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18th.-Society of Arts, 8. (Cantor Lectures.) "The History
of the Art of Coach Building," by Mr. G. A. Thrupp
Lecture V.--Rules of Coach-building, and Theories
applicable to the Carriages of the Future.
Medical, 8.

London Institution, 5.

TUESDAY, 19th.-Civil Engineers, 8.


WEDNESDAY, 20th.-Society of Arts, 8. "The Centennial Exhibition,
Philadephia, 1876,” by Prof. Archer.
Geological, 8.
Meteorological, 7.

THURSDAY, 21st.- Royal, 8.30.

Chemical, 8. Philosophical Club, 6.30. 22nd.-Quekett Club, 8.


A. de Noé Walker.-Apply to Messrs. Brooke, Simpson, and Spiller stating the purpose for which it is wanted. E. Bevan. Send us an account of the analysis when you have made it.



Second Edition, in One Large 8vo. Volume of 550 pages, strongly
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Price 215.

develops electricity, which acts upon the disks by attrac-
tion in the direction of the electricity evolved. (2) This
instrument being at rest, I poured upon it ether, and saw
immediately the disks hover, turn slightly, and soon stop.
The cause of this phenomenon is the same, the electricity
produced by evaporation-a fact well known to science.
(3) These facts (1 and 2) being incontestable, let us pro-
duce some analogous facts with the radiometer. (a) I
placed the radiometer in a part of the room so dark that
it did not turn. I then poured ether upon the covering,
and immediately the radiometer began to turn somewhat
quickly, but in a direction contrary to that which it takes
when exposed to the light. After having turned thus for
a few moments it stops, and resumes its former state of FRIDAY,
repose. According to the experiments 1 and 2 must not
this fact be ascribed to electric action? (b) M. Ducretet
has observed the change in the direction of the radiometer
when drenched with ether; let us do the same. Whilst
the radiometer is in motion, and turning from right to left,
let us pour a little ether upon it; we then see the radio-
meter change its direction, and turn from left to right.
After a few moments it stops, and finally resumes its nor-
mal course from right to left. Are we not to ascribe this
change of direction to an electric action? The experiment
of M. Govi, showing that the watery vapour circulating
round the radiometer gives it an accelerated motion,
which ceases in course of time, does it not show electricity
in action? The new facts observed above (1, 2, and 3),
should they not be attributed to electric action? Yet we
are still very far from believing that the experiment has
furnished us with sufficient data to arrive at a complete
explanation of the phenomena of the radiometer. (4) We
constructed a radiometer, in which three platinum wires,
sealed into the glass covering, support each at its interior
end a small copper disk. Two of the disks are vertical,
but one (to the left of the author's diagram) is horizontal.
With this instrument I experimer.ted as follows:-I placed
a lighted candle near this radiometer; it turned then from
the left to the right. I put out the light, and when the
radiometer was at rest I applied the current of a battery
of 3 or 4 elements to a small Ruhmkorff coil. The ends
of the fine wire of this coil were applied, the one to the
exterior end of the platinum wire to the left, and the other
to that at the right, the positive pole being connected with
the left hand, when the radiometer turned in the same di-
rection as above. If, whilst the radiometer was turning
under the influence of the electric current, a lighted candle
was brought near, the speed of the rotation increased con-
siderably, a proof that the two actions took place in the
same direction. We then placed the outer ends of the
two platinum wires sealed in the glass in connection with


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including an account of the most recent improvements in the Use and Manufacture of Aniline Colours.

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a galvanometer whilst the radiometer was turning under PATENTS.-Mr. Vaughan, F.C.S., British

the influence of a gas-jet. The needle of the galvanometer did not remain at rest, but described an angle of 5°. If the poles are inverted the radiometer stops. If the positive pole of the battery is brought near the exterior either of

the base or the summit of the instrument it stops. The author expresses his intention of explaining these results in a future paper.

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castoreum, membranous bag and all, down her lovely F. W. HART, Manufacturer and Dealer in

Apparatus and Chemicals for Scientific Pursuits. Latora. infant's throat, under the impression that it was a "very tory Fitter and Furnisher. Photographic Apparatus and Materials safe aperient."

8, KINGSLAND GREEN West Side), London.

