32 Chemical Notices from Foreign Sources. is, on the average, from forty to sixty minutes. With a set of ten vats of 6 cubic metres it is possible to lixiviate in fifteen hours 50 tons of 1000 kilos. each of fresh weed. The second stage of the operation consists in evaporating to dryness the successive saturated lyes, and then calcining very slightly in presence of a slight excess of carbonate of potash, carrying the process to the commencement of the aqueous fusion. This procedure yields a soda very rich in soluble salts, in utilisable salts of potash (chloride and sulphate), and in alkaline iodides. The incineration process gives, on an average, 15 per cent of potash salts, and I per cent, at the outside, of iodide. The new process yields 45 to 50 per cent of utilisable salts of potash, and 2, 3, or even 5 and 6 per cent of iodide if the weeds have been well selected. The residual weeds are still applicable in agriculture. Certain Experiments made with the Balance of Crookes.-M. G. Salet.-The author makes the discs of his radiometer of mica, and blackens both on the same side. He considers his results difficult to reconcile with the idea of a direct impulse due to light or to the ether, but contrary to the theory which seeks to explain the movements of the radiometer by the disengagement of gases condensed on the discs. Can the minimum quantity of gas which remains in an apparatus exhausted with such care suffice to occasion the movement, according to Tait's theory? Certain Derivatives of Normal Pyrotartaric Acid -M. Reboul.-A description of the salts of zinc, copper lead, silver, soda, and of the normal pyrotartrate of ethyl Volumetric Determination of Formic Acid.-MM. Portes and Ruyssen.-The authors remark that the quantitative determination of formic acid in acetic acid has a certain importance in solving the problem of the deter mination of wood-spirit in spirit of wine. They pour into a flask containing 5 grms. acetate of soda 25 c.c. of a solution at 10 per cent of the mixture in question, and add 200 c.c. of a solution of sublimate at 4'5 per cent (9 grms.). It is heated from one hour to an hour and a half in the water-bath until the supernatant liquid has become perfectly limpid. The whole is then made up to the volume of 500 c.c. and filtered. It is then ascertained, by means of a graduated burette, how much of the reduced liquid is required to saturate 1 grm. of potassium iodide. The number found by calculation must be corrected by the addition of one-fourth. Arragonite observed on the Surface of a Meteorite. -J. Lawence Smith.-Arragonite has been found as an incrustation on certain specimens of meteoric iron from the so-called Mexican Desert (Bolson de Mapini), situate in the provinces of Cohahuila and Chihuahua. The author is of opinion that the incrustation has been formed since the fall of the meteorite. Compounds of Carbon Found in Meteorites.-J. Lawrence Smith.-The author has pursued his studies on the crystalline hydrocarbides derived from terrestrial irons and doubtful meteorites, like that of Ovifak, searching for hydrocarbides in the carbon combined with these irons. That of Ovifak contains a notable proportion of this carbon. There was in these irons a substance similar to that already found in meteoric graphite and carboniferous meteorites. It has the same strong odour, and crystallises n small needles. If heated on platinum-foil it melts readily, and at higher temperatures it burns with a flame, and disappears. Use of Calcium Chloride in Watering the Paths of Promenades and Public Gardens.-M. A. Houzeau. The nature of this paper may be understood from its title. Experimental Researches on the Action of Aniline Introduced into the Blood and the Stomach.-MM. V. Feltz and E. Ritter.-The authors describe the symptons produced, both in men and dogs, by small doses of magenta. It is fortunate for them that they are not resident in England. A Differential Radiometer.-M. W. de Fonvielle.The author has had constructed a radiometer, the discs of which (of mica) are coated on both sides with lampblack, and the case is blackened in the same manner over half its surface. If the light is received perpendicular to the diametral section which separates the transparent hemisphere from the darkened hemisphere the apparatus remains motionless. If, on the contrary, the diametric plane is inclined to the left, the left-hand discs, more strongly illuminated than those on the right, are repelled more energetically, and the radiometer takes a regular movement from left to right. The same phenomenon is observed in the inverse direction if the diametric plane is inclined to the right. The rotation is the most rapid possible when the diametric plane is rendered parallel to the rays of light which illuminate ths apparatus. Researches on Cypressus Pyramidalis.