234: Dr. L. B. Loeb on the Relative Affinity 



It was presumably nitrogen which had been entrapped in 

 the pores cf the marble. 



The N 2 used came from a small commercial tank such as 

 is used by the dental profession. It was bubbled through 

 two flasks containing a concentrated fresh solution of FeS0 4 * 

 From there it passed through two CaCl 2 . drying tubes and a 

 tube of P 2 5 , through a trap kept at —70° 0. to remove the 

 more condensible impurities, and finally into another trap 

 where it was condensed out by frozen alcohol. From this 

 trap the liquid gas was fractionated, the intermediate por- 

 tion only being admitted to the measuring chamber. The 

 gas finally went through a system of NaOH, OaCl 2 , and 

 P 2 5 tubes before passing into the measuring chamber. 



In all cases the apparatus was filled by exhausting it to 

 20 mm. and then running in the gas to atmospheric pressure. 

 When this process had been repeated from four to seven 

 times, depending on what gas had been in the chamber 

 before, the filling was considered complete. The measure- 

 ments were carried out precisely as described in the earlier 

 work on air. The methods employed by Mr. Wahlin as well 

 as a detailed discussion of his results will be published sepa- 

 rately by Mr. Wahlin. The values of n obtained are given in 

 the Table on p. 2o5. 



The results .show that this quantity n varies through an 

 enormous range of values. In N 2 and H 2 it is doubtful 

 whether the electron may ever attach permanently to these 

 molecules. In Cl 2 , as far as experiments can show, the elec- 

 tron attaches within very few impacts to form chlorine ions. 

 For other gases, n has all values lying between these limits. 

 It is consequently obvious that in spile of the difficulties 

 encountered in determining its value accurately, the constant 

 of electron attachment n is, even in its order of magnitude, a 

 marked and characteristic property of the different kind of gas 

 molecules. 



In a paper on the u Arrangement of Electrons in Atoms 

 and Molecules," Langmuir * suggests that owing to the fact 

 that the structure of N 2 and C0 2 molecules is quite 

 alike, their properties as influenced by this structure should 

 be the same. This is shown to be wrong as far as the value 

 of n is concerned. The value of n for C0 2 when freshly 

 prepared is 1*5 x 10 7 , while that for N 2 is 6"! X 10 5 . 

 Furthermore, the value of n for C0 2 undergoes a rapid 

 decrease with time after preparation. This change is not 

 shown for N 2 or for any of the other gases studied. The 



* I. Langmuir, Journ. Am. Chem. Soc. xli. No. 6, p. 898 (June 

 1919). 



