éoé 



The two constituents of the starcli grain, which I described earlier, ^) 

 namely the amylopectose, non-soluble at boiling, which forms the 

 wall of the starch grain, and the graiuilose (aniylose), which does 

 dissolve at boiling and forms the inner part, change both at 150° 

 C. into erjstallisable starch. 



It is not diflicult to convert 407„ of the original starch into 

 needles or sphero-crystals. With a lower temperature or a shorter 

 time of heating the quantity of starch, which crystallises increases, 

 but at the same time the needles become shorter and less distinct. 

 When heated at 110° to 120° C. the solution, at first perfectly 

 clear, quite coagulates at cooling and becomes white as porcelain. 

 This coagulated substance or gel, must also be considered as con- 

 sisting of crystals, but the needles are nearly, or in fact ultra- 

 microscopic. Tliey do not show any orientation. 



As the temperature is taken higher, the quantity of dextrine, which 

 does not crystallise, increases. The iodine reaction shows that this 

 dextrine contains much erythrodextrine at lower temperatures, and 

 at higher consists only of leukodextrine, colouring light brown. At 

 temperatui-es of from 160° to 170° C. the 10 7o potato starch quite 

 changes into dexti'ine in from half an hour to three quarters of an 

 hour; besides, the presence of sugar, susceptible to alcoholic fer- 

 mentation, may then already be observed. 



The sphero-crystals and needles of the starch dissolve, when 

 heated in water, more slowly than soluble starch, which 1 ascribe 

 to the greater size of the artificial needles, compared with that of 

 the needles composing the natural and soluble starch. These needles 

 consist in my opinion of a substance (granulose) impermeable to 

 water, so that tiie dissolving must begin at the outside and will be 

 the slower as the needles are thicker. 



At 70° C. the solubility becomes very great, without any sign 

 of production of paste or of gelatinising. With iodine the colour 

 of the solution is pure blue. The effect of diastase on the granulose 

 needles is as usual: erythrodiastase extracted from crude barley- 

 flower, forms erythrodextrine and maltose, whilst leukodiastase pre- 

 pared from malt, produces leukodextrine and maltose. 



Of crystallisable dextrine and amylodextrine, so much discussed 

 in literature, !• perceived nothing in my experiments; the latter 

 substance is evidently crystallised starch, with so much erythro- or 

 leukodextrine between the needles, that the pure blue iodine colour 

 of the granulose is modified to violet or reddish brown. When the 



') Proceedings of tlie Academy of Sciences. Amsterdam, 11 April, 1912. 