-M. Hartsen. Les Mondes, Revue Hebdomadaire des Sciences, The Radiometer of Mr. Crookes.-Since the commencement of the century much attention has been paid to the electric, magnetic, and mechanical action of light. The author in the third volume of his " Repertoire d'Optique" has analysed at length the experiments made by Sommerville, Barlocci, Valt, Zantedeschi, Matteucci, Faraday, Davy, Moleyns, &c. Valt alone (p. 1011) obtained under the action of light the orientation, if not the rotation, of suspended discs, all other attempts having led to negative results. If M. Récamier caused his discs to revolve under the influence of light under closed bells, it was certainly because he set in action gaseous currents. Mr. Crookes obtains indefinite rotations with extreme facility. His experiments, which constitute one of the most brilliant discoveries of the age, engage all minds, and are like an enigma on which no one has yet given the final decision. It is time for the Academy of Sciences to elect a commission to study these phenomena from all sides. MISCELLANEOUS. Death of Dr. Hearder.-The Plymouth correspondent of the Pall Mall Gazette telegraphs on the 17th inst.,Dr. Jonathan Hearder died last evening from a sudden paralytic seizure. He was the last remaining of the group of men who made Plymouth famous for scientific discoveries forty years ago. Dr. Hearder's researches in science, especially in connection with electricity and chemistry, were not extensive, but profound. He had made his name well known among the leading physicists not only of England but Europe and America. Almost at the outset of his scientific career an accident befell him, which, in the case of a less determined lover of knowledge, would have put an end to reseach. While experimenting with a fulminating compound he was deprived of sight by an explosion. Yet his chief honours were won after that event. He was intimately associated with Sir William Snow in his electrical researches. His own discoveries and inventions in connection with the induction coil and the therapeutic appliance of electricity were many and valuable. Dr. Hearder was one of the earliest to perceive that a telegraphic cable across the Atlantic was not only important, but practicable, and he invented a cable for which he took out a patent, a slight modification of which was ultimately adopted for Atlantic telegraphing. Dr. Hearder had a marvellous memory, and was never at a loss for a connected with local antiquities and history. The bent of fact or a date. He was a zealous lover of all matters Dr. Hearder's mind was quite as practical as it was investigative. He invented special forms of stoves, gas and other, and was a specialist in the matter of fishing gear. He not only contrived medical electric apparatus, but practised as a medical electrician, and was electrician to the South Devon Hospital. CHEMICAL NEWS, July 28, 1876. } Development of the Chemical Arts. THE CHEMICAL VOL. XXXIV. No. 870. NEWS. INFUSORIA AND NITRATES. SOME very interesting observations regarding the reduction of nitrates by bacteria have recently been made by M. Meusel. It has been long believed that the nitrites found in waters are due to the oxidation of ammonia, but the author just named has proved in a satisfactory manner that they are not necessarily so produced. Water containing no compound of nitrogen except some alkaline nitrate was found after a certain time to contain no nitrites: this reduction was the effect of numerous bacteria visible in the microscope. It was stopped at once by phenol, salicylic acid, benzoic acid, alum, and salt. The following experiment shows under what circumstances this phenomenon occurs : A little pure water, containing some bacteria, has an alkaline nitrate added to it. At first there is no reduction, but after the addition of certain organic substances, more especially carbohydrates, such as sugar, &c., nitrites are produced at once and rapidly. Recently distilled water, mixed with sugar and a little alkaline nitrate, then boiled in a long-necked flask, the end of which is closed during ebullition, showed no reduction after many weeks. The conclusions drawn from these experiments areThat the nitrites found in ordinary waters are due to bacteria; that the latter are the agents of the transmission of oxygen, even when this substance is combined, and that this is probably the reason they are so dangerous to rendered immovable. REPORT ON THE 33 DEVELOPMENT OF THE CHEMICAL ARTS By Dr. A. W. HOFMANN. Chlorine, Bromine, Iodine, and Fluorine. By Dr. E. MYLIUS, of Ludwigshafen. Regeneration of Manganese according to Weldon.