The Chemical News and Journal of Physical Science

LONDON:

PRINTED BY WILLIAM CROOKES, CHEMICAL NEWS OFFICE,

BOY COURT, LUDGATE HILL, E.C.

JAN 74

THE CHEMICAL NEWS.

VOLUME XXIX.

EDITED BY WILLIAM CROOKES, F.R.S., &c.

No. 736.-FRIDAY, JANUARY 2, 1874.

ON THE ACTION OF HEAT ON GRAVITATING
MASSES.

By WILLIAM CROOKES, F.R.S., &c.

He describes an experiment to show that heat produces repulsion in the luminous arc given by an induction-coil in rarefied air.

The author describes numerous forms of apparatus successively more and more delicate, which enabled him to detect, and then to render very sensible, an action exerted by heat on gravitating bodies, which is not due to

THE experiments recorded in this paper have arisen from
observations made when using the vacuum-balance, de-air-currents, or to any other known force.
scribed by the author in his paper "On the Atomic Weight
of Thallium," for weighing substances which were of a
higher temperature than the surrounding air and the
weights. There appeared to be a diminution of the force
of gravitation, and experiments were instituted to render
the action more sensible, and to eliminate sources of

error.

In an historical résumé of the state of our knowledge on the subject of attraction or repulsion by heat, it is shown that in 1792 the Rev. A. Bennet recorded the fact that a light substance delicately suspended in air was attracted by warm bodies: this he ascribed to air-currents. When light was focused, by means of a lens, on one end of a delicately suspended arm, either in air or in an exhausted receiver, no motion could be perceived distinguishable from the effects of heat.

Laplace speaks of the repulsive force of heat. Libri attributes the movement of a drop of liquid along a wire heated at one end, to the repulsive force of heat; but Baden Powell has not succeeded in obtaining evidence of repulsion by heat from this experiment.

Fresnel describes an experiment by which concentrated solar light and heat caused repulsion between one delicately suspended and one fixed disk. The experiment was tried in air of different densities, but contradictory results were obtained, under apparently similar circumstances, at different times, and the experiments were not proceeded with.

Saigey describes experiments which appear to prove that a marked attraction exists between bodies of different temperatures.

experiment, comes to the conclusion that there is a repulForbes, in a discussion and repetition of Trevelyan's

sive action exercised in the transmission of heat from one

body into another which has a less power of conducting it. Baden Powell, repeating Fresnel's experiment, explains the results otherwise than as due to repulsion by heat. By observing the descent of the tints of Newton's Rings between glass-plates when heat was applied, Dr. Powell shows that the interval between the plates increases, and attributes this to a repulsive action of heat.

Faye has introduced the hypothesis of a repulsive force of heat to account for certain astronomical phenomena.

Abstract of a Paper sent to the Royal Society August 12, 1873. 1 Phil. Trans., 1873, vol. clxiii., part 1, p. 277.

The following experiment with a balance made of a straw beam with pith-ball masses at the ends enclosed in a glass tube, and connected with a Sprengel pump, may be quoted from the paper:

"The whole being fitted up as here shown, and the apparatus being full of air to begin with, I passed a spiritmovement by a low-power micrometer; the pith-ball (a, b) flame across the lower part of the tube at b, observing the descended slightly, and then immediately rose to con siderably above its original position. It seemed as if the true action of the heat was one of attraction, instantly overcome by ascending currents of air. . .

"31. In order to apply the heat in a more regular manner, a thermometer was inserted in a glass tube, having at its extremity a glass bulb, about 1 inch diameter; it was filled with water, and then sealed up. The water was kept heated to 70° C., the temperature of the laboratory being about 15° C.

"32. The barometer being at 767 millims., and the gauge at zero, the hot bulb was placed beneath the pithball at b. The ball rose rapidly; as soon as equilibrium ball at a, when it rose again, more slowly, however, than was restored, I placed the hot-water bulb above the pithwhen the heat was applied beneath it.

