from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An apparatus for measuring the heat generated by a chemical reaction, change of state, or formation of a solution.
- n. The part of this apparatus, usually a container for holding a sample, in which the heat measured causes a change of state.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An apparatus for measuring the heat generated or absorbed by either a chemical reaction, change of phase or some other physical change.
from the GNU version of the Collaborative International Dictionary of English
- n. An apparatus for measuring the amount of heat contained in bodies or developed by some mechanical or chemical process, as friction, chemical combination, combustion, etc. For combustion processes, a bomb calorimeter may be used.
- n. An apparatus for measuring the proportion of unevaporated water contained in steam.
from The Century Dictionary and Cyclopedia
- n. An apparatus for measuring the quantity of heat given off by a body under different conditions: used in determining the specific heat of different substances, the latent heat of fusion, expansion, or vaporization, and the heat of combustion, or of chemical combination in general.
- n. The calorimeter is used to determine, in thermal units, the heat liberated or absorbed in the course of any physical or chemical process, such as change of temperature, change of state, the solution of a solid in a liquid, the mixture of liquids, chemical action, or any mechanical, electric or magnetic process involving transformations of energy. The thermal unit almost universally employed is the calory, that is, the amount of heat required to raise one gram, or sometimes one kilogram, of water from 0° C. to 1° C.; but other thermal quantities, the relation of which to the calory is definitely known (such as the heat of fusion of ice, or the heat of vaporization of water), are sometimes used. For the determination of specific heat the calorimeter commonly consists of a metal vessel, the water-equivalent of which is known, containing a known quantity of water of known temperature. The substance the specific heat of which is to be determined is weighed, heated to some carefully measured higher temperature, and plunged into the water, and the change in the temperature of the latter is observed. The most serious error in this operation is that arising from the exchange of heat between the calorimeter and its surroundings, and numerous devices have been employed to reduce this error to a minimum. For this purpose the calorimeter (C) is sometimes suspended within an outer chamber (o, o) by non-conducting supports as shown in Fig. 1. The outer surface of the calorimeter and the inner surface of the containing-vessel, both of which are metal, are highly polished in order to diminish radiation. In the Waterman calorimeter the substance to be tested is heated in a vessel surrounded by a coil of wire through which an electric current flows. It is then placed in a cup (C, Fig. 2) with double walls, which serves as the bulb of an air-thermometer. Ice-cold water is added in quantity just sufficient to counterbalance the rise of temperature. The mercury column in the manometer tube indicates the temperature of the cup. Much more perfect isolation may be obtained by using as a calorimeter a Dewar flask. This consists of a glass vessel (Fig. 3) with double walls, from the space between which the air has been carefully removed. The outer surface of the inner flask and the interior of the outer one are silvered. The exchange of heat under these conditions is exceedingly slow, and such flasks form excellent calorimeters. The determination of specific heats by means of the fusion of ice was first suggested by Black, in the eighteenth century, who employed for this purpose a block of clear ice (Fig. 4). The substance the specific heat of which is desired is heated and then placed in a cavity (C) within the block. A slab of ice (S) serves as a cover. The amount of water melted by the inclosed body in cooling to 0°C. measures the specific heat. Lavoisier and Laplace substituted for Black's ice-block a calorimeter consisting of an inner cage containing the body to be tested, surrounded by a double-walled vessel packed with broken ice at the melting-point. The ice melted by the heat liberated from the cooling body was collected and weighed. In Bunsen's ice-calorimeter the amount of ice melted is determined by the change in volume which that substance undergoes when converted into the liquid form. The apparatus, which is shown in Fig. 5, consists of an inner tube of glass sealed into a larger vessel of the same substance , the neck of which is bent upward and ends in a horizontal capillary tube . The upper portion of the outer vessel surrounding the tube a is filled with water, below which is mercury extending continuously through the neck into the capillary tube. By means of a freezing-mixture in a, a mantle of ice is formed around the outside of the inner tube, after which the freezing-mixture is