Dec. 22, 1876.

Repulsion Resulting from Radiation.


VOL. XXXIV. No. 891.




ground perfectly flat. a, c, c', and c" can therefore be NEWS. sealed up by cementing flat transparent plates of glass, quartz, rock-salt, &c., a, d, d', d' on to them. At right angles to a b, and at the parts e, e', upright tubes, fe, f'e', are sealed, one of them having an arm (g) blown into it for the purpose of attaching the apparatus to the pump. h, i, h', i' are glass beams made as light as possible consistent with the necessary stiffness. jk, j' k' are glass fibres (103) cemented at j, j' to pieces of glass rod, and terminating at k, k' with a stirrup cut from aluminium foil, in which the glass beams h, i, h', i' rest. In front of these stirrups are thin glass mirrors (k, k'). At the ends of the beam (h, i) are cemented very thin pieces of blackened pith, each 1 centim. square; and at the ends of the other beam (h', i') are cemented pieces of platinum foil, also I centim. square. At land l' are narrow slits, with lamps behind them, so arranged that they send their rays of light respectively on to the mirrors (k, k'), whence they are reflected back to the divided scale m. When the torsion beams are not acted on by any force, the rays of light both meet at zero (m), and there overlap, the

(Concluded from p. 254).

115. IT has already been said that when radiation falls on a thin surface of pith, the neutral point is low, whilst with a moderately thick piece of platinum it is generally high. I have constructed a double torsion apparatus by means of which these actions can be easily studied. Fig. 10 shows the arrangement of apparatus. It consists of a

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torsion apparatus constructed as the one shown in fig. 7 (102), with the exception of the arms being double. Similar parts in each drawing are shown by similar letters. a b is a piece of thin glass tubing, sealed off at the end b, and ground perfectly flat at the end a. In the centre a circular hole (c") is blown, and two others are blown at the parts c and c'; the edges of these holes are also

A Paper communicated to the Royal Society, March 20, 1875. From the Philosophical Transactions o the Royal Society o London, vol. clxv., pt. 2.

slightest movement of either beam causing them to separate.

When the apparatus is full of air, a beam of radiation sufficiently wide to cover the whole window (c") being thrown upon the plates 1, h', the latter are instantly attracted, as shown by the movement of the reflected rays of light (k m, k' m). On exhausting the tube, and trying the effect of a hot body at the central window from time to time, it is seen that the movement of the pith surface (i) gradually diminishes, until at a certain point of ex


Repulsion Resulting from Radiation.

haustion (in this apparatas at about 50 millims. below a vacuum) the neutral point for pith is obtained. On increasing the rarefaction the pith is repelled by radiation, the platinum continuing to be attracted. On exhausting the air still further (to about 28 millims.) the neutral point for the platinum surface is obtained, higher rarefactions producing repulsion of each when radiation falls on the pith and platinum surfaces (i, h').

At a rarefaction intermediate between the neutral point for pith (50 millims.) and the neutral point for platinum (28 millims.), the curious effect is produced of the same beam of radiation thrown into the window (c") producing repulsion of the pith and attraction of the platinum, the two rays of light (k m, k' m) each moving to the right, and, if a piece of ice is presented to the central window, to the left. By adjusting the internal tension of the apparatus, a point may be reached (about 40 millims. below a vacuum) at which the repulsion of pith and the attraction of platinum are exactly equal, and then the two rays meeting at m do not separate, but together move to the right or left.

116. A series of experiments have been tried with a view to ascertain what influence the state of surface of the substance submitted to radiation has on the amount A torsion apparatus or the direction of its movement.

was prepared similar to the one shown in fig. 7 (102), and having a thin disk of ivory at each end. One was coated with lampblack, whilst the other retained its white polished surface. The average of a number of experiments showed that, under the influence of the same source of radiation acting for the same time (15 seconds), the white ivory was repelled so as to send the luminous index 415 divisions of the scale, whilst the blackened ivory caused the index to move 46.8 divisions. These experiments were, however, tried in 1873, when I had not succeeded in getting anything like the delicacy I now obtain in the apparatus; and I propose to repeat them under varied conditions before employing the results to found any arguments upon.

