88 Historical Sketch of Improvements in [AuG. 



residue left by the spontaneous decomposition of starch after it 

 has been treated with a sufficient quantity of cold water to take 

 up every thing soluble in that liquid. Boiling water dissolves the 

 amylin, and it may be obtained by evaporating the solution to 

 dryness. It is a pale semitransparent brittle substance, insolu- 

 ble in alcohol, soluble in 10 times its weight of cold water. 

 Water, of the temperature 144°, dissolves it in any quantity, and 

 retains in solution after cooling a much greater proportion than 

 can be dissolved in cold water. When the liquid is more con- 

 centrated, the amylin precipitates in part on cooling in the state 

 of a white opaque matter ; but it is redissolved on heating the 

 water to 144°. The aqueous solution assumes a blue colour 

 when treated with iodine. It is coagulated into a white paste 

 by the subtritacetate of lead, but not by the acetate. It is 

 copiously precipitated by barytes water ; but neither by lime 

 water, nor infusion of nutgalls. It dissolves in the aqueous 

 solution of potash, and the solution has no viscidity. From this 

 solution, it is thrown down by acids and by alcohol. 



The starchy ligHin was obtained from the residue of the spon- 

 taneous decomposition of starch after that residue had been 

 deprived of every thing soluble in cold water, hot water, alcohol, 

 and very dilute sulphuric acid, by digesting it in 10 times its 

 weight of an alkaline ley containing one-twelfth of potash. A 

 brown solution is obtained, from which dilute sulphuric acid 

 precipitates the starchy lignin under the form of a light-brown 

 combustible substance having the lustre of jet. It gives a blue 

 colour to the aqueous solution of iodine. This last property, 

 together with its solubility in a weaker alkaline ley, distinguishes 

 starchy lignin from common lignin. 



2. Gluten. — I noticed in a late number of the Annals of Phi- 

 losophy (xv, 390), that M. Taddey, an Italian chemist, has 

 recently discovered that the gluten of wheat may be decomposed 

 into two principles, which he has distinguished by the names of 

 gliadine and ziinome. These two substances are obtained by 

 kneading gluten with repeated portions of alcohol as long as that 

 liquid becomes milky when diluted with water. The alcohol 

 dissolves the ghadine, and leaves the zimome. 



Gliadine, obtained by evaporating the alcohohc solution, is a 

 brittle, straw-yellow, slightly transparent, substance, having a 

 weak smell, similar to that of honeycomb, and, when gently 

 heated, giving out an odour similar to that of boiled apples. In 

 the mouth, it becomes adhesive, and has a sweetish and balsamic 

 taste. It is pretty soluble in Ijoiling alcohol, but the greater 

 part precipitates as the solution cools. It softens, but does not 

 dissolve m cold water. The alcoholic solution of gliadine 

 becomes milky, when mixed with water ; it is precipitated in 

 white flocks by the alkaline carbonates. Dry gliadine dissolves 

 in caustic alkalies and acids. It swells on burning coals, and 

 then contracts in the maimer of animal bodies. It burns with a 



