Calcium as an absorbent of gases for the production of high vacua and spectroscopic research

This paper contains an account of researches carried out by the aid of an electric furnace designed to heat reagents in soft glass tubes up to temperatures far above the softening point of glass, and has special reference to the use of calcium under these conditions as a valuable absorbent of gases. Recent work on the generation of helium from the radio-elements has shown the necessity for more simple, certain, and powerful means of absorbing other gases and in particular nitrogen. The usual practice of Sir W. Ramsay and the writer when working together was to make provision for the removal of compounds of hydrogen, oxygen, and carbon, but to take the utmost precautions against the admission of air into the apparatus in the first place. If nitrogen was present in spite of the precautions taken, it was often possible, by gently running the spectrum-tube, to absorb it by the hot electrodes of aluminium, the lines of helium, if present, appearing as the nitrogen spectrum faded.