33. The pump was set to work, and when the gauge was 147 millims. below the barometer, the experiment was tried again; the same result, only more feeble, was obtained. The exhaustion was continued, stopping the pump from time to time, to observe the effect of heat, when it was seen that the effect of the hot body regularly action of the hot body was scarcely noticeable. At 10 diminished as the rarefaction increased, until when the gauge was about 12 millims. below the barometer the millims. below it was still less; whilst when there was only a difference of 7 millims. between the barometer and the gauge, neither the hot-water bulb, the hot rod, nor the spirit-flame caused the ball to move in an appreciable degree. The inference was almost irresistible that the rising of the pith was only due to currents of air, and that at this near approach to a vacuum the residual air was the inertia of the straw beam and the pith balls. A more too highly rarefied to have power in its rising to overcome delicate instrument would doubtless show traces of movement at a still nearer approach to a vacuum; but it seemed evident that when the last trace of air had been

removed from the tube surrounding the balance (when | the balance was suspended in empty space only), the pithball would remain motionless wherever the hot body were applied to it.

34. I continued exhausting. On next applying heat, the result showed that I was far from having discovered the law governing these phenomena; the pith-ball rose steadily, and without that hesitation which had been observed at lower rarefactions. With the gauge 3 millims. below the barometer, the ascension of the pith when a hot body was placed beneath it was equal to what it had been in air of ordinary density; whilst with the gauge and barometer level its upward movements were not only sharper than they had been in air, but they took place under the influence of far less heat; the finger, for example, instantly sending the ball up to its fullest extent." A piece of ice produced exactly the opposite effect to a hot body.

Numerous experiments are next given to prove that the action is not due to electricity.

The presence of air having so marked an influence on the action of heat, an apparatus was fitted up in which the source of heat (a platinum spiral rendered incandescent by electricity) was inside the balance-tube instead of outside it as before; and the pith-balls of the former apparatus were replaced by brass balls. By careful management, and turning the tube round, the author could place the equipoised brass pole either over, under, or at the side of the source of heat. With this apparatus it was intended to ascertain more about the behaviour of the balance during the progress of the exhaustion, both below and above the point of no action, and also to ascertain the pressure corresponding with this critical point.

After describing many experiments with the ball in various positions in respect to the incandescent spiral, and at different pressures, the general result appeared to be expressed by the statement that the tendency in each case was to bring the centre of gravity of the brass ball as near as possible to the source of heat, when air of ordinary density, or even highly rarefied, surrounded the balance. The author continues:

"44. The pump was then worked until the gauge had risen to 5 millims. of the barometric height. On arranging the ball above the spiral (and making contact with the battery), the attraction was still strong, drawing the ball downwards a distance of 2 millims. The pump continuing to work, the gauge rose until it was within 1 millim. of the barometer. The attraction of the hot spiral for the ball was still evident, drawing it down when placed below it, and up when placed above it. The movement was, however, much less decided than before; and in spite of previous experience (33, 34) the inference was very strong that the attraction would gradually diminish until the vacuum was absolute, and that then, and not till then, the neutral point would be reached. Within one millimetre of a vacuum there appeared to be no room for a change of sign.

"45. The gauge rose until there was only half a millimetre between it and the barometer. The metallic hammering heard when the rarefaction is close upon a vacuum commenced, and the falling mercury only occasionally took down a bubble of air. On turning on the battery current, there was the faintest possible movement of the brass ball (towards the spiral) in the direction of attraction.

"46. The working of the pump was continued. On next making contact with the battery no movement could be detected. The red-hot spiral neither attracted nor repelled; I had arrived at the critical point. On looking at the gauge I saw it was level with the barometer.

"47. The pump was now kept at full work for an hour. The gauge did not rise perceptibly, but the metallic hammer increased in sharpness, and I could see that a bubble or two of air had been carried down. On igniting the spiral, I saw that the critical point had been passed. The sign had changed, and the action was faint but unmistakable repulsion. The pump was still kept going, and an obser

vation was taken from time to time during several hours. The repulsion continued to increase. The tubes of the pump were now washed out with oil of vitriol, and the working was continued for an hour.

'48. The action of the incandescent spiral was now found to be energetically repellent, whether it was placed above or below the brass ball. The fingers exerted a repellent action, as did also a warm glass rod, a spiritflame, and a piece of hot copper."

In order to decide once for all whether these actions really were due to air-currents, a form of apparatus was fitted up, which, whilst it would settle the question indisputably, would at the same time be likely to afford info:mation of much interest.

By chemical means a vacuum was obtained in an apparatus so nearly perfect that it would not carry a current from a Ruhmkorff's coil when connected with platinum wires sealed into the tube. In such a vacuum the repulsion by heat is decided and energetic.

An experiment is next described, in which the rays of the sun, and then the different portions of the solar spectrum, are projected into the delicately suspended pith-ball balance. In vacuo the repulsion is so strong as to cause danger to the apparatus, and resembles that which would be prodcued by the physical impact of a material body.

