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CHEMICAL NEWB, Experimental Contributions to the Theory of the Radiometer.

radiometer, it follows that, other things being equal, the fly should revolve faster in a small bulb than in a large one. This cannot well be tested with two different radiometers, as the weight of the fly and the amount of friction would not be the same in each, but I have constructed a double radiometer which shows this fact in a very satisfactory manner. It consists of two bulbs, one large and the other small, blown together so as to have a wide passage between them. In the centre of each bulb is a cup, held in its place by a glass rod, and in the bulbs is a small four-armed fly with roasted mica disks blacked on one side. The fly can be balanced on either cup. In the smaller bulb there is about a quarter of an inch between the vanes and the glass, whilst in the larger cup there is a space of half an inch. The mean of several experiments shows that in the small bulb the fly rotates about 50 per cent faster than in the large bulb, when exposed to the same source of light.

One of the arms of another radiometer was furnished with roasted mica disks blacked on alternate sides. The other arm was furnished with clear mica disks. The two arms were pivoted independently of each other, and one of them was furnished with a minute fragment of iron, so that by means of a magnet I could bring the arms in contact, the black sur face of the mica then having a clear plate of mica in front of it. On bringing a lighted candle near the instrument, and allowing it to shine through the clear plate, on the blackened mica, the clear plate is at once driven away, till the arm sets at right angles to the other.

Two currents of force, acting in opposite directions, can exist in the same bulb. I have prepared a double radiometer in which two flys are pivoted one over the other, and having their blackened sides turned in opposite directions. On bringing a lighted candle near, the flys rapidly rotate in opposite directions.

Experiment shows that the force can be reflected from a plane surface in such a manner as to change its direction. If an ordinary radiometer is exposed to light the black surface is repelled, owing to the excess of pressure acting between it and the glass. If, however, a plate of mica were to arrest this force and reflect it back again, the motion should be reversed. Experiment shows that this is the case. A two disk radiometer was made, having fat opaque mica disks blacked on one side. In front of the black surface of the mica and about a millimetre off, is fixed a large disk of thin clear mica. On bringing a candle near, the molecular pressure streaming from the black surface is caught by the clear plate and thrown back again, causing pressure behind instead of in front, and the result is rapid rotation in the negative direction, the black side now moving towards the light.


| spiral, then drawing it out corkscrew fashion, blacking the upper surface and suspending it on a point, a spiral radiometer is made, which rotates like a screw on exposure to light. Here also the black surface need never be in darkness, the pressure acting continuously between the black side of the spiral and the cylindrical tube in which it is mounted.

The experiments with the double radiometer of different sizes showed that the nearer the absorbing surface was to the glass, the greater was the pressure produced. To test this point in a more accurate manner, a torsion balance was fitted up with a glass suspending fibre and reflecting mirror, as described in my previous papers. At one end of the beam is a disk of roasted mica blacked on one side. In front of this black surface, and parallel to it, is a plate of clear mica, so arranged that its distance from the black surface can be altered as desired, at any degree of exhaustion, without interfering with the vacuum. This apparatus is very sensitive, and gives good quantitative results. It has proved that when light falls on the black surface molecular pressure is set up, whatever be the degree of exhaustion. At the atmospheric pressure this disturbance can only be detected when the mica screen is brought close to the black surface, and it is inappreciable when the screen is moved away. As the barometer gauge rises the thickness of the layer of disturbance increases. Thus, retaining the standard candle always the same distance off, when the gauge is at 660 millims., the molecular pressure is represented by 1, when the space separating the screen from the black surface is 3 millims.; by 3 when the intervening space is reduced to 2 millims.; and by 5 when the space is I millim. With the gauge 722 millims. high, the values of the molecular pressure for the spaces of 3, 2, and 1 millims. are respectively 3, 7, and 12. When the gauge is at 740 millims. the corresponding values for spaces of 3, 2, and 1 millim. are 11, 16, and 23. With the gauge at 745 millims. the molecular pressures are represented by 30, 34, and 40, for spaces 3, 2, and 1 millims. When the gauge and barometer are level, the action is so strong that the candle has to be moved double the distance off, and the pressures when the intervening spaces are 12, 6, and 3 millims. are respectively 60, 86, and 107. A large series of observations have been taken with this apparatus, with the result not only of supplying important data for future consideration, but of clearing up many anomalies which were noticed, and of correcting many errors into which I was led at earlier stages of this research. Among the latter may be mentioned the speculations in which I indulged as to the pressure of sunlight on the earth.