117. In my former paper on this subject (74, 75, 76, 77, 78) Í have discussed various explanations which may be given of attraction and repulsion resulting from radiation; and in a lecture delivered before the Physical Society I entered more fully into the same arguments. The most obvious explanation is that the movements are due to the currents formed in the residual gas, which, theoretically, must be present to some extent even in those vacua which are most nearly absolute.

Another possible explanation is that the movements are due to electricity developed on the moving body, or on the glass apparatus, by the incident radiation.

A third explanation has been put forward by Professor Osborne Reynolds, in a paper which was read before the Referring to the Royal Society on June 18th, 1874. results of my experiments, Prof. Reynolds says that it is the object of his paper to prove that these effects are the result of evaporation and condensation. In my exhausted tubes he assumes the presence of aqueous vapour, and then argues as follows:-" When the radiated heat from a the lamp falls on the pith, its temperature will rise, and

pith from the lamp. The evaporation will be greatest on
that ball which is nearest to the lamp; therefore this |
ball will be driven away until the force on the other
becomes equal, after which the balls will come to rest,
On the other
unless momentum carries them further.
hand, when a piece of ice is brought near, the tempera-
ture of the pith will be reduced, and it will condense the
vapour and be drawn towards the ice."

It is not my intention to recapitulate the arguments I have already brought forward against these three explanations. They are all fully given in my above-quoted lecture before the Physical Society. I shall, however,

The torsion apparatus with ivory terminals was exhibited in action at the meeting of the Royal Society, Dec. 11, 1873. June 20, 1874 (Phil. Mag., August, 1871).

Dec. 22, 1876.

adduce a few experiments which have been devised
specially with the view of putting one or other of these
In giving what 1 conceive to be
theories to the test.
reasonable arguments against the explanations which
have already been proposed, I do not, however, wish to
insist upon any theory of my own to take their place.
Any theory will account for some facts; but only the true
explanation will satisfy all the conditions of the problem,
and this cannot be said of either of the theories I have
already discussed.

118. The pendulum apparatus, described and figured
in paragraph 99, was specially devised to bear upon the
air-current and the electrical theory. On referring to the
description of the experiments tried with it (Tables I.
and II.), it is seen that in air the ignited spiral produced
attraction, whilst in a vacuum the same source of radia-
tion gave strong repulsion. Now the effect of raising a
platinum spiral to whiteness in the air would be to rarefy
the air all round, and the suddenness of its ignition would
cause the air to be driven from it, as a centre, on all sides.
Hence I was prepared to find that the pendulum would
be mechanically blown on one side by what might be
likened to a miniature explosion of heated gas. But the
action was always one of attraction, whilst, when there
was no air at all present to be expanded and driven away
by the hot platinum, the action was one of violent repul-
sion. A possible explanation of the attraction in air in
this experiment may be given by assuming that the
pendulum was driven inwards by the rush of cold air
supplying the place of that rising upwards from the hot
spiral; but it is not likely that this action should so com-
pletely overcome the effect of expansive action; and,
moreover, it will only account for half the phenomenon
(that in air), and leaves the still stronger action in a
vacuum entirely unexplained."






119. I have tried special experiments to put the aircurrent theory to a decisive test. Bulb tubes (84) and torsion apparatus (102) have been prepared, containing terminals of metal, ivory, glass, mica, or pith, in the form of thin flat surfaces. These surfaces have been placed at an angle with the plane passing through the index and suspending thread in such a manner that the action of heat would be to cause currents and drive them round like the vane of a windmill. I, however, found the action of heat in vacuo to be repulsion, and in air to be attraction; and the latter was even strong enough to overcome the action of the air-currents, which could not fail to be developed under the circumstances of the experiment.


Dec. 22,

Physical and Chemical Properties of Ruthenium.

