484 REPOKT— 1888. 



in papers published by these authors in 1880.' But Humpidge worked 

 without knowledge of this, and the general result thus obtained inde- 

 pendently is conclusively established. 



Nilson and Pettersson recently made ^ a series of determinations, in a 

 new improved apparatus, of the vapour-densities of the chloride of beryl- 

 lium at temperatures from 490° to 1500°, and found that above 680° 

 the vapour-density remains constantly of the value corresponding to the 

 formula BeCl2 ; the vapour-densities for the chloride and the bromide 

 mentioned before as determined by Humpidge led to the same result 

 as to the atomic weight of beryllium, giving the formuljB BeCl2 and 

 BeBrj. 



Specific Seats at Different Temperatibres. 



The variation of specific heat with temperatui'e was investigated by 

 Bede ^ for certain metals ; he found that the specific heat between 0° and 

 t° was sufiBciently accurately expressed by the formula c=^h + at, in which 

 k and a are constants depending on the nature of the metal. The results 

 are given in the following table : — 



Copper Z; = ■0910 a = -000023 



Iron = -105.3 = -000071 



Lead = -0286 = -000019 



Tin = -OoOO = OOOOli 



Zinc = -0805 = -000044 



The smallness of the fractions a shows how slow the increase of specific 

 heat is with rise of temperature. 



This, as Pionchon's investigations show, can only hold for moderate 

 ranges of temperature. 



Pionchon. Specific Heats at High Temperature. 



Pionchon'' finds expressions for the total heat-capacities and the speci- 

 fic heats at tempei'atures from 0' to 1100° and over for the metals silver, 

 tin, iron, nickel, cobalt, giving formulae for these physical quantities for 

 various high temperatures and wide intervals of temperature. 



Thus, for silver, from 0° to 907° :— 



Q = -0578^ -I- 0544^2 -I- -OsCi^ 

 whence 



also for 907° to 1100° 



whence 



c=-0578 + -0j88i + -07l8i2 

 Q=-0748< + 17-20; 

 c=-0748: 



making for silver a nearly constant specific heat between 900° and 1100°. 



Similarly for iron he finds the specific heat constant at '218 between 

 720° and 1000° ; and again at -1987 between 1050° and 1200°. 



For silver at 0° specific heat is '05758, and at 900° it is -08008. 



Iron has atO°, 600°, 660°, 700° specificheats -11012, -19956, -2442, -32433. 

 These examples illustrate the great increase in specific heat as the tempera- 

 ture rises through hundreds of degrees in the case of these metals, and 

 the increase is very striking in the case of iron, seeing that at the highest 



» Ber. 13, 1451, 1784. "- Ann. CJdm. 6, 9, 1886, p. 554. 



' 3Ihn. couronnh jmr VAcad. Boy. de Belg. 27, 1855, p. 1. 

 * C. B. 103, 1886, p. 1122 ; Aim. Chim. 6, 1887, p. 1133. 