Hitherto most of my experiments had been carried on To still further test this view of the action I made ano- with bad conductors of heat. To get the maximum action ther radiometer, similar to the above, but having a clear of a radiometer it appeared necessary that no heat should mica disk on each side of the ordinary mica vane. This pass through to the back surface, but that all should be prevents the reflection of the pressure backwards, and kept as much as possible on the surface on which the light causes it to expend itself in a vertical plane, the result fell.* At first I used pith, but since learning the advanbeing an almost total loss of sensitiveness. tage of raising the whole apparatus to a high temperature during exhaustion, I have used roasted mica lampblacked on one side for the vanes; for this purpose it is almost perfect; being a good absorber on one face, a good reflector on the other, a bad conductor for heat, extremely light, and able to stand high temperatures. Many experiments have been tried with metal radiometers, some of the results being recorded in previous papers which I have read before the Society, but being less sensitive than pith or mica instruments, I had not hitherto worked much with them. I now tried similar experiments to the above, using the best conductors of heat instead of the worst; and for: purpose thick gold-leaf was selected for the surface on which to try the action of radiation.

The above actions can be explained on the "evaporation and condensation" theory, as well as by that of molecular movement, and I therefore devised the following test to decide between these two theories :-A radiometer has its four disks cut out of very clear and thin plates of mica, and these are mounted in a somewhat large bulb. At the side of the bulb, in a vertical plane, a plate of mica, blacked on one side, is fastened in such a position that each clear vane in rotating shall pass it, leaving a space between of about a millimetre. If a candle is brought near, and by means of a shade the light is allowed to fall only on the clear vanes, no motion is produced; but if the light shines on the black plate the fly instantly rotates as if a wind were issuing from this surface, and keeps on moving as long as the light is near. This could not happen on the evaporation and condensation theory, as this requires that the light should shine intermittently on the black surface in order to keep up continuous movement.

By cutting a thin plate of aluminium into the form of a

An apparatus was constructed resembling a radiometer

I have already shown that when a ray of light from any part of the spectrum falls on a black surface the ray is absorbed and degraded in refrangibility, warming the black surface, and being emitted as radiant heat. In this sense only can the repulsion resulting from radiation be called an effect of heat.


Experimental Contributions to the Theory of the Radiometer. (CHEMICAL NEWS,

with an opening at the top, capable of being closed with a plate of glass. Through this I could introduce disks of any substance I liked, mounted in pairs on an aluminium arm rotating on a needle point. The first disks were of goldleaf, blacked on alternate sides. After exhaustion, a candle repelled the black surface of one of the disks, but to my surprise it strongly attracted the black surface of the other disk. I noticed that the disk which moved the negative way was somewhat crumpled, and had the outer edge curved so as to present a slightly concave black surface to the candle. I soon found that the curvature of the disk was the cause of the anomaly observed, and experiments were then tried with disks of gold and aluminium; the latter being chiefly used as being lighter and stiffer, whilst it acted in other respects as gold.

Dec. 29, 1876.

quently more facing the side of the bulb, greatly increases its sensitiveness.

The above experiments show that shape has even a stronger influence than colour. A convex bright surface is strongly repelled, whilst a concave black surface is not only not repelled by radiation but is actually attracted. I have also tried carefully shaped cups of gold, aluminium, and other metals, as well as cones of the same materials. I will briefly describe the behaviour of a few typical radiometers made with metal cups, which I have the honour of exhibiting to the Society.

