A

II. Separation of Osmium and Ruthenium. The solution is placed in a glass retort of which the drawn out neck is fitted into the neck of a flask having a lateral tube, the central tube forming a hydraulic joint; such a flask is similar to the one used for the condensation of peroxide of ruthenium (Joly, "Encyclopædie Chimique de Frémy," vol. iii., No. 3, p. 236)). This flask is followed by two similar ones forming the condensing apparatus. They are all three plunged into iced water, and two-thirds filled with hydrochloric acid diluted with two volumes of water by grinding all the joints with emery, all loss of condensible vapours is prevented. The two first flasks will probably be sufficient, the third acts as a control. current of chlorine is passed through the retort, cold at first, then when the liquid commences to give off bubbles of oxygen, it is heated to about 70°. The osmium and ruthenium are transformed into volatile peroxides, OsO4 and RuO4, which condense in the flasks, the iridium into sesquichloride, which remains in the retort in solution, thanks to the excess of soda. The contents of the retort should remain alkaline until the end of the distillation, first on account of the action of hydrochloric acid on RuO4, and afterwards because the chlorine passing through the cold recipients, gives hydrate of chlorine which obstructs the tubes. (It is this hydrate that Joly must have mistaken for an emulsion of RuO4). If by chance the contents of the retort become acid, soda must be added. | The end of the operation can be determined by making sure that the drops, which distil over, do not blacken a solution of sulphuretted hydrogen.

Under the influence of hydrochloric acid, the peroxide, RuO4, is transformed into the sesquichloride, Ru2C16, which is stable; while the peroxide, OsO4, does not undergo any change. This reaction, commencing in the cold, ought to be completed by the action of heat. For this purpose the contents of the three flasks are placed together in a retort, connected with a system of three condensers similar to those in the preceding apparatus. The flasks are plunged into ice, they are filled up to two-thirds, the first with hydrochloric acid diluted with two volumes of water to arrest the incompletely transformed peroxide, RuO4; the two others are filled with a solution of soda at 12 per cent of NaOH, treated with 2 per cent of alcohol, to transform the peroxide, OsO4, into osmiate of sodium. The contents of the flask are heated to about 702, while passing a slow current of air. When no more peroxide of ruthenium distils over (the drops distilled should not colour hydrochloric acid brown), the contents of the first condensing flask are returned to the retort, and the flask is filled up to two-thirds with an alkaline alcoholic solution like that in the next two flasks. The distillation is then pushed to its completion; that is to say, until the drops no longer blacken sulphuretted hydrogen; as a rule, to obtain this result, it is necessary to distil half the contents of the retort. The osmium is then contained entirely in the condensing flasks, in the form of osmiate, and the ruthenium is in the retort in the form of sesquichloride; these two compounds not being volatile are easily determined in subsequent operations.

To make certain that the separation of the Os and Ru is complete we proceed in the following manner :-A solution containing OsO4 and RuO4 becomes brown under the influence of hydrochloric acid, owing to the formation of brown Ru2C16. A solution containing Ru2Cl6 and OsO4, treated with carbonate of baryta, freshly prepared and free from baryta, gives a precipitate of Ru203; the solution, freed from the chloride of barium formed by means of SO4 Na2, should not become violet in the presence of an alcoholic solution of soda (formation of violet osmiate).*

*We propose to substitute this method for the separation o' osmium and ruthenium for that of MM. Sainte-Claire Deville and Debray, adopted at first by M. Liedie, and which figures as his general method for the extraction and separation of the metals of the platinum group. (See above).

III. Separation of Iridium.

The contents of the retort from which the osmium and ruthenium have been driven in the first distillation, are acidulated with hydrochloric acid. The residue, insoluble in water, resulting from the attack of the osmide by Na2O2, is dissolved in hot dilute hydrochloric acid; this residue is easily soluble, while the other methods of attack (potash and nitrate of potash, for example) give a mass which is very difficult to dissolve, even with aqua regia. If any crystals of unattacked osmide are found, owing to their being insufficiently finely divided, they must be collected and subtracted from the original weight. The two solutions are united; the solution then contains all the iridium, as well as the iron in the ore, and the nickel from the crucible; it may contain traces of gold also, as well as rhodium and platinum, and any other foreign metal associated with the osmide, such as chromium, aluminium, silicon, manganese, copper, &c. The solution is heated, and to precipitate all the foreign metals, it is treated successively with nitrite of sodium and carbonate of sodium, following the instructions given by one of us à propos of the general method for the separation of the metals of the platinum group (Leidié, Comptes Rendus, vol cxxxi., p. 888; Bull. Soc. Chim., [3], vol. xxv., p. 9). Nothing remains in solution but the double nitrite of iridium and sodium; this is transformed into chloroiridiate by warm hydrochloric acid. Then, as the large amount of chloride of sodium present in the solution might be prejudicial, either to the precipitation of the chloroiridiate by chloride of ammonium, or to the precipitation of the iridium by magnesium, the cooled solution must be saturated with hydrochloric acid gas. The precipitated chloride of sodium tions, which only contain chloroiridiate of sodium with a is drained and washed with hydrochloric acid; the solulittle chloride of sodium, are added together.

