204. Messrs. Wright and Thompson on the Determination of 
tion of zinc- and aluminium-bromide solutions in the first 
case, but in the normal direction in the second case :— 
Zinc-Aluminium. |Cadmium-Aluminium. 
ees 
Mascaras sesecnraeeeeee — "323 + -037 
Mirman eee e ee — ‘278 +0138 
Average i tcanenacnabee — ‘296 +022 
Probable error ......... me OT +:005 
These numbers lead to the following valuations for the 
voltaic constant for bright aluminium in bromide solution 
25 Al,Br, 100 H,0 :— 
ZmG-aluminiin 62.09. eee eel Fn ees ene 
Zine-cadmium — Aluminium-cadmium 4 ee } = +'293 
Mean:-°)- «"“d)) 55 ee=220 
the constant being of + sign, since aluminium actually 
acquires the higher potential, although it might @ prior: be 
expected to acquire the lower potential. 
Julius Thomsen’s thermochemical data lead to the value 
Al,, Br. aq.= 136680; whence Hy=—1-008 volt, corre- 
sponding with 45720 gramme-degrees. Consequently 
H—EHy= + '295—(—1:008) = +1°303 ; 
1. e. the thermovoltaic constant for bright aluminium in 
bromide solution *25 AlzBr, 100H,O is a large positive 
quantity, slightly greater than that found with the corre- 
sponding chloride solution, viz. + 1°288. 
EF. Voltaic and Thermovoltaic Constants of Metals immersed 
in Solutions of their Lodides. 
I. Cadmium. 
203. The following values were obtained with a number of 
cells set up with amalgamated zinc and electro-cadmium 
immersed in solutions of their iodides of strength *25 MI, 
100 H,O :— 
Mia xamanenaas aS Re en Se ea ao 
Minimum? 60%." } Cea 
Averages) Shek i Eee 
Probable error . . . +°0008 
