Part 27 (2/2)
It would be difficult to procure such spheres of ices and inconvenient toapparatus, we have ree the naiven it, as derived partly froree open to criticisht deviation fro distinctness of idea, is excusable; and I could not derive the na too near to the names of known instruments employed for other purposes
The calorimeter is represented in Pl VI It is shown in perspective at Fig 1 and its interior structure is engraved in Fig 2 and 3; the for a horizontal, and the latter a perpendicular section Its capacity or cavity is divided into three parts, which, for better distinction, I shall name the interior, middle, and external cavities
The interior cavity f f f f, Fig 4 into which the substances sube of iron wire, supported by several iron bars; its opening or mouth LM, is covered by the lid HG, of the sa 2 and 3 is intended to contain the ice which surrounds the interior cavity, and which is to be melted by the caloric of the substance erate m m at the bottom of the cavity, under which is placed the sieve n n These two are represented separately in Fig 5 and 6
In proportion as the ice contained in the ed from the body placed in the interior cavity, the water runs through the grate and sieve, and falls through the conical funnel c c d, Fig 3 and tube x y, into the receiver F, Fig 1
This water may be retained or let out at pleasure, by2 and 3 is filled with ice, to prevent any effect upon the ice in theair, and the water produced froh the pipe ST, which shuts by means of the stop-cock r The whole7 made of tin painted with oil colour, to prevent rust
When this
2 and 3, the lid GH, Fig 4 of the interior cavity, the external cavity a a a a, Fig 2 and 3 and the general lid FF, Fig 7 are all filled with pounded ice, well rammed, so that no void spaces remain, and the ice of the middle cavity is allowed to drain The machine is then opened, and the substance sub placed in the interior cavity, it is instantly closed After waiting till the included body is co point, and the whole melted ice has drained fro 1 is accurately weighed The weight of the water produced during the experi the cooling of the included body, as this substance is evidently in a similar situation with the one formerly mentioned as included in a hollow sphere of ice; the whole caloric disengaged is stopped by the ice in theaffected by any other heat by7 and in the external cavity Experiments of this kind last from fifteen to twenty hours; they are so up the substance in the interior cavity ell drained ice, which hastens its cooling
The substances to be operated upon are placed in the thin iron bucket, Fig 8 the cover of which has an opening fitted with a cork, into which a small thermometer is fixed When we use acids, or other fluids capable of injuring the metal of the instru 10 which has a similar thermometer in a cork fitted to its mouth, and which stands in the interior cavity upon the s 10
It is absolutely requisite that there be no communication between the external and middle cavities of the calorimeter, otherwise the iceair, in the external cavity, would mix with the water produced froer be a measure of the caloric lost by the substance submitted to experiment
When the terees above the freezing point, its heat can hardly reach the7 and of the external cavity; but, if the teht cool the ice contained in thethe ice in the external cavity to fall, in the first place, below zero (32) It is therefore essential that this experi: Hence, in time of frost, the calorimeter must be kept in an apartment carefully heated It is likewise necessary that the ice employed be not under zero (32); for which purpose it must be pounded, and spread out thin for soher temperature
The ice of the interior cavity always retains a certain quantity of water adhering to its surface, whichto the result of the experi of each experiment, the ice is already saturated with as much water as it can contain, if any of the water produced by the caloric should remain attached to the ice, it is evident, that very nearly an equal quantity of what adhered to it before the experiment must have run down into the vessel F in its stead; for the inner surface of the ice in thethe experiment
By any contrivance that could be devised, we could not prevent the access of the external air into the interior cavity when the atmosphere was 9 or 10 (52 or 54) above zero The air confined in the cavity being in that case specifically heavier than the external air, escapes doards through the pipe x y, Fig 3, and is replaced by the war out its caloric to the ice, becomes heavier, and sinks in its turn; thus a current of air is forh the machine, which is the more rapid in proportion as the external air exceeds the internal in temperature This current of warm air must melt a part of the ice, and injure the accuracy of the experiainst this source of error by keeping the stop-cock u continually shut; but it is better to operate only when the temperature of the external air does not exceed 3, or at most 4, (39 to 41); for we have observed, that, in this case, theof the interior ice by the atmospheric air is perfectly insensible; so that we may answer for the accuracy of our experiments upon the specific heat of bodies to a fortieth part
