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Now let h and d be the height and ihe density of the merON PHYSICS, OR NATURAL PHILOSOPHY. cury in the branch a, at the temperature of 00 Centigrade ; No. XXXIV.
and h' and d' the same quantities in the branch y, at the temperature t; then, according to the hydrostatic principle just
d (Continued from page 95.)
referred to, we have k' d' =ld.
But d'=itke by our EXPANSION OF LIQUIDS.
former lesson, k being the co-efficient of the absolute expansion Apparent and Absolute Expansion.-In liquids, it is only cubic of mercury; therefore replacing d' by its value just referred expansion which is to be considered; and of this there are two to, we have
=hd; whence, we find that k = kinds, apparent and absolute expansion. Apparent expansion
1+kt is the increase in volume which a heated liquid assumes when | This formula shows how to find the co-efficient of the absolute it is contained in a vessel which expands less than the liquid expansion of mercury, when the heights h and h' of this liquid does under the same degree of heat; as the expansion of mer- in the two tubes have been measured, and the temperature t cury or alcohol in thermometers. The absolute expansion is of the bath in which the tube is immersed, are given. In the the real expansion which the volume of the liquid alone experiment of Dulong and Petit, this temperature was meaundergoes. The apparent expansion of a liquid is less than sured by a thernsometer and capsule, as explained in the next the absolute expansion by the amount of the expansion of the paragraph. As to the heights h' and h, they were measured by vessel in which it is contained. The expansion of the vessel means of a cathetometer (see fig. 18, vol. iv., p. 100). By this is rendered evident in the case of the thermometer, by immers- process, these experimenters found that the co-efficient of the ing it in boiling water, provided the bulb is large and filled absolute expansion of mercury, between 0° and 100° Centiwith coloured spirits of wine up to the half of the stem, At grade, was 7360. But they observed that this co-efficient the instant when the bulb enters the hot water, the spirits of increased with the temperature; for between 100° and 2009 wine sink in the tube, which evidently arises from the expan. Centigrade the mean co-efficient was only; and between 2000 sion of the sides of the bulb; but if the latter is kept immersed, and 3000 Centigrade it was 83'00. The same phenomenon was the spirits of wine become heated, and rise in the tube by a observed in other liquids; thus we see that these bodies do quantity equal to its absolute expansion, diminished by that of not expand regularly. It was found that their expansion was the vessel.
more irregular the nearer that their temperat: es reproached As in the case of solids, the increase in a unit of the volume those of congelation and ebullition. As to mercury, the expeof a body when its temperature is raised from 0° to 1o Centi- rimenters found that its expansion was very sensibuy regular grade, is called the co-efficient of expansion ; but then a distinc-between-36° and 100° Centigrade. tion is to be made between che co-efficient of the apparent espansion and the co-efficient of absolute expansion. Various
Co-efficient of the Absolute Expansion of Mercury.-In order to
capillary tube. The two tubes were surrounded each by a i It is composed of a cylindric glass reservoir or bulb, to which metallic jacket, of which the smallest, A, was filled with is cemented a llary glass tube hent at a right angle and open pounded ice, and the other with oil.gradually heated by means at its extremity. In order to make the experiment, the of a small furnace, represented open in the figure in order to instrument is weighed when empty, and also when filled with show the jacket. "The two tubes A and B were then filled with mercury at 0° Centigrade; the difference between the two mercury, which assumed the same level in each when the tubes weights gives the weight p of the mercury cont, ined in the had the same temperature ; but which rose in the tube when apparatus. Raising it, ihen, to a temperature denoted by t, the
mercury expands, and a certain quantity of it comes cut, which is received in a small capsule, and weighed. If the
weight of the mercury which has come out be represented by A jacket is a cylinder of metal or wood which surrounds another
P, that of the mercury which remains in the apparatus is cylinder of any kind, in order to preserve heat or maintain a fixed
denoted by P-p. Now, let v' be the volume of the mercury at 0°Centigrade, whose weight is P, and v the volume, also at 0.
it was heated.
ains in the apparatus, and tion. Several processes have been employed in order to deter
of me two qu ntities, mine the temperature of the maximum density of water. M. , se tbereiure proportional Hällstroin, by weighing, in water at different temperatures, a
glass ball ballasted with sand, found, taking into consideration But & is ihe expansion of the glass, that it was in water of the tempera
ture of 4° 1 Centigrade or 390.38 Fahrenheit, that the ball lost I rises, when heated from the most of its weight; whence he concluded that at this tem.
Das Lesti re, the co-effi- perature the maximum density of water takes plare. MM. ::TILLE : Eercury by d, we Munke and Stampter have stated the temperature of the
maximum density of water, at 30.75 Centigrade, or 389.75 27 222 2 messe which the unit Fahrenheit, according to their experiments
. But M. Despretz DE 5 1 9925:23 from 00 10 to has ascertained, by numerous experiments, that the tempera
ture of the maximum density of water is really that of 40
1 1: ??
Centigrade, as above stated. By gradually cooling a water-
thermometer (that is, a thermometer with water instead of
the maximum contraction of the water in the water-thermo.
meter took place. *L'S Est Lercury in glass was
TABLE OF THE CO-EFFICIENTS OF THE EXPANSION
According to the Centigrade Seale.
0.00015432 - No 54 p= (P-p) t; whence, t=
0.00042133 Sea Water, artificial
0.00041210 Sulphuric Acid, sp. gr. 1.836
Oil of Turpentine
Oil of Almonds
1.4405 Nitric Acid, sp. gr.
0.00114885 2 *1771.-1,' by taking the
Liquid Ainmonia, sp.gr 0.9465
Ether, sp. gr. 0733
Naphtha, sp. gr. 07813
I 2010 0000254. By
* j* *s* move yy** vxpansion of mercury LESSONS IN CHEMISTRY.-No. XXXIII.
