340 Mr. Take Sone on the Magnetic Susceptibilities 



(d) Purity of the Hydrogen Gas. 



Morley * stated that the nitrogen which was present in 

 the hydrogen obtained by his arrangement was less than 

 1/20000 of the hydrogen, and that the hydrogen is quite 

 free from oxygen. In my apparatus constructed on the 

 same principle as that of Morley, a similar result might have 

 been expected. As the volume susceptibility of the atmo- 

 spheric nitrogen is twice as large as that of hydrogen, the 

 presence of that amount of nitrogen can produce no sensible 

 change of susceptibility. But the oxygen which might be 

 present in the hydrogen owing to an imperfect purification 

 may be expected to have a serious effect on the value of the 

 susceptibility of the hydrogen. If we take as the volume 

 susceptibilities of oxygen and hydrogen, the values 

 * Oa = 0-139 X 10"° and tc H = -0*000166 x 10" G respectively, 

 we see that the susceptibility of oxygen is 837 times as large 

 as that of hydrogen, and hence a 1/837 volume of oxygen 

 present in hydrogen will cancel the diamagnetism of 

 hydrogen, and a 1/150000 volume of oxygen will diminish 

 its diamagnetism by 0'56 per cent. This is the the same 

 order of magnitude as that of the experimental error in the 

 measurement of the magnetic susceptibility. Hence at 

 least the upper limit of the oxygen content must be known. 

 From the fact that the molecular silver placed in the path 

 of the hydrogen did not show any change in appearance, 

 we know that no sulphur compound was present in the 

 gas. 



For this purpose an apparatus as shown in fig. 9 was 

 constructed, a is a eudiometer with platinum wires sealed 

 near its closed end for the electric discharge, and b a glass 

 tube forming a U-tube, the shorter arm being inserted into 

 the eudiometer with a rubber cock. The longer arm is 

 connected to a glass tube e with a rubber tube ; the tube e is 

 provided with a bulb f containing calcium chloride, which 

 is connected to a long rubber tube g. The eudiometer is first 

 filled with mercury, and then replacing it with the hydrogen 

 to be examined, the connexion of the eudiometer with the 

 tube b is made in a mercury bath. The eudiometer with 

 the tube is then brought in the tank t and supported firmly 

 in the vertical position. The tank has a capacity of about 

 160 litres and is filled with water. The eudiometer and the 

 tube are immersed in the water, leaving only a few centi- 

 metres of the upper end of the eudiometer above the surface. 



* E. W. Morley, loc. cit. 



