704 PRELIMINARY OBSERVATIONS. 



consisting of 1 hydrogen and 8 oxygen in 9 parts, and the 

 latter of 27.675 carbon and 72.325 oxygen in 100 parts : 



The hydrogen is one ninth of the increase of weight in the 

 chloride of calcium tube. 



The carbon is 27.67 per cent of the increase of weight in the 

 potash bulbs. 



The oxygen is the quantity obtained by adding the weights 

 of the hydrogen and carbon together, and deducting their sum 

 from the weight of matter originally employed. 



The following are the details of a particular analysis of sugar 

 (Dumas). 



Weight of Sugar. . . . 600 

 Weight of Carbonic Acid. 921 

 Weight of Water. ... 353 



These give by calculation : 



Carbon 254.6. .42.4 



Hydrogen. . . . 39.2. . 6.5 

 Oxygen 306.2. .51.1 



600 ..100 



The atomic constitution of sugar is obtained from these re- 

 sults, by dividing the quantities of carbon, hydrogen and oxygen 

 in the last column, by their equivalents, 76, 12.5 and 100. 

 We thus obtain 0.558 of an equivalent of carbon, 0.520 of an 

 equivalent of hydrogen and 0.511 of an equivalent of oxygen, 

 which are more nearly proportional to the following than any 

 other whole numbers, 12 carbon, 11 hydrogen, 11 oxygen; and 

 give C 12 H 11 O 11 , the usually received formula for cane sugar. 



The estimation of nitrogen, when present in an organic subs- 

 tance, requires another combustion in which that gas is deter- 

 mined by measurement. This gas generally escapes in a free 

 state, mixed with the carbonic acid and watery vapour ; but 

 frequently deutoxide of nitrogen is formed, which renders the 

 determination of the nitrogen difficult ; to decompose the latter 

 it is necessary to have a portion of copper turnings in the an- 

 terior part of the tube, which are kept at a full red heat during 

 the combustion, as from the screen m (Fig. 94) to the mouth of 

 the tube. This is followed by a layer of pure oxide from m to 

 B, and then the mixture from B to A -, as soon as the copper 



