Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

425 OK ENGINEERING FOKMULÆ. Workshop Recipes—continued. PARTING SAND. Burnt sand scraped from the surface of castings. LOAM. Mixture of brick, clay, and old foundry sand. BLACKENING FOK MOULDS. Charcoal powder; or, in some instances, flue coal-dust. BLACK WASH. Charcoal, plumbago, and size. MIXTURE FOR WELDING STEEL. 1 sal-ammoniac, 10 borax, Pounded together, and fused until clear, when it is poured out, and, after cooling, reduced to powder. Rüst-joint Cement (Quickly Setting'). 1 sal-ammoniac in powder (by weight). 2 flour of sulphur. 80 iron boring« made to a paste with water. Bust-joint (Slowly Setting). 2 sal-ammoniac. 1 flour of sulphur. 200 iron borings. The latter cement is the best if the joint is not required for immediate use. Rjjd-lead Cement for Face-joints. 1 of white-lead. 2 of red-lead, mixed with linseed oil to the proper consistency.