

Atomic Laws of Thermochemistry. 19 



relate to a temperature of 18° C. and to the ordinary states 

 of all the substances at that temperature ; that is to say, to the 

 gaseous state of CI, the liquid of Br, and the solid of I, the 

 metals all being solid except Hg, and the compounds mostly 

 solid. To pass from Thomsen's data to those given in our 

 next table for heats of formation with reagents and products 

 all gaseous, it is necessary to subtract from his heat of forma- 

 tion of each equivalent of a compound the value given in 

 Table IV. for the latent heat of the equivalent, and then to 

 add the latent heat of an equivalent of the metal, and finally 

 to add the latent heat of vaporization of the halogen, which 

 for gaseous CI is 0, for liquid Br is 3*6, and for solid I is 4*5. 

 In this way the following table has been prepared chiefly 

 from Thomsen's data, those for mercury being his later ones 

 (Abst. Journ. Chem. Soc. 1888); but the data for the bromide 

 and iodide of Li and Mg are due to Beketoff (Abst. Journ. 

 Chem. Soc. 1889, and Wied. Ann., Beibl. 16). The fourth 

 column of the table contains the differences of the heats of 

 formation of the chlorides and bromides, the fifth the differ- 

 ences for the chlorides and iodides, and the sixth the ratio 

 of the two sets of differences. 



Table V. 



Heat of Formation in kilocalories of gramme-equivalents of 

 the Haloid Compounds of the Metals, both reagents and 

 products being gaseous. 



01. Br. I. Ol-Br. 01 -I. ^}~^\ . 



(01— Br) 



Li 890 77-7 609 11-3 281 2-5 



Na 87'9 78-8 6313 91 24-3 2-7 



K 95-6 87-9 74-2 7*7 2L4 28 



Cu(ous) ... 82-3 76-3 66'5 6-0 15'8 2-6 



Ag 694 661 54-8 33 14-6 4'4 



pig 82-3 702 52-7 121 29-6 2b 



^Oa 911 79 9 638 11-2 27'3 2'4 



^Sr 96-7 88-5 ... 8-2 



£Ba 996 91-4 ... 8-2 



AZn 56-4 46-8 331 9-6 23-3 2-4 



^Cd 50-4 43-7 334 6-7 17'0 2-5 



£Hg(ic) ... 25-3 22-8 15-4 2-5 99 40 



iPb 46'2 40-2 301 6-0 161 2-7 



iAl 61-6 54-3 38-2 7'3 23'4 32 



£As 32-8 26-8 15-4 60 17'4 2-9 



^Sb 38-5 



iBi 36'4 



Additional data for H and for Ammonium Compounds, the 

 latter being formed from N and H and halogen all 

 gaseous : — 



H 22-0 12-2 -*6 98 22-6 23 



N,H. 75-8 690 53'8 68 220 33 



C2 



