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Let us return to Falkland-to our martyr of sweetness and light, of lucidity of mind and largeness of temper. Let us bid him farewell, not with compassion for him and not with excuses, but in confidence and pride. Slowly, very slowly, his ideal of lucidity of mind and largeness of temper conquers; but it conquers. In the end it will prevail, only we must have patience. The day will come when this nation shall be renewed by it. But O lime-trees of Tew, and quiet Oxfordshire field-banks where the first violets are even now raising their heads-how often, ere that day arrive for Englishmen, shall your renewal be seen!

MATTHEW Arnold.

RECENT SCIENCE.

(PROFESSOR HUXLEY has kindly read, and aided the Editor with his advice upon, the following article.)

THERE has been of late much lament in this country over the dearth of original research in chemistry, and German chemists have been often pointed to as model investigators. From Professor Kolbe's article, however, entitled 'Zeichen der Zeit,' published in a recent number of the Journal für praktische Chemie, we find that Germany is not without the warnings of a chemical Cassandra. If the younger men continue to indulge in philosophical speculation instead of applying themselves to solid work, the Leipzig Professor foresees the decadence of German chemistry. Professor Kolbe points to France as the country where real chemical research is at present being actively carried on, and this leads us to inquire what substantial additions to our knowledge have recently been made by French chemists. Among these additions we may perhaps single out the discovery of a new metal as sufficiently interesting to form the subject of our first note. It is true the existence of this metal was first made known many months ago, but it is only recently that we have been put in possession of full details respecting the preparation and properties of the element and the characters of several of its compounds.'

It was on the 27th of August, 1875, that M. Lecoq de Boisbaudron obtained the first indication of the existence of a new element in a substance on which he was then experimenting. The discovery can hardly be called accidental, for he had laboured for years in the hope of adding to our list of elementary bodies, and, after repeated failures, had decided to operate on very large quantities of raw material in order to detect the presence of any substances which might exist in only extremely minute proportion. He accordingly worked upon 52 kilograms (115 lbs. avoirdupois) of zinc blende, or sulphide of zinc, from Pierrefitte in the Vallée d'Argèles in the Pyrenees, and was ultimately rewarded by the discovery of the metal which he has

Sur un nouveau métal, le Gallium.' Par M. Lecoq de Boisbaudron. Annales de Chimie et de Physique, January 1877, p. 100.

patriotically called Gallium. Spectrum analysis, which had been so fruitful in previous discoveries of a like character, was the agent that first revealed the existence of this new element. To show the marvellous subtlety of our modern methods of research, we may say that the drop of liquid in which gallium was first detected did not contain more than the one-hundredth of a milligram of the metal. Other minerals were examined in the hope of finding a more prolific source of gallium, and the blende of Bensberg on the Rhine turned out to be much richer than that of Pierefitte. A yellow translucent blende from the Asturias also contained a notable proportion, but all the other minerals in which it was detected are excessively poor. Although the metal is thus seen to be rather widely distributed, it has hitherto been found only in extremely small quantity. In fact, 430 kilograms (948 lbs.) of blende have yielded not more than one gram of gallium, and of this quantity only 65 centigrams have yet been obtained in a free state. All experiments upon this precious material have therefore been performed under the disadvantage of dealing with excessively limited resources.

Without following the tedious processes of extracting and purifying the metal, we may remark that gallium in its purest condition is a malleable metal, exhibiting a grey-white colour and a brilliant lustre, but becoming tarnished in moist air by superficial oxidation. It has a remarkably low fusing-point (30-15° C.)—so low, indeed, that the metal is readily melted by the mere warmth of the hand. When completely fused, the silver-white globules may be preserved in a liquid state for some weeks, even at temperatures sinking nearly to zero. At a red heat in air the metal is not volatilised, but merely suffers superficial oxidation. Its mean specific gravity is 5·935; in other words, it is nearly six times as heavy as water, bulk for bulk. Cold nitric acid does not appear to attack it, but hydrochloric acid freely dissolves it; and it is also soluble in solution of caustic potash, with disengagement of hydrogen. The combining weight has not yet been definitely determined, but several compounds of the metal have been prepared, including the chloride and sulphate. A gallium-alum has likewise been obtained in a crystallised condition, which shows that it is isomorphous with the ordinary alums. It is a double sulphate of ammonium and gallium, in which the gallium therefore appears to play the part of aluminium. The combining capacity of the new element seems thus to be determined, and we shall probably not far err in assuming that the chloride of gallium is represented by the formula GaCl, and the oxide by Ga,O,. It is supposed that only one oxide exists.

