Electrode potential measurements and weight loss corrosion tests indicate that air or low concentrations of certain dissolved metals passivate titanium in hydrochloric acid solutions and that passivity is accompanied by more noble electrode potentials. Air passivates titanium in acid up to 3N. Two hundred mg/l Cu++ is effective in 10N hydrochloric acid and 2 mg Cu++ passivate titanium in 5N acid. The more noble electrode potentials indicate that a reaction involving oxygen, metal ions, or ions containing oxygen takes place at the passive surface but there is no visible deposit on, or change in, the appearance of the surface except for an occasional slight tarnish. Titanium in contact with small volumes of stagnant 10N hydrochloric acid containing 200 mg/1 Cu++ loses its passivity after a period of time. This time interval seems to be directly proportional to the ratio of solution volume to specimen area and the loss of passivity is attributed to the presence of atomic hydrogen.

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of that company entered into many constructive discussions and supplied the production data. E. F. Schweitzer made some of the measurements and calculations. The authors are greatly indebted' to E. J. Serfass for carrying out the gas microanalysis.

Procedures are given by which electrolytic manganese can consistently be deposited in the flexible gamma form rather than the usual brittle alpha form. With electrolytes containing manganese and ammonium sulfates and free of sulfur dioxide or colloidal sulfur, excellent deposits were obtained on copper cathodes at current efficiencies of 62 to 72 per cent; deposits on stainless steel cathodes were much poorer. The use of colorless ammonium sulfide for purification did not interfere with the deposition of gamma manganese, but the use of yellow ammonium sulfide, unless followed by a further purification step (presumably to remove colloidal sulfur), resulted in only slightly flexible deposits consisting of gamma manganese containing some alpha. Electrolytes containing sulfur dioxide yielded only alpha manganese. Gamma manganese deposits were used successfully as starting sheets for the deposition of alpha manganese. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-06-14 to IP Vol. 94, No. 2 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-06-14 to IP Vol. 9~, No. ~ ELECTRODEPOSITION OF GAMMA MANGANESE 65 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-06-14 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-06-14 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.