ig8 



colloid, whose presence makes the needles remain short, the shorter the more 

 of the colloid is present. It remains active unto about 100 C., but above this 

 temperature it slowly decomposes, quite to vanish at about 150 C. 



The hypothesis that this protecting colloid might be a phosphoric ester of 

 granulose, is contrary to the properties of soluble starch, for this behaves at 

 crystallisation of the solutions, prepared between 100 and 150 C., precisely in 

 the same manner as natural starch so that the protecting colloid is still present 

 in this substance, whereas it might be expected that an ester would be decom- 

 posed by the strong, io%-ic hydrochloric acid used for its preparation. 



Perhaps the colloid is the amyloplast itself, which, at the formation of the 

 starch grain, remains partly enclosed between the fine granulose needles. Its 

 greatest accumulation would then occur in the amylopectose wall of the grain, 

 which does not yet dissolve at boiling. That no difference could be found in the 

 rate of nitrogen between the granulose and the amylopectose of the starch grain, 

 to which circumstance I directed attention in my communication of n April 1912, 

 I ascribe to the extremely small absolute rate of nitrogen in both constituents; 

 but I think that the relative difference is considerable. 



I will not omit to draw attention to the existence of starch species, which 

 after heating, do not crystallise in the usual way. To these belongs arrowroot. 

 If a 10% paste of arrowroot is precisely treated as above described, it becomes 

 after cooling, as usually, turbid and precipitates; but instead of a crystalline deposit 

 we find in the microscopic preparation drops of various sizes, and homogeneous 

 structure (Fig. 4), which later, however, become turbid and granulous. With 

 iodine these drops turn deep blue and evidently consist of granulose like the 

 crystal needles of the other starch species. The liquid between the drops is also 

 a granulose solution, but less concentrated. The drops remind of a heavy oil, but 

 they differ from it by such a small surface tension that notwithstanding their 

 liquid state many may be pear- or egg shaped, and even pointed. Double refraction 

 I could not perceive, but, nevertheless, I think it probable that they must be 

 reckoned to the liquid crystals. That after some time the drops become turbid 

 can be explained by the growing in length and thickness of the ultra-microscopic 

 needles, which constitute the liquid crystal drops, hence, by the same process of 

 crystallisation by which the needles originate. 



The facts here briefly described deserve further attention from a physico- 

 chemical view. 



Explanation of the figures. 



Fig. i (600). Sphero-crystals of 10% potato starch, half an hour at 150 C. 



Fig. 2 (600). Bolidiscs or Jacquelain discs of potato starch, half an hour at 125 C. 



Fig- 3 (230). Bolidiscs or Jacquelain discs of wheat starch, three quarters of an hour 



at 160 C. 

 Fig. 4 (200). Drops or liquid crystals of 10% arrowroot, three quarters of an hour at 



140 C., coloured with iodine. 