-Recently Weldon has completely succeeded in attaining the object aimed at by so many. C. Binks and J. Macquent had previously sought to revivify the chloride by precipitating it with the quantity of hot milk of lime needful for decomposition, passing a current of hot air through the liquid, and utilising the precipitate thus converted into higher oxides in place of fresh manganese. But Weldon was the first who succeeded in making the process technically applicable. His most essential improvement consists in the point that he uses not a sufficient quantity of milk of lime, but an excess. Considering the importance which Weldon's process for the regeneration of manganese has already attained in the modern manufacture of chlorine, since its commercial value is fully proved by its introduction in many establishments, especially in England, it may be considered permissible to describe its principles at greater length than the procedures already mentioned. The following account is founded partly on Mr. Weldon's paper in the CHEMICAL NEWS (vol. xxii., p. 145), and partly on his letter to Dr. A. W. Hofmann, dated March 12th, 1874. Now M. Meusel has also asserted that nitrates are useful as manure, not only by the nitrogen they contain, but on account of the oxygen they supply to bacteria, which enables the latter to destroy cellulose, &c. If this is the case, it would appear, at first sight, that nitrate of soda would prove a more valuable manure than sulphate of ammonia. But not long since I applied sulphate of ammonia and nitrate of soda to two small plots of the same pasture land in such quantities as to supply the same amount of nitrogen in each case. 8 cwts. of nitrate of soda, and 64 cwts. of sulphate of ammonia were used in this experiment, and the result was as nearly as possible identical in both cases. As with the bacteria, when either substance was applied in excess the grass was killed, and turned brown or yellow within three days. When applied in the most favourable proportions the yield in both cases was almost identical. Now 6 cwts. of sulphate of ammonia supplied no available oxygen, whilst the 8 cwts. of nitrate of soda supplied about 1 cwts. of oxygen, the quantity of nitrogen being the same. Yet there was no apparent result for this difference of oxygen. Now, if M. Cloëz's theory is true, that C, H, and N are assimilated by plants as CO2, HO, and NO5, and that NH3 in the soil or the manure becomes NO5 to be assimilated, then the atmosphere would have supplied to the sulphate of ammonia the extra 1 cwts. of oxygen in question. This, of course, would require rather more time, and such, in fact, was the case in my experiments, the nitrate being the quickest of the two by about eight days. Laboratory of Analytical Chemistry, Whilst, according to Weldon, hydrated manganous oxide diffused in water can be only oxidised to manganic oxide, Mn2O3, by forcing oxygen through the paste, it is possible, in the presence of lime or magnesia in excess, to convert the whole of the manganese into peroxide. The latter remains united with the lime as a compound, CaO, MnO2, or CaMnO3, calcium manganite. This may be regarded either as an analogue of the hydrated peroxide of manganese, or as manganic oxide, Mn2O3, in which an atom of manganese is replaced by lime. Hence it follows that I mol. calcium manganite requires exactly as much hydrochloric acid in the preparation of chlorine as I mol. of Mn2O3. Nevertheless it is advantageous to oxidise the manganous oxide with the aid of lime, since, in the first place, the same amount of manganese performs double the duty as if it had been only converted into manganic oxide; and, secondly, the oxidation is effected with far greater ease in presence of an excess of lime. This is probably because manganous oxide is somewhat soluble in pure water or in solution of calcium chloride, and thus retards the oxidation. At least it has been experimentally proved that salts of manganese decidedly retard the progress of oxidation. If, on the other hand, there is an excess of lime, a brown solution of calcium manganite is rapidly formed, which, as experiments prove, greatly accelerates the absorption of oxygen by the deposit of manganous oxide. Latterly, however, it has been found possible to complete the oxidation of the manganese by an increased current of air along with a diminished dose of lime. Under these circumstances we may assume the formation of an acid manganite, CaMnO3,H2MnO3. In fact, in exceptionally successful operations, calcium manganite has been obtained in which only 1 mol. of lime was present to 2 mols. of peroxide of manganese. In most cases the manganese paste has the following composition: 0.80 MnO2, "Berichte über die Entwickelung der Chemischen Industrie Während des Letzten Jahrzenends." + Technologiste, 1862, Sept. 27. Wagner, Jahresberichte, 1862, 237. 