70 A STUDY OF THE ABSORPTION SPECTRA. 



The foregoing table shows that the Zeeman effect on related bands of 

 tysonite and parisite is very different (parisite is a carbonate of the didym- 

 ium group). An examination was made on yellow Spanish apatite, a flour- 

 phosphate of calcium and didymium. The apatite bands are quite broad. 

 The band X 5270 gave a circular vibration indicating + electrons, X 5750 + 

 electrons, X 5820 + electrons, and X 5860 electrons. 



A solution of neodymium nitrate in ethyl alcohol has also been tried. 

 The bands XX 5229, 5219, and 5239 were broken into two components by the 

 magnetic field, the amount being 0.5 Angstrom unit for H = 14,000 c.g.s. 

 units. The sense of the polarization indicated electrons. The bands 

 XX 5S15 and 5831 are affected but little and indicate + electrons. The effect 

 of the magnetic field seems to be independent of the solvent. The addition 

 of perchloride of iron had no effect. The spectrum was observed as the 

 solution was warmed so as to change the solid alcohol to liquid alcohol. 

 No discontinuous change in the spectrum was noticed. 



Neodymium chloride in alcohol (methyl) has a sensitive band at X 5096 

 giving a separation of 1.1 Angstrom units for H= 14,000. The sense in- 

 dicates a + electron. X 5207 gives a separation of 0.4 having a sense, 

 X 5220 a separation of 0.4 in a sense, while X 5225 does not show any 

 effect. The bands XX 5761 (0.4,+ electrons), 5787 (0.4, -electrons), 5796 

 ( electrons), and the two bands at 6800 ( electrons) gave measurable 

 Zeeman effects. No difference was found between "water" and " alcohol " 

 bands. 



The addition of small amounts of the nitrate of neodymium to the chlo- 

 ride in an alcoholic solution rapidly causes the disappearance of the bands 

 -M5207, 5225, 5727, 5745, and 5761. When equal amounts of the two salts 

 are present these bands have practically disappeared. The band X 5220 re- 

 mains. At the same time new bands appear at M5235, 5777, 5814, and 

 6229. The band X 5229 is due to - , X 5235 to - , and X 5814 to + electrons. 



Becquerel and Onnes ' continued the work on absorption spectra at 

 temperatures of liquid and solid hydrogen. The general effect of cooling 

 is to make the bands more intense and often to cause new bands to appear. 

 The reverse action very seldom occurs. But when the temperatures of 

 liquid hydrogen (20 absolute) or solid hydrogen (14 absolute) are reached 

 it is found that many bands have weakened, or even disappeared. The 

 band X 5235 of tysonite is a band of this kind. At very low temperatures, 

 then, the spectrum is much simpler than at higher temperatures. Some of 

 the bands even pass through a minimum of width. The band ^5176 of 

 tysonite passes through a minimum between 20 and 14. Becquerel 

 suggests that there should be a relation between the effect of temperature 

 on the absorption and the effect of temperature 2 on electrical resistance. 

 At very low temperatures the metals should be transparent. 



The effect of a magnetic field on the absorption bands was found to be 

 independent of the temperature, and this fact Becquerel believes is a strong 

 argument for the view that positive electrons exist within the atoms. 



1 Le Radium, Aug. (1908). 



'Onnes: Coram. Leyden, suppl., 9, 25 (1904); Onnes and Clay: Comm. Leyden, 

 V5j yy. 



