Mixter — Thermochemistry and the Periodic Lavj. 531 



per cent tungsten with sodium peroxide and Delepine and Hal- 

 lopeau's W + 30 = 196*3 Cal. The heat effect of 1 gram of 

 uranium trioxide uniting with sodium was found to be 327, 

 342, 338 and 330 c . With such small values the error may be 

 large. 



The thermochemistry of the halogens is commonly given for 

 chlorine gas, liquid bromine and solid iodine. For comparison 

 we must regard the three elements as in the gaseous state and 

 take into account the heats of vaporization of liquid bromine 

 and solid iodine. From data in Abegg's Handbuch, IV, 2. 

 Abtheilung, p. 226, is derived 7*5 Cal. for the heat of vaporiza- 

 tion of one gram molecule of liquid bromine at common 

 temperature. Nernst* calculated the heat of formation of two 

 molecules of hydrogen iodide from gaseous iodine to be 2 76 

 Cal., and Thomsen from solid iodine found it to be 12 07 Cal. 

 The heat of vaporization of the one gram molecule of solid 

 iodine at common temp'erature derived from these numbers is 

 therefore 14-8 Cal. 



Table V" is made from Thomsen's data with the addition of 

 7*5 Cal. and 14-8 Cal. to the values of the bromine and iodine 

 compounds respectively. 



2H 



2Na 



2K 



2Ag 



Zn 



Cd 



Pb 



2Cu 



2Hg 



2C1 

 44-0 

 195-4 

 211-2 

 58-8 

 97-2 

 93-2 

 82-8 

 65-8 

 65-2 

 54-5 



Table V. 

 2Br(gas) Linear values 



2I(gas) 



24-4 



" 24-0" 



2-8 Cal 



178-9 



'174-8' 



153-0 



198-1 



193-6' 



175-0 



52-9 



~ 50-8' 



42-4 



83-4 



81-0 



64-0 



82-7 



78-8 = 



63-6 



72-0 



= 69-1" 



54-6 



57-5 



' 56-8 = 



47-3 



58-5 



55-8' 



45-9 



49-4 



" 47-6" 



41-4 



Table V and fig. 7 show that the heats of formation of the 

 bromides are a little higher than the mean of those of the 

 chlorides and iodides. It would seem that this excess over the 

 mean in all cases cannot be due to a constant error. More- 

 over, the results cited which are Thomsen's agree fairly well 

 with those of Berthelot. When, however, we consider that, of 

 the compounds given, only the heat of formation of hydrogen 

 chloride has been found by direct synthesis and that all of the 

 other values are derived indirectly, we may question whether 

 the errors are not as great as the variations of the bromine 

 *Zeitschr. Electrochemie, 1909, p. 691. 



