all surfaces that are to be treated with phosphoric-acid type rust removers. 3-15. The following solution, mixed according to formula and in the order given is suitable for rust-removing purposes: Analysis Percent Phosphoric acid 75 percent Wetting agent 7.5 205 ~ Water Remainder To make 100 galions Phosphoric acid 75 percent 5.0 gallons Water Remainder Wetting agent 1.5 pounds 3-16. Suitable wetting agents are Dreft, Santomerse, Nacconol, Tergitol, Leather cleaner, or an approved equivalent. Heat to 180° to 212°. As a substitute for the rust-removing solution specified in 3-15, manganese phosphelene No. 7, procurable fran Western Reserve Laboratories, Cleveland, Ghio, or an approved equivalent, phosphoric-acid base canpound may be used. CAUTION! PHOSPHORIC ACID CLEANERS MAY ATTACK THE SKIN. SAFETY GLASSES, RUBBER GLOVES, AND RUBBER APRON SHOULD BE WORN, DO NOT SPREAD PHOSPHORIC ACID SOLUTION INDISCRIMINATELY OVER AREAS WHICH CANNOT BE THOROUGHLY CLEANED. THIS WILL CAUSE FURTHER RUSTING IN STORAGE, 3-17. AS an approved equivalent, vapor blast may be used for rust removal, polishing, and deburring. The methods of preparing the solution used in the vapor-blast unit are furnished by the mamfacturer and in general consist of an emulsion of water charged with abrasive and a cap- sule, all of which comprises a liquid honing material with rust inhibiter. This solution is discharged through a nozzle at high velocity within a glass-window cabinet. The density of the material can be changed to meet the specific requirement, and this technique will be quickly developed through experience in application, At the discretion of the responsible personnel high precision surfaces may be cleaned by vapor-blasting, how- ever, only the 5000-mesh abrasive shall be used on #uch parts. Abrasives of 250 to 500 mesh may be used on other noncritical surfaces. (The B-20 Dual Unit built by the Vapor Blast Mamfacturing Company, Milwaukee, Wis., is well suited to the operations described herein). 3-18. HANDLING OF PARTS AND ASSEMBLIES. Throughout the processing operations care shall be exercised in the utilization of proper equipment and refined methods of operation. Particular emphasis shall be placed on the following points: 18-30