HEATS OF FORMATION. 203 



From dissolved potash, the formation of dissolved saltpetre, N, 

 + 0, + K 2 dilute = 2KN0 3 dilute liberates + 281 only. 



2. Similarly we have for sodium nitrate 



N 2 + 6 +Na 2 = 2NaN0 3 crystallised + 110'6, 



and for the dissolved salt -f 105*9. 

 From anhydrous soda, oxygen and nitrogen 



N 2 4- 5 + Na^O = 2NaN0 3 crystallised + 60-5. 



From dilute soda the formation of dissolved sodium nitrate 

 liberates + 28 '0. 



3. The formation of ammonium nitrate 



N 2 + 3 -f H 4 = NH 4 lsr0 3 crystallised + 87-9. 



The dissolved salt + 817. 



If we suppose that the equivalent of water necessary to the 

 constitution of the ammoniacal salts is formed beforehand, we 

 have liberated for the salt supposed solid + 53 '4 CaL, for the 

 salt supposed dissolved + 47'2 Gal., or + 23'6 Cal. for each 

 equivalent of nitrogen entering into combination, in presence 

 of an excess of water. From ammonia gas and pre-existing 

 water 



N 2 + 5 + 2NH 3 + H 2 = 2NH 4 N0 3 crystallised + 41-2. 

 From dilute ammonia, the dissolved salt + 26'8. 



4. The formation of calcium nitrate 



N 2 + 6 + Ca = Ca(N0 3 ) 2 anhydrous + 101-3. 



For the dissolved salt + 103-3. 

 From anhydrous calcium oxide 



N 2 + 5 + CaO = Ca(N0 3 ) 2 anhydrous + 35-3. 



From dissolved calcium oxide, the salt being likewise dis- 

 solved, + 28-2. 



5. The formation of strontium nitrate 



N 2 + 6 + Sr = Sr(N0 3 ) 2 anhydrous + 109-8. 



For the dissolved salt -f 107'3. 

 From the anhydrous base 



N 2 + 5 +SrO = Sr(N0 3 ) 2 anhydrous + 41-1. 



From dissolved strontium oxide, the salt being likewise dis- 

 solved, + 28-2. 



6. The formation of barium nitrate cannot be calculated 

 from the elements, because the heat of oxidation of barium is 

 unknown. Fortunately, this total heat of formation never 

 intervenes in calculations relative to explosive substances. To 

 calculate the thermal effects which barium nitrate produces in 

 combustions it is sufficient to know its heat of formation 

 starting from anhydrous baryta. 



