densing the acid vapor to produce a volatile acid solution, and collecting the solution; feeding the concentrated acid mixture to an acid sorption unit in which acid is sorbed from the mixture and metal impurities in the mixture are rejected in a deacidified byproduct solution; eluting acid sorbed in the acid sorption unit with water; and re- cycling acid eluted from the sorption unit back to the evaporator.

Etching Aluminum Foil U.S. Patent 5,500,101. March 19, 1996 Y Yoneyama, assignor to Nihon Chikudenki Kogyo KK, Tokyo

In a method of etching aluminum foil for electrolytic capacitors by applying altemat- inp current to the aluminum foil in an electrolytic solution containing chloride ions, the improvement comprising forming two half waves during the positive side half period and the negative side half period of the alternating current with a least one of the waveforms; and forming a rest period between the half waves during the positive side half period and the negative side half period of the alternating current.

Bowed Shape Electroforms U.S. Patent 5500,105. March 79, 1996 73 Leenhouts, assignors to Xerox Corp., Stamford, Conn.

A method of forming a curved electro- form, comprising forming a substantially convex surface along a longitudinal axis of a mandrel by applying a first layer of ma- terial having a first thermal coefficient of expansion on the mandrel, applying a sec- ond layer of material having a second ther- mal coefficient of expansion on the first layer, the second thermal coefficient of ex- pansion being greater than the first thermal coefficient of expansion and heating the mandrel to expand the first layer and the second layer of the mandrel, differing amounts creating the convex surface; plat- ing the convex surface of the mandrel with a material to form the curved electroform; and separating the curved electroform from the mandrel.

Electroplating Process U.S. Patent 5,500,106. March 19, 1996 R.L. Goldberg, assignor to Shipfey Co. L.L.C., Mar/borough, Mass.

A process for plating a nonconductive substrate with a metal, comprising the steps of providing a porous coating of carbon particles on the substrate, providing a re- ducing agent within the pores of the porous coating of the carbon particles, said reduc- ing agent being of a strength sufficient to reduce ions of metal to be plated onto the substrate when in contact with the same, contacting the substrate having the porous coating containing the reducing agent within the coating with an electrolytic metal plating solution to form an initial coating of the metal on the conductive coating by reduction and electroplating the metal over the contacted substrate.

Process for Removal of Metal Ions From Aqueous Solutions U.S. Patent 5,500,126. March 19, 1996 W. Fries, assignor to Rohm and Haas Co., Philadelphia

A process for removal of metal ions from aqueous solutions that comprises add- ing a polyamine to an aqueous solution containing metal ions and a metal complex- ing agent capable of forming a metal com-

Nickel and Chromium Plating, Third Edition Ey JK. Dennis and lX Such

449 pages $128.00

In this book the authors describe the industrial processes for carrying out nickel and chromium plating. Although updated throughout, new material of particular interest appears on environmental and health concerns, electroless nickel, electro- forming, and alloy deposition.

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