86 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



They prepared diastase by two methods : According to the first method the sprouted 

 grains are crushed and macerated in water. The preparation is strained, and then filtered 

 and heated to 75, causing a cloudiness due to the precipitation of albuminous substances. 

 This is filtered and sufficient alcohol is added to the filtrate to cause a white flocculent pre- 

 cipitate, which when dried is in the form of a firm, white, uncrystallized mass, without taste, 

 neutral, and soluble in water and in weak alcohol, but not in strong alcohol. By the second 

 method the sprouted grains are crushed and the grains moistened with half their weight of 

 water, the liquid is filtered off, and sufficient alcohol is added to remove its mucilaginous 

 consistency and to precipitate the albuminous substances. The preparation is filtered 

 and the diastase is separated from the filtrate by the addition of sufficient alcohol. They 

 purified the diastase by repeated solution in water and reprecipitation with alcohol. They 

 note that one part of diastase is sufficient to saccharify 2,000 parts of starch, and that reac- 

 tion takes place in several minutes with a quantity of water less than four times the weight 

 of starch. They also recorded that diastase does not pre-exist in the ungerminating grains, 

 but is formed as needed for the transformation of starch into sugar during germination. 



During tliis and the following years, four articles appeared by Guerin-Varry (Ann. 

 de chim. et phys., 1834, lvi, 225; 1834, lvii, 108; 1835, lx, 32; 1836, lxi, 66), in which he 

 states the following conclusions: The starch-grain consists of three substances amicline, 

 a substance soluble in cold water; an integument, amidine tegumcntaire, which is insoluble 

 in cold water; and amidin soluble, which is insoluble in cold water by itself, but is rendered 

 soluble by the contained amidine. The amidin t^gumentaire was recorded as forming 

 2.96 per cent of the starch. Of the remaining 97.04 per cent, 60.45 parts per hundi-ed 

 were amidine, and 39.55 parts were amidin soluble. He made note of the fact that while 

 whole starch-grains are entuely insoluble in cold water crushed grains are partially dis- 

 solved; that broken grains as well as boiled grains are dissolved all but the integuments; 

 and that if the solution of starch be evaporated a residue will be obtained, a part of which 

 is soluble in cold water (amidine) and a part insoluble in cold water (amidin soluble) . He 

 gives the methods for preparing these substances and their properties, and he also records 

 the results of the elementary analyses of starch, and gives the molecular formula as CgHioOs. 



Guerin-Varry's conclusions regarding the existence of tlu-ee constituents of starch 

 were criticized by Payeii (Ann. de chim. et phys., 1836, lxi, 335), who states that the ami- 

 dine which is soluble before the evaporation of the solution is "swollen up" amidone 

 distributed thi'ough the water, but after evaporation it is amidone with greater cohesive- 

 ness than the starch; that the amidine tegumentaire is nothing else than amidone which, 

 by the method of treatment and by the presence of the integuments, has attained greater 

 cohesiveness; and that amidine is finely divided amidone. 



The literature of starch was added to this year by two contributions by Fritzsche 

 (Ann. d. Phys. u. Chem., 1834, xxxii, 129, 143), in which he reports studies on the morph- 

 ology, method of formation and dissolution of starch-grains, and also the microscopic 

 changes which occur in starch when heated in water on the stage of the microscope. He 

 disproves the statement of Raspail that the grains consist of an enveloping membrane 

 that is insoluble in water and an inclosed substance that is soluble in water. Raspail 

 states that when the grains are ruptured the contents are released from the integuments, 

 but Fritzsche found that when the grains were placed in water and pressed between glass 

 plates, by which some of the grains were broken, the inner mass was not dissolved, nor 

 were empty integuments observed. He studied the grains in the resting-stage of the potato 

 and during the period of erosion. From these studies he believed that the grains are formed 

 by the desposition of outer layers upon the inner and that erosion takes place layer by layer 

 from without inward, from wliich it follows, he states, that the grains do not consist of a 

 membrane and an inner substance that is soluble in water, or of membranous layers with 

 a soluble substance between them, but of a homogeneous mass arranged in concentric layers. 



