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The method is
carried out as follows: The articles are immersed in solution which contains
25 grams of phosphoric acid and 1½ grams of manganese dioxide per litre.
Boil for 2 to 4 hours, Rinse in warm water, then cold water and dry in
sawdust. Brush the articles and heat until water dropped on is thrown off.
At this temperature immerse the articles in linseed oil, drain and heat to
dryness.
Another process is
to boil articles in a solution of 150 grams of calcium hydrogen phosphate
per litre until they assume the proper color. Rinse and dry in sawdust-
immerse the articles in heavy oil at 100° F., for one hour. Drain and dry.s
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