IV. Estimation of the Metals.

Osmium. The contents of the flasks containing the osmiate of sodium are added together (if they are not decidedly violet they must be heated gently), and strips the metallic form, while the aluminium dissolves in the of aluminium are plunged in; the osmium is deposited in

soda. Care must be taken not to add too much aluminium at first, as the alumina formed, not finding a sufficient quantity of soda to enable it to go into solution, would precipitate an aluminate which is very difficultly soluble decolorised, the precipitated osmium, which is very dense, both in acids and in alkalis. When the solution is once aluminate of soda, and then with 5 per cent sulphuric acid is washed by decantation, first with water to remove the the iron accompanying this metal. to remove the remaining excess of aluminium, along with

with a filter-pump and well-washed; the filter must have been treated first with 20 per cent sulphuric acid, then washed, dried, calcined at a red heat, and weighed in a

This osmium is thrown on an asbestos filter connected

closed tube.

The osmium is dried in a bell-glass filled with hydrogen, then heated to dull redness, and cooled in a current of this gas; the hydrogen is only driven off by the carbonic acid when the whole has been cooled, as the latter gas oxidises the osmium when hot. The filter is weighed again in a closed tube.

As a check, the osmium may be driven off in the form of the peroxide, OsO4, by heating the filter to redness in a current of oxygen, and then weighing it again.

The

Ruthenium. The hydrochloric solution containing the sesquichloride, Ru2C16, is evaporated gently to a syrupy consistence, so as to drive off the excess of acid. residue is taken up with 50 or 60 c.c. of water, and a few fragments of magnesium added gradually; the solution becomes clear and takes a blue tint; this reaction is characteristic of ruthenium, and was wrongly attributed to osmium by Fischer, the latter being completely decolorised. The solution is then decanted, and the powder is washed with 5 per cent sulphuric acid, so as to remove the excess of magnesium. Throw on a filter, wash with water, dry,

July 3, 1903.

and after incinerating the filter at the lowest possible temperature, heat the whole in hydrogen to a red heat, then allow to cool in carbonic acid, and weigh.

Iridium. The solution containing the chloroiridiate of sodium is evaporated to drive off the large excess of hydrochloric acid present. The residue is taken up with water, and diluted to a volume of 500 c.c. From this we take 50 or 100 c.c., according to the probable proportion of iridium present, and add gradually some fragments of magnesium until it is completely decolorised. The powder is washed with 5 per cent sulphuric acid, then with water, and dried; after the incineration of the filter, it is heated to redness in hydrogen, cooled in a current of carbonic acid, and weighed.

In all these operations we use sulphuric acid rather than hydrochloric acid, which would dissolve a portion of the precious metal.

V.

Analyses conducted in this manner have been carried out on osmides from various sources. M. Riche, Directeur des Essais, at the Hôtel des Monnaies, has been good enough to supply us with osmides resulting from the operations to which gold is subjected during purification. In these osmides we have never met with any but the four following metals :-Iridium, osmium, ruthenium, and iron. On the other hand, in osmides from the residues from the treatment of the metals of the platinum group, we find traces of these latter metals, as well as the commoner ones

accompanying the ore; the separation of the precious metals is made then by the general method which has been given already by one of us (Leidié, see above).

It would seem thus to be well established, as MM. SainteClaire Deville and Debray were inclined to believe, that when osmide of iridium is perfectly freed from the metals of the platinum group with which it is often mixed; it does not contain any other metals than the four we have just mentioned above.

5

the sulphide of copper is transformed into binoxide or sulphate, and the whole of the iron into peroxide.