No. 1035. A two-disk, cup-shaped radiometer, facing opposite ways; both sides bright. The disks are 14'5 millims. diameter, and their radius of curvature is 14 millims.

3'37 seconds.

A screen placed in front of the concave side so as to let the light shine only on the convex surface, repels the latter, causing continuous rotation at the rate of one revolution in 75 seconds. When the convex side is screened off, so as to let the light shine only on the concave side, continuous rotation is produced at the rate of one revolution in 695 seconds, the concave side being attracted.

A radiometer, the fly of which is made of perfectly flat alu- Exposed to a standard candle 3'5 inches off, the fly minium plates lampblacked on one side, is much less sensi-rotates continuously at the rate of one revolution in tive to light than one of mica or pith, but as I proved in my earlier papers, it is more sensitive to dark heat. Exposed to light, the black face of a metal radiometer moves away as if it were black pith. When, however, it is exposed to dark heat, either by grasping the bulb with the warm hand, dipping it into hot water, or covering it with a hot gas shade, it rapidly rotates in a negative direction, the black advancing, and continuing to do so until the temperature has become uniform throughout. On now removing the source of heat, the fly commences to revolve with rapidity the positive way, the black this time retreating as it would if light shone on it. Pith or mica radiometers act differently to this, dark heat causing them to revolve in the same direction as light does.

The outer corners of the aluminium plates, which were mounted diamond-wise, were now turned up at an angle of 45°, the lampblacked surface being concave and the bright convex. On being exposed to a candle, scarcely any movement was produced; when one vane was shaded off the other was repelled slightly, but the turned up corner seemed to have almost entirely neutralised the action of the black surface. A greater amount of the same corner was now turned up, the fold going through the centres of adjacent sides. Decided rotation was now produced by a candle, but the black surface was attracted* instead of repelled. Dark heat still caused the opposite rotation to light, repelling the black surface.

The plates were now folded across the vertical diagonal, the black surface being still inside, and the bright metal outside. The actions with a candle and hot glass shade were similar to the last, but more decided.

The plates were now flattened, and put on the arms at an angle, still being in the vertical plane. When the bright surface was outside, scarcely any action was produced by a candle, but when the lampblacked surface was outside strong repulsion of the black was produced, both with a candle and with a hot shade.

Two square aluminium plates were mounted in the experimental apparatus, one being attached to the arm by the centre of one of the sides, and the other by an angle. The opposite corner of the one mounted diamond-wise was turned up at an angle. The outer convex surface of the diamond plate was blacked, and the side of the square plate facing the same way was also blacked, so that either two black or two bright surfaces were always exposed to the light, instead of a black and a white surface, as is usual in radiometers. As might have been expected both these black surfaces were repelled, but the turned up corner of the diamond-mounted plate proved so powerful an auxiliary to its black surface, that strong rotation was kept up, the square plate being dragged round against the action of light.

Folding the plates with the angle horizontal has not so decided an action as when the fold is vertical.

Sloping the plates and disks of a lampblacked mica radiometer so as to have the black outside, and conse

I use the word attraction in these cases for convenience of expression. I have no doubt that what looks like attraction in these and other cases is really due to a vis a tergo.

These experiments show that the repulsive action of radiation on the convex side is about equal to the attractive action of radiation on the concave side, and that the double speed with which the fly moves when no screen is interposed is the sum of the attractive and repulsive


No. 1037. A two-disk, cup-shaped aluminium radiometer as above, lampblacked on the concave surfaces.

In this instrument the action of light is reversed, rotation taking place, the bright convex side being repelled, and the black concave attracted.

That this attraction is not apparent only, is proved by shading off the sides one after the other. When the light shines only on the bright convex side, no movement is produced, but when it shines on the black concave side, this is attracted, producing rotation. No. 1038.

A cup-shaped radiometer similar to the above, but having the convex surfaces black and the concave bright.

Light shining on this instrument causes it to rotate rapidly, the convex black being repelled. No movement is produced on letting the light shine on the bright concave surface, but good rotation is produced when only the black convex surface is illuminated.

