1903-4.] The Viscosity of Aqueous Solutions of Chlorides , etc. 231 
The Viscosity of Aqueous Solutions of Chlorides, 
Bromides, and Iodides. By W. W. Taylor, M.A., D.Sc., 
and Clerk Ranken, B.Sc. Communicated by Professor 
Crum Brown. 
(Read March 21, 1904.) 
In a recent investigation on the aluminium anode, by one of us, 
in conjunction with Inglis,* a striking difference was found 
between chloride and bromide during some preliminary experiments 
on the rate of solution of aluminium in sulphuric acid : — 
addition of a small quantity of potassium chloride to the sulphuric 
acid greatly increased the rate of evolution of hydrogen, but 
addition of an equivalent quantity of potassium bromide , under 
the same conditions, appeared to have no effect at all. Subsequent 
investigation, not yet completed, has shown that, under similar 
conditions and with solutions of pure hydrochloric acid and 
hydrobromic acid which are isohydric (have the same concentration 
of H'), the rate of evolution of hydrogen from hydrochloric acid is 
about thirty times as great as from hydrobromic acid. No experi- 
ments have yet been made with hydriodic acid. 
Such marked differences between chloride and bromide are by 
no means common ; so far as we are aware, the only one previously 
recorded is by Ostwald,f that chloride, bromide, and iodide have 
very different effect on the periodic dissolution of chromium in 
acids. Another interesting instance has since been found by Elbs 
and Nubling | — that with a lead anode and hydrochloric acid as 
electrolyte, a compound of quadrivalent lead is formed ; but that 
when hydrobromic acid or hydriodic acid is the electrolyte, no 
similar compound is formed. It is a curious circumstance that in 
each of these cases the reaction is one which takes place at the 
* Phil. Mag. (6), 5, p. 312 (1903). 
t Zeit. fur Phys. Chem., 35, pp. 33, 204 (1900) ; 38, p. 441 (1901). 
X Zeit. fur Elektrochemie , ix. p. 776 (1903). 
