Page:Proceedings of the Royal Society of London Vol 60.djvu/475

Rh indication of the presence of any new element lias been obtained, nor has any abnormality been observed in the spectrum of any of the gases examined.

The mineral was ground to fine powder in an agate mortar, and then mixed with about twice its weight of acid potassium sulphate. This mixture was placed in a hard glass tube, which was connected with a Topler pump, and, after exhaustion, heated to a red heat by means of a large Bunsen burner. The gases evolved were pumped off and collected over mercury in a tube containing a little caustic potash solution. In some instances, however, the mineral was heated alone; the same result was obtained, but the evolution of gas takes place rather more slowly. In order to diminish any chance of leakage of air into the apparatus, the hard glass tube was connected with the pump in the manner shown in fig. 1. The tube was drawn out to a neck at the point A. A piece of thick-walled rubber tube was fitted over the end of the tube B connected with the pump, and it was then forced tightly into the neck of the hard glass tube. By pouring a little mercury into the cup C the joint could be made absolutely air-tight.

Several samples of fergusonite, monazite, and samarskite were first examined, and were found to give quantities of helium up to 1*5 c.c. per gram.

Columbite (a variety of tantalite), an isomorphous mixture of niobate and tantalate of iron and manganese, gave 1*3 c.c. of gas consisting chiefly of helium.

Pitchblende, containing zirconium, obtained by Dr. Hillebrand from Colorado, gave 0'36 c.c. of gas per gram, of which 0'3 c.c. was helium. Another sample gave 0'27 c.c. of helium per gram.