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require to be very massive on account of the is established; the hot gases as they rise the heat evolved. In this case they consist from the flame strike the top, and then as of platinum wire doubled upon itself six they come around again in the course of times. The platinums are continued by the circulation they pass sufficiently close iron wires going through glass tubes, and to the caustic alkali to insure an adequate attached at the ends to the copper leads. removal of the nitrous fumes. For better security, the tubes themselves There is another point to be mentioned. are stopped at the lower ends with corks It is necessary to keep the vessel cool: and charged with water, the advantage be- otherwise the heat would soon rise to such a ing that, when the whole arrangement is point that there would be excessive generafitted by means of an indiarubber stopper tion of steam, and then the operation would into a closed vessel, you have a witness that, come to a standstill. In order to meet this as long as the water remains in position, no difficulty the upper part of the vessel is leak can have occurred through the insul- provided with a water-jacket, in which a ating tubes conveying the electrodes.
circulation can be established. No doubt Now, if we switch on the current and ap- the glass is severely treated, but it seems to proximate the points sufficiently, we get stand it it in a fairly amiable manner. the electric flame. There you have it. It By means of an arrangement of this kind, is, at present, showing a certain amount of taking nearly three-horse power from the soda. That in time would burn off. After electric supply, it is possible to consume the arc has once been struck, the platinums nitrogen at a reasonable rate. The transcan be separated; and then you have two formers actually used are the · Hedgehog tongues of fire ascending almost independ- transformers of Mr. Swinburne, intended to ently of one another, but meeting above. transform from 100 to 2400 volts. By Mr. Under the influence of such a flame the oxy- Swinburne's advice I have used two such, gen and the nitrogen of the air combine at the fine wires being in series so as to accua reasonable rate, and in this way the ni- mulate the electrical potential and the trogen is got rid of. It is now only a ques- thick wires in parallel. The rate at which tion of boxing up the gas in a closed space, the mixed gases are absorbed is about seven where the argon concentrated by the com- litres per hour; and the apparatus, when bustion of the nitrogen can be collected. once fairly started, works very well as a But there are difficulties to be encountered rule, going for many hours without attenhere. One cannot well use anything but a tion. At times the arc has a trick of going glass vessel. There is hardly any metal out, and it then requires to be restarted by available that will withstand the action of approximating the platinums. We have strong caustic alkali and of the nitrous already worked 14 hours on end, and by fumes resulting from the flame. One is the aid of one or two automatic appliances practically limited to glass. The glass ves- it would, I think, be possible, to continue sel employed is a large flask with a single operations day and night. neck, about half full of caustic alkali. The The gases, air and oxygen in about equal electrodes are carried through the neck by proportions, are mixed in a large gasholder, means of an indiarubber bung provided al- and are fed in automatically as required. so with tubes for leading in the gas. The The argon gradually accumulates; and electric flame is situated at a distance of when it is desired to stop operations the only about half an inch above the caustic supply of nitrogen is cut off, and only pure alkali. In that way an efficient circulation oxygen allowed admittance.
In this way
the remaining nitrogen is consumed, so ciple consists in the circulation of the mixthat, finally, the working vessel is charged ture of nitrogen and argon over hot magwith a mixture of argon and oxygen only, nesium, the gas being made to pass round from which the oxygen is removed by ordi- and round until the nitrogen is effectively nary well-known chemical methods. I removed from it. At the end that operamay mention that at the close of the opera- tion, as in the case of the oxygen method, tion, when the nitrogen is all gone, the are proceeds somewhat slowly. When the changes its appearance and becomes of a greater part of the nitrogen is gone, the rebrilliant blue colour.
mainder seems to be unwilling to follow, I have said enough about this method, and it requires somewhat protracted treatand I must now pass on to the alternative ment in order to be sure that the nitogen method which has been very successful in has wholly disappeared.
When I say Professor Ramsay's hands—that of absorb- 'wholly disappeared,' that, perhaps, would ing nitrogen by means of red-hot magne- be too much to say in any case.
