for Equal Volumes under Constant Pressure. 



215 



Name of gas. 









Difference 









between 









theoretical 



Composi- 



Number 



Molecular 



and ob- 



tion. 



of atoms. 



weight. 



served 

 specific 

 heats. 



cr 2 



2 



71 



0058 



Br 2 



2 



160 



0069 



G9 2 



3 



44 



0059 



GS a 



3 



76 



0140 



NH 3 



4 



14 



-0006 



PCI 3 



4 



137-5 



0334 



AsCl 3 



4 



181-5 



0-397 



€H 4 



5 



16 



-0012 



CHC1 3 



5 



119-5 



0-307 



SiCl 4 



5 



170 



0-432 



ODiCl* 



5 



190 



0-507 



SnCl 4 



5 



2596 



0-502 



G 2 H'C1 



8 



64 



0167 



€2H 5 Br 



8 



109 



0-272 



G 4 H lo 



15 



74 



0547 



G l H 10 S 



15 



90 



0-566 



H 2 



3 



18 



0027 



H 2 S 



3 



34 



0014 



Boiling-point. 



Chlorine 



B romine 



Carbonic acid 



Sulphide of carbon 



Ammonia 



Terchloride of phosphoru 

 Chloride of arsenic 



Marsh-gas 



Chloroform 



Chloride of silicon 



Chloride of titanium 



Chloride of tin 



Chloride of ethyle 



Bromide of ethyle 



Ether 



Sulphide of ethyle 



Water 



Hydrosulphuric acid 



Gas. 

 47°-63° 



Gas. 



48° 



Gas. 



78° 



133° 



Gas. 



62° 



59° 

 135° 

 120° 



11° 

 41° 



34° -5 

 91° 



100° 1 Excep- 

 Gas J tion. 



§ 4. Comparison of the above method of calculating the specific 

 heat of gases ivith those proposed by Buff* and Clausiusf. 



The equations arrived at for calculating the specific heats of 

 perfect gases (namely, 



at constant volume y = (n + 3) a = (n + 3) . 0*034, 



gander constant pressure y=(/i-f 5)«= (ft + 5) .0*034) 

 necessarily lead, in most cases, to results which differ notably 

 from those which follow from a rule given by Professor H. Buff. 

 This rule directs us to u take the specific heat of a simple gas at 

 constant pressure as many times as there are gaseous volumes of 

 the constituents which go to make up the compound, and then 

 divide by the number of gaseous volumes occupied by the com- 

 pound produced. If to the quotients so obtained the heat of 

 expansion corresponding to the unit-volume (a quantity which 

 is the same for all gases) be added, the specific heat under con- 

 stant pressure is obtained "J. According to the way in which 



* Ann. der Chem. und Pharm. vol. cxv. p. 306 ; Lehrb. d. physik. u. 

 theoret. Chemie, von Buff, Kopp, und Zamrainer, p. 201. 

 t Ann. der Chem. und Pharm. vol. cxviii. p. 1 12. 

 X Buff has based this method (loc. cit. p. 305) upon the further hypo- 



