876 



mercury (lig. IB) was drawn into the burette a (fig. 1A). Pi-eviously 

 the absorption-apparatus h and the TöPLER-pump c had been exhausted 

 by means of the mercury pump k\ tap e was then closed and by 

 opening d the gas was transferred from fiie burette into b by means 

 of the mercury column in (J. On the bottom of the absorption- 

 apparatus (fig. IC) is the potassium, which is now heated to 200°C. 

 by means of a small electric furnace. An induction-coil is used to 

 send a glow-discharge through the evolved potassium-vapour. 



After a few hours — the time required depends on the percentage 

 of nitrogen in the mixture — the unabsorbed portion is transferred 

 back to the burette by means of the TöPLER-pump. 



In using the method the question arises, whether the potassium 

 which may be deposited from the vapour on the cooler parts 

 of the absorption-vessel ') may possibly absorb argon at its large, 

 freshly formed surface. It is well known, that sublimated metals 

 may absorb at their finely divided surface even the rare gases. 

 Fortunately argon often does not show the phenomenon "). It appeared, 

 moreover, that in our case an absorption of this nature was impro- 

 bable, from the fact that, after the nitrogen had been absorbed, 

 tiiere was always a residue of gas left which did not show any 

 further contraction hovvever long it remained exposed to the glow- 

 discharge. In the mean time the potassium goes on evaporating and 

 depositing on the colder surfaces, so that the metallic surface is 

 constantly being renewed. If an appreciable absorption of argon 

 took place, it would have been impossible to obtain a constant 

 filial volume. It may finally be noted, that a sample of the pure 

 argon which we had prepared did not show any contraction in the 

 absorption-apparatus. 



We have also tried to utilize for the purpose of analysis the 

 method of binding nitrogen recommended by Stark ') (electric dis- 

 charge thi'ough mercury vapour). It was found, however, that for 

 a sufficient rate of absorption we had to work at much lower 

 pressures — even wiien the electrodes were placed opposite each 

 other in the middle of the vessel. With potassium on the other hand 

 every gas-mixture, however high the percentage of nitrogen might 

 be, could be made to- react with the metallic vapour at relatively 

 high pressures. '') 



•) As well as the compound which is formed. 



') Travers. Proc. Roy. Soc. 60 449. Gomp. also Kohlschütter, Jahrb. 

 Radioakt. 9 402. (1912). 



») Phys. Zeitschr. 1913 p. 497. 



*) It is very probable that the reaclion is iu general started by the splitting of 