No. 1039. A cup-shaped radiometer like the above, but blacked on both sides.

With this a candle causes rapid rotation, the convex side being repelled. On shading off the light from the concave side the rotation continues, but much more slowly; on shading off the convex side the concave is strongly attracted, causing rotation.

When either of these four radiometers is heated by a hot shade or plunged into hot water, rotation is always produced in the opposite direction to that caused by the light. On removing the source of heat, the motion rapidly stops, and then commences in the opposite direction (ie., as it would rotate under the influence of light), the rotation continuing as long as the fly is cooling. Chilling one of these radiometers with ether has the opposite action to exposing it to dark heat.

The vanes of radiometers have also been formed of metal cones, and of cups and cones of plain mica, roasted mica, pith, paper, &c.; and they have been used either plain or blacked on one or both surfaces. These have also been balanced against each other, and against metal plates and cones. The results are of considerable interest, but too complicated to explain without great expenditure of time and numerous diagrams. The broad facts are contained in the above selections from my experiments.

The action of light on the cup-shaped vanes of a radio


Dec. 29, 1876.

New Tests for Anthracen.


meter probably requires more experimental investigation before it can be properly understood. Some of the phenomena may be explained on the assumption that the molecular pressure acts chiefly in a direction normal to the surface of the vanes. A convex surface would therefore cause greater pressure to be exerted between itself and the bounding surface of glass than would a concave surface. In this way the behaviour of the cup-shaped radiometer with both bright surfaces, No. 1035, can be understood, and perhaps also that of Nos. 1038 and 1039. It would not be difficult to test this view experimentally, by placing a small mica screen in the focus of a concave cup where the molecular force should be concentrated. But

it is not easy to see how such an hypothesis can explain the behaviour of No. 1037, where the action of the bright convex surface more than overcomes the superior absorp tive and radiating power of the concave black surface; and the explanation entirely fails to account for the pow erful attraction which a lighted candle is seen to exert on the concave surfaces in Nos. 1035, 1037, and 1039.

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THE following is a new test for the determination of pure anthracen, and also a more detailed account of the process by which the tar distillers may get a fair idea of the quality of their anthracen before it is sampled and tested by the analyst. This will save them the trouble at times of having the goods disputed on the point of quality.

In the rough sketch herewith, A is the tap-funnel containing the oxidising mixture, which drops through the half-inch pipe c, pass D condenser (containing cold water, to E) into flask н. F is india-rubber joint to prevent the water in condenser escaping: B is wire and support to apparatus; G, cork; J, wire gauze; K, stand; and L is Bunsen burner. Apparatus without stand, about 4 feet high; condenser about 2 inches diameter.

No. 1.-The oxidising solution is made by dissolving 100 grms. of chromic acid in 50 c.c. of glacial acetic acid and 50 c.c. of water. The whole is kept standing to allow the impurities to precipitate. I grm. of anthracen is placed in a flask fitted with a condenser, 45 c.. of glacial acid is added, the whole is heated to gentle boil; 21 c.c. of the oxidising mixture (about 15 grms. chromic acid) is now added by degrees, and the boiling continued until finished, as in the anthraquinon test. The quinon is then precipitated and washed in the usual way. It is now washed into a dish, and dried on a water-bath. The dry residue is treated with ten times its weight of concentrated sulphuric acid (about 184 sp. gr.), heated on a water-bath for one hour, or until it becomes a crystalline mass by absorbing water. It is then diluted with 100 c.c. of water, thrown on a counterpoised filter, and washed, first with water, then with a 1 per cent boiling solution of caustic potash, finally with water, dried, and weighed. From the weight of quinon thus obtained sub. tract the ash remaining after incineration, and calculate, with the allowance, into pure anthracen by the ordinary method.

It must be well understood that this test should only be used when the chosen analyst's decision is final for percentage for value.

