1896.] 



Constituent of certain Minerals. 



327 



weighings were trustworthy to one or two hundredths of a milligram. 

 The contraction of the globe on exhausting it of air amounted, to 

 0'0212 c.c. The weight of the empty bulb was therefore increased by 

 G'000026 gram. The concordance between the mean of the determi- 

 nations of the density of argon, 19-941, made with this bulb, and that 

 found by Lord Rayleigh with one of 2 litres capacity, 1994, shows 

 that it is possible to obtain accurate results by its use. 



Broggerite gas — 



Temperature, 17-00°; pressure, 60T2 mm. 



Weight of 162-843 c.c. of gas 0-02320 gram. 



Weight of 1 litre gas at 0° and 760 mm. . . 0*1949 



Density, compared with = 16 2'181 „ 



§ 5. A quantity of helium extracted from samarskite by fusion 

 with hydrogen potassium sulphate, after all gas which would come 

 off by heating in a vacuum had been removed, was circulated as 

 usual. It was difficult to get a sample of gas which did not show a 

 trace of the hydrogen spectrum ; many hours of circulation over red- 

 hot copper oxide, however, finally removed all hydrogen. It was 

 weighed, with the following results : — 



Samarskite gas, from mineral exhausted by heating with HKSO4 ' — 



Temperature, 18-60° ; pressure, 771*4 mm. 



Weight of 162*843 c.c. of gas 02860 gram. 



Weight of 1 litre gas at 0° and 760° mm. . . 0-1896 



Density, compared with O = 16 2-122 ,, 



§ 6. The density of helium extracted from samarskite by heating 

 in vacuo was determined. Here no nitrogen was visible in the spec- 

 trum, but, as before, the removal of all hydrogen was a long opera- 

 tion. Indeed this sample showed the red line of hydrogen distinctly. 

 This, however, does not imply that it contains more than a trace, for 

 one volume of hydrogen in 100,000 volumes of helium is still visible 

 in the spectrum. 



Samarskite gas, obtained by heating the mineral. 



Temperature, 16-90°; pressure, 781*8 mm. 



Weight of 162-843 c.c. of gas 0'02989 gram. 



Weight of 1 litre gas at 0° and 760 m.m. . . 0*1895 



Density, compared with = 16 .. , 2*121 „ 



To remove hydrogen, 10 c.c. of oxygen were mixed with this gas, 

 and circulation over red-hot copper oxide, soda-lime, and phosphoric 

 anhydride was continued for a day. The next day the circulation 

 was continued, a tube containing red-hot metallic copper being 

 included in the circuit, so as to remove the excess of oxygen. The 



