March 1, 1895.] 



KNOWLEDGE. 



51 



alluded, and which yielded interesting qualitative though 

 not quantitative results, was Graham's method of diffusion 

 or atmolysis. Every student of chemistry and physics 

 knows that when a mixture of two gases of different 

 densities is made to pass through a finely porous material, 

 such as the walls of a common clay pipe, the lighter gas 

 passes through the pores, or diffuses, more rapidly than 

 the heavier ; the rates of diffusion being inversely as the 

 square roots of the densities of the gases. To give an 

 example, oxygen has a density sixteen times as great as 

 hydrogen. When a mixture of those two gases is made to 

 diffuse through the walls of a clay pipe, or a cylinder of 

 unglazed earthenware, it is found that four volumes of 

 hydrogen pass through for one volume of oxygen. The 

 experiment can be tried very easily- with coal gas and air, 

 the former being, of course, the lighter of the two. By this 

 means the slower diffusing portion of atmospheric air was 

 found (after removal of the oxygen by red-hot copper) to 

 have a density greater than that of ordinary atmospheric 

 nitrogen, and that to an extent beyond the limits of experi- 

 mental error. This, of course, leads to the conclusion 

 that atmospheric nitrogen is a mixture of gases. It should 

 farther be mentioned that "chemical" nitrogen was treated 

 by methods (1) and (2), i.e., sparked with oxygen and 

 passed over red-hot magnesium, in exactly the same 

 manner as the atmospheric nitrogen had been, but in 

 neither case was more than a trifling amount of argon 

 obtained, an amoimt readily accounted for by errors of 

 experiment. We have in this a definite proof that argon 

 is not present in the nitrogen obtained from chemical 

 compounds. 



There has, of course, not been time yet to make a full 

 investigation of the properties of argon, although much of 

 interest in this respect has already been done. A number 

 of determinations of its density have been made, which 

 show this to be 19-9 (hydrogen = 1). A calculation made 

 by the discoverers on the assumptions (1) that the accu- 

 rately-known densities of atmospheric and of chemical 

 nitrogen differ only because of the argon present in the 

 former, and (2) that during the sparking with oxygen 

 nothing excepting nitrogen is oxidized, gave the figure 

 20'6 as the theoretical density. The difficulty in deter- 

 mining the density of the new gas accurately is to make 

 sure that every trace of nitrogen has been removed. The 

 sample of density 19-9 showed no spectrum of nitrogen 

 when examined in a vacuum tube. Even if this figure 

 should have to be amended slightly, it is obviously very 

 near the truth. Argon is thus nearly half as heavy again 

 as nitrogen, whose density is 14. 



The spectrum of argon was examined by Mr. Crookes, 

 the well-known authority on spectroscopy, who himself read 

 a short supplementary paper upon this at the meeting. 

 He found that it resembled nitrogen in that it gave two 

 distinct spectra, according to the strength of the induction 

 current employed. But while the two spectra of nitrogen 

 are different in character, one showing fluted bands and 

 the other sharp lines, the argon spectra both consist of 

 sharp lines. Under certain conditions of working the 

 spectrum is rich in red rays, and imder other conditions 

 in blue. Mr. Crookes was able to take photographs of 

 the two spectra of argon, partly superposed, when their 

 dissimilarity was readily seen. He further found that no 

 other spectrum-giving gas or vapour yielded spectra at all 

 like those of the new gas. Judging from the spectra, 

 therefore, he gave it as his opinion that argon was not 

 improbably a mixture of two or more gases (a contingency 

 which had hkewise been foreseen by Lord Eayleigh and 

 Prof. Ramsay from their own observations), one of those 

 gases glowing red and the other blue, and each having its 



own distinct spectrum. On the other hand, it must not be 

 forgotten that some elementary gases with which we are 

 well acquainted, e.;/., nitrogen, also possess two distinct 

 spectra. So far, therefore, as spectroscopic work can 

 decide. Lord Rayleigh and Prof. Ramsay have added one, if 

 not two members to the family of elements. 



The behaviom- of argon at very low temperatures was 

 investigated by Prof. Olszewski, of the University of 

 Cracow, who has made a special study of this branch 

 of chemistry. He found, among other things, that its 

 freezing point is — 189-6° C. and boiling point — 187° C, 

 while the density of liquid argon at the boiling point is 1-5 

 approximately (water =1). It is interesting to note here 

 that the density of liquid oxygen is only l-12i. Argon 

 thus belongs to the so-caUed permanent gases, and its 

 behaviour on liquefaction places it nearest to oxygen, which 

 boils at — 182-7= C. 



From the ratio of the specific heat at constant volume 

 to that at constant pressure, the discoverers have come 

 to the conclusion that argon, like mercury vapour, is a 

 monatomk gas ; its atomic weight is therefore about 40 {i.e., 

 19-9 X 2). This raises, however, some very difficult points, 

 which require fui-ther working out ; for, as Lord Rayleigh 

 himself said towards the close of the meeting, the mona- 

 tomieity of a gas is a subject about which we know 

 exceedingly little, mercury vapour being the only other 

 monatomic gas known. 



Argon dissolves in water to the extent of about four 

 volumes in one hundred of water at the ordinary tempera- 

 ture. Its solubility is thus much the same as that of 

 oxygen, and about two and a half times as great as that 

 of nitrogen. It has therefore been found, as was to be 

 expected, that the dissolved "nitrogen'' from rain-water is 

 relatively more than twice as rich in argon as atmospheric 

 nitrogen is. 



All attempts to induce the new gas to enter into 

 chemical combination with any other element h-ave up to 

 the present proved abortive — hence the name given to it — 

 argon or idle. It does not combine with oxygen in presence 

 of alkali under the influence of the electric discharge, nor 

 with hydrogen in the presence of acid or alkali, or when 

 sparked, nor with phosphorus or sulphur at a bright red 

 heat. Tellurium, sodium and potassium may be distilled 

 unchanged in a current of the gas. It is unaffected by 

 passing it over red-hot caustic soda, soda-Ume, potassium 

 nitrate, sodium peroxide, the persulphides of sodiurn and 

 calcium, nascent silicon and nascent boron. Platinum 

 black and platinum sponge do not absorb it, and wet 

 oxidizing and chlorinating agents — such as permanganate 

 of potash and aqua regia — are entirely without action 

 upon it. Experiments are in contemplation to see if it 

 will combine with fluorine, the most active, in a chemical 

 sense, of all the elements. These present, however, 

 exceptional difiiculties, and time will be required to carry 

 them out. An attempt will also be made to produce a 

 carbon arc in the gas. Under other conditions argon 

 may yet be found capable of entering into chemical 

 combination with some of the other elements, for, as the 

 authors pointed out in their paper, it is comparable at 

 the ordinary temperature with mercury vapour at about 

 800= C, and the compounds of mercury are by no means 

 stable at a high temperature in the gaseous state. 



In summing up the arguments which have been already 

 advanced in favour of argon being a new substance, Lord 

 Rayleigh and Prof. Ramsay call further attention to 

 the poSit that it is in the highest degree miprobable that 

 two processes so diff'erent from one another should manu- 

 facture the same product, whereas the explanation is 

 simple if it be granted that these processes merely eliminate 