34 Erythrogen and some of its Compounds. That the lime in the paste is chemically combined, and does not exist as a mere admixture, may be inferred because the product is perfectly neutral, and because lime cannot be withdrawn from it by a solution of sugar. The manganous oxide can also be oxidised by air when the lime is replaced by baryta, strontia, or soda. On a practical scale the process is carried out as follows:-The manganese liquor from the chlorine stills is let off into tanks provided with agitators. In these it is treated with finely-divided carbonate of lime, to neutralise the free acid and to throw down any iron which may be present as oxide. The liquid is then pumped off into settling-vats, in which it is left to become clear. Hence the clear neutral solution is run into the oxidiser-an iron cylinder, 3.66 metres in diameter and 6.61 in height. Into this, near the bottom, opens a narrow pipe which conveys steam, and one or more wider air-pipes. After the liquid has been heated to 55°-75° by a current of steam, milk of lime, prepared from finely-sifted hydrate of lime, is run in as rapidly as possible, whilst air is simultaneously forced in until no manganese can be detected in the filtrate. This occurs when not only all the manganese is converted into manganous oxide, but when an excess of hydrate of lime is already present. For this purpose 115 to 145 mols. lime are required to 1 mol. manganese. To be continued.) When cold pour off the naphtha, and having wiped the surface of the amalgam with a dry cloth, transfer it as quickly as possible to a dry stoppered bottle, and add to it a quantity of bisulphuret of carbon equal to about three times the weight of the potassium employed; then shake the whole well together until the mixture becomes solid, when it must be set aside for a few hours to cool and complete the combination. After this, the surplus bisulphuret of carbon is to be driven off by a current of air, and the erythride of potassium separated from the mercury by water and filtration in the usual way. But it is worthy of notice that a part of the mercury, under the influence of the potassium, is converted into erythride of mercury at the same time, and this holds out a hope that such metals as lead and antimony in a very minute state of subdivision may be useful in purifying coal-gas from bisulphuret of carbon; and, in fact, I am now actually trying the pyrophoric mixture of lead and charcoal formed by heating the tartrate of lead, and it seems to promise well. When the hydro-erythric acid is thrown down by acids from the solution of erythride of potassium, much of it is decomposed in carbonic acid and sulphuretted hydrogen, except at a very low temperature; but in either case it forms a fixed, chocolate-red, granular powder, most remarkably like selenium. Sandy, Bedfordshire, July 22, 1876. ERYTHROGEN AND SOME OF ITS COMPOUNDS. By LEWIS THOMPSON. WHEN We look at the vast extent of our gas-making industry, and the number of persons interested in keeping up an artificial cry about the "sulphur in gas," we may well wonder that so little has yet been done to remove the ex aggerated defect. But this display of inventive poverty is not altogether without its value, for it teaches us, beyond the possibility of doubt, that Governmental interference with any manufacturing industry is not a rapid road to improvement. About twenty-nine years ago I first became aware of the fact that such articles as liquor ammonia and carbonate of ammonia, when made direct from gas-liquor, always contained more or less of a peculiar red substance, which contaminated the ammoniacal products, and rendered them unfit for use in silk dyeing and some other arts; and a careful examination convinced me that this red matter ON THE AMALGAMATION OF IRON AND OF SOME OTHER METALS.