D. CHEMISTRY AND METALLURGY. 217 



the calorimeter, and its temperature had been raised one 

 third of a degree. By passing the oxygen current alone 

 through the apparatus under the same conditions for an 

 equal time, both before and after the experiment, the thermal 

 data were rendered complete. The arsenic solution was 

 treated with a graduated solution of potassium permanga- 

 nate in excess, and then titered back with a standard solution 

 of oxalic acid. In this way the amount of arsenous acid ox- 

 idized, and consequently the amount of ozone absorbed, Avas 

 determined. In two experiments, the oxygen absorbed was 

 30.3 and 51.9 milligrammes, corresponding to 90.9 and 155.7 

 milligrammes of ozone ; the heat set free being 118.2 and 

 223.7 calories respectively. Whence for one molecule, 48 

 grammes, the heat is equal to +68.8 calories. Subtracting 

 from this the heat produced in the oxidation of a molecule 

 of arsenous acid, determined by Favre and by Thomsen to be 

 -f 39.2 calories, we have -f 29.6 calories for the heat set free 

 by the conversion of one molecule of ozone into oxygen, and 

 of course 29.6 calories in the reverse process. This value 

 is one half greater than that given in the formation of the 

 same volume of nitrogen monoxide or of chlorine monoxide, 

 in both of which the value is 18. It is even two thirds of 

 that given in the formation of nitrogen dioxide, 43.3. In the 

 three' cases of direct synthesis of compound gases by the 

 electric spark, ozone, nitrogen tetroxide, and acetylene, the 

 heat values are all negative, being 29.6, 24.3, and 64 

 respectively; an obvious proof of the function of electricity 

 in chemical synthesis. Ozone is therefore a body in whose 

 formation heat is absorbed, and whose activity is due conse- 

 quently to this heat, which w^hen it combines is again set 

 free. It is a magazine of energy stored up under the influ- 

 ence of electricity. This foot is the more remarkable when it 

 is remembered that ozone is condensed oxygen, and that con- 

 densation sets free heat. 6 -S, LXXXIL, June^ 1876, 1281. 



MEDICO-LEGAL EXAMIXATIOX FOR ARSENIC. 



In a series of researches undertaken for the purpose of de- 

 termining certain physiological questions (and in the course 

 of which it was discovered that arsenic showed a special ten- 

 dency to localize itself in the nervous tissues, especially in 

 the brain and spinal cord), Gautier was led to suspect the 



K 