A

Then it is lixiviated methodically by means of a solution of sulphurous acid prepared in the ordinary manner. saturated solution of cuproso-cupric sulphite and sulphate of copper is obtained, containing at the same time a certain proportion of sulphite and sulphate of protoxide of iron. The sulphite of the sesquioxide of iron in the presence of an excess of sulphurous acid is transformed according to the reaction, SO2,Fe2O3 + SO2 = SO4Fe+ SO3Fe. The saturated solution of the salts of copper and iron is pumped into a copper boiler, where it is heated up to 180°, by which it is expected a pressure of 10 kilos. is produced. At this temperature the sulphite and the ferrous sulphate are completely insoluble, and are precipitated. As for the cuproso-cupric sulphite, it is dissociated and loses twothirds of its copper in the metallic state, and at the same time sulphate of copper is formed.

The cloudy liquid is forced by its own pressure through a filter-press heated by steam circulating round the plates, an apparatus I patented some time ago for the mechanical separation of cupric and ferrous sulphates, but which could be replaced by any other arrangement for the filtration of solutions at a high temperature.

In this manner we obtain a solution of sulphate of copper which can be cemented or treated for crystallised sulphate, and a precipitate containing metallic copper, and sulphite and sulphate of the protoxide. This precipitate is washed with pure water, which becomes saturated with sulphate of protoxide of iron, which may be extracted by crystallisation.

The residual sulphite is then oxidised by moist air, and gives sulphate of the protoxide, which can be eliminated by a fresh washing, and there remains finally metallic copper of great purity, which is melted and run into ingots.

3SO3Cu + CuO = SO3Ču2, SO3Cu + SO4Cu. Cuproso-cupric Sulphate sulphite.

of copper.

Cuproso-cupric sulphite is slightly soluble in water, but easily soluble in solutions of sulphurous acid or cupric sulphate.

On heating the solution to 180° (under a pressure of 10 kilogrms.) it loses sulphurous acid, while cupric sulphate and metallic copper are formed :—

(3). (SO3Cu2 + SO3Cu) = 2Cu + SO4Cu + SO2. If we group the formulæ 1, 2, and 3 together we see that, taken altogether, the reactions correspond to 4CuO +2SO2 =2Cu+2SO4Cu; that is to say, that half the copper can be obtained in the metallic state, and the other half in the form of sulphate.

On the above principles I have devised a process for the treatment of copper ores, utilising the sulphurous acid produced by roasting them in such a manner that the active reagents may be extracted entirely from the ore itself and from the atmosphere.

The ore is roasted in such a manner that the whole of

*A Paper read at the Fifth International Congress of Chemistry at Berlin. Section III.

INFLUENCE OF THE NATURE OF THE CATHODE ON THE QUANTITATIVE SEPARATION OF METALS BY ELECTROLYSIS.

By A. HOLLARD.

IN electrolytic analysis the metals are divided into two principal classes, according to whether they are or are not capable of being deposited on the cathode from a strongly acid solution. The metals which will not deposit in strongly acid solutions are those which require, for covering the cathode, electric tensions higher than the tension at which hydrogen commences to be given off. We see thus that, under the influence of these high tensions, a strongly acid solution (that is to say, a solution in which the proportion of H ions is very high) gives rise to a disengagemetallic precipitation becomes impossible thereon. ment of hydrogen at the cathode so abundant that all

The metals which are capable, on the other hand, of those which require for this precipitation, tensions lower depositing on the cathode in strongly acid solutions are than the tension of polarisation of hydrogen; their deposition therefore is not interfered with by the hydrogen.

If we call the tension of polarisation of hydrogen zero, we shall have the following values for the tension of polarisation of the principal metals (Nernst and Wilsmore, Zeit. f. Elektrochemie, November 8, 1900).

As can be seen, the classification of the metals into two groups, has for its basis the position occupied by hydrogen in the table of the tension of polarisation of the metals. But this position is only fixed in practice in electrolytic analysis if we always use platinum cathodes. As a matter of fact, hydrogen-as has been shown by Caspari (Zeit. fur Physik. Chem., 1899, vol. xxx., p. 89)-has a tension of polarisation which is variable with the metal constituting the cathode. If, therefore, we use, as we have done, cathodes formed of other metals than platinum,

NEWS

In fact, the tension of polarisation of lead (+015) is decidedly lower than that of hydrogen liberated on a lead cathode (+0.64); the same holds good with tin and cadmium.

As an example of the application of this new method of analytical separation, we will describe the separation of zinc and cadmium-metals that we have been unable to separate when using a platinum cathode,* on account of the closeness of their tensions of polarisation. On the other hand, we have been able to effect their separation with either a cadmium or tin cathode in a very acid bath. Our cadmium and tin cathodes were nothing more than platinum-gauze electrodes, covered electrolytically with cadmium or tin.

