526 Mixter — Thermochemistry and the Periodic Law. 



work 137-6 Cal., and Ba + O = 125*6 Cal. Guntz is the only 

 one who determined the heats of the reactions of all three 

 metals and hence his values are used in this paper. 



The values in Table IV are from Guntz's results and 

 Thomsen's data for heat of neutralization and solution. Cor- 

 rections are not made for the slightly lower atomic weights used 

 by Thomsen than at present adopted. The linear values for 

 the strontium compounds are derived as already described. 







Table IV. 









Calcium 



Strontium Linear values Bari 



R + 



151-4 



139-4 



"139-2" 



126-4 



RO + H 2 



15-5 



17-7 



18-8' 



22-3 



R + 2H + 20 



235-3 



225-5 



"226-5 = 



217-1 



R + 2C1 



190-4 



195-4 



193-5 = 



196-8 



R + S + 40 



338-8 



342-2 



= 340-0 = 



341-2 



RO + S0 3 



84-2 



99-6 



" 97'6 = 



111-6 



R + C + 30 



291-0 



291-8 



= 288"4 = 



285-6 



RO + CO, 



42-6 



55-4 



52-1" 



62-2 



Cal. 



The experimental values for the heat of formation of the 

 strontium compounds in the table average - 8 per cent higher 

 than the calculated values with variations in some cases of 

 about two per cent. The tabulated results make it appear 

 probable that the heats of formation of these compounds are 

 linear functions of the atomic weights. The thermochemistry 

 of magnesium, zinc, cadmium and mercury shown in fig. 3 

 exhibits no such regularity and the quantities of heat fall 

 irregularly with increasing atomic weights. 



The thermochemistry of the third group includes only boron, 

 aluminum, lanthanum and thallium and is not sufficient for use 

 in the discussion. 



The thermochemistry of the fourth group shown by fig. 4 

 presents certain abnormalities which will be considered later. 

 The heats of formation of the dioxides of the elements in the 

 even series are CO,, 135;* Ti0 2 , 218-4; Zr0 2 , 177-5; Ce0 2 , 

 221-6 ; Th0 2 , 322 Cal. In the odd series they are Si0 2 , 195f ; 

 Sn0 2 , 135-2 ; Pb0 2 , 62-4 Cal. 



The characteristics of the thermochemistry of the fifth 

 group are shown in fig. 5. The heats of formation, as Thom- 

 sen observed, of the antimony compounds are higher than the 

 arsenic. Phosphorus combining with oxygen gives a larger 

 quantity of heat than antimony, while with the halogens the 



* C (vapor) + 20 = CO, + 135 Cal. (T). 



fVon Wartenberg, Nernst Festschrift, 459, and Zentralblatt, 1912, II, 

 1095. 