* By P. CASAMAJOR. Ar the last meeting of this Society I was to speak to you on amalgation of iron, but was prevented by the lateness of the hour from reading the paper I had ready for you. Since that evening I have learned a great many things about iron amalgam, one of which is that most of the Processes that I was to describe had already been published, although in a very succinct form, about nineteen years ago. This discovery would have prevented me from appearing before you to-night if I had not found that the subject is deemed by chemists, to whom I have shown samples of amalgamated iron, to be not only new, but very interesting. I have, besides, much new matter to communicate, among which is a new process for amalgamating iron, which is so simple and economical that all the other processes are rendered obsolete and useless. That iron will combine with mercury is known to all was not sulphocyanide of iron, but had some mysterious chemists, although it is not deemed an easy operation, connection with bisulphuret of carbon. I have often sepa- and we may find in the books several processes for accomrated this red matter from gas-liquor, and also from gas-plishing the combination. One of these, which I believe lime refuse, and both shown and given it to several of my friends, but it has always been so mixed with other im purities that no decisive opinion could be formed regarding it, except the mysterious connection above alluded to. The mystery, however, appears to admit of solution if we suppose the bisulphuret of carbon to be a halogen body like cyanogen, and therefore capable of uniting directly with metals; a supposition which I have carried out into practice by combining it to potassium, with which it forms a compound remarkable for the blood-red colour of its solutions in water and alcohol, and therefore I propose to give the name Erythrogen (from "Erythros," red) to the bisulphuret of carbon in its combinations, and HydroErythric Acid to the acid set free from the solution of the erythride of potassium by an acid. Not to trouble your readers with any superfluous remarks, I will describe in as few words as possible the mode of making the erythride of potassium, from which the hydro-erythric acid and other compounds may be produced by the usual chemical processes. To make erythride of potassium, we must begin by making an amalgam of potassium, consisting of about I part by weight of potassium and 150 of mercury, which I easily done by fusing them together under naphtha. is due to Sir Humphry Davy, consists in immersing sodium amalgam in a saturated solution of ferrous is brought in contact with iron filings, in presence of a solution of ferric chloride. The filings become coated with chloride or sulphate. In another process zinc amalgam mercury. In still another process, the electrolysis of ferrous sulphate gives iron amalgam when the negative electrode is formed of mercury. By subjecting the re pretty firm consistency is obtained, which is composed of about equal parts of iron and mercury. sulting amalgam to enormous pressures a residuum of The processes of amalgamation which I am to describe to you this evening give products which have nothing in common with these iron amalgams. The samples of iron amalgam, such as I have here, are obtained from commercial wrought-iron, from cast-iron, and from steel, without altering the original shape of the material, a are analogous to the amalgam made from commercial zinc which we use in voltaic batteries. Before giving you the results of my labours I must give you a succinct account of the researches of Cailletet, * Read before the American Chemical Society, June 1st, 187 Communicated by the Author. Amalgamation of Iron and Other Metals. CHEMICAL NEWS, July 28, 1876. which came to my knowledge as follows:-Before pre- | senting myself before you at the last regular meeting it had been my endeavour to ascertain whether the results I was to announce were really new. Neither by my own exertions nor by inquiry from other chemists had I been able to discover that I had been forestalled, and had I confined my attention to iron I would not have been aware-perhaps even now-of the existence of a prior claimant. Having turned my attention to aluminium, I had occasion to consult Watts's "Dictionary of Chemistry," on the subject of aluminium amalgam, and came upon the following:-"According to Cailletet (Comptes Rendus, vol. xliv., p. 1250, aluminium (also iron and platinum) may be superficially amalgamated by contact with ammonium or sodium amalgam and water; also when it is immersed in acidulated water in contact with metallic mercury, forming the negative electrode of a voltaic battery." On consulting the 44th volume of the Comptes Rendus I found, at p. 1250, a memoir presented to the Academy of Sciences by Messrs. Chevreul and Dumas, at the sitting of June 15th, 1857, the title of which is "On the Influence of Nascent Hydrogen on Amalgamation," by M. L. Cailletet. The author uses ammonium amalgam, with which he agitates pieces of iron, aluminium, or platinum, and he finds that these metals become coated with mercury. The amalgam of sodium produces the same effect, only water is necessary to the reaction. If the surface of the sodium amalgam is covered with naphtha no action takes place, but one