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CHAPTEK XII. 



HEAT OF FORMATION OF THE SALTS PRODUCED BY THE OXYGEN- 

 ATED COMPOUNDS OF CHLORINE AND OTHER HALOGEN 



ELEMENTS. 



1. GENERAL NOTIONS. 



CHLORINE and the halogen elements form with oxygen a series 

 of compounds analogous with the oxygenated compounds of 

 nitrogen, and which comprise even an additional member, viz. 

 perchloric acid. Most of these compounds are energetic oxidis- 

 ing agents, either in the wet or in the dry way, and some of 

 their salts (especially the chlorates) play an important part in 

 the manufacture of explosive substances. This circumstance, 

 therefore, makes it desirable to measure their heat of formation. 



2. THERMAL FORMATION OF CHLORIC ACID AND CHLORATES. 



1. The thermal formation of chloric acid and chlorates has 

 been already examined by Favre, Frankland, and Thomsen, but 

 with very different results. 



Favre 1 tried to measure the heat liberated in the action of 

 gaseous chlorine on concentrated potash ; according to him, the 

 union of chlorine and oxygen to form chloric acid 



i[H 2 + C1 2 + B + water = H 2 0, C1 2 5 (diluted)], 



would absorb 65 '2 Cal. The decomposition of solid potassium 

 chlorate into oxygen and potassium chloride 



KC10 3 = KC1 + 3 , would then liberate + 64-9. 



But the learned author's calculation is complicated, and is based 

 on uncertain data, such as the supposed insolubility of the salts 

 formed in the alkaline solution. 



Frankland, 2 having oxidised various organic substances, some 



1 "Journal de Pharmacie et de Chimie," 3 6 srie, torn. xxiv. p. 316. 1853. 



2 " Philos. Magazine," vol. xxxii. p. 184. 1866. 



