1888.] and the Minimum-point, fyc, of a Voltaic Couple. 305 



Table XT. — KC1 in 465 grains of Water at 12° C. 



Grains. 



Volts. 



Grains. 



Volts. 



Grains. 



Volts. 



147 



1 -30436 



93 



1 -30436 



39 



1 -30436 



129 





75 





21 





111 





57 





3 



)) 



The strongest solution was a saturated one. Four other solutions 

 between those of 129 and 147 grains were tried, but they all gave 

 1*30436 volt. The abscissae of the electromotive forces in this table 

 formed a straight line. 



Table XII.— Ditto at 8° C. 



Grains. 



Volts. 



Grains. 



Volts. 



Grains. 



Volts. 



0-003 



1 -3056 



-001335 



1-2014 



-000224 



1-087 



-002667 



1 -2671 



-001001 



1-1728 



0-000112 



5) 



0-002334 



1 -2043 



0-000669 



11442 



water 



55 



-002001 



1 -2443 



0-000660 



1-087 







-001668 



1-230 



-000336 



55 







The smallest proportion of the salt necessary to disturb the voltaic 

 balance lay between 1 in 695,067 and 704,540 parts of water. The 

 variation of electromotive force in these solutions was not uniform. 



The following table shows the proportions of these three salts 

 required to upset the balance : — 



Table XIII. 



Iodide, between 1 in 15,500 and 17,222 parts of water. 

 Bromide „ 1 „ 66,428 „ 67,391 „ 

 Chloride „ 1 „ 695,067 „ 704,540 „ 



By comparing these numbers with those in Table IV, it will be 

 perceived that each of the haloid salts acted much more powerfully 

 than either of the oxygen ones, and that the order of degrees of 

 activity in the two series was reverse. 



(Suspecting a decomposition of the chloride solution by the couple, 

 I divided a solution of 8 grains of the salt per ounce of water into 

 two equal portions in two glass vessels, then immersed a piece of zinc 

 wire in one portion, and a second piece of the same wire in contact 

 with a piece of platinum in the other, and set the vessels aside. In 

 about 24 hours the liquid containing the couple was distinctly alkaline, 