120. The pendulum apparatus has also been used to show that electricity is not the cause of the attraction and repulsion. On referring to the description (99) it is seen that the mass of magnesium forming the weight was in metallic contact with the platinum wire which supported it, and that the upper end of this platinum wire was fused into the glass tube, and passed thence to the outside. With this I have tried numerous experiments bearing on the action of electricity. I have connected the projecting end of the platinum wire with "earth," with either pole of an induction-coil (the other pole being more or less insulated), with either pole of a voltaic battery, and with a delicate electroscope; I have charged it with an electrophorus, and have submitted it to the most varied electrical conditions; and still, on allowing radiation to fall on the suspended mass, I invariably obtain attraction in air and repulsion in a vacuum. The heat has been applied from the outside, so as to pass through the glass, and also inside by means of the ignited spiral; and the results show no difference in kind, but only in degree, under electrical excitement. I often obtain troublesome electrical interference with the usual phenomena, but never of such a character as would lead me to imagine that the normal results were due to electricity. I also obtain the normal actions whether the apparatus has been standing insulated in the air, or whether it has been completely immersed in water connected electrically with "earth" or surrounded with wet blotting-paper.

121. The following experiment was suggested by Mr. Cromwell F. Varley, F.R.S., who informs me that he considers the results conclusive against the electrical theory. A torsion apparatus was prepared, as shown in fig. 11. The inside of the tube (a b) is lined with a cylinder of copper gauze, having holes cut in the centre (c) for the passage of the supporting thread (d c) and the index ray of light, and holes at each end to admit of the plates (e, f) being experimented with. A hole drilled in the plate (b) allows a wire to pass from the copper gauze to the outside, so as to give me electrical access to the gauze lining. Under the most diverse electrical conditions, whether insulated or connected with "earth," this apparatus behaves normally when heated; neither can I detect any electricity when the plate e or ƒ is under the influence of radiation if I connect the wire g with a delicate electroscope. In experimenting with this apparatus I have also completely immersed it in liquids, such as water, solutions of metallic salts, ether, disulphide of carbon, &c. The heat has been applied in these cases by introducing a glass bulb containing water at different temperatures and a thermometer (28). Under all these varied circumstances the movements took place in a regular manner, and no electrical action whatever could be detected.

122. I have already discussed Prof. Osborne Reynolds's theory of evaporation and condensation somewhat fully in the already quoted Physical Society paper.* I will, however, describe the following experiments, which I think prove that Prof. Reynolds has not suggested a theory which accounts for all the facts of the case, and therefore has not hit upon the true explanation.

A thick and strong bulb was blown at the end of a piece of very difficultly fusible green glass, specially made for steam-boiler gauges. In it was supported a thin bar of aluminium at the end of a long platinum wire. The upper end of the wire was passed through the top of the tube and well sealed in for electrical purposes (120). The apparatus was sealed by fusion to the Sprengel pump, and exhaustion was kept going on for two days, until an induction spark refused to pass across the vacuum. During this time the bulb and its contents were several times raised to a dull red heat. At the end of two days' exhaustion the tube was found to behave in the same manner as, but in a stronger degree than, it would in a less perfectly exhausted apparatus, viz., it was repelled by light and heat of low intensity and attracted by cold.

Loc. cit.; also CHEMICAL NEWs, July 17, 1874.


A similar experiment was next tried, only water was placed in the bulb before exhaustion. The water was then boiled away in vacuo, and the exhaustion continued, with frequent heating of the apparatus to dull redness, for about forty-eight hours. At the end of this time the bar of aluminium was found to behave exactly the same as the one in the former experiment, being repelled by radiation. Similar experiments, attended with similar results, were tried with a platinum and with a glass index; and instead of water, iodine has been put into the bulb to begin with.

It is impossible to conceive that in these experiments sufficient condensable gas or vapour was present to produce the effects Prof. Osborne Reynolds ascribes to it. After the repeated heating to redness at the highest attainable exhaustion, it is difficult to imagine that sufficient vapour or gas should condense on the movable index to be instantly driven off by a ray of light or even the warmth of the finger with recoil enough to drive backwards a heavy piece of metal.

