Abstract: The organic coating deposited on a metallic substrate is quantitatively euated by measurement of electrical signals through an electrochemical cell having an electrode separated from the deposited coating by a porous pad within which a liquid medium is absorbed. Quality determining parameters of the coating are rapidly calculated through a data processor to which electrical current and phase shift measurements are fed together with data from the electrochemical cell. The method may be used to evaluate the quality of the coating on the steel hull of a marine vessel exposed to seawater.

Abstract: A purification system for producing extremely pure H.sub.2 from H.sub.2 gas streams containing water and small amounts of O.sub.2 comprises a single column with alternating layers of adsorbent and a catalyst for the reaction 2H.sub.2 + O.sub.2 .fwdarw. 2H.sub.2 O. The alternating layers are arranged so that the gas to be purified first meets an adsorbent layer, next a catalyst layer and finally an adsorbent layer. Two such columns can be operated alternatively, one being used to produce purified gas, while the other is backflushed with as little as 2% of the product gas of the operating column. By this technique, H.sub.2 gas can be produced having a purity as high as 99.9999% or higher. The inventive system can also be used to purify O.sub.2 gas streams containing water and small amounts of hydrogen.