charcoal are then added, and the whole is clarified 

 with the white of eggs, or other substances, then filtered through a 

 flock of wool, and the liquid concentrated by heat till of a syrupy con- 

 sistence. The basin is then removed, and its sulphate of lime precipi- 

 tated by cooling ; the syrup is decanted and evaporated to dryness. 

 Sugar and gum are also obtained by mixing starch with dried gluten. 

 1 part with 12 of water, fermented by dry gluten, yields 47 sugar, 22 

 sum, etc., in 100 parts. Starch is thought to be susar partly organ- 

 ized. 



Gluten and Vegetable Albumen are commonly combined and are the 

 most important of vegetable proximate nutritive principles. Wheat 

 flour owes to its gluten the property of forming light and spongy bread, 

 the mass being distended or raised by carbonic acid disengaged by its 

 fermentation. This substance abounds in wheat flour and gives to it 

 its advantages in making bread. Vegetable albumen resembles that 

 4* 



