Atomic Laws of Thermochemistry. 25 



and Berthelot and Moissan (Compt. Bend, cix.) have given C in 

 then H + Fgas = HFgas + C; 



R solid + + 2H + F gas = KOH solid + HFgas + B + C, 



and therefore = KF solid + A + B + C + H 2 solid ; 



but + 2H = H 2 solid + D, 



tflPFfM OTA 



Bsolid + Fgas=BFsolid + A + B + C-D, 



The value of D is 68*4 + 1*4 or 69-8, that of C is 87*6, and 

 the following are the values of A and B : — 



Na. K. ^Mg. fCa. £Sr. £Ba. 



A 39-9 38-2 284 33-3 35-9 35*7 



B 1019 103-2 1086 107*4 107*2 107 4 



The latent heats of vaporization of the gramme- molecule of 

 the fluorides are : — 



Na. K. pig. ^Ca. |Sr. ±Ba. 



25-7 230 13-2 14-0 152 162 



With these numbers the following heats of formation of the 

 fluorides (reagents and products gaseous) have been obtained, 

 and along with them are given their differences from the heats 

 of formation of the chlorides, and the same differences for the 

 chlorides and bromides : — 



Table IX. 



Heat of Formation of Fluorides, reagents and products 



gaseous. 



R F-Cl. Cl-Br. 



Na 97-8 9-9 91 



K 1001 45 77 



^Mg 1105 28-2 12-1 



|Oa 113-5 22-4 11-2 



|Sr 114-6 17-9 8-2 



£Ba 113-6 14-0 82 



According to our previous experiences we should expect the 

 ratios of the differences F — CI and CI — Br to be constant, but 

 they are far from being so; perhaps the irregularities are due 

 to polymerization not taken into account in our calculations, 

 because the strong combination between KF and HF to form 

 KHF 2 is suggestive of a molecular formula K 2 F 2 in place of 

 KF. All that can be said of the two columns of differences 



