On the Ionization of Air by Phosphorus. 477 



It would certainly be rash to pretend that the values o£ 

 the time of relaxation T which we have found for certain 

 liquids closely approach the true values. Nevertheless the 

 order of magnitude which we have been led to assign to them 

 does not appear to be impossible. 



XL VII. Simultaneous Volumetric and Electric Graduation 

 of the Steam-Tube with a Phosphorus Ionizer. — IV. By 

 C. Barus*. £ Q , / 



1. A FTER graduating the colour-tube in terms of the 

 1\- volume-influx per second of air saturated with 

 phosphorus emanation, it is next necessary to investigate 

 corresponding data for the degree of ionization of air as 

 related to the colour- effect. Indeed both graduations may 

 be made simultaneously by passing a known volume of 

 saturated air per second through a suitably constructed 

 tubulnr condenser, and observing coincident values of the 

 electrical leakage of the latter and the colour of the enclosed 

 steam-jet. Clearly the colours of the tube will each corre- 

 spond to a definite electrical current passing through the 

 condenser. Moreover, while the volumetric equivalent of a 

 given colour is dependent on the degree of initial saturation 

 of the phosphorus emanation conveyed by the current of air, 

 the electric equivalent should be independent of it. The 

 final graduation cannot at once be carried out, however ; for 

 in the case of the colour-tube constructed and used as below 

 the nuclei are injected into the air-current maintained by the 

 steam-jet. An arbitrary element is thus introduced, and the 

 results will only be comparable when all observations refer to 

 a tube the action of which has been left quite undisturbed. 

 True, there seems to be no objection to putting a vane- 

 anemometer into the influx-pipe (enlarged) of the colour- 

 tube, in which case the arbitrary factor w r ould be specified ; 

 and other methods of eliminating the factor will be indicated, 

 but the data following refer to the earlier methods of 

 experiment. 



2. In fig. 1, C (y is the colour-tube, with the jet j, the ther- 

 mometer T, and the influx-pipe C, bent for convenience. 

 K L is the tubular condenser, consisting (as showm in detail in 

 fig. 2) of a brass tube d, *6 centim. in internal diameter and 

 effectively 50 centims. long, surrounding a steel rod a, 

 "318 centim. in diameter, coaxially. Rod and tube are sepa- 

 rated symmetrically throughout by the short hard-rubber 



* Communicated by the Author. — See previous communications, Phil. 

 Mag. [5] xxxviii. pp. 19-35 (1894); [t>] i. pp. 572-578 (1901); ii. 

 pp. 391-403 (1901). 



