Inhaltsangabe
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1909. Excerpt: ... CUSHMAN'S METHOD OF COMPARING THE RELATIVE RATE OF CORROSION OF IRON OR STEEL SPECIMENS. In the masterly paper on "The Preservation of Iron and Steel,"' presented by Dr. Allerton S. Cushman to the meeting of the Iron and Steel Institute held in London in May 1909, the author points out that "the corrosion of iron, like that of other metals, is an electro-chemical phenomenon," and "that in studying iron and steel from the standpoint of their stability, under the conditions of service, we are not dealing with homogeneous, pure metal.' Further, he alludes to the fact that "the corrosion of iron does not take place evenly and uniformly over the surface, but that, on the contrary, it is a matter of common observation that iron corrodes rapidly at certain weak points, the effect produced being known as pitting." Dr. Cushman illustrates the progress of the reaction in ferroxyl mounts in the following manner:--"A per cent. solution of agar-agar is first made by dissolving a weighed quantity of powdered agar in the requisite amount of water. This solution is boiled for one hour, fresh water being added to replace that lost by evaporation. It is then filtered while hot, and 2 cubic centimetres of standard phenolphthalein indicator added to every 100 cubic centimetres solution, after which it is brought to a perfectly neutral condition by titration with a tenth normal solution of potassium hydroxide (KOH) or hydrochloric acid (IIC1), as the case may be. The addition of 7 cubic centimetres of a 1 per cent. solution of potassium ferricyanide to every 100 cubic centimetres of solution is then made, and the ferroxyl reagent while still hot is ready to use. Enough of the reagent should be poured into a Petri dish just to cover the bottom and the dish floated in cold wate...
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