ig6 



stituents of the starch grain, which I described earlier 1 ) namely the amylopectose, 

 non-soluble at boiling, which forms the wall of the starch grain, and the granulose 

 (amylose), which does dissolve at boiling and forms the inner part, change both 

 at 150 C. into crystallisable starch. 



It is not difficult to convert 40% of the original starch into needles or 

 sphere-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 per- 

 fectly clear, quite coagulates at cooling and becomes white as porcelain. This coagu- 

 lated substance or gel, must also be considered as consisting of crystals but the 

 needles are nearly, or in fact ultramicroscopic. They 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 leuko- 

 dextrine, colouring light brown. At temperatures of from 160 to 170 C. the 10% 

 potato starch quite changes into dextrine in from half an hour to three quarters 

 of an hour; besides, the presence of sugar, susceptible to alcoholic fermentation, 

 may then already by observed. 



The sphere-crystals and needles of the starch dissolve, when heated in water, 

 more slowly than soluble starch, which I 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 the 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 barleyflower, forms erythrodextrine and maltose, whilst 

 leukodiastase prepared from malt, produces leukodextrine and maltose. 



Of crystallisable dextrine and amylodextrine, so much discussed in literature, 

 I perceived nothing in my experiments; the latter substance is evidently crystallised 

 starch, with so much erythro- or leukodextrine between the needles, that te pure 

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

 the crystalline mass, which in fact sometimes colours red with iodine, is washed 

 out with much water, the dextrine, and with it the amylodextrine reaction* quite 

 disappears, to make place for pure blue. 



The crystals may also be obtained from soluble putato starch. Such starch 

 is prepared by keeping raw starch during 10 days under io%-ic cold hydro- 

 chloric acid. 



Crystal discs (bolidiscs) result very easily from wheat starch. The heating 

 must be somewhat longer and the temperature higher than for potato starch. 

 Besides, it is more difficult to obtain a perfectly clear solution from wheat paste. 



Fig. 3 shows, 230 times magnified, the discs formed in a beakerglass of 

 100 cm'\ in which wheat starch, previously boiled in distilled water, is heated to 



') Proceedings of the Academy of Sciences. Amsterdam, n April 1912. 



