[shaver] spectra of ARGON 143 



(b) The absorption tube was then re-exhausted and filled with 

 pure argon at a pressure of 155 mm. of mercury. To produce ioniza- 

 tion in the gas at this pressure necessitated a stronger discharge, so 

 that in this experiment the discharge terminals in the absorption tube 

 were connected in series with the argon discharge tube, which was 

 again used as a source of radiation. A heavy condenser discharge 

 was passed through the circuit, ionizing the gas in the absorption tube 

 and at the same time giving the blue argon discharge in the Geissler 

 tube. The light from the latter was passed through the absorption 

 tube and brought to a focus on the slit of the spectrograph. The 

 exposure in this case was twenty-five minutes but, as before, no definite 

 absorption was observed. 



This experiment was repeated, using a Tesla coil of heavy wire 

 wound about the absorption tube to produce ionization of the gas. 

 This coil was connected in series with the discharge tube and a strong 

 Tesla discharge passed through the circuit. No absorption of the 

 blue spectrum was detected with an exposure of thirty minutes. 



(c) The tube was refilled with argon at a pressure of 5 mm. of 

 mercury. Several experiments were performed similar to those 

 previously described in an attempt to produce an absorption spectrum, 

 but the results were again negative. 



(d) A quartz bulb 6 cm. in diameter was filled with argon gas at 

 a pressure which gave a brilliant glow when the bulb was placed in 

 a coil through which a Tesla discharge was passing. The bulb was 

 placed in the Tesla coil and mounted in front of the slit of the spectro- 

 graph. The coil was connected in series with the terminals of the 

 quartz Geissler tube filled with argon and a Tesla discharge from a 

 twenty volt induction coil passed through the circuit. The light 

 from the blue discharge in the Geissler tube was passed through the 

 quartz bulb and focused on the spectrograph slit. The time of 

 exposure was sixteen minutes, but there was no indication of any 

 absorption of the blue argon spectrum by the ionized gas in the bulb. 



III. Experiments with Argon at High Pressure 



The author has already investigated the absorption spectra of 

 oxygen and nitrogen between the wave-lengths X = 7000 Â.U. and 

 \ = 2150 A.U., and it was thought that it might prove interesting to 

 examine the absorption spectrum of argon in this region. The 

 absorption tube used and the arrangement of apparatus was precisely 

 as in the experiments with oxygen and nitrogen, which have already 

 been described in a previous paper.^" T he absorption chamber was 

 "Shaver, Trans. Roy. Soc. Can., p. 7, 1921. 



