1883.] the Electromotive Force and Resistance of Batteries. 5! 



•are then filled up to within 2 inches of the top with a weak acid 

 solution (one part of sulphuric acid to nine parts of water). 



The single-fluid bichromate cell is no more than the cell just 

 described, in which are placed nothing but a rod of amalgamated zinc 

 and a plate of carbon, each forming a pole of the cell. 



The Leclanche cell is made thus : — Into a glass jar a solution of the 

 ordinary commercial sal-ammoniac is poured. A zinc rod or plate 

 into which a connecting tinned iron wire has been cast, is then 

 placed in the solution, and a plate of carbon surrounded by a mixture 

 of broken gas-carbon or coke and peroxide of manganese, is fixed 

 in a small porous pot at the top of the jar. To make an attach- 

 ment for the terminal, the top of the carbon plate is capped with lead, 

 which makes good contact with the carbon and is not liable to be 

 attacked by ammonia. The carbon plate is then dipped in melted 

 paraffin, to fill up its pores and to check the ascension of the liquid 

 by capillary action. Lastly, the wire, the top of the zinc rod, and the 

 lead cap of the carbon plate are covered with pitch, ozokerit, marine 

 glue, or some other compound to protect them from local action. 



The results of the experiments are given in the tables below, in 

 which the electromotive force (e) is given in terms of that of a 

 Daniell cell (a standard cell) in good order and at about 14° 0., and 

 the resistance is given in B.A. units. The experiments were conducted 

 for me by Mr. R. Shida with great care and patience. Of the Tables 

 I, II, and III, which contain the results of the experiments on the 

 Daniell cell, the first two tables refer to the case where the solution of 

 copper sulphate was saturated at all temperatures (that is to say, the 

 crystals of copper sulphate were always present in the solution) and 

 the solution of zinc sulphate was kept the same, or nearly the same, in 

 strength (that is, the solution was saturated at about 14° C.) ; Table III 

 refers to the case where both copper sulphate and zinc sulphate solutions 

 were kept unaltered or nearly so in strength during the experiment 

 (that is to say, they were both saturated at about 10° C). Table IV 

 contains the results for the double-fluid bichromate ; Table V those for 

 the single-fluid bichromate ; and Table VI those for the Leclanche. 



(I.) The Electromotive Force. 



(a.) The Daniell Cell. — Tables I, II, and III show that, as the cell 

 was heated up from a comparatively low temperature to a higher and 

 higher temperature, the electromotive force of the Daniell cell de- 

 creased rather abruptly at first, but more gradually afterwards, until, 

 at a certain temperature it began to increase and continued to do so till 

 the temperature attained that of the boiling point of water ; but that 

 (which is rather singular) the electromotive force remained unaltered, 

 -or nearly so, while the cell was being cooled down from 100° C. to a 

 lower and lower temperature. These peculiar results (together with 



e 2 



