28 



Dr. Gr. Gore on Changes of 



this " categorical experiment renders manifest, in a very simple 

 case, the influence exercised by the heat of constitution upon 

 the energy of its chemical properties ; " and that " the available 

 chemical work which a body possesses depends not only 

 upon the specific nature of the atoms, but also upon the 

 total of calories which its maintenance in the physical state 

 determines." 



The object in making the following experiments was to 

 ascertain whether, consistently with the above observation, the 

 change of physical state of an alloy from solid to liquid by 

 fusion, and the large absorption of heat which then occurs, is 

 usually attended by a correspondingly large increase of voltaic 

 electromotive force, and whether the converse effect occurs 

 during solidification. The apparatus employed in the experi- 

 ments is shown by the annexed sketch. 



A is a glass cup, B a tobacco-pipe with a wide bowl, and C a 

 bent glass syphon-tube provided with a tap. A bar of the 

 alloy was placed vertically in A, and a second portion of the 

 alloy was melted in the bowl and some distance up the stem 

 of the pipe B, so as to exclude the production of thermo- 

 electric currents at the junction with the connecting wire, 

 and then allowed to solidify and cool. 



The electrolyte, at atmospheric temperature, was poured 

 into A and B, and a portion raised by suction into C so as to 

 connect the portions in A and B. The terminals of the 

 portions of alloy were connected by iron wires with a suitable 

 astatic galvanometer of 100 ohms resistance, and the needles 

 allowed to settle at zero. Heat was then gradually applied 

 by means of a small flame to the bowl of B until the alloy in 

 it melted, and the temperature of the electrolyte was raised 

 nearly to the boiling-point ; the flame was then removed. 

 The amounts of deflexion of the needles of the galvanometer 

 at definite intervals of time, during the heating and cooling, 

 and especially at the fusing and solidifying points, were care- 

 fully observed and recorded. 



