Table 40 (continued) 75 



PROBABLE VALUES OF THE GENERAL PHYSICAL CONSTANTS 



The Newtonian constant of gravitation (G). — The H.P. 1 gives a table of 

 seven determinations of G, ranging from 6.60 to 6.70 x io -8 dyne • cm 2 • g" 2 . 

 Henning and Jaeger adopt 6.65. In their list they omit Poynting's value 2 of 

 6.66 ±0.01. The I.C.T. adopt as one of their basic constants G — 6.66 ±0.01. 



Since the publication of these reviews, Heyl 3 has made undoubtedly the 

 most reliable determination of G. His final result is 



G = (6.664 ±0.002) x 10 8 dyne • cm 2 • g" 2 



This result is adopted here. It is based on five separate determinations vary- 

 ing from 6.661 to 6.667. 



Mean density of the earth. — Assuming ^ = 6.371 x io 8 cm as the mean radius 

 of the earth, as given in the H.P., and #45 = 980.616 cm • sec -2 , G •S(earth) 

 = 36.797 X io -8 sec -2 , where S(earth) is the mean density of the earth. From 

 the H.P. result 6 = 6.65 8(earth) =5.53 g • cm -3 . With the new result 

 G = 6.664 



S(earth) =5.522 ±0.002 g • cm" 3 



Relation of the liter to the cubic decimeter (1000 cm 3 ). — The liter is defined 

 as the volume of a kilogram of air-free water at its maximum density. In 

 other words, the maximum density of water is, by definition, one kg • l" 1 . The 

 kilogram is defined as the mass of the prototype kilogram preserved in Paris. 

 This original prototype was intended to be the mass of a cubic decimeter (dm 3 ) 

 of water, at maximum density. Later determinations have shown a slight 

 discrepancy. The various experimental results are discussed by Henning and 

 Jaeger. 4 The mean of the best determinations is 1 liter = 1000.027 cm 3 ; this 

 value has been accepted in all recent tables. Henning and Jaeger give no prob- 

 able error for the result, but one unit in the last place seems a reasonable 

 assumption. Hence 



1 liter =1000.027 ±0.001 cm 3 =1.000027 ±0.000001 dm 3 



The maximum density of water 8 m (H 2 0) is accordingly 



1/1.000027 = 0.999973 ±0.000001 kg ■ dm 3 or g • cm 3 



It should be noted in conclusion, that it is customary to define I cc as 

 liter/1000, while 1 cm 3 = liter/ 1000.027. 

 The normal mole volume of an ideal gas. — 



(v n cm 3 • mole -1 , or R n liter • mole -1 ) 



The normal mole volume of an ideal gas is the volume occupied by one gram 

 mole of an ideal gas, at o° C, under one normal atmosphere pressure. This 



1 H.P., 2, 507. a " Gravitation," Encyc. Brit., XI ed. 3 Proc. Nat. Acad. Sci., 13, 601, 

 1927. Heyl's more recent value is 6.670 X io" 8 cm 3 • g" 1 • sec." 2 Bur. Standards Journ. Res., 

 5, 1243, 1930. 4 H.P., 2, 491. 



Smithsonian Tables 

 5 



