186 



TABLE 180.— THERMOCHEMISTRY. CHEMICAL ENERGY DATA (concluded) 



Part 2. — Heats of formation of ions in kilogram-calories 



+ and — signs indicate signs of ions and the number of these signs the valency. For the ioni- 

 zation of each gram-molecule of an element divide the numbers in the table by the valency, e. g., 

 9.00 g Al = 9.00 g Al + + 40.3 kg cal. When a solution is of such dilution that further dilu- 

 tion does not increase its conductivity, then the heats of formation of substances in such solutions 

 may be found as follows: FeCliAq= + 22.2 + 2 X 39.1 = 100.4 kg cal. CuS0 4 Aq = — 15.8 

 -f- 214.0 = 198.2 kg cal. 



TABLE 181.— IGNITION TEMPERATURES OF GASEOUS MIXTURES 



Ignition temperature taken as temperature necessary for hot body immersed in gas to 

 cause ignition ; slow combination may take place at lower temperatures. Gases were 

 mixed with air. Practically same temperatures as with O2. 



Benzene and air 1062° C Ether and air 1033° C 



Coal gas and air 878 Ethylene and air 1000 



CO and air 931 Hydrogen and air 747 



TABLE 182.— HEATS OF NEUTRALIZATION IN KILOGRAM-CALORIES 



The heat generated by the neutralization of an acid by a base is equal, for each gram-molecule 

 of water formed, to 13.7 kg cal plus the heat produced by the amount of un-ionized salt formed, 

 plus the sum of the heats produced in the completion of the ionizations of the acid and the base. 



Base HC1 aq HN0 3 aq H = S0 4 aq HCN aq CH3COOH aq H 2 C0 3 aq 



KOH-aq 13.7 



NaOH-aq 13.7 



NH 4 OH-aq 12.4 



iCa(OH) 2 -aq 14.0 



iZn(OH) 2 -aq 9.9 



iCu(OH) 2 -aq 7.5 



TABLE 183.— HEATS OF DILUTION OF H 2 S0 4 



In kilogram-calories by the dilution of 1 gram-molecule of sulfuric acid by m gram molecules 

 of water. 



SMITHSONIAN PHYSICAL TABLES 