drop of water is sufficient to produce the desired effect. If in a vessel containing mercury and acidulated water we place the electrodes of a battery, and if the negative electrode be a piece of sheet iron in contact with mercury, the iron will be amalgamated as soon as hydrogen appears on this electrode. From these experiments Cailletet concludes that amalgamation in these cases is due to nascent hydrogen, and he seems throughout his memoir to be so intent upon proving this point that every other circumstance is mentioned in the most cursory manner. We may be allowed to doubt whether by covering sodium amalgam with naphtha, so that when iron comes in contact with the amalgam it is already covered with a film of naphtha, we have placed the iron in the best condition to combine it with mercury, and whether the non-combination under these circumstances is very conclusive of the necessity of nascent hydrogen to determine the combination between iron and mercury. The following experiment with a mercuric salt carries more weight with it:-The author wishes to show that amalgamation, in the case of iron and platinum, is due to nascent hydrogen, and not to the electrical condition of the iron or platinum electrode. He takes the case of the electrolysis of salts of copper, silver, and mercury, and recalls that at the negative electrode we obtain metallic copper, silver, and mercury, but no hydrogen. If we have a salt of mercury subjected to a voltaic current, the negative electrode being made of iron or platinum, we may notice after a while that globules of mercury appear on this electrode, but they show no tendency to combine with it. If, now, the electrodes are withdrawn from the mercury salt, and placed in a vessel holding acidulated water, as soon as the voltaic current passes and hydrogen escapes at the negative electrode the globules of mercury spread on this electrode, and it becomes amalgamated. The above account of the memoir presented by Cailletet contains substantially everything there is in it. The circumstance mentioned in "Watts's Dictionary," that the amalgamation obtained on iron and platinum is merely superficial, does not appear, even by implication, in the original paper. Amalgam of sodium and ammonium, and the voltaic battery: these are the agents mentioned by Cailletet; these were also the agents that I used a month ago to de 35 termine the combination of iron with mercury. Although I now use a much simpler and a cheaper process, which I propose to describe in a few minutes, there are some points in connection with the alkaline amalgams and with the action of the voltaic current which may be studied with advantage. Amalgam of potassium, which I first used for amalgamating iron, behaves in every way like amalgam of sodium. Sodium, however, behaves somewhat differently from potassium towards mercury, the combination with sodium taking place with greater violence, being accompanied by a flash of sodium light and the escape of alkaline vapours which are far from agreeable. These unpleasant manifestations may be reduced to a minimum by combining sodium at first with a very small quantity of mercury-a quantity not more than a fifth of the weight of the sodium. This gives rise to a violent reaction, but subsequent additions of mercury produce less and less effect, while, by bringing small pieces of sodium successively into a comparatively large mass of mercury, every fresh piece of sodium produces the same effect as its predecessor. If the sodium amalgam has sodium enough in it to make it pasty, it will cover iron with a silvery coat. This coat may be rubbed off, leaving the oxidised surface unaltered. If brought in contact with water, or, still better, with a solution of sal-ammoniac, the sodium amalgam is decomposed and the mercury will sink into the iron. If the sodium amalgam is liquid it will adhere in little drops all over the surface of a piece of iron shaken up in it; by the action of water, of acids, or of sal-ammoniac, the droplets will spread on the iron, which will become amalgamated. Ammonium amalgam will give up its mercury to iron when rubbed up with it very persistently. Even then there are in every piece of iron certain spots where the mercury will not adhere. The intervention of acidulated water, by decomposing ammonium amalgam with great energy, facilitates the amalgamation of iron in these difficult portions. From the foregoing remarks you will understand that the maximum of good effect may be obtained from a certain amount of sodium by the following method of procedure, while the combination of iron with mercury is very thorough and rapid :-We take four porcelain dishes and place them in a row, so