TRANSACTIONS OF SECTION B, 657 



nitric oxide the action begins at 15°, but does not attain its maximum till over 

 130°. 



MnOo behaves similarly, but the change is not so rapid. It attains a maximum 

 at 216°. In neither case is any but a trace of a nitrite foi'med. 



Silver oxide, if containing traces of moisture, yields a mixture of almost 

 equivalent parts of silver nitrite and metallic silver at the ordinary temperature. 

 At higher temperatures, with the dry oxide, nitrate and metallic silver are formed 

 almost entirely. 



Silver permanganate behaves, when treated with nitric oxide, very much as a 

 compound of oxide of silver and a higher oxide of manganese might be supposed 

 to do. It begins to be attached at the ordinary temperature, and at 80° the 

 alteration is very rapid. The residue was found to consist of metallic silver, silver 

 oxide, silver nitrate, and manganese dioxide. Very little, if any, manganese 

 nitrate was formed. 



Potassium permanganate is much more stable than the silver salt. It is not 

 appreciably attacked till a temperature of over 100° is reached, and tbe increase 

 in weight becomes rapid at 190°. 



The residue on moistening was not alkaline, and no manganese could be dis- 

 solved out. The potassium is converted into nitrate, and the manganese into 

 oxide. 



Interesting differences were noted in the behaviour of other silver and potassium 

 salts, notably, the chlorate and iodate. 



Potassium chlorate is attacked by nitric oxide at the ordinary temperature, 

 chlorine being evolved in considerable quantity, and nitric peroxide being formed. 

 The gaseous product was condensed in a tube immersed in a freezing mixture, and 

 the percentage of chlorine in the brown liquid obtained was determined. It was 

 found to be much in defect of that required to form nitrosyl or nitroxyl chloride. 

 So that the reaction does not consist simply in the formation of an oxychloride of 

 nitrogen. On analysis of the residue in the boat, no chloride of potassium was 

 found to be present. Nitrate was formed, and also a irace of perchlorate. This 

 seems to be direct proof that in potassium chlorate the potassium and chlorine are 

 separated. 



With barium chlorate a similar reaction takes places. 



With silver chlorate (prepared according to Stas's method from silver oxide) 

 chlorine was given off, but a considerable amount of silver chloride was also 

 formed, nearly one-third of the silver present being found as chloride. This may 

 be due to a difference in constitution between the chlorates of silver and of 

 potassium, or to a difference in the stability of the salts and the products of 

 reaction. 



That some difference of constitution exists between the silver and potassium 

 salts appears to derive confirmation from the behaviour of their iodates when 

 treated with nitric oxide. 



Potassium iodate heated to 80° in nitric oxide begins to give off iodine, and 

 the reaction becomes rapid at 110°, crystals of iodine condensing on the cool 

 portion of the tube ; no trace of iodide, however, is formed, as is shown by there 

 being no liberation of iodine on acidifying a solution of the residue after adding 

 some potassium iodate. The residue is not alkaline, the potassium being converted 

 into nitrate, recognised by the evolution of ammonia when the residue is warmed 

 with zinc dust and caustic soda. 



Silver iodate, on the other hand, is stable up to a rather higher temperature 

 than the potassium salt, and when heated above this temperature, about 110°, 

 no trace of iodine is given off, but all the silver is converted into iodide, none being 

 dissolved out by water, and the yellow residue being insoluble in dilute nitric 

 acid. 



The perchlorates and periodates which have been examined show themselves 

 more stable than the corresponding chlorates and iodates. 



Of the salts so far examined the chromates have shown themselves the most 

 stable, being analogous in this respect to the sulphates. 



Lead chromate was unaltered at temperatures exceedi:ig 4C0°. 



1895. ^T u 



