l62 



NA TURE 



[December 19, 1901 



explanation ; and that we ultimately traced the discrepancy to 

 the presence in " atmospheric nitrogen " of a gas nearly half as 

 dense again as nitrogen. 



A convenient form of ap]>aratus for isolating this gas is shown 

 in l'"ig. I. The gas, air mixed with oxygen, is confined over 

 mercury in an inverted test-tube, in contact with a few drops of 

 a solution of caustic potash ; and by connecting the rings with 

 wires from the secondary coil of an induction apparatus, sparks 

 pass between the platinum terminals in the interior of the test- 

 tube. The volume of the gas rapidly diminishes ; and in a few 

 hours the gas is removed to a clean tube, and the excess of 

 oxygen absorbed by burning phosphorus; the inert gases 

 remain behind. 



On a larger scale, the apparatus used by Lord Rayleigh, con- 

 sisting of a balloon of six litres capacity, in the interior of 

 which an electric flame is kept alight by means of a transformer, 

 while a jet of caustic alkali forms a fountain in the interior, 

 gives good results. By its help seven or eight litres of mixed 

 gases can be made to combine per hour. 



Such experiments show the inactive nature of the argon 

 group of gases towards an electro-negative element, oxygen. 



Q Q 



glass tube. Indeed, the operation is a very easy one and can be 

 carried out with the very simple apparatus .shown in Fig. 2. 

 M. Guntz has also found that lithium, an element belonging to 

 the same column in the periodic table as sodium and potassium, 

 is an exceedingly good absorbent for nitrogen, for it tarnishes in 

 nitrogen even at atmospheric temperature owing to the formation 

 of a nitride. 



On a large scale the magnesium turnings are contained in 

 iron tubes and the gas-holders are made of copper or of gal- 

 vanised iron. By this means fifteen litres of argon were separated 

 from about two cubic yards of air. 



The inactivity of argon in contact with such highly electro- 

 positive elements as lithium, magnesium and calcium again 

 demonstrates its want of electric polarity. No other elements 

 would have resisted such treatment except those of the argon 

 group. But these are not the only data from which such a con- 

 clusion can be drawn, for it was found that no .action takes place 

 between argon and hydrogen, phosphorus, sulphur, tellurium, 

 caustic soda, potassium nitrate, sodium peroxide, sodium per- 

 sulphide, nitro-hydrochloric acid, bromine-water and many 

 other reagents which it would be tedious to mention, all of 

 which are remarkable for their chemical activity. We may 

 therefore take it that the name " argon," which means " inactive," 

 has been hap]iily chosen. 



In attempting to form compounds of argon, however, another 

 consideration was not lost sight of; if compounds of argon 

 were capable of existence they ought to exist in nature, and, 

 as in all probability they would be easily decomposed by heat, 

 it ought to be possible to decompose them with evolution of 

 argon, which could be collected and tested. Prof. Miers, in a 

 letter which he wrote me the day after an account of the fruit- 

 less attempts to cause argon to combine li:i'l been given to the 



The gases are absolutely incombustible. No other elements can 

 withstand such treatment, save platinum and its congeners and 

 gold. But even the.se metals combine with fluorine or chlorine 

 when heated in a current of one or other gas. Argon, however, 

 is wholly unaffected when electric sparks are passed through its 

 mixture with chlorine or fluorine, the two other most electro- 

 negative elements. To them, too, it shows itself completely 

 indifferent. 



.\ more convenient method of separating the nitrogen from 

 its admixture with argon in atmospheric air is by means of red- 

 hot magnesium. The metal magnesium, which is now made on 

 a considerable scale for photographic and signalling purposes, is 

 a white, silvery metal, which can be planed or turned into 

 shavings. In the early experiments a measured quantity of 

 atmospheric nitrogen dried by passing over suitable drying 

 agents was brought into contact with magnesium turnings, 

 heated to redness in a tube of hard glass I', nas ueen found, 

 however, by M. Maquenne that the metal calcium, which, for 

 this purpose is most easily produced by heating together a mix- 

 ture of magnesium filings and pure dry lime, is a more elificient 

 absorbing agent for nitrogen, for it does not require such a high 

 temperature and can be effected without danger of melting the 



NO. 1677, VOL. 65] 



Royal Society, drew my attention to experiments by Dr. Ilille- 

 brandofthe United States Geological Survey, in course of which 

 he obtained a gas, which he believed to be nitrogen, by treating 

 the rare mineral clevite, a .substance found in fclspathic rocks in 

 the south ol Norway, with sulphuric acid. The chief constituents 

 of clevite are oxides of the rare elements uranium and thorium, 

 and of lead. The gas obtained thus, after purification from 

 nitrogen, was examined in a I'liicker tube with the spectroscope 

 and exhibited a number of brilliant lines, of which the most 

 remarkable was one in the yellow part of the spectrum, similar 

 in colour to the light given out by the glowing tube. The 

 position of this line, and of others which accompany it, estab- 

 lished the identity of this gas, not with argon, as was hoped, but 

 with a supposed constituent of the sun's chromosphere, first 

 observed by M. Janssen of Paris, during an eclipse which was 

 visible in India in 186S. The late Sir Edward Frankland and 

 Sir Norman Lockyer, who studied the spectrum of the chromo- 

 sphere, gave to the supposititious element, which they regarded 

 as the cause of these lines, the name "helium," a word derived 

 from "ijAiof," Greek for " the sun." Having been placed on 

 the track, I examined, with the assistance of Dr. Collie and Dr. 

 Travers, no fewer than 51 minerals, while Sir Norman Lockyer 

 examined 46 additional ones, which we had not examined, and 

 in 19 minerals, almost all of them containing uranium, helium 

 was found. Only one gave an argon spectrum, namely malacone. 

 We also sought for argon and helium in meteorites, which all 

 give off gas on heating ; but in only one specimen, a meteorite 

 from Augusta County, Virginia, was helium found, in this case 

 accompanied by argon. All natural waters contain argon, for 

 that gas is .somewhat soluble in water (4-1 volumes per too of 

 water at 15° C.) ; but some also contain helium, as for instance 



