“…72 The special applications of electrolytic processes include a rapid method of separating silver, copper, and bismuth by the use of graduated potentials,73 and a rnicro-method for separating gold from potassium cyanide solution. 74 An electrometric method of titrating silver ions in the presence of colloidal silver 75 has been devised. To obtain accurate results in the electrometric titration of mercury with ammonium thiocyanate, it is essential that mercury ions should not be present ; the uncertain end-point in titrating mercuric nitrate is due to hydrolysis, and to prevent this a large excess of acid should be added.…”