Chemistry and Physics. 



109 



author, after a short introduction, describes in detail his mode of observa- 

 tion and proceeds then to his results. The following table exhibits these 



results. 



Substance. Equivalent (0=100). Spec. heat. Product. 



Osmium, 1244*2 0-03063 38*10 



Rhodium, 652*1 0*05408 35*26 



Iridium, 1233*2 0*03630 44*76 



Aluminium, 170*98 0*20556 35*15 



The same corrected for impurities, 170*98 0*21810 37*29 



The same nearly pure, 170*98 0*21224 36*64 



Cobalt, 369*00 0*10696 39*47 



Nickel, 369*70 0*11095 41*00 



Sodium, 287*20 0*2934 84*20 



Tellurium (not distilled), 806*50 0*05165 41*65 



The same (distilled), 806*50 0*04737 38*20 



Selenium (fused), 491*00 0*10310 



The same (vitreous), " " 0*07468 36*66 



The same (metallic), " " 0*07446 36*55 



The author remarks that the product of the equivalent by the specific 

 heat in almost all these cases falls within the limits formerly assigned by 

 himself, namely, between 36 and 41. The differences he attributes 

 partly to impurities, partly to inaccuracy in the received equivalents, and 

 partly to the fact that the observed spec, heats do not represent the 

 spec, heats of the atoms alone, but also the spec, heat of expansion and 

 of molecular changes. The spec, heat of an equivalent of sodium is 

 twice as high as that of an equivalent of either of the other substances. 

 The author infers that the true equivalent of sodium is half the received 

 equivalent, viz. 193*6 ; the formula of soda is therefore Na20. The 

 melting point of sodium was found to be 97°*63, that of potassium could 

 not be accurately determined, as the liquid became pasty long before 

 solidifying completely. A specimen of sodium in the author's possession 

 was very brittle and exhibited in its fracture perfectly regular pentagonal 

 dodecahedra. 



Regnault's experiments on selenium confirm those of Hittorf and 

 Mitscherlich as to the two allotropic forms of this body. The spe- 

 cific heats of the two allotropic modifications do not sensibly differ, 

 and the same result had already been obtained for the two allotropic 

 forms of phosphorus. The author suggests that the high spec, heat of 

 fused selenium may be owing to the fact that the vitreous selenium fuses 

 much more easily than the metallic selenium, and that at the tempera- 

 ture of 80° or 90° it already contains a volatile proportion of its latent 

 heat of liquefaction. The spec, heats of the two modifications above 

 given were taken at low temperatures. The author's experiments on the 

 quantity of heat set free during the passage of vitreous to metallic 

 selenium shew that this is sufficient to raise the temperature of the latter 

 by more than 200° C. It will be remembered that Regnault's former 

 experiments shewed that a much less quantity of heat is evolved when 

 sulphur changes its form from the soft to the ordinary condition. — Ann, 

 de Chemie et de Physique, xlvi, 257. w. o. 



