1895 The Lancet  
44 MENTAL DISORDERS AND BODILY DISEASE. element has been separated from helium its density will be brought down still lower. To clear up a possible misconception we may state that argon has never been obtained from any other source than the air, and that helium has been extracted from various rare minerals by the action of acids. It is impossible for helium to exist in our atmosphere, as the gravitational force of the earth is not able to keep these light atoms, which are thrown off into space
more » ... own off into space by the centrifugal force of the earth's rotation. All the uncombined helium of our planetary system is probably concentrated in the sun, unless that enormous planet Jupiter has managed to retain some. It is interesting to note that helium is by far the most insoluble gas known, for water dissolves only about half as much helium as hydrogen or nitrogen. This will afford a convenient means of separating helium from other gases, and as it seems to be contained in many rare minerals of the uranium and thorium type we may hope that before long larger quantities will be available for the purposes of experiment. Besides the isolation of the two hypothetical gases we have spoken of, Professor Ramsay looks forward to investigating the actual condition in which helium exists in minerals, for he has found that these substances will not reabsorb helium when once it has been extracted from them. The last meeting of the British Association was marked by the discovery of argon, and it is reasonable to hope that the forthcoming session may witness further additions to our knowledge of these remarkable gases. -MENTAL DISORDERS AND BODILY DISEASE.
doi:10.1016/s0140-6736(00)80386-4 fatcat:24jtzcrmbze4locfeuu7grjteu