removed and the whole apparatus is packed in melting ice. If now a body the specific heat of which is to be determined is introduced into a, a portion of the ice-mantle will be melted, and, in consequence of the diminution of volume, the mercury column in the capillary tube will recede toward the neck of the calorimeter. Its movement affords a measure of the volume of ice melted, and thus of the heat liberated by the cooling body. The Bunsen ice-calorimeter is an instrument of great delicacy and is specially adapted for the measurement of very small quantities of heat. Unfortunately, the density of the ice depends somewhat upon the rapidity with which it is formed, and considerable errors are thus introduced. The heat of vaporization of water has been utilized by Joly and others for calorimetric purposes. The July steam-calorimeter depends upon the determination of the amount of moisture condensed upon the surface of a substance when the latter is plunged into an atmosphere of steam. This apparatus consists of a steam-chamber with thin metal walls, within which, suspended from an arm of a balance, hangs a small platinum scale-pan of conical form. A known weight of the substance the specific heat of which is to be determined is placed on the pan, and its temperature is noted. Steam is then introduced into the chamber, and condensation occurs on the surface of the cool body, adding to its weight. When the substance has attained the temperature of the steam, and condensation is complete, the increase of weight is determined. For the determination of the specific heat of liquids and gases, various forms of calorimeter have teen devised. One of these, the continuous-flaw calorimeter of Callendar and Barnes, which has been employed in the determination of the specific heat of water at various temperatures, is shown diagrammatically in Fig. 6. It consists essentially of a capillary tube (AB) connecting at the ends with larger tubes and sealed into a glass vacuum-jacket. The liquid the specific heat of which is to be determined enters the tube at i and flows out at o at a measured rate. By means of a fine wire stretched through the bore of the capillary tube and supplied with a known electric current, heat is imparted to the liquid. The temperatures of the inflowing liquid at A and of the outflowing liquid at B are determined by means of the resistance of coils of platinum wire inserted in the larger tubes. From the amount of liquid passing in a given time and the amount of heat delivered to it electrically from the heating-wire, together with the difference of temperature at the ends of the tube, the specific heat of the liquid can be determined with great accuracy. For the determination of heats of combustion, heats of solution, and other thermochemical processes, a number of special forms of calorimeter have been devised. Among these are the Favre and Silberman calorimeter, in which the heat of a chemical reaction is imparted to mercury contained in a bulb with a capillary neck, and the expansion of the liquid is noted; the Junker calorimeter and the bomb calorimeters of Berthelot and Stohmann, for the study of heats of combustion; and the respiration calorimeter, for the determination of the heat evolved by animals or by human subjects. Other forms, called electrocalorimeters, are employed for measuring the heat developed by the electric current.
- n. A form of bomb calorimeter for the determination of the heat of combustion. See calorimeter.
- n. The essential features of the calorimeter are the following: a metal chamber, furnished with a chair, table, and bed, in which the subject of the experiment (usually a man) lives, eats, drinks, sleeps, and sometimes works, during a period of several days and nights.
- n. Arrangements for ventilating the chamber and for analyzing and measuring the air supplied to and received from the chamber.
- n. Facilities for passing food and drink into the chamber and for removing excreta. These materials are weighed and analyzed by sample, and their heat of combustion determined.
- n. Facilities for measuring the heat given off by the body and the heat-equivalent of any muscular work done. The income and outgo of energy of the body are expressed in terms of heat, the total heat of combustion of the food eaten being compared with the total heat given off by the body. The analyses of the food and excreta also show the digestibility of the food; that is, the proportion of the nutrients actually utilized in the body. The complete apparatus is complicated, and each experiment is laborious and expensive. Observations are taken constantly, day and night, by several observers during the entire period of the experiment, usually lasting from four to eight days. The results obtained have been of the highest scientific value.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a measuring instrument that determines quantities of heat
Latin calor, heat; see kelə-1 in Indo-European roots + -meter.(American Heritage® Dictionary of the English Language, Fourth Edition)