TUANSACTIONS OF SECTION B. 493 



composition, the double sodium and potassium citrate appears more like a 

 molecular grouping of the constituent salts, and both constituents are capable 

 of causing disruption, whereas in Rochelle salt and the magnesio-sodic citrate, 

 there is evidence of a closer binding of the component salts. In the case of 

 Rochelle salt only one constituent produces disruption, and in the case of the 

 magnesio-sodic citrate, neither constituent has any action. It is to be hoped that 

 experiments carried out on these solutions may assist in the examination of the 

 condition of such salts when in a state of solution. 



6. On, the Decomposition hy Heat of Chlorate of Potassium. By Albert 

 RiLLiET and Professor J. M. Crafts. 



The cause and circumstances which favour this decomposition have been the 

 subject of much study, and the elder Mitscherlich and other great authorities have 

 offered solutions of the question, but none has met with general acceptation. 

 The authors desire to present a few new facts without dwellmg further upon any 

 theory than is necessary to bring out certain analogies, which have guided their ex- 

 periments, and which they hoped might lead to a partial explanation of some 

 points connected with the phenomenon. 



They have enlarged the knowledge of the number of bodies favouring the dis- 

 engagement of oxygen, and the discovery that pure metallic silver, reduced by 

 hydrogen from the chloride at a high temperature, has this action, appears to 

 destroy the usual theories regarding the function of the metallic oxides, which 

 produce the same effect. 



There is no necessity for recognising here any difference between the affinity 

 ■which comes into play during an act of solution, and that which governs any 

 chemical combination, and they supposed that the so-called catalytic bodies might 

 have the property in common of absorbing oxygen. Black oxide of manganese 

 was exposed to oxygen at exactly the conditions of the experiment in which it had 

 promoted the decomposition of chlorate of potash, but no action could be discovered 

 which w^ould explain the possibility that it might have a strong attraction for an 

 oxygenised body presented to it. 



A curious case was noticed, in which chemical affinity might be supposed to 

 determine the reaction. Gas-retort carbon can be completely burnt, chiefly to 

 carbonic acid, by contact at about 340 degrees with pulverised chlorate of potash. 

 There is no fusion ; every trace of the carbon gradually disappears, and the 

 greyish powder becomes white. The operation lasts one or two days. An 

 admixture of more than 10 per cent, of carbon provokes a violent reaction, with 

 disengagement of heat. 



In the same way that chemical formulas are used to express certain charac- 

 teristic qualities of bodies, symbolized under a conventional image of their con- 

 stitution, it is allowable to present possibilities of molecular action by a picture, 

 which bears little or no relation to the probable physical conformation of matter. 



Suppose all the atoms of a compound to be equidistant, and the distances to be 

 equally increased by an accession of heat, the sphere of chemical attraction might, 

 after passing a certain point, be overcome, and the only limit to a decomposition 

 ■with explosive rapidity would be the absorption of heat during the process. If 

 the condition of the molecule is more truly to be symbolised by atoms at irregular 

 distances irregularly affected by heat, which would cause from time to time a 

 single atom to overlap the boundary, a slow decomposition by heat is xuiderstand- 

 able. One can also imaghie heat from different sources, or conveyed through 

 different media, although producing this same mean movement of the particles, 

 still affecting them differently, in one case causing a large increase of movement in 

 a small number of atoms, in another producing the equivalent temperature by a 

 smaller movement imparted to a larger number of atoms. This last conception 

 may perhaps explain the intervention of certain bodies in the decomposition, and 

 it may be that their contact imparts heat-impulses of different qualities from those 

 of the substances, like silica and chloride of silver, which have no decomposing 



