476 Scientific Intelligence. 



lars from the ordinary forms of this substance. Tims its odor is 

 exactly that of chlorine, its permanence is greater at high temper- 

 atures, as is shown by the mode of its production, it does not 

 act upon a mercury surface, and organic bodies such as caout- 

 chouc, are far less readily attacked by it. Moreover, the author 

 observed that while pure potassium chlorate yields perfectly pure 

 oxygen, the slightest trace ot any indifferent substance such as 

 potassium chloride or even silica, causes the production of ozone. 

 Hence the purest chlorate of commerce yields an oxygen contain- 

 ing ozone. A mixture of equal parts pure chlorate and manga- 

 nese dioxide gave on heating a gas containing 0*3 per cent of 

 ozone; and when the dioxide was increased to 25 times the mass 

 of the chlorate, the ozone present amounted to l - 55 per cent. 

 Investigation showed that this action was not produced by all 

 oxides, and that oxides maybe divided into three classes: (1) 

 those which are indifferent, such as the oxides of iron, copper 

 and zinc ; (2) those which heated by themselves in an atmosphere 

 free from oxygen to the temperature of decomposition, yield 

 ozone, this ozone increasing in amount by heating them in a cur- 

 rent of oxygen but is absent when the oxide is heated with chlo- 

 rate, such as the oxides of silver and mercury and the peroxides 

 of lead and probably barium ; and (3) those which give ozone 

 only when heated to the temperature of decomposition in presence 

 of oxygen and which evolve ozone also when heated with potas- 

 sium chlorate to a temperature considerably below the decompo- 

 sition-point of this salt, such as cobalt oxide, manganese dioxide 

 and nickel sesquioxide. The author notices the curious fact that 

 the admixture of a small quantity of sodium carbonate with the 

 chlorate and manganese dioxide entirely prevents the production 

 of ozone, the sodium being left in the residue as peroxide. — Ber. 

 Berl Ghem. Ges., xxvi, 1790, July, 1893. g. f. b. 



4. On the Preparation and Properties of pure Nitrogen. — 

 The preparation of pure nitrogen by various processes has been 

 examined by Threlfall. He finds that the method depending 

 on the absorption of the oxygen from air by passing it over 

 heated copper is a very objectionable one, since besides the me- 

 chanical difficulties of connecting the various tubes to one another 

 at these high temperatures and of preventing their permeability' 

 to gases, the chemical difficulties are also serious. The prepara- 

 tion of the pure hydrogen or carbon monoxide for the reduction 

 of the copper oxide is one of the greatest. Removal of the oxy- 

 gen by passing air over heated phosphorus is also unsatisfactory. 

 And the nitrogen obtained by heating ammonium dichromate, 

 even when this salt was purified with the greatest care, contained 

 nitrous compounds. The method finally adopted was the absorp- 

 tion of the oxygen from air by means of metallic copper and 

 ammonia, the last traces of oxygen being removed by chromous 

 chloride, prepared by Resoura's method and evaporated in an 

 atmosphere of carbon dioxide under diminished pressure. All 

 india-rubber was excluded from the apparatus, the joints were 



