^Intelligence and Miscellaneous Articles. 527 



the anticipation that metals would diffuse into each other at tem- 

 peratures far below their melting-points. Reference is then made 

 to the important work by Spring in 1886 on the lead-tin alloys, 

 which retained a certain amount of molecular activity after they 

 had become solid ; and special importance is attached to the proof 

 afforded by Spring, that alloys may be formed either by the strong 

 compression of the finely divided constituent metals at the ordinary 

 temperature (1882) or (1894) by the union of solid masses of 

 metal compressed together at temperatures which varied from 

 180° in the case of lead and tin, to 400° in the case of copper and 

 zinc ; tin melling at 227° and zinc at 415°, 



The evidence as to the volatilization of solid metals is then 

 traced, and allusion is made to the expression of Robert Boyle's 

 belief, that even such solid bodies as glass and gold might respec- 

 tively "have their little atmospheres, and might in time lose their 

 weight." 



Merget's experiment on the evaporation of frozen mercury is 

 quoted in relation to Gay-Lussac's w T ell-known discovery that the 

 vapours emitted by ice and water both at 0° C. are of exactly equal 

 tension. 



Demar§ay's experiments on the volatilization of metals in vacuo 

 at comparatively low temperatures is connected with the evidence 

 afforded by Spring (1894), that the interpenetration of two metals 

 at a temperature below the melting-point of the more fusible of 

 the two is preceded by volatilization. 



The author then points out that, interesting as the results of 

 the earlier experiments are, as affording evidence of molecular 

 interpenetration, they do not, for the purpose of measuring cliff u- 

 sivity, come within the prevailing conditions in the ordinary 

 diffusion of liquids, in which the diffusing substance is usually in 

 the presence of a large excess of the solvent, a condition which has 

 been fully maintained in the experiments on the diffusion of liquid 

 metals described in the first part of the paper. Van't Hoff has 

 made it highly probable that the osmotic pressure of substances 

 existing in a solid solution is analogous to that in liquid solutions, 

 and obeys the same laws : and it is probable that the behaviour 

 of a solid mixture, like that of a liquid mixture, would be greatly 

 simplified if the solid solution were very dilute. 



The author proceeds to describe his own experiments on the 

 diffusion of solid metals. They are of the same nature as in the 

 case of fluid metals, except that the gold, which is the metal 

 chosen for examination, was placed at the bottom of a solid cylinder 

 of lead instead of a fluid one. 



In the first series of experiments, cylinders of lead, 70 millims. 

 long, with either gold, or a rich alloy of gold and lead at their base, 

 were maintained at a temperature of 251° (which is 75° below the 

 melting-point of lead) for thirty-one days. At the end of this 

 period the solid lead was cut into sections, and the amount of gold 

 which had diffused into each of them was determined in the usual 



