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orbit is definitely known, and it may or may not be found to be nearer the mean-plane than at present.*

The reason for the relation of Jupiter's plane to the minor planet planes is evident. The secular perturbation of the orbit of a minor planet by Jupiter is such that the inclination of the orbit plane is not greatly changed, but the node has a constant motion. The pole of the planet's plane therefore is constantly describing a curve, not widely departing from a circle, around the pole of Jupiter's plane. This motion is greater for some minor planets than for others. Hence whatever be the distribution of the poles at one epoch, the tendency of the secular perturbation by Jupiter is to finally distribute the minor-planet poles symmetrically around the pole of Jupiter's plane.

SCIENTIFIC INTELLIGENCE.

I. CHEMISTRY AND Physics. 1. On the Presence of Argon and of Helium in Uraninite.At a meeting of the Chemical Society of London on March 27th, RAMSAY announced that he had discovered both argon and helium in the mineral clevéite, a variety of uraninite. His attention was first called to this mineral by Miers of the British Museum, since Hillebrand had shownt ihat when treated with dilute sulphuric acid and warmed, the uraninite gave off two per cent or more of a gas which from the tests he applied to it appeared to be nitrogen. On sparking with oxygen however, in presence of soda, Ramsay found that the gas which he obtained from this mineral contained only a trace of nitrogen introduced probably during its extraction. In a Plücker tube its spectrum showed all the more prominent argon lines and in addition a brilliant line close to, but not coincident with, the D lines of sodium. Besides these there were a number of other lines, one in the green being especially prominent. Moreover argon obtained from the atmosphere shows three lines in the violet which are not to be seen apparently in the gas from clevéite. Hence the author suggests that possibly atmospheric argon contains some other gas in admixture, not yet separated, which may possibly account for the anomalous position of argon in its numerical relations with other elements. Further results are promised, especially in relation to the density of the mixture, a point of very great interest.

* If we consider the planes of the orbits of the eight principal planets. Jupiter's plane is not the nearest to the mean-plane of the system. But by omission of the plane of Mercury, the mean-plane of the seven other principal planets is a little nearer to Jupiter's plane than it is to any other planetary plane.

+ This Journal, III, xl, 384, November, 1890.

At the same meeting, CROOKEs reported upon the spectrum of this gaseous mixture from clevéite, two Plücker tubes containing it having been sent to him by Ramsay, the nitrogen in which had been previously removed by sparking. By far the most prominent line was a brilliant yellow one occupying apparently the position of the sodium lines. With higher dispersion, however, the lines remained single under conditions which would have widely separated the lines of sodium. Moreover, on throwing sodium light simultaneously into the spectroscope, the spectrum of the new gas was seen to consist almost entirely of a bright yellow line, a little to the more refrangible side of the sodium lines, and separated from them by a space a little more than twice that which separated the two components of the sodium line. This line appeared as bright and as sharp as D, and D. Careful measurements gave 587.45 as its wave-length; the wavelengths of the sodium lines being for D. 589.51 and for D. 588.91. So that while the difference between the D lines is 0.60, that between D, and the new line is 1:46. It appears, therefore, that this line is the spectrum of the hypothetical element helium, discovered by Lockyer in the chromosphere of the sun and indicated as Dg. Its wave-length according to Ångström is 587.49 and according to Cornu 587.46. Besides this line of helium, there were seen traces of the more prominent lines of argon. Comparing the visible spectrum of the new gas with the band and the line spectrum of nitrogen, they were found to agree closely at the red and the blue ends, and to differ entirely between these points through a broad space in the green. The complete spectrum of the helium tube is as follows:

Wave-lengths.
(a) D, yellow

587.45 Very strong. Sharp
(b) Yellowish green 568.05 Faint.
"

566.41 Very faint.
(d) Green

516:12 Faint.
(e) Greenish blue 500.81
(f) Blue

480-63 Photographs of this spectrum at first glance show in the violet portion, a close resemblance to the band spectrum of nitrogen. But a more careful examination shows that some of the bands and lines of the nitrogen spectrum are absent from the spectrum of the helium tube, while there are many fine lines in the latter spectrum which are absent from the spectrum of nitrogen. Measurements of these lines are in progress.— Nature, li, 512, March, 1895. Chemical News, lxxi, 151, March, 1895. G. F. B.