Section V. (continued).
investigate that simple body in relation to the phenomena of
Chlorine as a Supporter of Combustion.-In determining ma ein Burime -': *reating of the it is only natural that we should begin with the example of a
whether any medium be or be not a supporter of combustion, 31 iv render combustible in the ordinary sense of the term.
We will, fm: spasons of therefore, take a candle or small taper mounted upon a bent
.: zary always wire, and furnished with disc and cork, as frequently des.
je *** se "11t ***1-3 point of fig. 36.
is formula, the
PRI L.! ve taken, because
1.4 1 215 5 217 expand, the
13. Teilwered, it only
the liquid expands Brand 16 piace, of course, at 0° mis mzimum of condensa| bottle of chlorine, and observe the result. The taper buras
Exp. Having lighted the taper, plunge it into the jar of
after a fashion, but a strange sort of burning it is; only a small denly extinguished, and the copper support will vehemently
How shall we now designate chlorine in relation to com-
Exp. Procure some Dutch leaf, and hanging a few pieces of this on a properly-mounted hooked wire, as represented in fig. 37,
their contained hydrogen. Combustion, in point of fact, is one consequence and direct evidence of intense chemical action. Without chemical action resulting in combination there can
be no combustion ; and inasmuch as chemical union between plunge it into a jar of chlorine gas. The metallic leaf will chlorine and carbon does not ensue, for this reason, charcoal generally take fire, again proving that under certain circum- and carbon generally are not able to burn in an atmosphere of stances, and for certain bodies, chlorine is a remarkably good chlorine gas. There is, however, a combination of chlorine and supporter of combustion.
hydrogen, the result being hydrochloric acid gas-the gas Erp. Having procured some powdered antimony-real which, when absorbed by water, constitutes the well-known metallic antimony, not the sulphuret-throw a little of the nuriatic acid, or spirit of salt. Hence it follows, that when we powder into a jar of chlorine gas. Immediately the antimony ignite a material holding both carbon and nitrogen, such for will take fire. In all these cases, be careful to confine as much example as a taper, or oil of turpentine, and dip either thus as possible the results of combustion, as they are very injurious ignited into a jar of chlorine, hydrogen is alone consumed and when taken into the lungs. They may be confined by dexte carbon deposited. rously sliding over the mouth of the bottle or jar a greased It may be well in this place to say a few words relative to
an insufficient definition formerly offered, and during many Erp. Our next experiment shall have reference to the years retained, of the function of combustion, which was curious phenomenon already noticed in the instance of the defined to be a rapid combination of bodies with oxygen. If burning taper, of the development and evolution of carbona- this definition be accepted, then it follows that the experiments ceous fumes, but it shall manifest that phenomenon in a still we have just performed, and the phenomena we have just higher degree. Dip a slip of bibulous or absorptive paper into oil witnessed, are not tho.e of combustion ; indeed certain systeof turpentine, then plunge it into a bottle of chlorine, and close matic writers have excluded them from the category, seeing under these circumstances, the paper will take fire, and the however, is unphilosophical. No definition should do violence peculiar black carbonaceous fumes will be still more evident to a natural and well-established idea. Surely, then, violent than before when we employed a taper. But a still more chemical action, attended with the evolution of light and heat, expressive demonstration of the incombustibility of carbon in ought to be regarded as an instance of combustion. chorine gas will be afforded by the ensuing experiment, for I'he definition of combustion as the rapid chemical union of a the performance
of which we made preparations in our last body with oxygen originated in a remarkable period, of which it olap
. Take the piece of charcoal, properly mounted on first or great French revolution : a period when the genius copper wire as described in that lesson, and light the charcoal of innovation was active, and human inteilect unbridled in its luoroughly, by directing against it the point of a blowpipe- pride. Then it was that the chemical nomenelature of Lavoisier
When thus thoroughly ignited, plunge the whole into a facts then known, but totally incapable of expansion. In Collow, although one in strict accordance with previous deduc- should be so, either all its facts should be well-known, ce tions. The charcoal, though fully ignited, will become sud- should be deducible from such simple elements
, as in Geometry,
Centigrade, of the mercury which remains in the .
; dt being the increase w
11 dt of the volume of mercury takes in passing f Centigrade.
Whence, it follows that ?
Co-efficient of the Expansion of Glass.—T! sion of a liquid being equud to its apparent expansion of the vessel which contains it, ** expansion of glass in the preceding experi' difference between the co-efficient of the of mercury and that of its apparent expai. have the co-efficient of the cubic expansi 0.00002586; for 3360 - uiro = TATT Regnault has found ihat the co-efficien with different kinds of glass, and even wi. of the vessels. For the common glass tub he found that the co-tfficient of expans' multiplying the co-efficient of the absolute for 10 Centigrade by 8, we obtain this e renheit; thus to X=nu; and we obtain this co-efficient for 1° Rea' =11.
The co-efficient of the absolute expar can be found in the same manner a determined ; and thence by adding to expansion of glass, the co-efficient of t can also be found.
Correction of the Height of the Baro; barometer, p. 258, col. 2, we remarke its indications in different places ar the year comparable with each oth to refer the height of the column or fixed temperature, such as that water. This correction is made in the height of the barometer at t° C and its height at 0° Centigrade b mercury being compared to a m heated from 0° to to Centigrade t cht
; whence h= 55 6550
657 ficient of the absolute expan: ficient of its apparent expa
value of n is the same as if .ght of the mercury in the ba e diameter of the tube, and co
Maximum Density of Water." phenomer in, that when its te contracts as far as 4o Centigra this point, although the loweri not only does the contraction even to the freezing point, w Centigrade or 320 Fahrenhe 390-2 Fahrenheit, water expe