Part 27 (1/2)

_Calculation before Combustion_

The air in the jar before combustion was 353 cubical inches, but it was only under a barometrical pressure of 27 inches 9-1/2 lines; which, reduced to deciives 2779167 inches; and from this we must deduct the difference of 4-1/2 inches of water, which, by Tab II corresponds to 033166 inches of the barometer; hence the real pressure of the air in the jar is 2746001 As the volume of elastic fluids dihts, we have the following statement to reduce the 353 inches to the volume the air would occupy at 28 inches barometrical pressure

353 : x, the unknown volume, :: 2746001 : 28 Hence, x = 353 2746001 / 28 = 346192 cubical inches, which is the volume the same quantity of air would have occupied at 28 inches of the barometer

The 210th part of this corrected volurees of teives 8255 cubical inches; and, as this correction is subtractive, the real corrected volume of the air before combustion is 337942 inches

_Calculation after Combustion_

By a similar calculation upon the volume of air after combustion, we find its barometrical pressure 2777083 - 051593 = 2725490 Hence, to have the volume of air under the pressure of 28 inches, 295 : x :: 2777083 : 28 inversely; or, x = 295 x 2725490 / 28 = 287150 The 210th part of this corrected volurees of therives the subtractive correction for te the actual corrected volume of air after combustion 278942 inches

_Result_

The corrected volu after co combustion 59000

SECT VIII

_Method of deter the Absolute Gravity of the different Gasses_

Take a large balloon A, Pl V Fig 10 capable of holding 17 or 18 pints, or about half a cubical foot, having the brass cap bcde strongly ce is fixed by a tight screw This apparatus is connected by the double screw represented separately at Fig 12 to the jar BCD, Fig 10 which er in dimensions than the balloon This jar is open at top, and is furnished with the brass cap h i, and stop-cock l11

We first deter it ater, and weighing it both full and empty When eh its neck d e, and the last re it once or twice in an air-puas is to be ascertained, this apparatus is used as follows: Fix the balloon A to the plate of an air-pu, which is left open; the balloon is to be exhausted as coree of exhaustion by means of the barometer attached to the air-pu is shut, and the weight of the balloon determined with the most scrupulous exactitude It is then fixed to the jar BCD, which we suppose placed in water in the shelf of the pneu 1; the jar is to be filled with the gas weand l as ascends into the balloon, whilst the water of the cistern rises at the same time into the jar To avoid very troubleso this first part of the operation, to sink the jar in the cistern till the surfaces of the water within the jar and without exactly correspond The stop-cocks are again shut, and the balloon being unscrewed frohed; the difference between this weight and that of the exhausted balloon is the precise weight of the air or gas contained in the balloon Multiply this weight by 1728, the number of cubical inches in a cubical foot, and divide the product by the number of cubical inches contained in the balloon, the quotient is the weight of a cubical foot of the gas or air submitted to experiment

Exact account ht and te the above experiht of a cubical foot is easily corrected to the standard of 28 inches and 10, as directed in the preceding section The s the vacuum must likewise be attended to, which is easily determined by the barometer attached to the air-pump If that baroht it stood at before the vacuum was forinally contained reas was introduced from the jar into the balloon

FOOTNOTES:

[58] According to the proportion of 114 to 107, given between the French and English foot, 28 inches of the French barolish Directions will be found in the appendix for converting all the French weights and lish denominations--E

[59] When Fahrenheit's therree must be sree of Reaurees of Fahrenheit; hence we must divide by 4725, and finish the rest of the calculation as above--E

CHAP III

_Description of the Calori Caloric_

The calori the relative quantities of heat contained in bodies, was described by Mr de la Place and me in the Memoirs of the Academy for 1780, p 355 and from that Essay the materials of this chapter are extracted

If, after having cooled any body to the freezing point, it be exposed in an atradually become heated, from the surface inwards, till at last it acquire the sa air But, if a piece of ice be placed in the same situation, the circumstances are quite different; it does not approach in the sree towards the temperature of the circumambient air, but re ice, till the last portion of ice be completely melted

This phenomenon is readily explained; as, to melt ice, or reduce it to water, it requires to be combined with a certain portion of caloric; the whole caloric attracted fro bodies, is arrested or fixed at the surface or external layer of ice which it is employed to dissolve, and combines with it to form water; the next quantity of caloric combines with the second layer to dissolve it into water, and so on successively till the whole ice be dissolved or converted into water by co at its former temperature, because the caloric has never penetrated so far as long as any intermediate ice remained to melt

Upon these principles, if we conceive a hollow sphere of ice at the temperature of Zero (32) placed in an atree of te, it follows, 1st, That the heat of the external atmosphere cannot penetrate into the internal hollow of the sphere of ice; 2dly, That the heat of the body placed in the hollow of the sphere cannot penetrate outwards beyond it, but will be stopped at the internal surface, and continually employed to melt successive layers of ice, until the te all its superabundant caloric above that temperature carried off by the ice If the whole water, for the reduction of the temperature of the included body to Zero, be carefully collected, the weight of the water will be exactly proportional to the quantity of caloric lost by the body in passing fro ice; for it is evident that a double quantity of caloric would have melted twice the quantity of ice; hence the quantity of ice melted is a very exact measure of the quantity of caloric employed to produce that effect, and consequently of the quantity lost by the only substance that could possibly have supplied it

I have made this supposition of ould take place in a hollow sphere of ice, for the purpose ofthe method used in this species of experiment, which was first conceived by Mr de la Place