ELECTROLYSIS

Wanganui Chronicle, Volume LXXXI, Issue 18791, 28 May 1923, Page 4

ELECTROLYSIS

Last week’s cable news included a message from Melbourne stating that tiie City Engineer had issued a warning as to the menace of electrolysis. He -was reported to have said that much damage had, already been caused, that if the leakages were not stopped it would be only a matter of time when many buildings would crumble into ruins, and that in the meantime properties valued at hundreds of thousands of pounds were* being ruined. Electrolysis, vide expert definition,

means a “loosening” or breaking up bv electricity when current passes from a metal conductor in to a liquid conductor (which may be a selected solution or nioisure accidentally present), and again into a metal conductor. Chemical charges occur first in the liquid, and secondarily in the metals. The liquid is broken up by the cur-! rent, and if it is of a suitable kind, | cue result is that the conductor by 1 which the current enters the solution! is dissolved. The process is industrially useful. In electro-plating, for instance, the effect is that metal is dissolved from the entrance plate (the arrode) and a corresponding amount goes out of the liquid solution (the electrolyte, as it is called), and is deposited on the article being plated (the cathode). Such accidental electrolysis as may occur in the ground results in a loss of metal at one point without as a rule any building up at the other. A probable effect in such a case is the production of oxygen where current enters, causing destructive action there, and the production of hydrogen (which causes no damage, and escapes) where the current leaves the ground and re-enters the metallic circuit. It is gratifying to have the assurance of Wellington’s City Electrical Engineer that this alarming Melbourne prediction has no application to New Zealand. Mr Cable assured a Post representative that there was no ground for suspecting any destructive action in Wellington of the kind indicated, and if the conditions obtaining in connection with Wellington’s electrical service may be regarded as common to similar services in other parts of the Dominion his assurance is of general application. That it docs apply in the case of Wanganui is affirmed by Mr Taiboys, our Tramways Engineer and Manager, while Mr Turner, the engineer to the Christchurch Tramway Board, bears similar testimony as to the immunity of that city from trouble of this character. The position in Melbourne is that there

arc no electrically driven trams in the city, and the greater proportion, of the power and lighting supply is delivered by direct current, whereas in Wellington the tramways use practically all the direct current and the rest of the supply is alternating current. Consequently, according to Mr Cable, the

only recognisable cause of electrolysis, due to the power supply, is leakage from the tram rails, which are used as the return conductors for the whole of the power used by the trams. This being a -well-recognised risk, is met by proper precautions. In. accordance with British practice, which is governed by the Board of Trade’s rules, a cheek is kept on the remaining leakage by having at the power-house large earth plates connected to the generators, through a meter, so that any leakage through the earth can be measured and the efficiency of the return conductors is thus checked. The leakage thus indicated in Wellington ia very small, and the same, we understand, may be said of Wanganui.