The preparation of oxygen by electrolysis of baryta

Abstract

Morley, in his classical researches, pointed out that various impurities were present in the gases produced by electrolysis of sulphuric acid and potassium hydroxide solutions. Using the latter method, Lord Rayleigh, by addition of a small quantity of baryta, attempted to minimize the amount of hydrocarbons present in the hydrogen as impurity, derived from the carbonate present in the alkali. Baker pointed out that the action of baryta on potassium carbonate is a reversible one, particularly in the presence of such a large excess of potash, and concluded that Rayleigh's precaution might not be particularly effective. Baker recommended the electrolysis of pure barium hydroxide solution, in which barium carbonate is insoluble, and which consequently must give hydrogen tree from hydrocarbons. He also noted that, with the use of pure baryta solution, the oxygen is apparently free from ozone and hydrogen peroxide. It is to be noted that Baker gave no details concerning the shape and material of his electrodes, or of the currents employed in the electrolysis. The method of electrolysing baryta, using nickel electrodes has become a standard method of preparing small quantities of pure oxygen. The present author has employed the apparatus shown in fig. 1 for this purpose during the past few months. The apparatus consists of two vessels, A and B, constructed from 1-inch internal diameter tubing, carrying nickel electrodes, the upper ends of which are welded to platinum wires sealed through the glass, the seals being sufficiently strong to allow currents up to 2 amperes to pass without cracking the glass. The use of nickel is justified owing to its low hydrogen and oxygen over-voltages. The electrodes are constructed from 18 S. W. O. pure nickel wire, 3 feet of which is coiled up as shown. These electrodes have a fairly large surface area—approximately 34 sq cm. The baryta solution was saturated at room temperature and a layer of pure barium hydroxide was allowed to settle on the bottom of the outer jar. The electrolysis was carried out, using a current of 1 ampere, which kept the temperature of the solution at about 60°C. The oxygen was used in experiments, and was found at first to be highly satisfactory.