li'll] on a New Motltod of Chemical Analysis. l-A"* 



Thus, whenever the electric current passes through a gas, and 

 probably whenever a gas is ionized, the gas becomes a mixture of 

 many different substances. We can thus readily understand why in 

 the spectra of many elements many of the lines may be grouped 

 together so as to form different series — the principal series, the first 

 co-ordinate series, and so on — and the spectrum of the discharge- 

 tube regarded as the superposition of a number of different spectra 

 whose relative intensities may be subject to very great variations. 

 This, indeed, is just what would happen if some or all of the sub- 

 stances which are present when the gas is in the ionized state gave 

 rise to different spectra. 



Another feature which I think is of great interest from the point 

 of view of the theory of chemical combination is the occurrence of 

 particles with negative charges. Let us consider for a moment how 

 these are formed. They are formed after the particles have passed 

 through the cathode ; the path between the cathode and the photo- 

 graphic plate contains abundance of corpuscles produced by the 

 ionization of the gas ; a neutral particle after passing through the 

 cathode picks up a negative corpuscle and so becomes negatively 

 charged. For this to occur the attraction between the corpuscle and 

 the neutral particle must be exceedingly strong, for it is not a 

 question of a particle at rest attracting to itself a negatively electrified 

 corpuscle sauntering about in its neighbourhood ; in our case the 

 neutral particle is rushing past the corpuscle with a velocity of the 

 order of 10^ cm. per sec. In order that the particle may under these 

 circumstances be able to drag the corpuscle along with it, the 

 attraction between the two must be so great, that to move a corpuscle 

 against this attraction from the surface of the particle away to an 

 infinite distance must require an amount of work of the same order 

 as that required to communicate to the corpuscle a velocity of 

 10^ cm. per sec. : this is equal to the work required to move the 

 atomic charge against a potential difference of about 3 volts, and is 

 therefore comparable with the work required to dissociate some of 

 the most stable chemical compounds. 



The fact, then, that some particles get negatively charged shows 

 that in the neutral state these particles have an exceedingly strong 

 affinity for a negatively electrified particle, while the absence of a 

 particular particle from the negative side shows that its affinity is 

 much less, but does not imply that it vanishes altogether. From what 

 we have said, it should follow that the more slowly the neutral par- 

 ticles are moving relatively to the corpuscles, the more easily will 

 the negatively electrified systems be formed. This is confirmed in a 

 very striking way by our experiments, for when the discharge is 

 passing very easily through the tube, and the velocity of the neutral 

 particles is relatively small, the number of negatively electrified 

 particles is very much increased ; indeed, in some cases the brightness 

 of the part of the photograph corresponding to the negative particles 



YOL. XX. (No. 105) L 



