408 Pwfessor W. Chandler Boherts- Austen [March 26, 



the constituent metals is not sufficiently intimate to enable a uniform 

 alloy to be obtained by a single compression. The alloy we have 

 thus produced fuses, you will observe, in boiling water, actually at 

 9»° Cent., although the melting point of the most fusible of its con- 

 stituents, the tin, is 228^ Cent. I agree with Professor Spring in 

 thinking that the formation of alloys by pressure affords the most 

 complete proof which can be given of the accuracy of the views he 

 has adduced. The formation of fusible-metal by compression leads 

 me to deal with an objection which may, no doubt, have suggested 

 itself to many of us. It may be urged that by compressing these 

 metallic powders heat is evolved, and that this heat may be 

 sufficient to produce incipient fusion in the metallic powders, or, 

 at all events, may exert a material influence on the result obtained. 

 This objection has been experimentally anticipated by Professor 

 Sirring. First, the compression is effected with extreme slowness, 

 and therefore there can be no question as to the sudden evolution 

 of heat, as would be the case if the powders were compressed 

 by impact instead of by a slow squeeze ; and to sum the matter 

 up briefly. Spring calculates, taking an extreme case, that, if it 

 be granted that all the work done in compressing the powders 

 were actually translated into heat, it would only serve to heat a 

 cylinder of iron 10 mm. in height and 8 mm. in diameter (the dimen- 

 sions of cylinder produced in his apparatus), 40 * 64° Cent. In order 

 that direct experimental evidence might not be wanting. Spring took 

 the organic body phorone, a hard crystalline substance which melts at 

 28° Cent., and compressed it exactly as in the case of the metallic 

 powders.* He took the precaution to place a shot of lead on the top 

 of the powder before submitting it to compression : only imperfect 

 union of the particles of phorone resulted. The conclusion of the 

 experiment proved that the shot remained where it had been placed 

 at the top of the column, and therefore the 28° necessary to melt the 

 substance had not been evolved, for if it had the shot must have fallen 

 through the fluid mass. I think, then, it is absolutely safe to conclude 

 that, in the compression of bismuth, for instance, there can be no 

 question of the evolution of the heat necessary for the fusion of the 

 metal. There is, however, other evidence to which I may incidentally 

 appeal. M. Spring has shown that by compressing powders together, 

 chemical combination may be induced, and he has in this way produced 

 arsenide and sulphide of zinc, sulphide of load, and of bismuth, and 

 arsenide of lead. These are not merely intimate mechanical mixtures. 

 Take, for instance, the sulphide of magnesium produced by com- 

 pression ; it is soluble in hot water ; treatment with dilute hydro- 

 chloric acid evolves sulphuretted hydrogen, which is not the case 

 with mere mixtures of magnesium and sul2)hur. Further, Sju-ing has 

 shown that by pressure a body may be made to pass from one allo- 

 tropic state to another. Plastic sulphur is, under a pressure of 6000 



Bull. Soc. Chim.' Paris, 1884, t. xli. p. 488. 



