JULV 25, 1895] 



NA TURE 



507 



and the pump. After most of the gas had been evolved, the 

 temperature was raised until the hard-glass bullj bejjan to 

 ccjllapse. 



Many of the minerals evolved hydrogen ; hence, after the gas 

 had entered the pump, the bulb was completely exhausted, and 

 the gas was sparked with oxygen, no alkali being present. The 

 oxygen was then absorbed with caustic soda and pyrogallic acid, 

 and the gas was transferred to a vacuum-tube. As this process 

 of transference proved very convenient, it is worth while to 

 describe it in full. 



The apparatus is shown in the annexed figure. It consists of 

 a tube provided with a perfectly-fitting stop-cock ; this tube is 

 cimnected with a Tiippler's pinup. The vacuum-tube or tubes 

 to be fitted are sealed to a lateral branch above the stop-cock. 

 The lower part is bent into a sharp U , and the end drawn out 

 to a point and sealed. The stop-cock is then turned full on, 

 and the whole tulje is completely exhausted, until the vacuum- 

 tube shows lirilliant phosphorescence, or, indeed, as often 

 happens, ceases to conduct the discharge ; the stop-cock is then 

 closed. A mercury trough is placed lielow the bend of the 

 tube, and the latter is sunk until the clo.sed end disappears 

 below the mercury. A small tube, which need not contain 

 more than i c.c. of the gas to be introduced into the vacuum- 

 tulw, is then placed over the closed end of the bent tube, and 

 the mercury trough is lowered. The sealed end is then broken 

 by pressing it against the interior of the gas-tube, when gas 

 enters up to the stop-cock. On carefully opening the stop-cock 

 a trace of gas is passed into the vacuum-tube ; this gas is then 



))umped out and collected below the delivery tube of the 

 Topjiler's pump. One such Hashing with gas is usually 

 sufficient. The stop-cock is again opened, and a sufficient 

 amount of gas introduced into the vacuum-tulje to show the 

 spectrum. The vacuum-tube is then removed by sealing, and 

 the gas still remaining in the bent tube may be transferred to the 

 pump and collected. It is seen that this method jiermits of the 

 filling of a vacuum-tube absolutely without loss, and it may be 

 added with great expedition. 



The results obtained with the minerals examined are given in 

 the following table. 



The spectrum of helium is characterised by five very brilliant 

 lines ; these occur in the red, the yellow, the blue-green, the 

 blue, and the violet. In every case, except with hjelinite, 

 fergusonite, and xenotime, in which cases the lines were merely 

 seen, all these lines were identified by simultaneous comparison 

 in the same spectroscope with the spectrum of helium from 

 cicveile. With the gas from samarskite and in some other 

 cases a still more careful comparison was made, and the absolute 

 coincidence of every visible line was ascertained. 



Krom many of these minerals, a hydrocarbon was extracted : 

 this was manifested by the non-absorption of the gas by caustic 

 potash until after explosion with oxygen. It would be interest- 

 ing to ascertain whether the hydrocarbon is present as such in 

 the mineral, or is formed during the heating, for in all cases 

 where a hydrocarbon was evolved, a large quantity of hydrogen 

 was also obtained. If a vacuum-tube be charged with the crude 



NO. 1343, VOL. 52] 



gas, merely deprived of carbon dioxide by caustic alkali, the 

 spectrum consists almost wholly of the fluted bands of carbon. 



Name of mineral. 



Vttrotantalite . 

 Samarskite 



Kachwane, Ceylon 

 Unknown 



Rt:-^ull. 



Iljclmite. 



Fergusonite 



Tantalite 



Pitchblende 



Fahlun, Sweden... 



\'tterby, Sweden.. 

 Fahlun, Sweden.. 



Cornwall 



Hydrogen and helium. 



A little hydrogen and 

 nitrogen. After spark- 

 ing with oxygen over 

 caustic soda, 15 grams 

 yielded approximately 4 

 c.c. of helium. At high 

 pressure (4 mm.) the 

 unsparked gas shows 

 fluted carbon spectrum. 

 At low pressures this is 

 invisible. 



No hydrogen ; trace of 

 helium. 



Do. do. 



Trace of helium. 



50 grams yielded about 

 o"5 c.c. of helium. After 

 fusion with hydrogen 

 potassium sulphate a 

 further very small quan- 

 tity was obtained. 



Small quantity of helium. 

 Do. do. 



Contains hydrogen and 



helium in fair quantity. 



Do. do. 



Do. do. 



Do. do. 



Hydrogen, and, after 

 explosion with oxygen, 

 a trace of helium. 

 Easily gave a good 

 spectrum of pure 

 helium. 



Much hydrogen ; no 

 helium. 

 i 



I Very little gas ; partly 

 I hydrogen. 

 I lardly any gas : trace of 

 hydrt)gen. 

 I Fair quantity of hydro- 

 ; gen. 



Carbon dioxide ; glass 

 etched. 



I Carbon dioxide and 

 - small quantity of 

 \ hydrogen. 



Do. do. 



90 grams gave 50 c.c. of 

 gas, leaving i '3 c.c. 

 after explosion with 

 oxygen. Alter spark- 

 ing and absorbing oxy- 

 gen, o'l c.c. remained. 

 Not examined. 



