You are watching: Can latent heat be measured with a thermometer
Two class of instruments are employed for the measure up of heat, namely, thermometers and also pyrometers. Thermometers are only employed to measure up comparatively low temperatures, and we chandelier confine our remarks completely to this class in the current article.Modern physics having actually demonstrated that warmth is just a setting of movement in matter, the values upon i beg your pardon its measurement depends are, perhaps, more an overwhelming to recognize than the false theory prevalent before the establishment of this doctrine. So long as warm was thought about a substance, also thoagh one imponderable one, the was no difiicult come understand how its absorption into a body might certainly enlarge that body, as wood is enlarged through the absorb of water. Why a body becomes enlarged by the increased motion the its corpuscle is more difficult of comprehension. If we, however, fall the consideration of the why in this case, and confine ourselves come the legislation or manner in i m sorry this expansion takes place, we might arrive in ~ definite and practical results. That is, nevertheless, proper to state the the ultimatum which science has actually reached in regard come the reason for this development is, that hedt is in some way opposed come cohesion. At present it is entirely futile to seek to go more than this. The fact, however, the such growth takes ar in both solids and also liquids, and that it is, within particular limits, sufficiently uniform in certa,in substances to end up being a method of measure the temperatures to which this substances are exposed, is the basis of thermometric measurement.But another allude must be distinctly borne in mind ; thermometers only measure judicious heat. Therefore one lb of heavy steam at 313 Fah. Contains heat enough to progressive five and also one half pounds that water to the very same temperature, a fact quickly demonstrated through experiment. It adheres to that the pure or total variety of heat units consisted of in any substance, need to be figured out by part other method than the thermometer, and also that a degree on the thermometer can not be taken into consideration a unit that heat. What then is a unit of warm It has actually been agreed to think about the amount of heat crucial to raise one pound of water native 33 Fah. To 33 Fah. As a unit that heat, and although doubtless there are some small sources the error in the metliod, that is sufficiently specific to regard the quantity of heat essential to advanced one lb of water one degree, anywhere between 33 Fah. And also 313 Fah. As a continuous quantity.It is likewise a exactly inference the any particular substance in a uniform state, as regards the cohesive strength of that particles, must exhibit the exact same temperature so lengthy as it maintains that condition, because heat is the opposite force to cohesion. The an ext heat the much less cohesion, and also vice versa. Water, as soon as passing native the liquid to the heavy state, maintains such a uniformity of condition ; that is temperature may, therefore, be related to as constant. It additionally maintains the exact same uniformity of condition while passing from the liquid state into steam at the cook point. The freezing and boiling points of water may as such be considered as the two influential landmarks that temperature indigenous which the amount of expansion of some uniformly, or nearly uniformly expanding substance, as mercury, immersed in water in the two problems named, being detailed on a scale, divisions may it is in arbitrarily make each method on the very same scale, which will suggest temperatures over or listed below these points.The Centigrade scale renders the hight of a mercury obelisk immersed in freezing water, zero, and divides the distance between this allude and the hight that the same obelisk immersed in boiling water, right into one hundred degrees, if the Fahrenheit Scale makes the first named hight 33 degrees above zero, and divides the room between this hight and also the hight at which the mercury was standing in cook water, right into one hundred and also eighty divisions, or degrees.How it is possible to recognize the lot of warmth in any kind of body from thermometric indication next claims our attention. The following law has been established. The total amottnt of warm in any body is the sum of its implicit heat and also its cautious heat. The latent warmth is established by the well-known capacity the the human body under examination, at offered temperatures to absorb heat, or, in various other words, come render the latent. This term, implicitly heat, is not a great one, though we room still obliged to use it for want of a better. We usage it just to differentiate the heat which, exhilaration within a mass of matter, and expending its energy in antagonism to cohesive attraction, cannot be known by sensation, Mke the cost-free or wise heat. The latent, or details heat of miscellaneous bodies has actually been do the subject of careful study, and tables of reference have actually been built to purchased a ready method of computation ; but the details heat of all bodies is adjusted by any cause i m sorry lessens or rises the distance between the corpuscle which consist of their mass. The compression of vapor lessens its certain heat while it rises its temperature, and also vine versa. The certain heat that steam, then, is only continuous at a constant pressure.It will currently be checked out that the complete amount of heat consisted of in any body have the right to be identified by the aid of a thermometer, only once its specific heat for every temperatures has actually been predetermined. This has actually been done for countless substances, consisting of water and also steam, to which the applications of warmth measurement is the the greatest importance, together it is only by such measurement that concerns of economic situation in heavy steam generators deserve to be settled. The lot of water evaporated native a continuous temperature per pound of flammability consumed, under a consistent pressure, being the only reliable test of the economic situation of a steam boiler.
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When the evaporation takes place at 313 the forced uniformity the pressure and consequently the temperature is conveniently maintained, which would certainly not be the situation if an engine were moved by the heavy steam generated, or if an effort were made to produce the steam at a constant higher temperature. The temperature of the feed water might be quickly maintained at a continuous point, one of two people at 313, or at a lower temperature, and also the lot of this water which a lb of fuel will convert into steam at 313 is specific index the the strength of the boiler come transmit warmth through the shell right into the consisted of water.