23 



traction of the vesicles is already visible and it reaches its maximum at about o,i% 1 ). 

 With still stronger concentrations an accrease in thickness of the precipitated layer 

 is observed, probably because the vesicles then lose somewhat of their weight in the 

 heavier liquid 2 ). As non-electrolytes such as cane sugar, urea, aethylalcohol, and 

 inethylalcohol, even in i% solutions, cause no sedimentation at all, it is evident that 

 we have to deal here with an ionreaction, which perhaps will prove to be very well 

 apt for exact measure. Aethylalcohol of 5% and methylalcohol of 6%, however, 

 distinctly bring the vesicles to precipitation, but then the superstanding liquid becomes 

 rather turbid, the dissolved granulose precipitating also. Above 10% methylalcohol 

 the precipitation is complete. 



If the starch is boiled in dilute salt solutions, the volume of the sediment after 

 standing is as large as if the salt had been added later to the starch boiled in distilled 

 water. 



When the sedimentation is caused by ammonium sulphate it is easy to show that 

 as well the ammonium as the sulphuric ion are present in stronger concentration in 

 the precipitate than in the liquid above it. 



The foregoing is quite in accordance with the results of an investigation of Mme 

 Z. Gatin-Gruzewska 3 ). By extraction of starch with dilute caustic soda she 

 obtained a soluble substance, amylose, and an insoluble rest of amylopectose in about 

 the same proportion as the above (0.6 and 0.4). Her view, however, of the localisation 

 of the two constituents is another than that which follows from my observations. 



She says that amylopectose forms little scales or sacs, evidently corresponding 

 with the layers of the starch-grain, so that this constituent would occur as well within 

 as outside the grain, whilst, according to my experience, the whole inner portion 

 dissolves in boiling water and is homogeneous, the outerwall only being insoluble and 

 thus materially different. 



The words amylose and amylopectose have first been used by L. Maquenne 

 and E. Roux 4 ), but they consider both these substances as perfectly mixed and 

 say : L'empoix d'amidon est constitue par une solution parfaite d'amylose, epaissie 

 par l'amylopectose (1. c. pag. 219). 



That Maquenne, even after the communication of Mme. Gatin-Gru- 

 zewska, had by no means the view here given follows from the observations which 

 he adds to the said communication r> ). 



The change of the terms amylocellulose and granulose, so long existing in 

 the literature, into amylopectose and amylose by Maquenne, seems not 

 necessary. 



1 ) No great difference in the thickness of the precipitated layer (ca. 4 cm. from a 

 liquid layer of 17 cM.) was perceptible after 24 hours at room temperature when using 

 o,i / KsHPCh, KC1, Na Cl, (NH 4 ) 2 SC>4, CaCh, Al, Cls, K NOs, HC1, or Na 2 COi. 



2 ) More dilute solutions of sugar and urea do cause some sedimentation for a not 

 yet explained reason. Stronger solutions do the same perhaps because of contamination 

 by electrolytes. 



*) Comptes Rendus T. 146 p. 540, 1908. 



4 ) Recherches sur 1'amidon et la saccharification diastasique. Ann. d. Chimie et de 

 Physique, 8e Serie. T. 9, pag. 179, 1906. 



5 ) Observation sur la Note de M me Gatin-Gruzewska. Comptes Rendus T. 106, 

 p. 542, 1908. 



