and of Combustion of Acetylene, Ethylene and Methane. 353 



carbon. Thomsen* made three determinations of the heat of 

 combustion of hydrogen in which 18,928 grams of water were 

 produced, and obtained as the mean 68,357°. Berthellot and 

 Matignonf adopt as the results of their experiments the num- 

 ber 69,000. Thomsen^: used the number 96,960 for C0 2 

 obtained by Farve and Silbermann,§ and Berthellot|| found 

 97,650°. Thomsen, and Farve and Siibermann made the com- 

 bustion slowly at atmospheric pressure, while Berthellot made 

 them almost instantly in his bomb. The former worked with 

 large quantities and the latter with small, in case of hydrogen 

 with about 23 milligrams. Berthellot's results are somewhat 

 higher than the others. The sum of the heats of combustion of 

 the components of acetylene is, according to Thomsen, 262,277°, 

 to Berthellot 264,300°. The former^ found for the combus- 

 tion of acetylene 310,050° and the latter** 315,700° at constant 

 pressure. The writer's result is 313,800°. Thomsen made the 

 heat of formation of acetylene —47,770°. If we calculated it 

 from Berthellot's figures it is —51,400°. 



Ethylene. 



The ethylene gas was prepared by the action of zinc on pure 

 ethylene bromide dissolved in alcohol. It was freed from 

 oxygen by ferrous hydroxide but contained several per cent of 

 hydrogen gas and doubtless a little nitrogen. It was dried by 

 sulphuric acid. 



Experiment 10. — Gas containing 93*7 per cent by volume of 

 ethylene, 602°° at 18-5° and 748 mm pressure equal to 0*655 gram 

 of ethylene ; acetylene added 4*828 grams ; jacket 1*4°. The 

 gas after explosion was free from hydrocarbons. 



Minutes. Temperature. 



Water and water equivalent of 

 calorimeter, 3252 grams. 



Temperature interval, 



4-362 — 1 -22.4-0*026 = 3*168° 







1-22 



3 



1*22 



6 



1*22 



9 



4*329 



12 



4*362 



15 



4-343 



18 



4-330 



21 



4 314 



24 



4-300 



The thermal result is 10,300°. 



The heat of dissociation of 4*828 grams of acetylene is 

 ),900 calories; subtracting this from 10,300 we have 400 calories 



*Thermochemische Unlersuchungen, ii. 52. f Ann. Ch. Phy. [6], xxx, 553. 

 % Thermochemische Untersuchungeo, ii. 283. § Ann. Ch. Phys. [3], xxxiv, 357. 

 || Ann. Ch. Phys. [6], xviii, 89. \ Thermochemische Untersuehungen, vi, 74. 

 **Ann. Ch. Phys. [6], xxx, 556 



