( 621 ) 



the iieigliboiirhood of the criticcil point through considerations on tlie 

 increase of the virial of attraction in consequence of the differences 

 of density ^). 



§ 6. Remarks on further experinients on the mist in the neigJi- 

 bourhood of the critical state. 



a. AVhen through measurements as treated in § 3 the way in 

 whicli the intensity of the light scattered -by the mist depends on 

 temperature and density, will have been sufficiently brought to light, 

 the determination of this intensity at different heights in a Cagniakd- 

 Latour tube may be substituted for the method of the floating bulbs 

 for the determination of the density at different heights in the tube 

 (See Comm. N°. 98, Sept. '07). If the establishing of the thermo- 

 dynamic equilibrium is effected by keeping the temperature for a 

 long time sufficiently constant, the determination of the intensity of 

 the scattered light as function of the height in the tube would 

 supply a method for the accurate determination of the experimental 

 equation of state in the immediate neighbourhood of the critical state 

 (cf. Comm. N°. 98 § 1 p. 218). 



b. Besides the before-mentioned measurements on the condition of 

 polarisation (§ 2) and the measurements for the sake of the correc- 

 tions mentioned in § 4, measurements on the ratio between the inten- 

 sity of the scattered light and that of the incident light would also 

 be desirable. (Cf. § 3 p. 616 and § 5 p. 620). For this purpose 

 measurements might serve in which the ethylene is replaced by a 

 silver mirror forming an angle of 45° ^vith the axis of the tube ^). 



1) Gf. M. V. Smoluchowski, Boltzmann Festschrift 1904, p. 62fi 



2) We have in the meantime made a preliminary measurement of the absolute 

 intensity of the scattered light by comparing it with the light reflected from a 

 silver mirror (reflection constants for light polarized perpendicular and parallel to 

 the plane of incidence calculated according to Quincke, Pogg. Ann. 128 (1866) 

 p. 541 from determinations of the principal angle of incidence and the principal 

 azimuth by Jamin, Ann. cbim. phys. (3j 22 (1848) p. 311). For this measurement 

 the comparison spectrum had to be intensified by replacing the systems of lenses 

 Lq and ig by stronger combinations. From the angles p j = Sl'^SS' and p^^ = 



5°4.'5 we derive that at <=11°.93 the intensity of the light of wavelength D 

 scattered by 1 cM.^ of ethylene perpendicular to the direction of incidence per 

 unit angle of vision is Sj^ = 0,0007, if the intensity of the incident (unpolarized) 



hght = 1. 



If we calculate according to Rayleigh, Phil. Mag. (5) 12 (1881) p. 86—88, 



LoRENz, Oeuvres Scientif. I p. 496, s— ^r=— ^(iV = number of light-scattering 



