TABLE 363.— EVAPORATION OF METALS* 



363 



For the range of pressures for which the corresponding values of r°C are given in the 

 table (Part 2), the pressure as a function of T(=t + 273) may be represented to a satis- 

 factory degree of approximation by the relation 



log p = A -BIT. (1) 



Part 1 gives values of A and B used in calculating the values of t°C in Part 2, where 

 p is expressed in microns of mercury. The symbols (s) and (/) refer to the solid and 

 liquid states, respectively. 



The rate of evaporation is given by the relation 



log W = 5.7660 + 0.5 log M + log p — 0.5 log T 

 = c + log p — 0.5 log T, 



(2) 

 (3) 



where IV is expressed in g cm" 2 sec" 1 , and p in microns. 



Explanation of data in Part 2.— The first row for each metal, which is designated t, 

 gives the temperatures in °C corresponding to the pressures in microns at the head of 

 each column. These were calculated by means of equation 1. The second row, designated 

 11', gives the rates of evaporation (in a good vacuum) in grams per square centimeter 

 per second (g cm" 2 sec" 1 ), at the values of t immediately above in the same column. These 

 were calculated by means of equation 3. 



In addition to the values of t given in the first row, which are to be regarded as, in 

 the writer's opinion, the more reliable, there are also given, in the case of a number of 

 the metals, a series of other values of t, which have been observed by some investigators ; 

 The fact that for the same value of the vapor pressure in microns two or more values of 

 t are quoted by different authorities indicates the degree of uncertainty that exists for 

 some of the data given in the tables. For metals for which the data are very questionable, 

 it has not been considered worth while even to calculate values of IV. 



The column headed t m gives the melting point in degrees C, and pm gives the vapor 

 pressure in microns at the melting point. For values of t below f m , the metal is obviously 

 in the solid state, and for values of t above tm, the metal is in the liquid state. 



* Prepared by Saul Dushman, General Electric Research Laboratory, Schenectady, N. Y. 

 Part 1. — Constants in relations for evaporation of metals 



Metal A 10-'XB 



Li 10.50(1) 7.480 



Xa 10.71(1) 5.480 



K 10.36(1) 4.503 



Rb 10.42(1) 4.132 



[10.53(1) 4.291] 



Cs 9.86(1) 3.774 



[10.02(1) 3.883] 



Cu 12.81 (s) 18.06 



11.72(1) 16.58 



Ag 12.28(s) 14.85 



11.66(1) 14.09 



Au 11.65(1) 18.52 



Be 12.99(s) 18.22 



11.95(1) 16.59 



Mg 11.82(s) 7.741 



Ca 11.30(s) 9.055 



Sr 11.13(s) 8.324 



Ba 10.88 8.908 



Zn 11.94(s) 6.744 



Cd 11.78(s) 5.798 



B 14.13(s) 21.37 



Al 11.99(1) 15.63 



Sc 11.94 18.57 



Y 12.43 21.97 



La 11.88(1) 18.00 



Ce 13.74(1) 20.10 



Ga 10.79(1) 13.36 



In 10.93(1) 12.15 



Tl 11.15(1) 8.92 



C 14.06(s) 38.57 



f + 4 



.1867 

 .4468 

 .5621 

 .7319 



.8278 



.6678 



.7825 



.9135 

 .2436 



.4590 



.5675 

 .7373 

 .8349 

 .6737 

 .7914 



.2831 

 .4814 

 .5931 

 .7405 

 .8374 



.8392 

 .6877 

 .7959 

 .9212 

 .3056 



Metal A 



Si 13.20(s) 



12.55(1) 

 Ti 11.25(s) 



11.98(1) 

 Zr 12.38(s) 



13.04(1) 



Th 12.52(1) 



Ge 10.94(1) 



Sn 9.97(1) 



Pb 10.69(1) 



V 13.32 



Nb 14.37(s) 



Ta 13.00(s) 



Sb, 11.42 



Bi 11.14(1) 



Cr 12.88(s) 



Mo 11.80(s) 



W 12.24(s) 



U 12.88(1) 



Mn 12.25(s) 



Fe 12.63(s) 



13.41(1) 



Co 12.43 



Ni 13.28(s) 



12.55(1) 



Ru 13.50 



Rh 13.55 



Pd 11.46 



Os 13.59 



Ir 13.06 



Pt 12.633 



SMITHSONIAN PHYSICAL TABLES 



(continued) 



