220 Mr, V. H. Yeley. Examination of Physical and [Nov. 23, 



Refractive Indices of above Compoionds. 



I am indebted to Mr. J. J. Manley, M.A., of tlie Laboratory, Magdalen 

 College, Oxford, for these determinations, made with the Becker-Meyerstein 

 spectrometer and quartz prism described in previous communications.* 



As the instrument and prism had been out of use for some time, it was 

 thought desirable to remeasure the angle of the prism, and to determine the 

 refractive index njy of " conductivity " water. The following values show that 

 the apparatus had remained in perfect order : — 



Angle of Prism. 

 Present values. Past values. 



60° 6' 8" to 60° 6' 24". 60^ 6' 0" to 60° 6' 24". 



Eefractive Index of " Conductivity " Water. 



/tD = 1-333400 ±0-054. /^d = 1-333393. 



Kem.-' ohm-i = 1-3 . 10-«. Ken,.-' ohm-1 = 1-2 . 10-«. 



TetracMorethane. — Five independent determinations of fi-o, made at tem- 

 peratures 15°-2 to 17°-3, and corrected to a standard temperature 17° gave the 

 following results : — 



(1) 1-495602 (3) 1-495595 



(2) 582 (4) 550 



(5) 1-495007 



The above lead to a final value 1-495587 ±0-056 calculated by Bessel's 

 function. 



The determinations give for Gladstone's factor yu, — l/(Z = 0-3095, and for 

 Lorenz' factor fi'^—l/(/j,^ + 2)d = 0-1824 ; and if miiltiplied by the molecular 

 weight 53-0 (50-6 Kaiionnikoi'f), and 30-7 respectively. 



Trichlorethylenc. — Six independent determinations of /xu at temperatures 

 varying from 15-2 to 17-3 (Nos. 1 to 4 with one portion, 5 to 6 with another) ; 

 these, corrected to standard temperature, 17°, gave the following results: — 



(1) 1-479144 (4) 1-479125 



(2) 38 (5) 31 



(:!) 50 (6) 56 



The above led to a final value 1-479141 ±0-063, calculated as before. 



Tlio determinations give 0-326 for Gladstone's factor, and 0-193 for Lorenz' 

 factor, which, wlieii innltii)lied by the molecular weight, give 42*7 and 25*8 

 respectively. 



• 'Koy. Soc. I'roc.,' I!K)1, vol. fi!), p. 105 ; /'hi,f., lOOr), A, vol. 7f!, p. 472. 



