418 Tables 491 (continued) and 492 



TABLE 491 (continued)- — Resistivities at High and Low Temperatures 

 (Ohms per cm cube unless stated otherwise.) 



Pt. low, Nernst, I.e. high, Pirrani, Ber. Deutsch. Phys. Ges. 12, p. 305, Pb. low, Schimank, Nernst, I.e. high. 

 Northrup, see Zn. Bi. low, means, high, Nonhrup, see Zn. Cd. low, Euchen, Gehlhoff, Verh. Deutsch. Phys. Ges. 14, 

 p. 169, 1912, high, Northrup, see Zn. Sti. low, Dewar, Fleming, high, Northrup, see Zn. Carbon, graphite, Metallurg. 

 Ch. Eng. 13, p. 23, 1915. Silica, Campbell, Nat. Phys. Lab. n, p. 207, 1914. Alundum, Metallurg. Ch. Eng. 12, p. 

 125, 1914. 



* Diamond 1030 C, p >io 7 ; 1380 , 7.5 x '° 5 i v - Wartenberg, 1912. 



TABLE 492. — Volume and Surface Resistivity of Solid Dielectrics 



The resistance between two conductors insulated by a solid dielectric depends both upon the surface resistance and 

 the volume resistance of the insulator. The volume resistivity, p, is the resistance between two opposite faces of a cen- 

 timeter cube. The surface resistivity, <r, is the resistance between two opposite edges of a centimeter square of the 

 surface. The surface resistivity usually varies through a wide range with the humidity. (Curtis, Bui. Bur. Standards, 

 "> 359> '9'5> which see for discussion and data for many additional materials.) 



Material. 



a ; megohms 

 50% humidity. 



<j ; megohms 

 90% humidity. 



Megohms-cms. 



Amber 



Beeswax, yellow 



Celluloid 



Fiber, red 



Glass, plate 



" Kavalier 



Hard rubber, new .... 



Ivory 



Khotinskv cement .... 



Marble, Italian 



Mica, colorless 



Paraffin (parowax) .... 

 Porcelain, unglazed .... 



Quartz, fused 



Rosin 



Sealing wax 



Shellac 



Slate 



Sulphur 



Wood, parafined mahogany . 



6 X 10 8 



6 X 10 8 

 5 X 10 4 



2 X io< 

 5 X io 4 



4 X io 6 



3 X io 9 



5 X io 3 



7 X io 8 

 3 X io 3 



2 X io 7 

 9 X io 9 



6 X io 5 



3 X io 6 

 6 X io 8 

 2 X io 9 



6 X io 7 

 9 X 10 



7 X io 9 

 4X io 6 



2 X io 8 

 6 X io 8 



2 X io 4 



3 X io 3 



6 X 10 



4 X io 3 

 1 X io 8 



1 X io 3 

 3 X io 8 



2 X io 2 

 4 X icV' 



7 X io 9 

 7 X 10 s 



2 X io 3 



3 X io 8 

 6 X io 8 



3 X io 6 

 3Xio 



4 X io 9 



5 X io 5 



1 X 

 5 X 



2 X 

 2 X 



2 X 



1 X 



2 X 



3X 

 5 X 

 2 X 

 8 X 

 6X 

 5X 

 2 X 

 2 X 

 9X 

 7 X 

 1 X 

 1 X 

 7 X 



S X 10 

 2 X io ! 

 2 X 10' 

 5 X io ; 

 2 X 10 

 8 X io ! 



1 X 10 



2 X io : 

 2 X 10' 



1 X 10 



2 X 

 1 X 10 



3 X io 1 

 5 X 10 

 5 X 10 

 8 X io' 

 1 X 10 

 1 X io ; 

 1 X 



4 X 10' 



Smithsonian Tables. 