123. It seems to me that a strong argument against Prof. Reynolds's theory (and also against the electrical and air-current theories) may be drawn from the fact that the repulsion in a vacuum is not confined to those red and ultra-red rays of the spectrum which mainly produce dilatation of mercury in a thermometer, excite an electrical current between antimony and bismuth couples, and cause a sensation of warmth when falling on the skin, but that any ray from the ultra-red to the ultra-violet will produce a similar effect. It cannot be reasonably argued that a ray of light, filtered through plates of glass and alum (109), can instantly vapourise a film of moisture or condensable gas from a surface on which it is caused to shine, or that it can produce air-currents in the almost perfect vacuum surrounding the surface shone upon, or that it will produce electrical excitement on such a surface. 124, Facts tested and verified by numerous experiments, but scarcely more than touched upon in the present paper, are, I think, gradually shaping themselves in order, in my mind, and will, I hope, aid me in evolving a theory which will account for all the phenomena. But I wish to avoid giving any theory on the subject until I have accumulated a sufficient number of these facts. The facts will then tell their own tale; the conditions under which they invariably occur will give the laws; and the theory will follow without much difficulty. In the eloquent words of Sir Humphry Davy, "When I consider the variety of theories which may be formed on the slender foundation of one or two facts, I am convinced that it is the business of the true philosopher to avoid them altogether. It is more laborious to accumulate facts than to reason concerning them; but one good experiment is of more value than the ingenuity of a brain like Newton's."




RUTHENIUM, if heated in oxygen, is not transformed, like osmium, into a product volatile at 100°, but yields an oxide, RuO2, which does not sublime appreciably unless heated to bright redness. To obtain the hyper-ruthenic acid (RuO4) of Claus, the analogue of osmic acid (9s04), it is necessary to attack ruthenium, well purified from osmium, with a mixture of nitre and potassa. It is thus converted into an orange-yellow soluble rutheniate, and the solution of this salt, saturated with chlorine and distilled in the water-bath in a current of this gas, yields volatile hyper-ruthenic acid, which condenses in goldcoloured globules or crystals. The ruthenium employed in the further experiments of the authors was obtained by


Physical and Chemical Properties of Ruthenium.

the reduction of this acid, and consequently cannot con- |
tain any trace of the other metals of the platinum group.
A solution of hyper-ruthenic acid in potassa, treated
with alcohol, gives oxide of ruthenium, which is reduced
to a metallic state by coal-gas at a temperature slightly
elevated. The metal is afterwards alloyed in a crucible of
charcoal made in a retort, purified by chlorine, with five
or six times its weight of pure tin. The ingot, treated
with boiling muriatic acid, which dissolves the excess of
tin, leaves an alloy of ruthenium and of tin crystallised in
cubes, having the planes of a rhomboidal dodecahedron
(angles at 90° and 135°), and containing equal equivalents
of tin and ruthenium. We grind it finely in a glass mor-
tar, and it is introduced into a small boat of purified
charcoal, which is strongly heated in a porcelain tube
traversed by a current of dry and pure muriatic gas until
the matter no longer loses weight. The tin is volatilised
entirely in the state of protochloride, and we recover, with-
out any loss, the weight of the ruthenium upon which we
have operated, but it is transformed into a crystalline
matter. We obtained for the density of this matter the
following numbers :-

Weight in the air at 21° and 760 m.m...
Loss of weight in water at 21°
Density at zero ..

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74 2490 grm.

6.0265 grm.


We admit in all these calculations the coefficients of dilatation published by M. Fizeau in the Annuaire du Bureau des Longitudes.

The determination of pulverulent matters like ruthenium requires minute precautions, without which we dot not obtain accordant numbers, even if we operate on one and the same substance. But we cannot describe here in detail the apparatus which we were obliged to employ to moisten completely the matter, and not to leave in the interior of the powder any trace of gas, and to avoid other causes of error.

When hyper-ruthenic acid is prepared by passing chlorine into a concentrated solution of the orange rutheniate of potassa, there is a moment when the liquor becomes deep green, and is filled with small black crystals. If we decant at this moment we may isolate the crystals, purify them from their mother-liquor and from chloride of potassium by a rapid washing, and finally dry them, first on unglazed porcelain, then in a vacuum over caustic potash and lime. These crystals have very brilliant planes, which are orthorhombic octahedra, derived from a prism of 117°. They are isomorphous with permanganate of potassa. The solution of this salt is a deep greenish black, like the salt itself. It decomposes very rapidly into oxide of ruthenium, which is deposited, and into orange rutheniate of potassa. Hyper-ruthenic acid, RuO4, does not seem able to combine with bases. If a fragment of it is dropped into solution of potassa it is dissolved very slowly, disengaging oxygen, and producing the deep green salt with which we are now engaged. This salt is composed of―