Experiments are next described in which various substances are used as the gravitating masses. Amongst these are ivory, brass, pith, platinum, gilt pith, silver, bismuth, selenium, copper, mica, (horizontal and vertical), charcoal, &c.

The behaviour of a glass beam with glass ends in a chemical vacuum, and at lower exhaustion, is next accurately examined, when heat is applied in different ways. On suspending the light index by means of a cocoon fibre in a long glass tube, furnished with a bulb at the end, and exhausting in various ways, the author finds that the attraction to a hot body in air, and the repulsion from a hot body in vacuo, are very apparent.

Speaking of Cavendish's celebrated experiment, the author says that he has experimented for some months on an apparatus of this kind, and gives the following outline of one of the results he has obtained :"A heavy metallic mass, when brought near a delicately suspended light ball, attracts or repels it under the following circumstances.

"I. When the ball is in air of ordinary density.

a. If the mass is colder than the ball, it repels the ball.

b. If the mass is hotter than the ball, it attracts the ball.

"II. When the ball is in a vacuum.

a. If the mass is colder than the ball, it attracts the ball.

b. If the mass is hotter than the ball, it repels the ball."

The author continues:-" The density of the medium surrounding the ball, the material of which the ball is made, and a very slight difference between the temperatures of the mass and the ball, exert so strong an influence over the attractive and repulsive force, and it has been so difficult for me to eliminate all interfering actions of temperature, electricity, &c., that I have not yet been able to get distinct evidence of an independent force (not being of the nature of heat) urging the ball and the mass together.

Experiment has, however, showed me that, whilst the action is in one direction in dense air, and in the opposite direction in a vacuum, there is an intermediate pressure at which differences of temperature appear to exert little or no interfering action. By experimenting at this

*This can be effected without interfering with the exhaustion.

NEWS

critical pressure, it would seem that such an action as was obtained by Cavendish, Reich, and Baily, should be rendered evident."

After discussing the explanations which may be given of these actions, and showing that they cannot be due to air-currents, the author refers to evidences of this repulsive action of heat, and attractive action of cold, in Nature. In that portion of the sun's radiation which is called heat, we have the radial repulsive force possessing successive propagation required to explain the phenomena of comets and the shape and changes of the nebula. To compare small things with great (to argue from pieces of straw up to heavenly bodies), it is not improbable that the attraction now shown to exist between a cold and a warm body will equally prevail when, for the temperature of melting ice is substituted the cold of space, for a pith ball a celestial sphere, and for an artificial vacuum a stellar void. In the radiant molecular energy of cosmical masses may at last be found that "agent acting constantly according to certain laws," which Newton held to be the cause of

gravity.

CHEMICAL REAGENTS.

By R. H. RIDOUT.

In chemical analysis, where small quantities of the reagent are wanted frequently, much time is lost in taking the stoppers out of the bottles, and then, no matter what care may be exercised, there is always a small quantity of the reagent left to evaporate on the rim of the neck of the bottle, and many reagents which are deteriorated by exposure to the air have to be prepared only in small quantities. To obviate these petty annoyances, I have adopted the following plan with the best results:-

AIR COMPRESSED

SHELF

The bottles to contain the reagents are about two or more times the size of the bottles in which they are ordinarily contained. A is a bottle having a glass tube passing through a first-rate cork in the narrow neck. The end of the tube in the bottle is within' about inch of the bottom; the other end makes a complete arch, and is connected to the glass tube, BC, by an indiarubber junction. D is a fine glass jet, fixed also to BC by an india-rubber junction, the ends of the tubes being just far enough apart to allow a pinch-cock to be placed on the india-rubber tube. The reagent is placed in a wash-bottle, its jet being connected to the jet в by an india-rubber tube. A bladder is attached to the mouth-piece, and the liquid forced up CB into the bottle, thereby compressing that air in the bottle above the reagent. The pinch-cock being put up in c, the reagent is prevented escaping. When the pinchcock is opened, the air on the surface of the liquid A will force it through the tubes and out of the jet D drop by drop, or in a rapid stream, as may be desired.

It will be seen that the liquid, never comes into contact with any air except that in the bottle, and this may either be purified from harmful compounds, or another gas substituted having no action upon the liquid.

The india-rubber junction [prevents its application .o strong acids, but by far the greater number of reagents are unaffected by one form or another.

