Spectrum of Liquid Oxygen* 209 



The determination of the refractive indices for liquid 

 nitrous oxide did not present so great difficulties. The 

 minimum deviations for the rays C, D, F, G, and for the 

 lithium ray X 6705*5, and the indium ray X 4509*6, were 

 found to be, respectively, 22° 53', 23°, 23° 18' ; 23° 33', 22° 52'. 

 and 23° 28'. The corresponding values for p are 1*329, 

 T3305, 1-3345, 1-3378, 1'3257, and 1*3368. 



The specific gravity of liquid nitrous oxide at its boiling- 

 point of — 90° 0. was found, by weighing 100 cubic centim. 



of the liquid, to be 1*255. 



-« 



This gives, for the D ray, ^ , =0*2634 and for the mole- 

 cular refraction 11*5^87. Or, if we take the other formula, 



At 2 — 1 

 7—5 — ^7- T = *163and the corresponding molecular refraction 

 ({i 2 + 2)d r & 



7*163. Subtracting the refraction- equivalent for oxygen we 



get for the molecular refraction of nitrogen 8*405 or 5*139 



according to the formula used. Mascart's determination of 



the index of refraction of gaseous nitrous oxide for the D ray 



was 1*000516 and the corresponding molecular refraction 



11*531, or 7* 69, according to the formula used, and in this case 



the older formula for the refraction-equivalent satisfies the 



condition of continuity between the gaseous and liquid states 



better than the newer. 



It was more difficult to obtain the refractive indices for 



liquid ethylene on account of its irregular boiling. Liquid 



oxygen and nitrous oxide boil steadily, but ethylene in sudden 



bursts of large volumes of vapour. The minimum deviation 



for the D ray was found to be 25° 29 r , approximately. This 



gives fi = 1*3632, and, since the density of the liquid at its 



boiling-point of -100° CL is 0*58, *^p =0-627 and l '^ "^ 



= 0*3£4. The corresponding numbers for gaseous ethylene, 

 according to Mascart, are 0'578 and 0-385. The agreement 

 for the second formula is close, but we doubt if much stress 

 can be laid on this, inasmuch as we know that the liquid 

 ethylene contained a small quantity of ether. 



angle corresponding to the index of refraction found above for liquid 

 oxygen is 50° 45', and one of us has found that when liquid oxygen is 

 cooled to —200° by its own evaporation at reduced pressure so as to 

 present a steady surface, and the image of a candle is viewed by reflexion 

 at that surface, the light is very completely polarized when the incidence 

 is at that angle. 



Phil. Mag. S. 5. Vol. 34. No. 207. Aug. 1892. P 