No. 2.-Place I grm. of anthracen in the glass flask, H, which will hold about 500 c.c. (through the cork of which a glass pipe with a glass condenser is fitted), add 45 c.c. glacial acetic acid; now fix in the cork with pipe and condenser, and gently boil; place in the other end of the pipe above the condenser a glass tap-funnel. Pour into the funnel 21 c.c. of the chromic acid mixture (which should contain about 15 grms. chromic acid), keep flask at gentle boiling heat, and by turning on the tap of the funnel let a few drops of the chromic acid mixture fall at in









tervals into the flask H, occupying about two hours in adding all: the liquid must then be boiled fully two hours longer; the heat is then shut off, and the flask with its contents allowed to stand about twelve hours in the cold. The cork with pipe and condenser is then removed, and about 400 c.c. of cold water are mixed with the contents of the flask; it is then allowed to stand for about three hours longer. The liquid is now filtered, the precipitated anthraquinon collected on the filter, washed with cold water, then with I per cent boiling solution of caustic potash, finally with pure hot water. The quinon is now

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liquid above it.

CHEMICAL NEWS, Dec. 29, 1876.

When reversing the bottle it is necessary to avoid allowing the acid to run into the glass tap connected with the centre bulb. The production of gas can be stopped by restoring the bottle to its original position, which will cause the acid to flow away from the sulphide of iron.

washed from the filter into a dish, and evaporated to dry-, downwards, and be hermetically sealed by the layer of ness on a water-bath. The dry residue is now dissolved in ten times its weight of concentrated sulphuric acid (about 184 sp. gr.), and heated on a water-bath for one hour until it becomes a crystalline mass by absorbing water. It is now diluted with 100 c.c. of water, thrown on a counterpoised filter, washed, first with water, then with a 1 per cent boiling solution of caustic potash, finally with pure hot water, then dried, and weighed. The anthraquinon is now volatilised from a platinum crucible, and the weight of ash remaining deducted.

As a check two tests should be made at the same time, requiring, of course, another apparatus.

The anthraquinon is calculated into pure anthracen by multiplying the net weight of anthraquinon by o'856; as, for example,

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IT often occurs that the study of chemistry has been prevented in consequence of the disagreeable and noxious vapours of sulphuretted hydrogen, which is one of the chief reagents employed in the ordinary course of analysis. Few private houses contain rooms which can be furnished with the regular fittings of the laboratory, including the expensive chamber for conveying away noxious fumes. In order to obviate this difficulty I have devised the following apparatus:

A gas bottle, consisting of three glass bulbs, one somewhat larger than the other two; these bulbs are connected by necks of about a quarter of an inch internal diameter. The larger bulb is furnished with a neck, tightly closed with an india-rubber plug, and the centre bulb is fitted with a stopcock.


To charge this gas-bottle it is necessary to fill the small bulb with diluted sulphuric acid; about one part of acid to five parts of water will be found a convenient strength. If the acid be either too strong or too weak the evolution of the gas is hindered. A piece or so of sound sulphide of ion, previously washed to remove powder and small pieces which might fall through the necks, is then placed in the large bulb, and to produce the gas the bottle is reversed, so as to cause the acid to flow from the smal bulb into the large one containing the sulphide of iron which will then have the neck containing the rubber plu

It will be found convenient to fix the bottle by a piece of copper wire twisted round its necks, and fastened in a cork to some stand or support, upon which it may be easily reversed.

The gas-bottle is connected by rubber tubing with a cork, preferably a rubber one, containing two glass tubes, and fitting into the mouth of a very stout test-tube, about 7 inches in length and I in diameter. It is necessary that the test-tube should be stout, or it will be liable to break upon corking and uncorking, and it is advisable to procure several which will fit the cork bearing the gas delivery-tubes, one of which, connected by the india-rubber tube with the gas-bottle, passes to the bottom of the test-tube, and serves to convey the sulphuretted hydrogen through the liquid to be tested, and the other just penetrates the cork, and is also attached to a rubber tube, which conveys the excess of gas to the receiver in which it is to be absorbed. The test-tube is loosely fitted by means of a bung into a jar which contains hot water, as the precipitates formed by sulphuretted hydrogen are produced most favourably when the liquid assayed is kept warm. This jar also serves as a stand for the test-tube, and prevents its being upset by the twist of the india-rubber tubes. Small flasks can be used instead of the test-tubes, but, on the whole, the latter are preferable, not being so liable to upset.

