Carbon at High Temperatures, 463 



proportional to the number of oxygen atoms combined. The 

 two metals experimented on by Andrews were copper and tin ; 

 but recently Thomson has shown the same law is applicable to 

 the oxides of nitrogen, and even to the oxides of manganese. 

 The numbers obtained_, starting from the first oxide in the latter 

 series, diminish by a constant quantity. 



The author has communicated some preliminary experiments 

 to the British Association which induce him to believe the same 

 law is applicable in the negative direction, viz. to the oxides of 

 chlorine. 



We are therefore justified in concluding that the two oxides 

 of carbon ought either to have the same thermal value, or the 

 first one may evolve 15,000 or 16,000 units more per oxygen 

 atom than the second. Taking into consideration the general 

 chemical analogies existiag between the oxides of tin and the 

 oxides of carbon, we may in the first instance suppose the 

 thermal value identical. It is to be observed that the fact of 

 carbonic oxide being an incondensible gas, and carbonic acid a 

 condensible one, does not interfere with the applicability of An- 

 drews^s law, as the total latent heat of vaporization of each sub- 

 stance would be nearly identical. 



This is confirmed by noting that the following total latent 

 heats of elements and compounds do not difi'er much, although 

 their physical properties are very different : — 



C02, solid .... 6100 



SO^ liquid .... 5600 



N^^O, liquid .... 4400 



CS2 6500 



Br 4000 



I 5500 



H in Pd 4200 



As a fair mean we may accept 4000 units as the absorption 

 value per atom for real latent heat of vaporization ; and as the 

 latent heat of fluidity in the case of non-metallic bodies is very 

 small, we may suppose it included in the above value. Taking 

 now the thermal values of the oxides of carbon, we have 



C, 02 . . . =96,000 



C0,0 . . . =68,000 



therefore C, ... =28,000 



The difference, therefore, between CO, — C, =40,000 units, 

 which must be regarded as the total number of heat-units required 

 to raise 12 grammes of carbon into the gaseous state. If we de- 

 duct from this number 4000 units for liquefication and evapori- 



