Physical and Chemical Behavior of Solids. 245 



this line have shown by direct metallographic evidence that no 

 appreciable amount of a true alloy is produced by compression 

 at temperatures below the melting point of the alloy. 



Thus Rosenhain and Tucker* write : " Powdered lead and 

 tin, mixed in the correct proportion of the eutectic composi- 

 tion, were compressed . . . pressures up to 35 tons per square 

 inch (about 5000 atm.) being put on the metal. The small 

 buttons of solid metal produced in this way were subsequently 

 cut and polished for microscopic examination. ... It will be 

 seen at once [from the microphotographs, reproduced in the 

 original] that the compound mass of metal can scarcely be 

 regarded as a true alloy at all ; the particles of lead and tin are 

 merely juxtaposed and held together by surface cohesion. It 

 is intended to observe these specimens from time to time, both 

 when kept at the ordinary temperature and when maintained 

 at temperatures just below the melting point of the eutectic, 

 with a view to detecting the process of diffusion which will 

 probably occur, but so far the time has been too short to allow 

 of definite results being observed." 



The same conclusion was reached by Speziaf, from analogous 

 observations with copper and silver. The most thorough and 

 detailed work along this line is that of Masing4 who in his 

 introduction writes : 



u The work of Spring was performed at a time when the 

 structure of alloys had been little investigated. Now Rose's 

 alloy is a conglomerate of crystals of the pure components, and 

 it is only in such a case that one can expect that the crystalline 

 conglomerates obtained by fusion and by pressure can be iden- 

 tical (except for certain secondary structural differences). This 

 is highly improbable, however, when compounds or mix- 

 crystals are formed on fusing together the components. We 

 know that high pressure has in general little effect on the 

 reaction velocity, and it is not to be expected that its influence 

 on the rate of diffusion is very marked. Hence, it is impossi- 

 ble that notable amounts of compound or of mix-crystals should 

 be formed in the course of a few hours by pressing together a 

 mixture of powdered metals. There is therefore every reason 

 to believe that in those cases in which mix-crystals or com- 

 pounds appear the alloys obtained by fusion will differ con- 

 siderably from the masses which result from compression. "§ 



From this standpoint Masing investigated binary systems 

 belonging to the three following types, with results which are 

 summarized below : 



* Phil. Trans. Roy. Soc. London, A, ccix, 120-1, 1909. 

 f Atti Accad. Sei. Torino, xlv, 1. 1910. 

 JZs anorg. Chem., lxii, 265-310, 1909. 

 §Loc. cit., p. 266. 



