150 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



The combustion was carried out in a current of oxygen, 

 which was freed from carbonic anhydride by means of 

 potash and dried by means of sulphuric acid. The carbon, 

 contained in a platinum boat, was burnt in a porcelain tube 

 heated strongly in a furnace (Fig. 34). The carbonic 

 anhydride was absorbed by potash and weighed directly, 

 with the help of absorption-apparatus devised by Liebig. 

 A small tube containing sulphuric acid was provided to 

 collect any water that might be produced, but in none of the 

 experiments was any gain in weight observed. The numbers 

 obtained were as follows ( Works, I. p. 252) : 



Carbon. Carbonic Anhydride. Percentage of Carbon. 



i -ooo 3-671 27-24 



Natural 0-998 3 '660 27-27 



Graphite 0-994 3-645 27-27 



i -216 4'46i 27-26 



i-47i 5*395 2 7 '27 



0-992 3-642 27-24 



Artificial 0*998 3-662 27-26 



Graphite i'66o 6*085 27-28 



1-465 5-365 27-31 



0708 2-598 27-25 



0-864 3*1675 27-27 



Diamond 1-219 4*4^5 27-30 



1-232 4-517 27-26 



1-375 5'04i 27-28 



Mean ...... 27-27 



The composition of carbonic anhydride was therefore 

 Oxygen = 72'73% 



The reduction in the percentage of carbon from 27-67 to 

 27-27 provided the correction that was needed in the 

 analysis of the hydrocarbons, which now gave : 



Naphthalene H 6-24 C 94*02 Total 100-26 



H 6*30 C 93*80 ,, roo'io 



H 6-29 C 93-86 ,, 100-15 



H 6-31 C 93*84 ,, 100-15 



Benzene H 77 C 92*2 ,, 99-9 



