1835.] Improvements in Science. 197 



obtained, mixed with some impurity, which may be removed 

 by digestion in cold water, and solution in hot, at the tem- 

 perature 176°, and drying it in vacuo after repeating the 

 process several times. Amidone is insipid, neutral, colour- 

 less, diaphanous, elastic, absorbs moisture from the atmos- 

 phere ; dissolves in water of the temperature 149°, but is 

 not acted on by cold water unless the two be agitated 

 together, when a notable portion is taken up. It is insoluble 

 in alcohol, which extracts some essential oil, and precipitates 

 it from its aqueous solution. If a solution of tannin be 

 poured into an aqueous solution of amidone, a copious milky 

 precipitation ensues, which is re-dissolved by an excess of 

 the latter. Iodine forms with it a blue compound, which 

 is insoluble in water below the temperature 149° ; gelatinous 

 alumina, animal charcoal, phosphate of lime, and isinglass, 

 remove it from its mixture in water, and several acids 

 and salts produce the same effect. 



A number of experiments, made by the authors, prove 

 that the amidone of the fecula and of the incomplete re-action 

 of diatase only differs in its degree of division. Barytes 

 forms a white bulky precipitate in a solution of amidone. 

 Subacetate of lead affords an insoluble precipitate, as well 

 as lime water. 



If to fecula, mixed with five times its weight of water, 

 we add 0*005 of diatase, at the temperature 158°, the whole 

 of the amidone is destroyed, as may be proved by the absence 

 of any action upon adding iodine. It is converted into 

 sugar and gum, which are distinguished from the substance 

 from which they were produced, by being soluble in water 

 and weak alcohol, in not being' precipitated by tannin, 

 subacetate of lead, or any of the re-agents mentioned. 

 Alcohol of -816 to -794 does not dissolve them. The gum 

 and sugar are distinguished from each other by the sugar 

 dissolving in alcohol of -850, without leaving any residue, 

 while gum is precipitated by the same agent. 



The sugar, by the agency of yeast and heat, is converted 

 into alcohol and carbonic acid, while the gum of amidone, 

 under the same circumstances, does not produce alcohol, 

 but by the action of sulphuric acid it is converted into 

 sugar. According to Biot, the gum obtained from fecula, 

 by means of diatase, produces on the plane of polarization 



