. The London, Edinburgh and Dublin philosophical magazine and journal of science. he constants determinedby him. I add a description of this apparatus in its latestform. Apparatus for Detection and Measurement of Thorium. The electroscope in which the thorium was estimated wasmade and calibrated by Prof. Joly (Phil. Mag. July 1909)from solutions containing a known quantity of thorite. Thevacuum-pump P, which is fed from an overhead tank main-tained at a constant level, is first started, the partial vacuumcaused in the apparatus being observed by the rise of theoil in the tube T, reading on to
. The London, Edinburgh and Dublin philosophical magazine and journal of science. he constants determinedby him. I add a description of this apparatus in its latestform. Apparatus for Detection and Measurement of Thorium. The electroscope in which the thorium was estimated wasmade and calibrated by Prof. Joly (Phil. Mag. July 1909)from solutions containing a known quantity of thorite. Thevacuum-pump P, which is fed from an overhead tank main-tained at a constant level, is first started, the partial vacuumcaused in the apparatus being observed by the rise of theoil in the tube T, reading on to an arbitrary sc;de S behind,which thus serves as an indication of the velocity of the air-current. The vessels B, B serve to steady the influx of air,and thus keep the indicator steady. The actual rate of flow of the air is about 4 per sec, andis measured by means of the 100 c\c. flask F. The stopcock 0 Radioactivity of the Leinster Granite. 109 is first closed and C, opened, so that the air is drawn entirelythrough the measuring flask. The end of the tube Tx is Fifif. SKki then dipped below the surface of the water in the vessel Vplaced in position for the purpose, and the time of filling tothe fixed mark noted. The friction opposing the entry ofthe water into the measuring flask is compensated for bylengthening the inner limb of the tube at M, so that thistakes the character of a siphon and a slight static head isgiven to the entering water. The additional length—about3 cms.—was found by trial and error, the exact length beinghit when no motion of the oil in the gauge was observed toattend the flow of water into the flask. The air flow was regulated by means of the stopcock X,which was then allowed to remain untouched throughout theremainder of the work. The standard height of the oil inthe gauge was adhered to as far as possible throughout thesuccessive experiments, by regulation of the stopcock C is of course allowed to remain permanentlyopen, a
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
