276 



Tables 255 and 256 



TABLE 255. — Thermal Conductivity of Various Insulators 



kt is the heat in gram-calories flowing in I sec. through a plate i cm thick per sq. cm for i°C 

 drop in temperature. 



Substance. 



Asbestos fiber 



85% magnesia asbestos . . 

 Cotton 



Eiderdown 



Lampblack, Cabot number 5 

 Quartz, mesh 200 .... 

 Poplox, popped Na 2 Si0 3 . 

 Wool fibers 



00017 



OOOI 1 1 



000071 



00015 



000046 



000074 



000107 



00024 



000091 



000160 



000 1 1 8 



0000S5 



000054 



Asbestos paper 

 Blotting paper . 

 Portland cement 

 Cork, t,o°C . 

 Chalk .... 

 Ebonite, t, 49 . 

 Glass, mean 



Ice 



Leather, cow-hide 

 " chamois 



Linen .... 

 Silk .... 

 Caen stone, limestone 

 Free stone, sandstone 



.00043 



.00015 



.00071 



.0007? 



.0020 



.00037 



.002 



.0057 



.00042 



.00015 



.00021 



.000095 



.0043 



.0021 



Authority. 



Lees-Chorl- 

 ton. 



Forbes. 

 H, L, D, 



see p. 205. 

 Various. 

 Neumann. 



Lees-Chorl- 



ton. 



i H,L, D. 



Left-hand half of table from Randolph, Tr. Am. F:iectroch. Soc. XXI ., p. 550, 1912 ; k t (Randolph's values) 

 is mean conductivity between given temperature and about io°C. Note effect of compression (density). The 

 following are from Barratt Proc. Phys. Soc, London, 27, 81, 1914. 



The following values are from unpublished data furnished bv C. E. Skinner of the Westinghouse Co., Pitts- 

 burgh, Penn. They give the mean conductivity in gram-calories per sec. per cm cube per °C when the mean 



temperature of the cube is that stated in the table. Resistance in thermal ohms (watts/inch 2 /inch/°C ) = — - 



conductivity. 



Substance. 



Air-cell asbestos 



Cork, ground 



Diatomit 



Infusorial earth, natural . . . 



" " h'd pressed blocks 



Magnesium carbonate .... 



Vitribestos 



Grams, 

 per cm 3 



168 

 326 

 506 

 321 

 450 

 362 



Conductivity. 



100° C 



0.00034 

 .00015 

 .00028 

 .00034 

 .00030 

 .00023 

 .00049 



200° C 



. 00043 



.00019 

 .00032 

 .00032 

 .00029 

 .00025 

 .00066 



300° C 



0.00050 



.00037 



.00040 



.00033 



.00025 

 .00079 



4 oo°C 



0.00042 

 .00036 

 .00090 



500 c 



0.00046 



Safe 

 temp. 



320 

 180 

 600 



400 

 300 

 600 



TABLE 256. — Thermal Conductivity of Water and Salt Solutions 



Smithsonian Tables. 