When compounds of gallium are strongly heated, and the light emitted is examined in the spectroscope, it is seen that the spectrum is extremely simple, consisting, in fact, of two violet lines, one of

which, distinguished as Ga a, is very strongly defined and eminently characteristic. We may remind the reader that gallium is the fifth metal which has been discovered by the modern method of spectrum analysis. In 1860 Profs. Bunsen and Kirchhoff discovered casium, and in 1861 the closely related metal rubidium, both occurring in the mineral waters of Dürkheim in Rhenish Bavaria. Mr. Crookes, in 1861, discovered thallium in the residue from a sulphuric-acid chamber in the Hartz where seleniferous iron pyrites had been used; and in 1863 Profs. Reich and Richter proved the existence of indium in the zinc blende of Freiberg in Saxony. And we have just seen that in 1875 M. Lecoq de Boisbaudron announced the existence of gallium in certain kinds of blende from the Pyrenees. The discoveries have been divided, it will be observed, between Germany, England, and France-Germany, however, taking the honour of finding three out of the five new metals.

Considerable interest naturally attaches to all researches on the rarer metals, and we therefore gladly call attention to a valuable investigation on the atomic weight of the metal glucinum, recently undertaken by Dr. Emerson Reynolds, of Dublin.2 This metal has but a very limited distribution in nature, existing only in some halfdozen rare minerals, of which the best known is the emerald. But emeralds in quantity are scarcely within reach of the ordinary chemist, and consequently it is not often that we hear of the preparation of glucinum. There are, however, certain coarse varieties of emerald, utterly useless for the purpose of the jeweller, which enjoy a much wider distribution than the more precious varieties, and which are found even in the British Isles, especially in the north-west of Ireland. All these are alumino-glucinic silicates. The coarser and less finely coloured varieties pass under the name of beryl, and hence the metal glucinum is likewise known as beryllium. The Irish beryls occur in the form of opaque green prismatic crystals, shooting through the granite rocks of the Gwebarra Mountains in county Donegal, and are also found more sparsely distributed through the granite of the Mourne Mountains in county Down. Possessing these beryls, it occurred to Dr. Reynolds that the Irish chemists ought to improve the opportunity, and he accordingly set to work some years ago to collect the necessary raw material. this way he managed to accumulate 3 kilograms (about 6 lbs.) of dressed beryl, from which he prepared 350 grams (about 5,400 grains) of pure glucinic oxide. By acting upon this oxide with chlorine at a red heat, in the presence of finely divided carbon, a

In

2. On Glucinum; its Atomic Weight and Specific Heat.' By J. Emerson Reynolds, M.D. Philosophical Magazine (Taylor & Francis), January 1877, p. 38.

chloride of glucinum was obtained, and from this chloride the metal was ultimately reduced by the action of sodium; the process being indeed very similar to that employed in the preparation of the wellknown metal aluminium. Having in this way obtained a small coherent mass of metallic glucinum, Dr. Reynolds proceeded to employ it in the attempt to determine the atomic weight of this element. The chemical equivalent of a body is necessarily obtained by direct experiment, but its atomic weight is determined by a variety of considerations familiar enough to chemists. Admitting 4.6 to be the equivalent of glucinum, the question remains whether the atomic weight is a multiple of this equivalent by 2 or by 3whether it is 9.2 or 13.8. If the latter, the only known oxide of glucinum must resemble alumina; if the former, it must resemble magnesia. Each view has its supporters, and as there are chemical difficulties involved in seeking a decision Dr. Reynolds resorted to a well-known physical aid.

It was long ago shown by the eminent French physicists, Dulong and Petit, and afterwards confirmed by Regnault, that an interesting relation might be traced between the specific heat of a body and its atomic weight. If equal weights of different substances be taken, it is found that they require very different quantities of heat in order to raise their temperature to the same extent; each kind of matter has, in fact, its own specific heat. But if, instead of taking equal weights of the different elements, we take quantities in proportion to their several atomic weights, then it is found that the application of the same quantity of heat produces in all an equal rise of temperature. If the atomic weight be high, the specific heat is low; if the atomic weight is low, the specific heat is high. In other words, the specific heat multiplied into the atomic weight gives a constant quantity, and to this product we apply the term atomic heat. It is true there appear to be many exceptions to this law, but the exceptions are growing fewer and fewer as our researches become more refined. In seeking to determine the atomic weight of glucinum, Dr. Reynolds has availed himself of Dulong and Petit's law. The first step was to determine the specific heat of glucinum, and this he effected by means of a calorimeter not unlike the ingenious little instrument devised by Bunsen about six years ago. Some preliminary experiments with silver as a standard substance gave Dr. Reynolds the number 6.157 as the atomic heat of silver. Using this as a constant, and dividing it by the specific heat of glucinum, determined experimentally, it is clear that the quotient will give approximately the atomic weight of glucinum. In this way he found the atomic weight to be 9.2. This investigation serves to illustrate the way in which the chemist is frequently driven to seek aid from the researches of the physicist.

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