740 AMYLACEOUS AND SACCHARINE SUBSTANCES. 



granules or solid matter in any other form can be perceived in 

 the liquid by the microscope. The tegumentary portion of the 

 starch, which amounts to three or four thousands of the whole, 

 remains on the filter, but may also be dissolved by continued 

 boiling. When the quantity of starch dissolved by hot water 

 is considerable, much of the starch separates in a gelatinous 

 state, on the cooling of the solution. The peculiar character 

 of the solution of starch in water has been the object of much 

 research by M. Payen, which lead to the observation that by 

 the freezing of a solution of starch that substance separates from 

 the water and contracts into a species of tissue, which is not 

 dissolved again on the thawing of the ice. It is the opinion of 

 the same chemist that the organisation of the starch is not 

 altogether effaced or its cohesion destroyed, so long as it is 

 gelatinous and possesses the property of being stained by iodine 

 of a blue, or of different shades of violet to red, according to 

 the degree of its division.* 



Granules of starch of M. Jacquelain. When starch is heated 

 under pressure in a Papin's digester to 302 (150 cent.), with 

 from five to fifteen times its weight of water for two hours, 

 the whole is dissolved except the tegumentary matter, and the 

 solution is so thin that it may be filtered at the boiling tem- 

 perature. This solution when it cools deposits a considerable 

 mass of pulverulent matter, white and opaque and entirely 

 composed of a species of granules, first observed by M. Jacque- 

 lain. These granules when examined by a microscope having 

 a power of 200 diameters, present themselves as circular or 

 spherical bodies, transparent, and uniformly -r^h of an inch 

 (-rtfWths of a millimetre) in diameter. When dried they have 

 the whiteness of starch without its lustre. They are denser 

 than water, and subside from that liquid almost as quickly as 

 fecula. These granules are scarcely soluble at 32, slightly so 

 at 53.6, but dissolve in a considerable proportion about 158, 

 and in still greater quantity at the temperature of ebullition. 

 This increased solubility is the most remarkable chemical change 

 which the starch has undergone, by its solution in water at a 

 high temperature. Anhydrous alcohol precipitates completely 

 a solution of the granules and the aqueous solution of iodine 



* Annales de Cbimie et de Physique, tome 5, p. 225. 