2. On the Combination of Argon with Benzene vapor.-By means of the silent electric discharge, BERTHELOT has succeeded in effecting the combination of argon with the vapor of benzene. The argon was received from Ramsay and had been circulated in the apparatus for the absorption of nitrogen until the nitrogen bands disappeared and there was no further contraction. The

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density of the gas thus purified was 19.95 and the ratio of its specific heats was 1.65. Its volume was 37 cubic centimeters. In order to bring about the combination of argon with other substances, the author used the silent discharge, since he had found it, in his experience, much more effective than the spark in securing the permanence of unstable compounds. Thus nitrogen in presence of hydrocarbon vapors gives rise under these conditions to the most varied products of condensation-products, too, which decompose with elevation of temperature; while under the influence of the spark, hydrogen cyanide, because of its stability at high temperatures, is the sole product. Again the silent discharge, acting on a mixture of nitrogen and hydrogen, produces several per cent of ammonia, while the spark gives only infinitesimal quantities. Under the action of the silent discharge nitrogen reacts with water vapor to produce ammonium nitrite, a compound which, on standing, is decomposed at the ordinary temperature. Moreover the vapor of benzene was employed for the first experiment, because the author had found it very effective in the case of nitrogen. The apparatus used was that already employed in similar experiments (Ann. Chem. Phys., V, x, 76–79, 1877), and the conditions were those described in the author's “Essai de Mechanique Chimique,” the silent discharge being effected with the variable potential producible with an induction coil. With this apparatus the author had succeeded in bringing about the direct union of free nitrogen with hydrocarbons, carbohydrates and other organic substances. On submitting the mixture of argon and the vapor of benzene to the action of the silent discharge, combination took place though with more difficulty than in the case of nitrogen. The action is accompanied with a faint violet glow visible in darkness. In one of the five experiments there was finally formed a fluorescent substance which gave out a magnificent greenish light and afforded a special spectrum. A careful quantitative experiment, made with 10 c. c. of argon, yielded the following results: 100 volumes of this gas, put in contact with a few drops of benzene (by which its volume was increased about onetwentieth), was introduced into the discharge-tube and subjected to the discharge for ten hours under moderate tensions. After removing the benzene vapor by concentrated sulphuric acid, the remaining gas occupied 89 volumes; showing a condensation of 11 per cent. It was again mixed with benzene vapor and again subjected to the discharge, much higher tensions being employed. The diminution in volume was much more rapid, amounting in tbree hours to 25 per cent. The 64 remaining volumes was mixed anew with benzene vapor and again exposed for several hours to the discharge under still higher tensions. There remained 32 volumes of gas, consisting of hydrogen 13.5, benzene vapor 1.5 and argon 17.0 volumes. So that of 100 volumes of argon, benzene had condensed 83 into a state of chemical combination under the action of the silent discharge; or about five-sixths. The quantity of the products was too small to permit of any extended examination. They resemble those produced by the similar action of the silent discharge on nitrogen mixed with benzene vapor and consist of a yellow resinous odorous substance condensed on the surface of the two glass tubes between which the electric action is exerted. Submitted to the action of heat this substance decomposes, yielding volatile products and leaving a bulky carbonaceous residue. The volatile products turn red litmus paper blue. Evidently therefore the conditions under which argon is condensed by hydrocarbons tend to affiliate it still closer to nitrogen. Indeed it it be permissible to increase its molecular mass from 40 to 42—which seems not unreasonable—this mass would represent one and a half times that of nitrogen; so that argon would bear to nitrogen the same reaction that ozone does to oxygen. Thus far, however, argon and nitrogen are not transformable the one into the other. Under the conditions now described it is evident that the supposed inactivity of argon ceases to exist. — C. R., cxx, 581, March, 1895; Chem. News, lxxi, 151, March, 1895.