What we sium. By the kindness of Professor Ram- can say is that the spectrum test is adesay and Mr. Matthews, his assistant, we quate to show the presence, or at any rate have here the full scale apparatus before us to show the addition, of about one-and-aalmost exactly as they use it. On the left half per cent. of nitrogen to argon as pure there. is a reservoir of nitrogen derived as we can get it; so that it is fair to argue from air by the simple removal of oxygen. that any nitrogen at that stage remaining The gas is then dried. Here it is bubbled in the argon is only a small fraction of onethrough sulphuric acid. It then passes and-a-half per cent. through a long tube made of hard glass and I should have liked at this point to be charged with magnesium in the form of able to give advice as to which of the two thin turnings. During the passage of the methods—the oxygen method or the maggas over the magnesium at a bright red nesium method—is the easier and the more heat, the nitrogen is absorbed in a great to be recommended; but I confess that I degree, and the gas which, finally passes am quite at a loss to do so. One difficulty through is immensely richer in argon than in the comparison arises from the fact that that which first enters the hot tube. At the they have been in different hands. As far present time you see a tolerably rapid bub- as I can estimate, the quantities of nitrogen bling on the left, indicative of the flow of eaten up in a given time are not very difatmospheric nitrogen into the combustion ferent. In that respect, perhaps, the magfurnace; whereas, on the right, the outflow nesium method has some advantage; but, is
very much slower. Care must be taken on the other hand, it may be said that the to prevent the heat rising to such a point magnesium process requires a much closer as to soften the glass. The concentrated supervision, so that, perhaps, fourteen hours argon is collected in a second gasholder of the oxygen method may not unfairly and afterwards submitted to further treat- compare with eight hours or so of the magment. The apparatus employed by Profes- nesium method. In practice a great deal sor Ramsay in the subsequent treatment is would depend upon whether in any particexhibited in the diagram, and is very effect- ular laboratory alternate currents are availive for its purpose; but I am afraid that able from a public supply. If the alternate the details of it would not readily be fol- currents are at hand, I think it may probably lowed from any explanation that I could be the case that the oxygen method is the give in the time at my disposal. The prin- easier; but otherwise, the magnesium method would, probably, be preferred, espe- conditions such as might have been expected cially by chemists who are familiar with to tempt it into combination. I will not operations conducted in red-hot tubes. recapitulate all the experiments which have
I have here another experiment illustra- been tried, almost entirely by Professor tive of the reaction between magnesium Ramsay, to induce the gas to combine. and nitrogen. Two rods of that metal are Hitherto, in our hands, it has not done so; suitably mounted in an atmosphere of nitro- and I may mention that recently, since the gen, so arranged that we can bring them publication of the abstract of our paper read into contact and cause an electric arc to before the Royal Society, argon has been form between them. Under the action of submitted to the action of titanium at a red the heat of the electric arc the nitrogen will heat, titanium being a metal having a great combine with the magnesium; and if we affinity for nitrogen, and that argon has rehad time to carry out the experiment we sisted the temptation to which nitrogen could demonstrate a rapid absorption of succumbs. We never have asserted, and we nitrogen by this method. When the ex- do not now assert, that argon can under no periment was first tried, I had hoped that circumstances be got to combine.
That it might be possible, by the aid of electricity, would, indeed, be a rash assertion for any to start the action so effectively that the one to venture upon; and only within the magnesium would continue to burn inde- last few weeks there has been a most inpendently under its own developed heat in teresting announcement by M. Berthelot, the atmosphere of nitrogen. Possibly, on of Paris, that, under the action of the silent a larger scale, something of this sort might electric discharge, argon can be absorbed succeed, but I bring it forward here only when treated in contact with the vapor of as an illustration. We turn on the electric benzine. Such a statement, coming from current and bring the magnesiums together. so great an authority, commands our attenYou see a brilliant green light, indicating tion; and if we accept the conclusion, as I the vaporisation of the magnesium. Under suppose we must do, it will follow that the influence of the heat the magnesium argon has, under those circumstances, comburns, and there is collected in the glass bined. vessel a certain amount of brownish-looking Argon is rather freely soluble in water. powder which consists mainly of the nitride That is a thing that troubled us at first in of magnesium. Of course, if there is any trying to isolate the gas; because, when one oxygen present it has the preference, and was dealing with very small quantities, it the ordinary white oxide of magnesium is seemed to be always disappearing. In tryformed.