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The salt, if weighed in a platinum boat placed in a glass tube, and gently heated in a current of hydrogen, takes fire, disengaging much water. If we replace hydrogen by carbonic acid a fresh quantity of water distils. If this water is collected in a chloride of calcium tube, and its weight determined, we may deduce the quantity of oxygen contained in the acid of the salt. There remains in the boat a mixture of ruthenium and of carbonate of potassa, which is weighed with the usual precautions, and which is separated with the greatest facility. Chlorine decomposes the new salt, Ru207,KO, or Ru2O8K, taking possession of the potassium, and giving even at a common tem

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perature hyper-ruthenic acid, Ru2Os, in vapour, without sensibly disengaging oxygen.

On this property is founded another method of analysis, which we have tried, and which gave results corresponding with those cited above. Conforming to the nomenclature adopted by M. Fremy when he discovered osmious acid, and respecting as much as possible the nomenclature of Claus, we shall propose to call

Ruthenous Acid, RuO3, giving with potassa yelloworange solutions.

Hepta-ruthenic Acid, Ru2O7, giving with potash a black salt, of which the solution is deep green. Finally, Hyper-ruthenic Acid, the acid RuO4 of Claus, which does not combine with potassa, and of which the characteristic property is to be volatile, to possess even below 100° a considerable vapour-tension, and to decompose with explosion at 108°, as we have unhappily learnt at the expense of our stock of ruthenium. Analysis of Ruthenium and its Alloys.-Though the purity of the ruthenium employed in our researches was guaranteed by its method of preparation, we have nevertheless analysed it. We shall describe in detail the method used for this analysis, which is suitable, as well for pure ruthenium as for its alloys. We attack 0'5 grm. of ruthenium with a mixture of 5 grms. potassa and 2 grms. pure nitre in a gold crucible, and heat to redness. The metal disappears entirely, yielding a limpid liquid, which we dissolve in water after solidification and cooling. The crucible is washed with pure hypochlorite of soda, and the whole liquid transferred to a distillatory vessel of glass consisting of a balloon with a ground stopper, and fitted with two tubes blown to the balloon, one of which serves to introduce a current of chlorine into the liquid, and the other serves for the exit of the vapours disengaged, and conducts them into another balloon containing a solution of potassa. The ruthenite of potassa is first saturated with chlorine; the solution, at first orange, becomes a blackish green and then a golden yellow, because there are formed successively hepta-rutheniate, KO,Ru207, and hyper-ruthenic acid. We heated then the balloon in the water-bath to 80°, continuing to pass a slow current of chlorine. Yellow globules or crystals of hyper-ruthenic acid are condensed in the tube which connects the balloon of the receiver, and were gradually carried into the alkaline liquid. With 30 grms. of potassa in the receiver we are sure not to let hyper-ruthenic acid escape, if the current of chlorine is not intense enough completely to saturate the potassa. Nevertheless, we adapt to the receiver an abducting tube plunging into alcohol, which would arrest the least traces of hyper-ruthenic acid, and convert them into chloride of ruthenium. It must be noted that neither corks, nor especially caoutchouc, can serve to close or to connect the different pieces of this apparatus.

We must not expect to distil all the rutheniumin a single operation. We let the liquid of the balloon cool, we render it alkaline by adding a few pieces of potassa, and we recommence the preceding operation by putting into the receiver a fresh solution of potassa. If the liquid is no longer coloured, at first green then orange-yellow, on the first contact with alcohol, this is a proof that the distillation no longer gives hyper-ruthenic acid: the operation is then terminated.

To withdraw ruthenium from the alkaline solutions where it is condensed, we add to these a small quantity of alcohol; the greenish liquor becomes orange-yellow, then turbid, and deposits even in the cold oxide of ruthenium, retaining a little alkali, which is carried off by washing first with water, afterwards with a dilute solution of sal-ammoniac, and finally with pure water. The filter upon which we received the oxide of ruthenium is introduced into a counterpoised boat of porcelain, which is itself placed in a larger capsule covered with a funnel, by the tube of which coalgas is caused to enter. When the air has been expelled from the funnel we heat the capsule on a gas-furnace at a temperature not exceeding 500°; the oxide of ruthenium is reduced at first, and the paper is carbonised. We then

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