148 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



Oxygen 50-54 grains =54-1% J 

 Carbon 26 '68 ,, =28-5% 

 Hydrogen 16*28 ,, 3*17*4% 



or, as Lavoisier preferred to express it : 



Carbon 26 '68 grains =28-5% 

 Hydrogen 7-36 = 7-9% 

 Water 59-46 -63 '6% 



Similar combustions of olive oil and of candle-wax gave 



Oil. Wax. 



Carbon 79% 82-3% 



Hydrogen 21% 177% 



Both substances contain oxygen, out the quantity was not 

 sufficient to be detected by Lavoisier's method of analysis. 



Dumas and Stas (1841) on the composition of carbonic 

 anhydride. About the year 1840 it became evident that 

 the numbers for the composition of carbonic anhydride, given 

 twenty years previously by Berzelius and Dulong, must be 

 erroneous, since careful analyses of compounds rich in 

 carbon often gave totals exceeding 100%. Thus two 

 typical HYDROCARBONS (i.e. compounds of hydrogen and 

 carbon) extracted from coal-tar gave the following figures 

 (Stas's Works, I. 270 and 275) : 



Naphthalene. Benzene 



Hydrogen 6'2 4 % 770% 



Carbon 95-40% 93 '53% 



io i -64 101-23 



" 

 In these substances the proportion of hydrogen was so 



small that no large error could be produced by uncertainty 

 as to the weight of water produced, or the weight of hydrogen 

 which it contained. The excess above 100 per cent, could 

 only be due to over-estimating the proportion of carbon in 

 the carbonic anhydride formed on combustion. To test 



1 The numbers now accepted for pure alcohol are : Oxygen 34 '8%, 

 Carbon 52-2%, Hydrogen 13-0% ; Lavoisier's spirit of wine evidently 

 contained about half its weight of water. 