The cadmium and the zinc, brought into solution in the state of sulphates, were treated with 10 grms. of sulphate of ammonia and an excess of 5 c.c. of concentrated sulphuric acid. The solution, diluted to 300 c.c., was electrolysed with a current of o'3 ampère. The following results were obtained :

Experimental Results.
@Amount weighed.t

Cd deposited.

Grms.

It is conceivable, therefore, that, by the choice of a suitable metal for the cathode, we may succeed in separating two metals of the same group, of which the tensions of polarisations are too near together to enable us to separate by means of a platinum cathode. For this purpose it suffices to choose a metal for the cathode which gives hydrogen a tension of polarisation between those of the two metals to be separated. The element whose tension of polarisation is the lowest will be precipitated then alone in a strongly acid solution.

O'2000

2

0'0002

But it is not sufficient, however, to choose for the cathode a metal that has the property of raising the tension of polarisation of hydrogen above that of the metal to be precipitated, for this property of the metal constituting the cathode disappears at the moment it is covered by the precipitated element, and then the cathode plays the same part as if it were made exclusively of the metal precipitated. It is therefore necessary, further, for the continuation of the precipitation, that the latter metal also should have the property of raising the tension of polarisation of hydrogen above its own tension of polarisation.

By using cathodes formed of the same metal that it is proposed to deposit, we see from the preceding table that we can precipitate from strongly acid solutions, not only the metals of which the tensions, in Table I., are lower

PROCEEDINGS OF SOCIETIES.

CHEMICAL SOCIETY.

Ordinary Meeting, Wednesday, June 17th, 1903.

Prof. W. A. TILDEN, D.Sc., F.R.S., President, in the Chair.

MESSRS. E. S. Beaven and C. Rawson were formally admitted Fellows of the Society.

Certificates were read for the first time in favour of Messers. Percy W. Gent, 7924, Ridge Street, Newark, N.J., U.S.A.; Henry William Lawrence, Wellington, New Zealand; Herbert Stanley Redfern, B.Sc., Ningpo, China; Frank Gurney Smith, 7, Luxemburg Gardens, Brook Green, W.

PRESENTATION OF THE LONGSTAFF MEDAL. The PRESIDENT spoke as follows:-We have so recently celebrated the Centenary of the Atomic Theory that it is a matter of interest to notice that, in the award of the Longstaff Medal on the present occasion, we honour the practical fulfilment of the deductions from that great conception. Dalton himself represented in his diagrams atoms of solid bodies like ice arranged with reference to the crystalline form of the solid, but for three-quarters of a century

* Both in slightly acetic solutions and in cyanide solutions and no matter how small the current used.

The cadmium used in the first three experiments contained Pb=0'231 per cent, Fe=0'000 per cent, Zn=0'000 per cent. The cadmium used in the next three experiments contained:-Pb-0 245 per cent, Fe 0193 per cent, Zn=0'000 per cent. This amount of impurity

has been subtracted from the amounts actually weighed, and it is the

differences thus obtained that figure in the column "Amount weighed."

CHEMICAL NEWS, July 3, 1903.

7

Dr. Millar) to which Professor Pope had referred. Nevertheless, the name of the donor of the medal would have remained obscure except for the reflected light thrown on it, as it were, by the great names of an already long succession of eminent medallists.

To Professor William Jackson Pope the Council has awarded the Longstaff Medal by a unanimous vote, for his researches on the stereo-chemistry of compounds of elements other than carbon. In 1893, Professors Kipping and Pope prepared the d-bromo- and d-chlorocamphorsul. phonic acids, and by the use of these and other powerful optically-active acids, Mr. Pope has succeeded, not only in resolving into their active components certain racemic bases which had been found irresolvable by the use of tartaric acid, but in 1889, by the use of d-camphorsulphonic acid, he separated the dextro- and lævo-modifications of a synthetical tetralkylammonium base, and thus definitely established the existence of asymmetric optically active nitrogen compounds.

Since that time, by similar methods, he has obtained the dextrorotary methylethylthetine, a dextrorotatory tin compound, and both forms of a selenetine, thus demonstrating the fact that the elements nitrogen, sulphur, tin, and selenium are each capable, like carbon, of producing asymmetric combinations possessing optical activity. We therefore now possess direct experimental evidence in regard to the compounds of carbon, tin, sulphur, and selenium, as tetrad elements, and of nitrogen as a pentad, so that it may confidently be expected that not only will the phosphorus series of elements be found capable of producing pairs of enantiomorphous compounds, but, possibly, similar modifications of oxonium bases may be discovered, and some of the metals, such as platinum, cobalt, and chromium, may be found to exhibit similar phenomena. The doctrine of valency, no less than the doctrine of atoms, in its application to all ordinary terrestrial chemical phenomena, is thus triumphantly established.