The absorber consists of an upright cylinder on a foot, with a neck near the base, usually called upright chloride of calcium jar, and is connected with the second glass tube in the cork of the test-tube. This cylinder is filled with sawdust mixed with coarsely powdered sugar of lead, and it is as well if before being used it is moistened with a saturated solution of sugar of lead. The top of the cylinder is loosely closed with a cork. When not in use it may be corked up at top and at the neck at the foot. A small brush, such as is ordinarily used for cleaning tobacco pipes, will be found useful for cleaning the glass tube which leads the sulphuretted hydrogen into the testtube, and it is convenient to have several pieces of such tubing of equal length and diameter.

When sufficient gas has been passed through an assay the gas-bottle is reversed, the tap turned off, and the rubber tube disconnected from the glass tap. A piece of the glass tubes mentioned above can then be slipped into the end of the rubber tubing, and the remnant of the gas above the assay in the test-tube blown into the absorptioncylinder.

Digestions with sulphide of ammonium can be made with the test-tube and the absorption cylinder alone.

The gas-bottle, for cheapness, can be made without the glass stopcock; in which case the rubber tube between it and the test-tube should be of two portions connected over a piece of glass tubing. When an operation is over, and the gas-bottle reversed, the piece attached to the bottle is slipped off the connecting glass tubing, and its orifice is closed with a piece of solid glass rod or a pinchtap.


German Chemical Society.-At the annual meeting of the German Chemical Society, held at Berlin Dec. 22, the following officers were elected for the year 1877 :President, Prof. F. Wöhler; Vice Presidents, Profs. Kekulé, Baeyer, Hofmann, and Liebermann. The retiring President (Prof. Hofmann) stated in his annual report that the present number of members was 1598, showing an increase of 225, during the past year, and that 423 original scientific communications had been presented before the Society during this time twelve months. The Berichte for 1876 form a volume of about 1900 pages.


Dec. 29, 1876.

On Thymo-Quinon.



Thursday, December 21st, 1876.

Professor ABEL, F.R.S., President, in the Chair.

AFTER the minutes of the preceeding meeting had been read and confirmed the names of Messrs. A. Gaved Phillips and F. Kopfer were read for the first time. The President read a letter from the Secretary of the Royal Society as to the nature and conditions under which grants would be made from the £4000 given by Government in aid of original research.

The first paper, entitled "A further Study of Fluid Cavities," was read by Mr. W. N. HARTLEY, and the results of his examination of a large number of topazes selected from the magnificent collection in the British Museum showed that the cavities scarcely ever contained anything but water. If the view be accepted that topaz has been formed by the action of alkaline fluorides or cryolite on kaolin no carbon dioxide would be liberated, so that it might not necessarily be found in the fluid cavities. This is corroborated by the fact that in one and the same topaz cavities may exist side by side, one of which is nearly filled with liquid carbon dioxide, the other onethird with water, one-third with liquid, and one-third with gaseous carbon dioxide, the space occupied by the gaseous CO2 having been produced by the contraction of the water on cooling. He inferred, moveover, that the critical temperature of water had not been reached, otherwise the contents of the adjacent cavities would have

been uniform.

The author has also examined a very large number of rock sections, principally granites and porphyries, almost all of which contained water cavities, but in none of them was the presence of carbon dioxide distinctly proved. A curious phenomenon in connection with the bubbles in the water cavities of rock crystal was sometimes observed, namely, that when heated the bubble became more dense than the liquid, and sank; so that in large deep cavities they went entirely out of focus when observed with a half-inch objective. In one specimen of quartz it was found that the bubble began to sink at 150° C., but not before it had reached this temperature. The cause of this motion appears to be that the bubble consists of a gas so highly compressed that it is nearly of the same density as water at the ordinary temperature. On heating, the water expands, thus still further condensing the gas in the cavity, which then becomes heavier than the liquid and consequently sinks in it. It is very remarkable that the cavities are not only frequently arranged symmetrically around the axis of the crystal, but in some cases they take the form of the crystals in which they are enclosed, each side of the cavity being parallel to a face of the crystal. Drawings of sections of crystals were exhibited in which this was very clearly shown. This is probably caused by the water exerting a resistance to compression comparable to a solid body at the high temperature at which the crystal was formed, but being mobile the shape of the enclosed water was altered so as to conform to the planes of crystallisation of the mineral as the silica molecules grouped themselves around it.

