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sidered to be peculiar to strings. Another invention of his is a string which, to the great surprise of those who attempted it, could not be put out of tune. Mr. Hamilton is still engaged in perfecting his inventions, which promise to give us the effect of an organ in a piano-forte, and that of a pianoforte in a cottage instrument.-12 A, XI., 99.

HARMONY IN MUSICAL INSTRUMENTS.

In a course of lectures on the science of music Mr. Ellis has explained the defects of the ordinary keyed instruments, toned by a system which he characterizes as the worst possible, in that every element of harmony is violated. In the piano-forte the errors of temperament are not so offensive as in the organ and in the harmonium. In olden times organs were tuned on a temperament which put the principal keys in good tune, but more recently organists, having made up their minds to play in all sorts of remote keys, a great change has taken place, and an equal temperament has been attempted. For show organs this course may be defended, but not for church organs, where nothing but the simplest keys are required. The organ of half a century ago was a sweet-sounding instrument compared with the harsh ones of modern days. A curious proof occurred a few years ago of the mischief done to the tone of an organ by the equal temperament. Dr. Pola had to construct two organs of tolerable size. In the one he gave way to popular prejudice by having it tuned equally; in the other he adopted the old tuning; and though the instruments were precisely alike in other respects and made by the same builder, the latter or gan acquired the reputation of being peculiarly sweet-toned, while the former was considered harsh.-12 A, XI., 89.

D. CHEMISTRY AND METALLURGY.

VANADIUM IN ROCKS.

Vanadium, hitherto regarded as one of the rarest metals, is now said by Dr. A. A. Hayes to be very widely diffused. It occurs as vanadic acid, associated with phosphoric acid, in minute traces in very many of our commonest rocks. In fact, it seems to be almost as frequently met with as manganese. Dr. Hayes has detected it in green and plum colored slates and porphyries, in sandstones, and in various rock aggregates.-1 A, April 16, 1875, 166.

CRYSTALLIZED CADMIUM.

Hermann Kämmerer has obtained fine crystals of metallic cadmium by distilling the metal in a current of hydrogen in a combustion tube. These crystals were silver white, and seemed to belong to the regular system, there being regular octahedrons, dodecahedrons, and other more complicated forms. The experiment can be performed in the lectureroom before a class.-21 A, May, 425.

OXIDATION OF RUTHENIUM.

Ruthenium, the rarest metal of the platinum group, differs from its associates in the ease with which it undergoes oxidation. Its properties in this respect have recently been investigated by Deville and Debray, who worked chiefly with the tetroxide, RuO4. This substance is easily formed by the fusion of ruthenium before the oxyhydrogen blowpipe. The metal then oxidizes almost as readily as antimony, giving off a blackish vapor which smells strongly of ozone. Strangely enough, however, the oxide, although formed at such a high temperature, can not be heated without decomposition. By simply heating a specimen of it to about 108° Centigrade, it can be made to decompose with a very violent explosion, yielding a large quantity of highly ozonized oxygen. These peculiarities seem to distinguish it from all other known oxides.-Annales de Chimie et de Physique, April, 537.

METALLIC BARIUM.

Although the compounds of barium have been so long and so thoroughly known, the metal itself has been but little studied. Sergius Kern, of St. Petersburg, has lately succeeded in preparing it by several methods in a state suitable for examination. The best process seems to be to heat barium iodide with metallic sodium. A violent reaction ensues, accompanied by an evolution of heat and light; the resulting mass is treated with mercury to form a barium amalgam, from which, finally, the mercury is distilled. The barium so obtained resembles calcium very closely, is apparently tough and ductile, and has a specific gravity of 3.75.-1 A, June 4, 243.

PURIFICATION OF TIN BY FILTRATION.

Curter has proposed an interesting method of freeing tin from less fusible metals by means of filtration. The filter was constructed as follows: Common tinned iron of ordinary thickness was cut into strips about 150 millimeters long by 100 wide. Five hundred of these, with their sur faces parallel, were wedged together in an oblong iron frame, and this frame was tightly fitted into an opening in the bottom of a large graphite crucible. The tin to be purified was then melted in another crucible, and allowed to cool until crystals began to form on its surface, when it was transferred to the above-described filter. Of course the heat sufficed to melt the tinning of the iron strips, thus leaving narrow spaces between them through which the molten metal could flow, its solid impurities remaining behind. More than fifty centners of impure Bohemian tin was thus rendered almost chemically pure, the iron, copper, and arsenic with which it. had been contaminated being left, alloyed with some of the tin itself, upon the filter.-14 C, March, 469.

