640 REPORT— 1903. 



Lithium chloride prepared from the carbonate, and then fused and ground up 

 into a fine powder, exhibited phosphorescence ; when, however, the trace of 

 moisture present became excessive it ceased to phosphoresce. 



Colour Change. — Sodium chloride is changed in a few hours to an orange or 

 buff colour; the freshly ignited substance turns somewhat pinker in tint. Lithium 

 chloride is not changed under the same circumstances. The absence of change in 

 the lithium chloride and the change of colour of the sodium chloride, and also 

 the order of the change in sodium chloride, are all colour facts of the same 

 character as those which the author has grouped under the term ' metachromatism,' 

 where inorganic bodies are changed in colour in the order of the metachromatic 

 scale under the influence of sensible heat, and where the tendency to this change 

 is least evident in the lightest members of a comparable group. ' Bicarbonate of 

 soda is changed to a light violet tint in twenty-four hours. This has direct 

 bearing on the now well-known change of soda glass which was first observed by 

 the Curies, but which the French observers usually attribute to the presence of a 

 trace of manganese. 



Emissioti of Heat. — -An experiment has been devised in which the usual con- 

 ditions of observation are reversed. A radium bromide tube is inclosed in a 

 cylinder of filter paper which has been painted with one of Meusel's sensitive 

 colour-changing salts. It was argued that in a medium of gradually rising 

 temperatiu'e the heat from the radium compound within plus the heat from 

 without would cause the transition colour change of the paper to be observed 

 earlier in those parts in contact with the radium salt than in those not in contact. 

 The result looked for was not observed. It was in several repetitions of this 

 experiment that the fact was ascertained that a mixture of barium chloride and 

 radium chloride placed in a moist atmosphere loses its remarkable properties of 

 phosphorescing and of exciting phosphorescence in barium platinocyanide.- These 

 facts appear to the author to be opposed to the doctrines of the electronists and to 

 support the hypothesis that one of the sources of the energy of radium com- 

 pounds is obscure heat coming from surrounding bodies. 



' Chem. Kens, xxxiv. p. 7fi ; Phil. Mag., Dec. 1876; Chem. News, Ixvii. pp. 27 

 and 64. 



•^ Compare F. W. Branson, Nature, July 30, p. 302. 



