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On the ultimate Composition of simple alimentary Substances; with 

 some preliminary Remarks on the Analysis of organized Bodies in 

 general. By William Prout, M.D. F.R.S. Read June 14, 1827. 

 [Phil. Trans. 1827, p. 355.] 



The author commences by observing, that the present Is the first 

 of a series of communications, which he hopes to have the honour of 

 laying before the Royal Society, on the same subject ; and that the 

 object of the whole series is to determine the exact composition of 

 the three great divisions, viz. the saccharine, the oily, and the albu- 

 minous, in which the alimentary matters employed by the more per- 

 fect animals may be comprehended ; and afterwards to inquire into 

 the changes induced in them by the action of the stomach and other 

 organs, during the subsequent stages of assimilation. 



The present paper includes some preliminary observations on the 

 analysis of organized bodies in general, and the composition of the 

 first of the above classes, viz. the saccharine. 



After an historical sketch of the principles and progress of the 

 analysis of organized substances, the author makes some remarks on 

 the difficulties attending the use of oxide of copper as now employed. 

 He observes that it is not only hygrometric, but, like many other 

 powders, also condenses air. He likewise found, that when the ox- 

 ide was removed from the tube in which the combustion had been 

 effected, and retriturated, and reburnt (as in most instances was 

 necessary), it almost invariably gained, instead of losing, weight ; a 

 circumstance which he ascribes to the combination of the oxygen of 

 the air contained in the tube, with the partially reduced oxide of 

 copper. These sources of error, from their variable and uncertain 

 character, he found it impossible to ascertain, and was at length 

 obliged to adopt another principle. 



When a substance composed of hydrogen, carbon, and oxygen, is 

 burnt in a given quantity of oxygen gas, one of three things must 

 happen ; either the volume of the gas will not be changed, in which 

 case the hydrogen and oxygen must exist in the substance, in the 

 proportion in which they form water ; or, secondly, the volume may 

 be increased, in which case the oxygen must exceed that proportion ; 

 or, lastly, it may be diminished, when the hydrogen must predomi- 

 nate. These well-known facts the author has taken advantage of for 

 determining the composition of vegetable substances, and proceeds 

 to describe the apparatus he employed for that purpose, which con- 

 sists essentially of accurately graduated syphon gasometers, placed at 

 a convenient distance from one another, so that they may be readily 

 connected by means of an intermediate tube, in which the substance 

 to be analysed is introduced. Heat is applied to this tube by means 

 of a spirit-lamp, and the oxygen gas transferred, by means of mer- 

 cury, from one gasometer to another, through the ignited tube. After 

 the operation, the difference of volume, as compared with that of the 

 oxygen originally employed, shows the composition of the substances. 

 The author then details some precautions necessary to be observed in 