Professor Pope, it gives me great pleasure to be the medium of communicating to you the congratulations of the Council, and in handing you the Longstaff Medal I express the feelings of the whole chemical world when I say that we trust you will have health, and strength, and time to continue the researches which have already yielded such a rich harvest of splendid results.

Professor POPE, in expressing his sense of the honour done him by the award of the Longstaff Medal, desired to acknowledge gratefully the assistance which the Research Fund Committee had given to his work; it would be difficult to over-estimate the extent to which the Research Fund of the Chemical Society has contributed to the encouragement of chemical investigation in Great Britain. He wished also to record his indebtedness to his old friend and teacher, Dr. H. E. Armstrong, who first taught him to look upon our science as a living and growing branch of knowledge, and inspired him with a desire to contribute something towards its development.

Dr. G. B. LONGSTAFF, in expressing his great pleasure at being present on this occasion, said that the researches for which Professor Pope had been awarded the medal considerably advanced our conceptions of the atomic theory in so far as they broke down some of the apparent barriers between carbon and the other elements. He recalled the fact that his father, who had been a friend of Dalton's, was not only a Fellow of this Society from its commencement, but also the founder of Chemical Societies in Edinburgh and Glasgow, and was, moreover, instrumental in placing

A ballot for the election of Fellows was held and the following were subsequently declared duly elected :Henry James Aubrey; George Barger, B.A., B.Sc.; Colin Bibby; Henry J. W. Brennand, B.A., M.B.; William Noel Bennett; Wilfrid W. O. Beveridge; Charles Drake Godsell Burghard; Ernest Bury, M.Sc.; Thomas Campbell; Albert James Carrier, B.Sc.; Edwin Jesse Fairhall; William George King; Henry Wolff Levy; John Howard William Hunter Gandy; Francis Gerald Harmer; Frank Linday; Charles Edwin L. Livesey, B.Sc.; John Christopher Mann; Alfred Ernest Moore, B.A., B.Sc.; Arthur Moore; George Marshall Norman, B.Sc.; George Harry Parry; Charles Stanley Purcell; Thomas Rhind, M.R.C.S.; Charles Joseph Smith; James Cruickshank Smith, B.Sc.; Dennis Tyrrell; Norbert Van Laer; Sydney H. Woolhouse, M.A., B.Sc.

*

Of the following papers those marked were read :THORPE. *96. "The Estimation of Arsenic in Fuel." By T. E.

An account was given of a method of estimating the amount of arsenic in fuels which is accurate, fairly rapid in execution, and which has the additional merit of directly distinguishing been the arsenic which is volatilised on burning the fuel and that which remains fixed in the ash. of the finely powdered coke or coal in a stream of oxygen, The process consists simply in burning a known quantity passing the products of combustion through a suitable absorbing apparatus, and determining the amount of arsenic so absorbed as well as that left in the ash.

The estimation of the arsenic in the solutions may be made by means of the Marsh apparatus and comparison with standard deposits of arsenic, or preferably with the electrolytic method described in the subsequent communication. The accuracy of the method was tested by burning fuels containing known quantities of arsenic, added in the form of arsenical pyrites.

*97. "The Electrolytic Estimation of Minute Quantities of Arsenic, more especially in Brewing Materials." By T. E. THOrpe.

An electrolytic method for detecting arsenic appears to have been first suggested by the late Prof. Bloxam (Quart. Journ. Chem. Soc., 1861, xiii., 12 and 338), but in its original form it had several disadvantages which have prevented it from being generally adopted by chemists. The process has been carefully investigated in the Government Laboratory, and in the form described in the present communication it is easy of application, and is capable of giving trustworthy results with a comparatively small expenditure of time and trouble.

The test may be applied to malt and malt substitutes, wort, hops, and hop substitutes, beer, yeast and yeast foods, finings, &c.

The advantages of the electrolytic method are :— 1. That it obviates the use of zinc.

2. It is simple in execution, is under perfect control, and may be carried out under such conditions that the results obtained by different operators are strictly comparable, inasmuch as with a current-strength of fair regularity the evolution of the gas is practically constant and uniform.

3. The whole of the solution to be tested for arsenic may be added to the apparatus at once, so that during the whole time of testing the arsenic is under the influence of the "nascent" hydrogen.

4. It has been established that such amounts of arsenic as are present in beer or its ingredients are evolved as hydrogen arsenide during the thirty minutes occupied by the test. The nature of the material associated with the arsenic is found to exercise no inhibiting effect on the