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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

h'd

h' -

=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

Fig. 182.
methods have been employed in order to determine these two
Co-efficients of expansion. The following is that employed by
MM. Dulong and Petit.

Co-efficient of the Absolute Expansion of Mercury.-In order to
determine the co-efficient of the absolute expansion of mercury,
the influence of the expansion of the vessel containing it must
be avoided. MM. Dulong and Petit effected this by the
application of the hydrostatic principle, that in two communi-
cating vessels the heights of two liquids are in the inverse ratio Co-efficient of the Apparent Expansion of Mercury. The co.
of their densities ; a principle which is independent of the efficient of the apparent expansion of a liquid varies with the
diameters of the vessels, and consequently of their expansion. nature of the vessel which contains it. That of mercury, in a
Their apparatus was composed of two glass tubes A and B, glass vessel, was determined by MM. Dulong and Petit by
fig. 181, supported in a vertical position and connected by a means of the apparatus represented in fig. 182.

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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.

112

it was heated.

feinperature.

TOL. Y.

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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-
1+ dt

thermometer (that is, a thermometer with water instead of
mercury) in a bath whose temperature was given by a mer-
curial thermometer, he found that it was at 4° Centigrade that

the maximum contraction of the water in the water-thermo.
*** manner, that the co-

meter took place. *L'S Est Lercury in glass was

TABLE OF THE CO-EFFICIENTS OF THE EXPANSION
** quering experiment, we

OF LIQUIDS.
Vse therine meter has
V P and p. For, since

According to the Centigrade Seale.
Liquids.

Co-efficients.
=Tir we find by clearing this
Mercury, real exp. ...

0.00018018
Mercury, app. exp. in glass

0.00015432 - No 54 p= (P-p) t; whence, t=

Water

0.00042133 Sea Water, artificial

0.00041210 Sulphuric Acid, sp. gr. 1.836

0.00057850

0.00070000

Oil of Turpentine
Lok**
p13-The absolute expan-

Oil of Almonds

0.00078701
aetexpansion plus the
Fat Oils

0 00080000
***... **bi in the cubic

1.4405 Nitric Acid, sp. gr.

0.00114885 2 *1771.-1,' by taking the

0.00019831

Liquid Ainmonia, sp.gr 0.9465
1-1 11,2 awule expansion

0.00025360
Whence, we
Liquid Muriatic Acid, sp.gr. 1.1978

0.00063524

Ether, sp. gr. 0733
.* Irigor '. +257); of glass +qual to

0 00080966
*1* = 5n = 002596, M.
Bisulphuret of Carbon

0.00106006
* > 长

Naphtha, sp. gr. 07813
o el'ansion raries
************ diff rent forms
"11 nigh. **med in Chemistry,

I 2010 0000254. By

* j* *s* move yy** vxpansion of mercury LESSONS IN CHEMISTRY.-No. XXXIII.
***** 9ficient for 1° Fah-
grond by multiplying by 4.

Section V. (continued).
umur; thus, zaso x Resuming the consideration of chlorine, we have now to
153 3**** 13 STOELE of different liquids combustion, a subject which, as the reader is well aware, formed

investigate that simple body in relation to the phenomena of
11. 1*21** 2* *.2: of m-rcury was Section 6 of our preceding lesson, a numbering to which we
a's "Ime co-efficient of the may as well adhere.

**
200t expansion

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.
S.T.:***?"- a constant cribed already, and as represented in our subjoined diagram,

je *** se "11t ***1-3 point of fig. 36.
* 13 'Pr. Diner: let
enq** W * 6:<d by H,

Fig. 36.
€ column of
1 luoti auto Vw.ch in being
sa & Dept. 2, we have

is formula, the
2 - #1 Letsry, and not the

PRI L.! ve taken, because

1.4 1 215 5 217 expand, the
se ! "independent of

*****-**.Tetits expansion.
one *** TURI's this remarkable

13. Teilwered, it only
Het su 2 Fahrenheit; below
del * A pérature continues,

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

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after a fashion, but a strange sort of burning it is; only a small denly extinguished, and the copper support will vehemently
pale powerless flame appearing, whilst copious black fumes burn.
are liberated on all sides. Now, why is this? Charcoal is a The functions of chlorine, as developed by our preceding
very combustible material under all ordinary circumstances : experiments, considerably enlarge the sphere of our notions
it is indeed the combustible par excellence of man; wherefore, relative to combustion, and we arrive at the remarkable con-
ihen, does it not burn in our present experiment? The young clusion that, if in place of our own atmosphere of oxygen and
chemist will perhaps jump to the conclusion, that chlorine, nitrogen, we were surrounded with an atmosphere of chlorine,
although a supporter of combustion, is a very bad supporter. carbon, including charcoal, coke, and coal, would be absolutely
Conclusions, however, can seldom be justly arrived at from the incombustible, and carbon holding materials such as oils, fats,
consideration of one isolated experiment; let us therefore try a coal-gas, etc., would only be combustible to the extent of
few others,
Exp. Dry a small piece of phosphorus, not larger than a

Fig. 38.
pea in size; place it in a copper deflagrating ladle properly
mounted, and immerse it in a jar of chlorine. These directions
having been followed, the phosphorus will spontaneously burst
into fame, but the flame will not possess any great illumina-
ting power.

How shall we now designate chlorine in relation to com-
bustion, after having witnessed the evidence of our last
experiment: We surely must not term it a bad supporter of
combustion, seeing that it will accomplish a result quite out of
the power of even oxygen gas to accomplish; namely, it will
cause the spontaneous ignition of phosphorus.

Exp. Procure some Dutch leaf, and hanging a few pieces of this on a properly-mounted hooked wire, as represented in fig. 37,

Fig. 37.

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glass plate.

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,

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110

Centigrade, of the mercury which remains in the .
whose weight is p-p. The weights of these tw
which are at the same temperature, are therefore
to their volumes ; that is, we have
exactly the volume to which v rises, when
0° to to Centigrade. Representing, therefore
cient of the apparent expansion of mercu'

1 have

; dt being the increase w

11 dt of the volume of mercury takes in passing f Centigrade.

Whence, it follows that ?

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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

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