32 M. A. F. Sundell on the Electromotive and Thermoelectric 



In the alloys commercial (impure) metals were employed. 

 During the investigation it was observed that both the electro- 

 motive and the thermoelectric force diminished as the time pro- 

 ceeded. This diminution, especially remarkable immediately 

 after casting, depended doubtless on physical (perhaps also che- 

 mical) molecular changes in the alloys. As the electromotive 

 force was usually determined immediately after the casting, but 

 the thermoelectric not till some days subsequently, one could 

 not be sure that both determinations corresponded to the same 

 molecular state of the alloys. It was consequently necessary 

 with most of the alloys to repeat the experiments. This later 

 investigation was effected perhaps six weeks after the first ; and 

 the same pair of wires was employed. As it could be assumed 

 that at the end of this time the molecular changes had for the 

 most part ceased, and since also the determination of the ther- 

 moelectric force was now taken immediately after the ascertain- 

 ing of the electromotive force, the values of the two forces thus 

 obtained correspond to the same molecular state and are compa- 

 rable with each other. 



3. The determination of the thermoelectric force was effected 

 in the following manner. The copper wire which was soldered 

 to the alloy was bent, near the soldering, twice at right angles, 

 and so made parallel to the alloy at a distance of about 2 cen- 

 tims. The soldering was inserted in a test-tube, which was im- 

 mersed in cold water, whereby the place of contact was cooled 

 7-10° C. below the temperature of the room (15-18° C.) . The 

 free ends of the wires were joined to the ends of the galvano- 

 meter-wire by means of binding-screws ; these were surrounded 

 by a wooden case, the ends of which were perforated for the 

 wires to pass through. The difference of temperature of the 

 places of contact was ascertained by two exactly similar very 

 sensitive thermometers. The bulb of one of them was put close 

 to the place of contact in the test-tube, that of the other near 

 the binding-screws in the box ; and then the mouth of the test- 

 tube and the perforations of the box were stopped with cotton- 

 wool, in order to prevent currents of air. After the contacts 

 had acquired the temperature of the air surrounding them, the 

 two thermometers and the deflection of the galvanometer were 

 read off simultaneously several times at brief intervals. The 

 galvanometer was furnished with the usual mirror-reading. The 

 conducting-power, measured by means of an inducing magnet, 

 could be modified by a rheostat interpolated in the circuit. 



4. We come now to the narration of the observations. The 

 experiments made at the later determination of the electromotive 

 and thermoelectric forces will be given in full. Of the experi- 

 ments first made the results only will be stated, in order to render 



