3l0 



TENTH ANNUAL REPORT OF 



Thus if the charge which produces 10° of deflection he denoted by 

 1, the electrical charges, which produce 40°, 60°, and 80°, are re- 

 spectively equal to 4.39, 8.30, and 18.33. 



Kohlrausch's table gives results for whole degrees, 

 2. The instrument can be ajjplied in a second manner for measuring 

 electrical charges. If after placing the needle and strip at right 

 angles, both being in communication, electricity is imparted and the 

 connexion then broken, we are able, by turning the torsion circle, to 

 make the angle of deflection a constant quantity, say 30°. According 

 to well known principles the electrical charge is then also propor- 

 tional to the square root of the toi,-sion necessary to maintain the 

 needle at the deflection of 30°. 



Kohlrausch determined the tension at the poles of diflerent simple 

 batteries by both methods ; the batteries being arranged as follows : 

 The two metals were soldered together ; one was immersed in the 

 liqvud of the vessel A, (Fig. 10,) the other in the liquid 

 of the vessel B ; in each vessel a brass vfire was placed, 

 forming the poles. One of the wires was connected 

 with tiie ground, the other with the collector-plate of 

 a condensing apparatus. The tension of the positive 

 as well as of the negative pole was determined for each 

 battery by many esperimenta, amd the mean of all 

 taken. 



The electro-motive force of the different; galvanic elements Kohl- 

 ya,uscli determined according to Wheatstone's method, which will 

 presently be i^entioned. The following table contains the results of hi® 

 measurement ■; 



Fisr. 10. 



DescriptioQ. of battciy. 



'Electro- 



: motive 



fosce. 



1. Zinc in sulphate of zinc ; platinum in nitiic acid of «JeK- 



sity 1. 357 -- - 



2. Zinc in sulphate of 7/iuc ; the nitric acid of 1. 213 sp. gr._ 



3. Zinc in sulphate of zinc; carbon in nitric acid of 1. 213sp. gr. 



4. Zinc in sulphate of zinc ; copper in sulphate of copper. .- 



5. a. Silver in cyanide of potassium — common salt; copper in 



sulphate of copper - --- 



b. The same, later 



c. The same, still later 



2S- 22 

 28,43 

 2t>. 29' 

 liv &3- 



14. OS 

 13. 07 

 12.35 



Tertsion of open 

 LaiiteTj. 



I. 



27.71 

 2ff. 15 

 18.88- 



14. 27 

 13. 84 

 12.36 



II. 



28.22 

 27. 75 

 2G. 1!T 



14. 23 

 13.83 

 12.26 



The tension of the open battery is determined by the above-described 

 methods. The numbers under I and II were obtained by the first and 

 second methods respectively. 



Since the square roots of the torsions, as well as the numbers of tlw 

 table on page 385 of volume LXXII of Pogg. Ann., denoting the 

 tensions corresponding to the different angles of deflection, and also 

 the number expressing the electro-motive force, are all measured by 

 different units,, Kohlrausch, in order to make the data comparable, 



