176 Prof. H. W. Beetz on Normal Elements 



sulphate solution to about the consistency employed in making 

 plaster casts, and some more with concentrated zinc-sulphate 

 solution. A U-shaped glass tube, of 4 millim. diameter and 

 with legs 22 centim. long, was partly filled with the one paste, 

 and after it had set was filled up with the other, so that the 

 two were in close contact. A copper wire was introduced 

 into the copper paste before it had set, and a zinc wire into 

 the zinc paste. The upper part of each leg was cleared from 

 plaster and filled up with paraffin. 



Several dry Daniell elements thus prepared were compared 

 with an element put together with concentrated solutions of 

 copper sulphate and zinc sulphate, and tested in respect of 

 the effect of change of temperature and of short-circuiting. 

 Taking the electromotive force of the liquid element as equal 

 to unity, the three dry elements I., II., and III. gave, when 

 measured on different days : — 



i. n. in. 



0-996 0-993 l'OOO 



0-998 0-996 0'996 



1-000 0-999 0-993 



0-998 0-998 



Mean . . 0-998 0-996 0-997 



The temperature varied in all these observations by a few 

 degrees only ; the small apparent variations in the electro- 

 motive force of the dry elements are partly at least accounted 

 for by small changes in the electromotive force of the fluid 

 element, which was put together fresh each time. On the 

 whole, however, the dry element is a little weaker than the 

 fluid element ; it contains no amalgamated zinc, because such 

 amalgamated wires are very brittle. 



A second series of experiments was concerned with the 

 influence of temperature. The elements II. and III., some- 

 times at the temperature of the air, sometimes in baths of 

 different temperatures, were compai-ed with the fluid element, 

 which had always a temperature of nearly 20 °C. On account 

 of the small conducting-power of the dry elements for heat, 

 they remained always three quarters of an hour in the bath 

 before the measurements were made. If the electromotive 

 force of the fluid element is again taken as unity, that of the 

 dry element was as follows: — 



n. 



At 0-996 



„ 20 0-993 



„ 39 0-983 



ni. 



At 1 1-007 



„ 21 1-000 



„ 32 0-995 



„ 55 0981 