Monmouth, Nov. 28, 1873

Ir is well known that some difficulty has been experienced in making a complete extraction of the fat which exists in milk. This difficulty appears to arise partly from the presence of water, which appears to protect the fat from extraction, it appears to be necessary first to get rid of the action of the ether; and, in order to effect a complete the water of the milk by evaporation, and then to boil the dry residue repeatedly with ether.

;

Since the publication of my recent "Manual of MilkAnalysis, I have adopted a very convenient form of apparatus for carrying out these and analogous extractions and, although the device is apparently trifling, it may possibly be of service to describe it at the present time. quantity of milk, and afterwards the boiling of the residue The operations are first of all the drying up of a small

with ether; and a vessel, which is alternately an evaporating basin and a flask, is exactly that which is called for.

These conditions are fulfilled as follows:-A thin platinum dish, capable of holding about 50 c.c. is employed, and in it the portion of milk (5 or 10 c.c. accurately measured), is evaporated to dryness. The dish, during this evaporation, is heated in the water-bath, which consists simply of a beaker half-filled with water which is boiled over the lamp. The milk, as it is being evaporated, may be stirred up with a small glass rod, or small platinum spatula. The milk-residue having been obtained in a state of tolerable dryness, it is covered with 20 or 30 c.c. of ether, and a small inverted funnel is fitted moderately tightly into the platinum dish, which is thereby converted into a flask. The further details are obvious.

By the adoption of this apparatus, the determination of the fat in milk becomes perfectly easy.

ON THE ENERGIES OF THE IMPONDERABLES, WITH ESPECIAL REFERENCE TO THE MEASUREMENT AND UTILISATION OF THEM.* By the Rev. ARTHUR RIGG, M.A. (Concluded from page 392).

THE amount of steam converted into visible vapour, and cause of excessive loss of power in ordinary steam-engines may be made clear in this way. There is in the receiver of the air-pump a piece of sponge with a little water on it; if a portion of the air saturated with vapour be pumped out, a small portion of the water is converted into vapour, which you see deposited in a film on the glass. This is caused by the air being rarefied, and becoming colder, therefore not competent to hold in solution as much vapour as it had previously done. Now, what takes place in this receiver is taking place in hundreds of steam-engine cylinders, and wasting pounds and pounds of fuel. As soon as the steam enters the cylinder it fills it, or rather it fills the part of the cylinder below the piston. Arrangements are usually made that a portion of the stroke may be accomplished by the expansive action of the steam. Now, as soon as the opportunity for expansion is presented, there is at once this deposit of moisture, and the deposit is indicative of a sacrifice of heat.

Now, this action of heat is not confined to liquids, it also extends to solids. Here is a piece of unannealed glass. Those present who have to deal with steamengines, know that it very often happens from some apparently unaccountable cause, that what are called the

*The Cantor Lectures. delivered before the Society of Arts.

removed from the tube surrounding the balance (when | vation was taken from time to time during several hours.

the balance was suspended in empty space only), the pithball would remain motionless wherever the hot body were applied to it.

Numerous experiments are next given to prove that the action is not due to electricity.

44. The pump was then worked until the gauge had risen to 5 millims. of the barometric height. On arranging the ball above the spiral (and making contact with the battery), the attraction was still strong, drawing the ball downwards a distance of 2 millims. The pump continuing to work, the gauge rose until it was within 1 millim. of the barometer. The attraction of the hot spiral for the ball was still evident, drawing it down when placed below it, and up when placed above it. The movement was, however, much less decided than before; and in spite of previous experience (33, 34) the inference was very strong that the attraction would gradually diminish until the vacuum was absolute, and that then, and not till then, the neutral point would be reached. Within one millimetre of a vacuum there appeared to be no room for a change of sign.

The repulsion continued to increase. The tubes of the pump were now washed out with oil of vitriol, and the working was continued for an hour.

"48. The action of the incandescent spiral was now found to be energetically repellent, whether it was placed above or below the brass ball. The fingers exerted a repellent action, as did also a warm glass rod, a spiritflame, and a piece of hot copper."

"A heavy metallic mass, when brought near a delicately suspended light ball, attracts or repels it under the following circumstances.

"I. When the ball is in air of ordinary density.

a. If the mass is colder than the ball, it repels the ball.

b. If the mass is hotter than the ball, it attracts the ball.

"II. When the ball is in a vacuum.

a. If the mass is colder than the ball, it attracts the ball.

b. If the mass is hotter than the ball, it repels the ball."

* This can be effected without interfering with the exhaustion.

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