494 BEPORT — 1882. 



action. The authors have devised no experiments suited to test this hypothesis in 

 a satisfactory manner, hut the following account of the mode of decomposition of 

 chlorate of potash at a constant temperature is not inconsistent with its adoption. 



The temperature was maintained at a fixed point to within 0"-2 by means of 

 mercury boiling imder a constant pressure. 



Pure chlorate of potash begins to give oif oxygen at 330° to 340°, far below its 

 melting point, and the decomposition goes on for several weeks before it becomes 

 imperceptibly small. After the limit is reached, if the temperature is raised, a 

 fresh decomposition tending towards a new limit takes place. At the tempera- 

 tures chiefly used, only a small percentage of the salt undergoes decomposition. 



The first stage of the decomposition is marked by a lower melting point of the 

 mixture of the residual salts, which usually fuse after several days. 



Pure chlorate of potash must undergo decomposition before fusion, although 

 the change of weight may be slight in a rapidly conducted operation. 



The addition of 10 to 20 per cent, of any of the substances known to favour the 

 decomposition has an effect exactly similar to the raising of the temperature : the 

 limit of decomposition is reached as before after a certain time. 



6. Hydrocarbons of the Formula (C^ Hg)^.^ By Professor 

 W. A. TiLDEN, F.B.S. 



To existing knowledge of isoprene the author adds the facts that its tetrahromide 

 CjHgBr , is a liquid which refuses to solidify at — 18°, and which cannot be dis- 

 tilled without decomposition. The oxidation of isoprene by nitric acid leads to 

 the formation of a considerable quantity of oxalic acid, whilst chromic acid produces 

 formic and acetic acids. The remarkable production of caoutchouc by the action 

 of certain chemical agents upon isoprene led the author to make some experiments 

 with a view to ascertain whether this hydrocarbon coidd be obtained from other 

 sources, and bearing in mind the polymerisation of isoprene into a true turpentine 

 by the action of heat, it seemed not improbable that turpentine oil might be made 

 to yield it. On passing turpentine vapour through a i-ed-hot tube, a complex 

 mixture of hydrocarbons is obtained, from which may be isolated about 2 per 

 cent, of a volatile liquid, having the composition of isoprene and, so far as at 

 present observed, all its properties. The paper includes a theoretical discussion of 

 the formidss assignable to the eight possible compounds having the composition 

 OjHg, and of their relation to the terpenes. 



7. Oil the Activity of Oxygen, and the Mode of Formation of Hydrogen 

 Dioxide." By C. T. Kingzett, F.I.C., F.G.8. 



In this paper the author discusses the mode of formation of ozone and peroxide 

 of hydrogen by processes of slow oxidation. Referring to the views of Tbenard, 

 Lament, and others, and considering, in connection therewith, the results obtained 

 in his investigations of the atmospheric oxidation of phosphorus and the terpenes, 

 he discards the notion that in such processes molecular oxygen is split up into free 

 atoms by any outside act, so to speak. Turpentine and other terpenes absorb the 

 whole molecules of oxygen and ozone, and in Ijoth cases yield an identical organic 

 peroxide, which, by mere contact with water, produces hydrogen dioxide as a 

 secondary product. This secondary change is the result of a simple transference of 

 oxygen, or re-distribution of molecules. 



The author further criticises the views of Traube ('Ber.' 15, 659-675), and 

 adduces evidence against the idea that in the formation of hydrogen dioxide it is 

 water that is decomposed. Finally, he proposes a new representation of the consti- 

 tution of hydrogen dioxide. Believing that oxygen has a variable acidity, and may 

 behave as a triad or tetrad, he represents peroxide of hydrogen as oxygenated 

 water, OOHj rather than hydrogen dioxide, HOOH ; this new representation more 

 adequately explaining the changes that the substance is known to undergo. 



' Published in extenso in the Chemical News, vol. xlvi. p, 120. 

 ^ See Chemical News, vol. xlvi. p. 141. 



