Physics. — “On Centres of Luminescence and Variations of the 
Gas Pressure in Spectrum Tubes at Electrical Discharges.” 
By L. HAMBURGER. (Communicated by Prof. H. A? Lorentz). 
(Communicated at the meeting of April 23, 1920). 
1. Zntroduction. 
Three years ago’) we published the results of some observations, 
in which among others the fact was stated that when discharges are 
sent through a spectrum tube, variations of the gas pressure may 
occur at the anode and the cathode. 
They owe their existence to the difference in properties of positive 
and negative ions. As J, Stark *) already observed, the difference existing 
between the two kinds of ions gives rise to the two following effects: 
a. The appearance of phenomena connected with the electrical 
wind (in general the electrostriction). 
6. Mass transportation by means of the electric current. 
The object of this paper is among other things to examine which 
of these two effects, which are in connection with each other, as 
they both rest on the difference in properties of the ions, has a greater 
part in the observed variations of the gas pressure. In connection 
with this the centres of electro-luminescence will then be considered. 
2. Klectrostriction. 
A Duteh physicist D. Bos*) has already made an extensive study 
of this. He finds for gases such slight variations of volume, resp. of 
pressure, (loc. cit. p. 92 et seq.), that it is clear that with the pressure 
effects observed by us — to an amount of 30°/, and more of the 
total pressure — electrostriction cannot have had an appreciable 
direct influence. . 
In the case of discharges through a spectrum tube the phenomena 
of the electrical wind connected with electrostriction may be considered 
as a consequence of the friction between the ions and the neutral 
gas molecules. It is clear that the electrical pressure will be the 
greater as the difference in properties of the positive and negative 
ions is greater. As we already mentioned, this electrical pressure is 
of an entirely different order of magnitnde than the variations of the 
gas pressure observed by us. 
1) L. HAMBURGER, Diss. Delft 1917. These Proc. 20, 1045 (1917). 
2) J. STARK. BoLTZMANN-Festschrift 1904. 
3) Diss. Groningen 1880. 
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Proceedings Royal Acad. Amsterdam. Vol. XXIII. 
