Septembeb 28, 1906.] 



SCIENCE. 



407 



water would be contaminated with salt-water 

 leakage. 



It soon became evident by observation of 

 the several combinations in these cells, that 

 there was a violent local action between the 

 zinc and the copper of the brass tubes which 

 were in contact with the electrolyte, and that 

 this increased in the reaction as it progressed 

 in stagnant conditions. 



It then became necessary to find a method 

 more comprehensive than the proposed simple 

 counter-electromotive force for the neutraliza- 

 tion of the traction companies' stray currents. 

 Further experiments with plates immersed in 

 the cooling water samples showed that by 

 interposing a counter electromotive force 

 against the galvanic couple which should ex- 

 ceed in pressure the voltage of the galvanic 

 couple, the actions of the electrolytic cor- 

 rosion ceased. The difference in potential be- 

 tween the zinc and the copper for the Long 

 Island City harbor water was found to be 0.4 

 of a volt. Zinc and copper were selected in 

 these experiments because the condenser tubes 

 were to be made of 60 per cent, copper and 40 

 per cent. zinc. It became evident that when 

 unconnected, or electrically separated, plates 

 were placed in this electrolyte, if they were 

 of composite construction and had sharp 

 projections into the fluid, raised by cutting 

 and prying up with a knife, they would have 

 these projections promptly destroyed, and that 

 if an electric battery having a pressure ex- 

 ceeding that of the couple in the East River 

 water was caused to act to produce a counter 

 current, and having a pressure exceeding that 

 of tlie galvanic couple, the capacity of this 

 electrolyte to drive off atoms of the mechan- 

 ically combined metals in the alloys used was 

 overcome and corrosion was arrested. 



It, therefore, became desirable to not only 

 carefully provide the balancing quantity of 

 current to equal the stray traction currents 

 arising from the ground returns of railway 

 and other service, but to add to this the neces- 

 sary voltage through a cathode placed in the 

 circulating water in such a way as to bring 

 to bear electrolytic action which would pre- 

 vent the galvanic action due to this current 



coming into contact with alloys of mechan- 

 ically combined metals such as the brass tubes. 



It became evident that the influence of 

 various foreign substances in the East Kiver 

 water made the galvanic couple as between an 

 atom of zinc and an atom of copper greater 

 than for open sea water, and it was found to 

 be at times as high as 0.42 of a volt. With 

 this known it was planned to put a pressure 

 of 0.6 of a volt on the anode in order to over- 

 come this action and prevent the separation of 

 the zinc molecule from the surfaces and the 

 consequent breaking down of the tubes. 



In order to accomplish these two things, it 

 was first necessary to so install the condensers 

 as to prevent undue amounts of stray currents 

 flowing through them, thus tending to reduce 

 the amount of power required to prevent in- 

 jurious action of these currents and otherwise 

 to neutralize them. This was done by insula- 

 ting the joints in the piping and from ground 

 connections and even lining the large water 

 connections with glass melted on to the sur- 

 face. 



To furnish electromotive force, a 3-K.W. 

 motor generator was provided. It was of the 

 form used for electroplating. By means of a 

 system of wiring, switchboard apparatus and 

 appliances, together with ammeters and 

 voltmeters for measuring quantities and pres- 

 sures, and a connection to an outlying anode 

 in the condensing supply intake at its harbor 

 end, this generator was planned to provide 

 current to neutralize the stray currents in 

 the condenser structure to any extent that 

 they had passed the insulated joints in the 

 supports and connections, as well as through 

 the columns of water in the pipe connections, 

 and then to adjust the additional voltage 

 needed to counteract and prevent the galvanic 

 action. 



This led to much discussion as to methods 

 and the reasons why the corrosion was pre- 

 vented; and it became necessary, in order to 

 get at the facts in the matter, to review the 

 history of electrolytic conduction. A refer- 

 ence to Earaday's Laws and to the results of 

 the experiments of Helraholtz and Clausius, 

 explained the nature of this electrolytic con- 