THE ARTIFICIAL IMITATION OF NATIVE MAGNETIC PLATINUM.

It is known that occasional pieces of native platinum not only act upon the magnetic needle, but are themselves magnetic, like the true iron magnets. Berzelius and Kokscharof have contributed somewhat to our knowledge of the chemical and other properties of this platinum, and have shown that there is always a certain quantity of iron associated in

these specimens, so that Breithaupt has proposed for it the name of iron-platinum. The subject has recently undergone a very thorough study by Daubrée, who from his experiments upon the native material shows that the presence of iron in proper proportion suffices to account for the polarity of the native specimens. He still more firmly establishes his conclusions by artificially producing magnetic platinum, similar to that which occurs in nature. An alloy of 99 parts of iron and one of platinum, after a complete fusion, instead of becoming strongly magnetic, did not give any trace of polarity. Two other alloys, of 75 and 50 parts of iron respectively, behaved in very nearly the same manner. Alloys formed some time ago by Berthier, containing 78 parts of platinum and 21 of iron, although imperfectly melted, are, however, susceptible of magnetism. It appears, then, that however pronounced may be the magnetic power of the iron, the alloys where this metal predominates do not acquire polarity under the same conditions as do alloys obtained with a smaller quantity of iron. Thus an alloy of 17 parts of iron and 83 parts of platinum has very strong magnetic properties, so that we must admit that platinum alloyed with iron in proper proportions becomes exceptionally susceptible of acquiring the magnetic state. In nature this magnetic state would naturally be produced by strong induction, attributable to the magnetic forces of the globe; and Daubrée has therefore, as a last experiment, placed a small bar of the alloy during its fusion exactly in the plane of the magnetic meridian. As soon as it was solidified, it was inclined so as to be parallel to the inclination needle, until its cooling was complete, and it was then recognized that the bar actually presented at its two extremities very energetic magnetic poles, the upper end being the south pole of the needle, showing that the earth's magnetism had actually produced this effect. On heating the same bar to a red heat, and giving it the diametrically opposite position during its cooling, it was found that the magnetism of the bar was reversed by the earth's induction.-Bulletin Hebdomadaire, XVI., 40.

PRECIPITATION OF METALS BY ZINC.

Every chemist knows that when metallic zinc is placed in a solution of either copper or silver, the latter metal is pre

cipitated. J. L. Davies has found it to be possible to precipitate nickel in a similar manner, it being necessary, however, to render the nickel solution strongly ammoniacal. The zinc is used in the form of filings, and the nickel is thrown down distinctly metallic and in a weighable condition. The experiments were made with solutions of the sulphate and the chloride of nickel.-21 A, April, 311.

ABSORPTION OF HYDROGEN BY METALS.

Not long ago Troost and Hautefeuille announced that sodium, potassium, and palladium absorbed hydrogen to form alloys of definite composition. They now present the results of similar investigations with iron, cobalt, and nickel. These metals absorb hydrogen largely, but to different degrees under different circumstances, not forming genuine compounds. Thus an ingot of nickel under favorable conditions will absorb one fifth its volume of the gas. The same metal in an electrolytic film can be made to take up forty volumes, while pulverulent nickel can dissolve nearly one hundred times its bulk of hydrogen. With each of the three abovenamed metals the pulverulent or pyrophoric modification has the highest absorptive power, and the compact form the lowest. Finely divided iron was found to differ from cobalt and nickel in its power of decomposing water, a phenomenon which takes place slowly at ordinary temperatures, and rapidly at about 100° Centigrade. Iron thus resembles manganese more closely than either of the other metals. – 6 B, March 29, 788.

OZONE IN THE LIBYAN DESERT.

Professor Zittel, during a recent journey in the Libyan Desert in Egypt, made some observations of atmospheric ozone, from which it appears that the air over the desert is richer in ozone than that at the oases and the valley of the Nile, the ratios being as 73 to 48. The Libyan Desert, therefore, seems to be the richest in ozone of all portions of Europe. The ozone was observed to be always less in the daytime than in the night-greatest during clear weather and with northwest or west winds. Vegetation has been gener ally looked upon as an important source of ozone, whereas Ebermayer says that in all wooded regions the air in winter

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