We have caused make two of the above described machines; one, which is intended for such experiments as do not require the interior air to be renewed, is precisely foriven; the other, which answers for experiments upon combustion, respiration, &c in which fresh quantities of air are indispensibly necessary, differs fro two small tubes in the two lids, by which a current of atmospheric air may be blown into the interior cavity of the machine
It is extremely easy, with this apparatus, to determine the phenoaged or absorbed If ish, for instance, to ascertain the quantity of caloric which is disengaged frorees, let its temperature be raised to 80 (212); it is then placed in the interior cavity f f f f, Fig 2 and 3 of the calorimeter, and allowed to remain till we are certain that its temperature is reduced to zero (32); the water produced byis collected, and carefully weighed; and this weight, divided by the volume of the body subrees of temperature which it had above zero at the coives the proportion of what the English philosophers call specific heat
Fluids are contained in proper vessels, whose specific heat has been previously ascertained, and operated upon in thecare to deduct, fro the experi vessel
If the quantity of caloric disengaged during the combination of different substances is to be determined, these substances are to be previously reduced to the freezing degree by keeping them a sufficient time surrounded with pounded ice; the mixture is then to be made in the inner cavity of the calorimeter, in a proper vessel likewise reduced to zero (32); and they are kept inclosed till the teree: The quantity of water produced is athe coaged during co animal respiration, the combustible bodies are burnt, or the animals are made to breathe in the interior cavity, and the water produced is carefully collected Guinea pigs, which resist the effects of cold extremely well, are well adapted for this experiment As the continual renewal of air is absolutely necessary in such experiments, we blow fresh air into the interior cavity of the calorimeter by means of a pipe destined for that purpose, and allow it to escape through another pipe of the same kind; and that the heat of this air may not produce errors in the results of the experiments, the tube which conveys it into the h pounded ice, that it may be reduced to zero (32) before it arrives at the calorimeter The air which escapes h a tube surrounded with ice, included in the interior cavity of the machine, and the water which is produced must ed from this air is part of the product of the experiment
It is somewhat more difficult to deterasses, on account of their sree of density; for, if they are only placed in the calorimeter in vessels like other fluids, the quantity of ice melted is so small, that the result of the experiment becomes at best very uncertain For this species of experih two h which the air passes, and becomes heated in its way to the calori water, and the other, through which the air circulates within the calorie its caloric, is placed in the interior cavity, f f f f, of that machine By means of a small thermometer placed at one end of the second worm, the temperature of the air, as it enters the calori out of the interior cavity is found by another thermometer placed at the other end of the worm By this contrivance we are enabled to ascertain the quantity of icea certain nurees of terees of specific caloric
The same apparatus, with some particular precautions, aged by the condensation of the vapours of different liquids
The various experiments which may be made with the caloriive us the measure of relative quantities; we have therefore to fix a unit, or standard point, from whence to form a scale of the several results The quantity of caloric necessary to melt a pound of ice has been chosen as this unit; and, as it requires a pound of water of the temperature of 60 (167) to melt a pound of ice, the quantity of caloric expressed by our unit or standard point is what raises a pound of water from zero (32) to 60 (167)
When this unit is once determined, we have only to express the quantities of caloric disengaged frorees, in analogous values: The following is an easy mode of calculation for this purpose, applied to one of our earliest experirs of plate-iron, cut into narrow slips, and rolled up, or expressing the quantity in deci water to about 78 (2075), were quickly introduced into the interior cavity of the calorimeter: At the end of eleven hours, when the whole quantity of water hly drained off, we found that 1109795 pounds of ice were78 (1755) having melted 1109795 pounds of ice, how60 (135)? This question gives the following statement in direct proportion, 78 : 1109795 :: 60 : x = 085369 Dividing this quantity by the weight of the whole iron employed, viz 77070319, the quotient 0110770 is the quantity of ice which would have been h 60 (135) of temperature
Fluid substances, such as sulphuric and nitric acids, &c are contained in aa thermometer adapted to the cork, with its bulb immersed in the liquid Thewater, and when, froe the liquid is raised to a proper temperature, the matras is placed in the calorimeter
The calculation of the products, to determine the specific caloric of these fluids, iscare to deduct from the water obtained the quantity which would have been produced by the matras alone, which must be ascertained by a previous experiment The table of the results obtained by these experiments is omitted, because not yet sufficiently co occasioned the series to be interrupted; it is not, however, lost sight of; and we are less or more employed upon the subject every winter