256 



ANNUAL, REPOET SMITHSONIAN INSTITUTION, 1910. 



possible by an accurate determination of e. The Faraday constant 

 is taken as Ne = 9,655 absolute electromagnetic units. 



e = 4.891 X 10" 10 E.S.U. 

 N = 5.922 X 10 23 

 n = 2.644 X 10 19 

 a = 2.106 X 10~ 16 ergs. 

 e = 5.750 X 10~ 14 ergs. 



tlie smallest quantity of electricity capable of sepa- 

 rate existence. 



the number of molecules in one gram molecule of 

 any substance. 



the number of molecules in 1 cubic centimeter of 

 any gas at 0° 0, and 76 centimeters. 



the constant of molecular energy. Molecular en- 

 ergy e = aT. 



the kinetic energy of agitation of a single molecule 

 at 0° C. and 76 centimeters. e =273a. 



the weight of the hydrogen atom. 



m = 1.702 X 10- 24 gms. 



Weight* and diameters <>f molecules. 



Substance. 



Hydrogen 



Helium 



Carbon monoxide 



Ethylene 



Nitrogen 



Air 



Nitric oxide 



Oxygen 



Argon 



Carbon dioxide . . 



Nitrous oxide 



Chlorine 



Water vapor 



Ethyl chloride... 



Molecular 



weight 



(//=1). 



2 



4 



27.8 

 27.8 

 27.8 

 28.9 

 29.81 

 31.8 

 39.6 

 43.7 

 43.7 

 70.4 

 17.9 

 64.0 



Absolute 



weight. 



Grams. 



3.40X10-^ 



6.81X10-M 



47.4 X10-2* 



47.4 X10~ 24 



47.4 X 10-24 

 49.2 X10-2« 

 50.8 XIO--^ 

 54.2 X10-" 



67.5 X lO- 2 ^ 

 74.4 X lO- 2 ^ 



74.4 X10-24 



119.8 XI 0-24 



30.5 X 10-24 



108.9 X10-2' 



Diameter.' 



Centimeter. 

 2.28X10-8 

 2.00X10-8 

 2.89X10-8 

 3.40X10-8 

 3.06X10-8 

 2.99X10-8 

 2.69X10-8 

 2.89X10-8 

 2.78X10- S 

 3. 11X10-* 

 3.48X10-8 

 3.01X10- 8 

 3(?)X10"8 

 4(?)XlO-« 



Absolute 



density. 



'.. an. 

 0.55 

 1.63 

 3.76 

 2.34 

 3.17 

 3.53 

 5.00 

 4.30 

 6.01 

 4.73 

 3.39 

 3.90 



My thanks are due to Profs. Crew, Carman, and Guthe for loaning 

 to me tubes of radium when my own supply met w r ith an accident. I 

 wish also to acknowledge my great indebtedness to Mr. Harvey 

 Fletcher who has most ably assisted me throughout the whole of this 

 investigation. 



1 These diameters have been obtained from the above value of it and the viscosity 

 equation 



^J2"nD- ' 



Sutherland's correction for cohesional force (Phil. Mag., 17, p. 320, 1909) and Jean's 

 correction for persistence of velocities being added. This procedure is thought to yield 

 more reliable results than applying the above corrections to means of D obtained from 

 viscosity, diffusion, heat conduction, and departures from Boyle's law, since computa- 

 tions based on the last three phenomena involve both theoretical and experimental 

 uncertainties of large magnitude. 



