254 H. von Mohl on Cellulose in Starch-grains. 



In reference to the chemical reactions, I met with the follow- 

 ing distinctions, in detailing which I shall, for the sake of bre- 

 vity, simply use the terms starch-grains and cellulose, without 

 especially mentioning that in each case I refer to starch-grains 

 exhausted by saliva, and cellulose purified by Schulze's method. 



Solution of caustic potash dissolves the starch- grains suddenly; 

 cellulose swells up in it, but remains undissolved after many 

 hours. 



Solution of chloride of zinc and iodine, when concentrated, dis- 

 solves starch-grains instantly into a brownish-red fluid ; cellulose 

 does not swell perceptibly in it, and resists solution for days. 



Ammoniated oxide of copper, to which so much carbonate of 

 ammonia has been added that it will no longer act upon cellu- 

 lose, dissolves the starch-grains instantly ; when still more car- 

 bonate of ammonia is added, the starch is no longer dissolved. 



Ammoniated oxide of nickel dissolves the starch-grains in- 

 stantly ; but cellulose is insoluble in it. 



Nitric acid dissolves the starch-grains instantly ; but cellulose 

 bears long boiling in this acid mixed with chlorate of potash. 



Hydrochloric acid dissolves the starch-grains immediately ; 

 cellulose is not perceptibly attacked by this acid. 



Among these diversities, the different behaviour with polarized 

 light forms the sharpest contrast; the other differences might 

 be regarded rather as gradual, since they all agree in showing 

 that the substance contained in the starch-grains is soluble in a 

 number of media in which cellulose is only slightly or not at all 

 soluble. Hence a question might be raised whether these diver- 

 sities were sufficiently great to warrant the conclusion that the 

 substance of the starch-grains is different from cellulose. In 

 regard to this it must be fully borne in mind, in reference to 

 the distinctions between the two substances relating to their 

 solubility in many of the media named, especially in ammoniacal 

 oxide of nickel, chloro-iodide of zinc, nitric and hydrochloric 

 acids, that I tested the behaviour with these media of purified 

 cellulose derived from a considerable number of plants which 

 exhibited no important differences whatever in the behaviour of 

 the membranes ; so that these differences are as constant and 

 striking as the difference between the various kinds of sugar. 



If therefore we desire to distinguish from one another the 

 hydrates of carbon of which the organic structures of plants are 

 composed, by such reactions, there is abundant ground against 

 ranging the substance of starch-grains exhausted of starch with 

 cellulose, and for giving it a proper name (say farinose) . How- 

 ever, I will not in this respect forestall the chemists, before whom 

 the whole matter must come for definitive settlement. 



Tubingen, February, 1859. 



