152 MB. J. S. TOWXSEND ON THE DIFFUSION OF IONS INTO GASES. 



TABLE IV. Coefficients of diffusion of ions in moist gases. 



REMARKS ON THE EXPERIMENTS. 



The values of y which were found in these experiments are probably correct to 

 3 per cent., but on referring to the curves it will be seen that the error in K is larger 

 than the error in y. For example, considering Curve I. at the point y = '5, it will 

 be seen that a 4 per cent, error in y gives rise to a 6 per cent, error in K. We would 

 therefore expect that the values of K are correct to about 5 per cent. In order to 

 diminish y without changing the apparatus, the velocity of the gas in the tubing has 

 to be diminished, and this has the effect of increasing in importance the correction for 

 recombination. It was therefore considered best to use velocities of the blast which 

 give y about '5. 



It has been assumed that the velocity of the gas is given by the formula 



2V 

 W = (a 2 r 2 ), and that the motion takes place in straight lines parallel to the 



axis of the tube. According to Professor REYNOLDS, the motion of a fluid in a tube 

 is not in straight lines when the velocity exceeds a certain critical value, and eddies 

 are produced even when the motion is initially in lines parallel to the axis. When 

 the velocity is less than another critical velocity, any irregular motion will tend to 

 return to the straight line motion. In order to ensure that the motion of any fluid, 

 whose density is p, and viscosity /i, should tend to be in straight lines and obey the 



2V 

 formula W = -^ (a 2 r*), the value of V/xt//* must be less than 700. 



In the present experiments Vpa//x is less than 100, so that the velocities used are 

 ^ of the second critical velocity. 



THE ATOMIC CHARGE. 



The most interesting results which can be deduced from the coefficients of diffusion 

 are obtained by comparing the velocity under an electromotive force with the coefficient 

 of diffusion. 



Considering one of the equations of motion 



dx 



