Thermal Conductivity

    The instruments on this page are generally called Ingenhousz' apparatus, after the late 18th century plant physiologist, Jan Ingenhousz (1739-1799), who was the Physician to the Imperial Family in Vienna. In all cases metal rods of different composition, but the same length and diameter, are held at a constant temperature at one end, either with a water bath or by being attached to the same piece of copper. Blobs of wax are attached to the ends of the rods, and fall off when the temperature pulse supplied to one end of the rod reaching them.

   The coefficient of thermal conductivity is a measure of the steady-state rate at which a rod of a given material conducts thermal energy when the two ends of the rod are held at different temperatures. The rate at which a temperature pulse travels down the rod depends on the thermal conductivity, and the reciprocals of the density and the specific heat capacity; this combination is called the diffusivity. All of the devices on this page demonstrate transient phenomena, and therefore really illustrate differences in the diffusivity of various materials.

   The Harvard apparatus is listed as a Conductometer of Ingenhouse [sic] in the 1881 Queen catalogue, and cost $5.00. The Kenyon apparatus, in the same catalogue, cost $3.00. The Wooster apparatus is listed in the 1916 L.E. Knott Apparatus Co. catalogue as the Harcourt Combination Vertical Conductometer.The accompanying text notes that "each rod is provided with cavities in the upper end for phosophorus and in addition is coated with a heat indicating paint." The cost was $3.90. The Mississippi apparatusd may be made by Lerebours et Secretan. If so, it cost 25 francs (about $5) in the 1850s.
 
                                                        Harvard University                                                         Kenyon College
 
 
                       Smithsonian Institution                                                               Transylvania University
 
                             Dartmouth College                                                                     College of Wooster
 

From an E-Bay auction


University of Mississippi

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