118 



SCIENCE, 



[N. S. Vol. VIII. No. 187. 



Specific Heats of Cobalt astd Nickel. 

 Piu-e fused. 



The value arrived at for cobalt is much 

 lower than that (.1067) derived from Eeg- 

 nault's experiments, while that for nickel is 

 practically identical with Regnault's, which 

 is .1092. This is certainly too high. 



Further experiments will be made, be- 

 cause a single well-established case of this 

 kind is sufiScient to decide the question. 

 Already, however, I feel certain that 

 Kopp's conclusion is right, and that the 

 law of DuloDg and Petit, even for the 

 metals, is an approximation only and can 

 not be properly expressed in the words of 

 the discoverers. For, although the exact 

 values of the atomic weights of these two 

 elements, cobalt and nickel, are not known, 

 it is certain that they are not so far apart 

 as would be implied by these values for the 

 specific heats. 



Two other examples of somewhat similar 

 kind are shown by gold and platinum, cop- 

 per and iron. 



For the gold I naturally applied to my 

 colleague, Professor Roberts- Austen. The 

 platinum I prepared from ordinary foil, by 

 resolution and re-precipitation as ammonio- 

 chloride and subsequent heating. Both 

 metals were fused into buttons before use. 

 The atomic heats come closer together than 

 those of Co and 'Ni. 



Copper and iron differ considerably in 

 melting point, but both at the temperature 

 of 100° are far removed Irom even incipient 

 fusion. The copper was prepared from pure 

 sulphate by electrolysis, the iron by reduc- 

 tion of pure oxide in pure hydrogen. Not- 

 withstanding all our care, it was disappoint- 

 ing to iind it contained .01 per cent, of 



carbon, the source of which I am at a los& 

 to explain. This iron is purer than any ex- 

 amined by Regnault or Kopp. 



Specific Heats of Gold and Platinum. 

 Pure fused. 



.03052 

 .03017 

 .03035 



Platinum, S. G. t: 



.03147 

 .03150 

 .03144 



Specific Heats of Copper and Ieon. 



Fused. 



Copper (pure) S. G.5^8.522. Iron, S. G. ^r^^ 7.745, coutaina 



15° 

 0.01 per cent, carbon 



.11022 



.11037 



Arith. mean 11030 



Atomic heat .. .. 6.13 



.09248 



.09241 



.09205 



.09234 



Arith. mean I 



Atomic heat .. . . 5.^ 



The differences observed between cobalt 

 and nickel, and between gold and platinum,^ 

 are manifestly not due to allotropes or to 

 differences of melting point, which in these 

 cases can have no effect on the result. So 

 large a difference must be due to peculiari- 

 ties inherent in the atoms themselves ; and 

 differences of atomic heat are to a certain 

 extent comparable with the differences ob- 

 served in other physical properties, which, 

 like specific volume, specific refraction, 

 etc. , are approximately additive. 



If we try to think what is going on in the 

 interior of a mass of solid when it is heated, 

 the work done is expended not only in set- 

 ting the atoms into that kind of vibration 

 which corresponds to rise of temperature,, 

 that is, it makes them hotter, but partly in 

 separating the molecules or physical units 

 from one another (:= expansion) and pai'tly 

 in doing intei-nal work of some kind, the 

 nature of which is not known. A differ- 

 ence between metals and non-metals has 

 been brought out by the researches of Hey- 

 cock and Neville, who find that metals dis- 

 solved in metals are generally monotomic j 

 whereas it is generally admitted that iodine, 

 sulphur and phosphorus in solution are poly- 

 atomic. It is moreover remarkable that, 