ing to accumulate it we made no progress. The gas thus isolated is proved to be inert After a sufficient quantity had been preby the very fact of its isolation. It refuses pared, special experiments were made on to combine under circumstances in which solubility of argon in water. It has been nitrogen, itself always considered very inert, found that argon, prepared both by the does combine—both in the case of the magnesium method and by the oxygen oxygen treatment and in the case of the method, has about the same solubility in magnesium treatment; and these facts are, water as oxygen-some two-and-a-half times perhaps, almost enough to justify the name the solubility of nitrogen. This suggests, which we have suggested for it. But, in what has been verified by experiment, that addition to this, it has been proved to be the dissolved gases of water should contain inert under a considerable variety of other a larger proportion of argon than does atmospheric nitrogen. I have here an appa- tube is not sufficient for the projection of its ratus of a somewhat rough description, spectrum. Under some circumstances the which I have employed in experiments of light is red, and under other circumstances this kind. The boiler employed consists it is blue. Of course when these lights are of an old oil-can. The water is applied to examined with the spectroscope and they it and drawn from it by coaxial tubes of have been examined by Mr. Crookes with metal. The incoming cold water flows great care—the differences in the color of through the outer annulus between the two the light translate themselves into different tubes. The outgoing hot water passes groups of spectrum lines. We have before through the inner tube, which ends in the us Mr. Crookes' map, showing the two interior of the vessel at a higher level. By spectra upon a very large scale. The upper means of this arrangement the heat of the is the spectrum of the blue light; the lower water which has done its work is passed on is the spectrum of the red light; and it will to the incoming water not yet in operation, be seen that they differ very greatly. Some and in that way a limited amount of heat lines are common to both; but a great many is made to bring up to the boil a very much lines are seen only in the red, and others larger quantity of water than would other- are seen only in the blue. It is astonishing wise be possible, the greater part of the to notice what trifling changes in the condissolved gases being liberated at the same ditions of the discharge bring about such
These are collected in the ordinary extensive alterations in the spectrum. way. What you see in this flask is dis- One question of great importance, upon solved air collected out of water in the which the spectrum throws light is: Is the course of the last three or four hours. Such
argon derived by the oxygen method really gas, when treated as if it were atmospheric the same as the argon
derived by the magnitrogen, that is to say after removal of the nesium method ? By Mr. Crookes' kindoxygen and minor impurities, is found to ness I have had an opportunity of examinbe decidedly heavier than atmospheric nitro- ing the spectra of the two gases side by side, gen to such an extent as to indicate that and such examination as I could make rethe proportion of argon contained is about vealed no difference whatever in the two double. It is obvious, therefore, that the spectra, from which, I suppose, we may dissolved gases of water form a convenient conclude either that the gases are absolutely source of argon, by which some of the labor the same, or, if they are not the same, that of separation from air is obviated. During at any rate the ingredients by which they the last few weeks I have been supplied differ cannot be present in more than a from Manchester by Mr. Macdougall, who small proportion in either of them. has interested himself in this matter, with My own observations upon the spectrum a quantity of dissolved gases obtained from have been made principally at atmospheric the condensing water of his steam engine. pressure. In the ordinary process of spark
As to the spectrum, we have been in- ing, the pressure is atmospheric, and if we debted from the first to Mr. Crookes, and wish to look at the spectrum we have nothhe has been good enough to-night to bring ing more to do than to include a jar in the some tubes which he will operate, and circuit and to put a direct vision prism to which will show you at all events the light the eye. At my request, Professor Schuster of the electric discharge in argon. I cannot examined some tubes containing argon at show you the spectrum of argon, for unfor- atmospheric pressure prepared by the oxytunately the amount of light from a vacuum gen method, and I have here a diagram of a characteristic group. He also placed the density of a gas, and also the velocity upon the sketch some of the lines of zinc, of sound in it, we are in a position to infer which were very convenient as directing this ratio of specific heats; and by means one exactly where to look. (See Fig.) of this method, Professor Ramsay has de
Within the last few days Mr. Crookes termined the ratio in the case of argon, has charged a radiometer with argon. arriving at the very remarkable result that When held in the light from the electric the ratio of specific heats is represented by lamp the vanes revolve rapidly. Argon is the number 1.65, approaching very closely anomalous in many respects, but not, you to the theoretical limit, 1.67. The number
1.67 would indicate that the gas has no Next, as to the density of argon. Pro- energy except energy of translation of its fessor Ramsay has made numerous and care- molecules. If there is any other energy ful observations upon the density of the gas than that, it would show itself by this numprepared by the magnesium method, and he ber dropping below 1.67. Ordinary gases, finds a density of about 19.9 as compared oxygen, nitrogen, hydrogen, etc., do drop
see, in this.
with hydrogen. Equally satisfactory obser- below, giving the number 1.4. Other gases vations upon the gas derived by the oxygen drop lower still. If the ratio of specific method have not yet been made, but there heats is 1.65, practically 1.67, we may infer is no reason to suppose that the density is then that the whole energy of motion is different, such numbers as 19.7 having been translational; and from that it would seem obtained.
to follow by arguments which, however, I One of the most interesting matters in must not stop to elaborate, that the gas connection with argon, however, is what is must be of the kind called by chemists known as the ratio of the specific heats. I monatomic. must not stay to elaborate the questions in- I had intended to say something of the volved, but it will be known to many who operation of determining the ratio of specific hear me that the velocity of sound in a gas heats, but time will not allow. The result depends upon the ratio of two specific heats is, no doubt, very awkward. Indeed, I —the specific heat of the gas measured at have seen some indications that the anomaconstant pressure, and the specific heat lous properties of argon are brought as a measured at constant volume. If we know kind of accusation against us. But we had