that the piece of iron to be amalgamated may be placed successively in each. The first dish contains a liquid sodium amalgam; the second a solution of sal-ammoniac; the third water, acidulated with either sulphuric or hydrochloric acid; and the fourth aqueduct water. The piece of iron to be amalgamated is taken up with tongs, and agitated in contact with the sodium amalgam of the first dish. This operation covers it with liquid mercury containing sodium amalgam. When the surface seems sufficiently coated the iron is left for a few seconds in the solution of sal-ammoniac, on emerging from which it is found covered with the curious and interesting compound which we call ammonium amalgam. The piece of iron is placed next in the acidulated water, and finally in aqueduct water, to wash off the acid. This series of operations is generally sufficient to leave a good coat of mercury on a piece of iron. If there should be spots left bare, a second series of immersions is generally sufficient to leave the surface perfectly covered. I need not say that the surface of the iron must be previously made clean by immersion in diluted acid. By making the negative electrode of a voltaic battery of iron, and placing it in contact with mercury and with acidulated water, the iron will, after a time, become amalgamated. I have obtained the same result by a single voltaic element, the positive plate of which is a piece of zinc and the negative plate a piece of iron, one portion of which is in contact with mercury at the bottom of the cup, the exciting fluid being acidulated water. addition of chloride of sodium to the liquid in the cup seems to hasten the reaction. An 36 Measuring Air in Mines. Iron may be amalgamated also by the use of zinc amalgam. This process gives the best results, and renders superfluous all the other processes we have mentioned. The use of zinc amalgam for the purpose had been attempted before, as, for instance, in the process I have mentioned where iron filings are rubbed with zinc amalgam in presence of a solution of ferric chloride, the reaction being assisted by heat. I also find in "Watts's Dictionary" that, "according to Aikin, iron amalgam is formed by the action of zinc amalgam on ferrous chloride." No particulars are given about this process, but the results must have been, to say the least, difficult to obtain, as we find, immediately af er that, "according to Damour, it cannot be obtained in this way." I came upon the process I am about to describe by a mere chance. I was trying to test the soundness of the theory of Cailletet, which attributes the amalgamation of iron to the presence of nascent hydrogen. In a beaker glass I had placed mercury, and over it acidulated water, and also a horse-shoe nail of Norway iron, which rested on the mercury. A moderate escape of hydrogen took place from the surface of the iron nail; but after twentyfour hours no trace of amalgamation had appeared, which showed very conclusively that unassisted nascent hydrogen was certainly not sufficient to do the work. Having to amalgamate a small piece of zinc for another experiment, I found that I had no other mercury within my reach than the one on which the nail of Norway iron rested. As I had given up hopes of accomplishing any thing by this arrangement, I had no scruple to use the mercury in this beaker glass, and in it I placed my piece of zinc: the result was that the escape of hydrogen from the nail increased very perceptibly, which circumstance induced me to leave the zinc in the mercury. On looking again at the iron nail I found it amalgamated and partly sunk into the mercury. To amalgamate iron with zinc amalgam, mercury should be placed in a vessel and covered with dilute sulphuric or hydrochloric acid. If, now, a piece of iron is agitated, in contact with the mercury and the acid, no combination will take place; but if pieces of zinc are placed in the mercury, in a few minutes iron placed in the above conditions will become coated with mercury. If after a while the power of the mercury seems to decline, more zinc must be added. The zinc is only attacked when iron, or some other metal more electro-negative than zinc, is brought in contact with the zinc amalgam and the acid, so that the expense in zinc is very slight. The coat of mercury left on iron by the various agencies I have mentioned is not a superficial layer, for the mercury sinks into the metal, modifying its physical and chemical properties. In the case of pure soft iron it is difficult to notice any decrease of tenacity after amalgamation. With hard-tempered steel, however, the increased brittleness is very marked. In the case both of iron and steel a fresh fracture