G. F. B. 3. On the Presence of Argon lines in the Spectrum of Atmospheric Air.-In a communication to the Royal Society on February 21st, NEWALL has called attention to a line spectrum which appeared frequently upon the photographs of the air spectrum taken by him a year ago, and which he called “the low pressure spectrum.” The lines of this spectrum were then unknown, but it now appears that they belong to argon, constituting seventeen out of the sixty-one lines of the air spectrum. To obtain this argon spectrum, a glass bulb was sealed hermetically to a HagenTöpler mercury pump, having a layer of strong sulphuric acid above the mercury. On reducing the pressure to 0:14mm (about 180 millionths of an atmosphere) a bright alternating discharge could be passed through the residual gas simply by surrounding the bulb with a coil of wire carrying the current from a condenser. After 30 minutes the pressure fell from 0:13am to 0·085mm (from 174 M to 112 M) and the photograph then taken showed the bands of nitrogen strong, mercury and nitrocarbon lines strong, hydrogen weak and no oxygen or argon lines. After thirty minutes more, the pressure has fallen from 0.76mm to 0·015mm (from 100 M to 20 M) and in the photograph the nitrogen spectrum had faded considerably and a number of fine new lines appeared, constituting this “low pressure spectrum.” Recent measurements show the practical coincidence of seventy-two lines belonging to this spectrum with the lines of argon as measured by Crookes. A table of the wave-lengths of these lines is given, with those of the red and blue spectrum of argon in parallel columns as given by Crookes. “ It is interesting,” says the author, “ to find argon asserting itself unsolicited in quite new circumstances, and under conditions which practically constitute one more mode of separating argon from nitrogen-namely the getting rid of nitrogen by passing electric discharges through it in

the presence of hydrogen, or moisture and acid.” Proc. Roy. Soc., Feb. 21, 1895 : Chem. News, lxxi, 115, March, 1895.

G. F. B. 4. On the Spark Spectrum of Argon as it appears in the Spark Spectrum of Air.-On the 21st of March, HARTLEY read to the Royal Society a paper pointing out that certain lines obtained by himself and Adeney in 1884, in their photographs of the air spectrum, now appear to be due to argon. In their investigations, they used electrodes of aluminum, copper, platinum and palladium, and a condensed spark produced with a coil with a Leyden jar in circuit; the partial pressure-since argon constitutes about i per cent of the atmosphere-being about 7.5inm. Since these are practicaily the conditions which as Crookes has shown give the brightest and purest spectrum of argon, the author thought it reasonable to expect the recognition of the blue and ultra-violet lines of this substance among some of the weaker lines in the spectrum of air. A table containing the wave lengths of 50 or more lines thus observed in the air spectrum is given in the paper, with the characteristic lines of the blue and the red spectra of argon in parallel columns for comparison. He considers of little importance the fact that argon gives two spectra ; the red being apparently the spectrum of the first order or of the corresponding lower temperature, while the blue is the line spectrum at the higher temperature. “ It is therefore more likely," he concludes, “that argon is one substance and not two. Whether it is a compound or an element is a question into which the following considerations may enter. There are at present no gaseous substances known which can withstand the temperature of the condensed spark without exhibiting the spectra of one or other of the elements of which it is composed. If therefore, argon were N, it would disclose the spectrum of nitrogen. As the spectrum is not that of any known substance it follows that if a compound, it must be a compound of a new element.”_ Proc. Roy. Soc., March 21, 1895. (From advance sheets received from the author.)

G. F. B.

II. GEOLOGY. 1. Reconnoissance of the Bahamas and of the elevated reefs of Cuba in the Steam Yacht Wild Duck," January to April, 1893; by ALEXANDER Agassiz. 204 pp. 8vo, with 47 plates. Bulletin of the Mus. Comp. Zool. of Harvard College, vol. xxvi, No. 1.–The coral reefs of the West India seas may be regarded as the subject of Prof. Agassiz's Report, although only the Bahamas and Cuba are mentioned in the title. For, after the very full descriptions relating to the region of more special study, the report devotes 20 of its 200 pages to the coral reefs and banks of the Caribbean district, including therein the reefs of the north shore of South America, the Yucatan Bank and British Honduras. The origin of coral reefs is the concluding AM. JOUR. Sci.—Third SERIES, Vol. XLIX, No. 293.—MAY, 1895.

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