The PRESIDENT, in thanking the author, remarked that this investigation in his hands had been prolific in interesting results. He hoped that his ingenious speculations, bearing on the formation of these crystalline substances and the cavities contained in them, would give

rise to a valuable discussion.

In reply to a question put by Dr. ARMSTRONG with reference to the occlusion of hydrogen by trap rocks, recently investigated by an American chemist, Mr. HARTLEY said that in samples of trap from the neighbourhood of Edinburgh, which he had examined, he had

noticed cavities, but they contained nothing; cavities
containing liquefied carbon dioxide had been observed,
however, in trap. He had not considered the question as
to whether such cavities contained hydrogen, his attenticn
having been chiefly confined to quartz, granites, por-
phyries, &c., as most likely to have cavities containing
liquefied carbon dioxide, the special object of his search.
Dr. H. E. ARMSTRONG then gave a paper "On Thymo-
quinon.” In a
recent communication to the Berlin
Chemical Society, Liebermann pointed out that the


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and that when it is oxidised to naphtha-quinon, the NH2 group is displaced by OH; in other words, the OH group and one of the NH2 groups in diamido-naphthol are concerned in the formation of the quinon, and not both the NH2 groups as Graebe and Ludwig supposed. It is to be presumed, therefore, that in the formation of oxythymoquinon diamido-thymol (recently effected by Carstanjen) by oxidation, a similar reaction takes place, namely, that only one of the NH2 groups and the OH group are concerned in the production of this quinon, the other NH2 group being merely replaced by hydroxyl. Carstanjen has also obtained the same oxythymo-quinon by treating the monobromo derivative of thymo-quinon with potassic hydrate. Ladenburg has employed these results as the basis of a speculative theory as to the value of the several hydrogen atoms in benzene, in which he makes the perfectly gratuitous and unsupported assumption that in the first instance the thymol OH group remains unaffected, only the two amido groups taking part in the formation of the quinon; whilst in the second instance the thymol OH group does take part in the formation of the quinon. This, Liebermann points out, is not only unproved but is improbable. Dr. Armstrong stated that for a long time he had been engaged in an investigation of thymol and its derivatives, and had already obtained results which show that Ladenburg's assumption was incorrect, even if it had not been contrary to our knowledge of the law governing substitution in the phenol derivatives that para and ortho compounds are first formed.

The author had found that monamido

thymol from nitroso-thymol, in which the NH2 group occupies the para-position relatively to the OH group, yielded thymo-quinon when distilled with ferric chloride equal in weight to more than half the weight of the thymol employed in the preparation of the nitroso-derivative. He also stated that the formula suggested by Liebermann for "oximido-naphthol," &c., had already been suggested by Mr. C. E. Groves and himself in a foot-note in the new edition of Miller's "Organic Chemistry" they are now preparing, the proof sheet containing the note being handed in to the President.

The PRESIDENT having thanked the author for his communication,

A paper "On High Melting-Points with Special Reference to those of Metallic Salts (Part II.)," by Dr.T.Carnelley, was read. The method to be employed depends on the principle that if three salts, A, B, and C, whose fusion points are in the order A, B, C, be arranged on a cold block of iron, and then introduced into a muffle kept at a constant high temperature the ratio is approximately constant for the same three salts, whatever the temperature of the muffle; x being the number of seconds which elapse between the melting of A and B, and y that between the melting of B and C. The arrangement of the muffle


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