shows that mercury has penetrated deeply into the metal. Of the chemical change operated on iron by amalgamation I can call attention to only one point, which is the analogy which exists with the properties of zinc amalgam. When a piece of zinc* has been amalgamated it is not attacked by acids as readily as zinc free from mercury; but if a piece of amalgamated zinc is connected to a piece not amalgamated, the amalgamated zinc becomes the positive plate in a voltaic couple. These properties of amalgamated zinc are found, although in a less degree, in amalgamated iron. Two pieces of sheet iron, presenting exactly the same surface, were placed in diluted sulphuric acid, so that the action of the acid was exactly the same on each. One of these plates was amalgamated, the other not. After prolonging the action for over two hours, it was found that the amalgamated plate had lost two-thirds as much in weight as the other. * This observation relates to impure zinc. Amalgamation makes impure zinc behave towards acids like pure zinc. CHEMICAL NEWS, If, however, two pieces of iron-one amalgamated and the other not-are connected by a metallic wire, the amalgamated plate is attacked, and the other plate plays the part of a negative. In iron amalgam, made in the way I have described, the quantity of mercury in combination is very small. A piece of sheet iron, presenting on both sides a total surface of 3 square inches, was amalgamated and left to soak in mercury for over an hour. The mercury was then wiped off very thoroughly, and the piece of sheet-iron weighed. The increase over the original weight was 13 centigrammes, which showed an absorption of mercury equal to a little over 4 centigrammes per square inch. The increase of weight in this thin sheet of iron was only 3 per cent. Still in this sheet the fracture was silvery, and globules of mercury stood on the rough edge of the fracture. For the sake of comparison I treated a piece of sheet zinc, of the same dimensions, in the same manner, leaving it, however, only a few minutes in contact with mercury. After rubbing off the excess of mercury, and weighing, I was surprised to find a loss instead of a gain in weight. This was doubtless due to a certain quantity of zinc being dissolved by the mercury. I must now, to fulfil the programme offered by the title of this paper, speak to you of the amalgamation of some other metals, by which are meant some of those whose point of fusion is very high, and which have always shown themselves exceedingly adverse to combining with mercury. Those that I have tried are platinum, palladium, aluminium, nickel, and cobalt. Except in the case of aluminium there seems nothing of peculiar interest to notice about their amalgams, after what has been said of iron amalgam. These metals all take mercury very readily by the processes which are effective in the case of iron. Aluminium deserves mention on account of its eccentric behaviour: it seems to take mercury in the same manner as the other metals, but shortly after being taken out and dried it becomes very hot, the mercury seems to boil, and the aluminium remains covered with a chalky crust. On brushing this off, the metal is found beneath without a sign of amalgamation. In conclusion, I will point out that two inquiries suggest themselves in connection with these amalgams. One relates to the determining cause of these combinations, and the other is whether these amalgams-particularly amalgam of iron-can be applied to useful purposes. To both these questions the answer is, that I have nothing satisfactory to offer, although great many things suggest themselves as plausible. I am sure you will readily excuse me from presenting theories that are merely plausible, as to the cause of these phenomena, and feel equally certain that I need offer no apology to this enlightened auditory for calling their attention to these combinations of mercury with iron and other metals, because these have not yet become of practical utility, although it may be befitting to offer an apology for the manner in which the task has been performed. ON MEASURING AIR IN MINES.† WITH such a wide choice of anemometers, let it not however, be supposed that there is no difficulty in ascertaining the true average velocity of some air currents. It is only when the current is regular that implicit reliance may be placed upon such instruments. In an intermitting current the pulsations are shown plainly enough by either the counterpoised fan-plate of the Dickinson anemometer or the pendant of other similar instruments, and This is more easily noticed with steel than with pure soft iron. t A Paper read before the Manchester Geological Society. |