ling castings," as it is called, is performed in the following manner:—
The castings are placed on two wooden stages, covered with lead, each being 20 feet by 12 feet wide, and supported by two rollers, about 18 inches from the floor.
The trough containing the pickle (which consists of 2½ parts of water to 1 of acid) is of the same length as the stages, which are inclined towards it, to enable it to receive the drainings. The diluted acid is poured over the castings by hand from a long ladle, and when they are dry, the operation is repeated as often as necessary.
The stages are then inclined in the opposite direction, and cleansed from the coating of acid and sand by a powerful stream of water directed upon them from a hose pipe.
In England when the process of pickling is adopted for light castings, it is usual to immerse them in the liquid. The American method was probably adopted in consequence of the high price commanded by manual labour.
9. Annealing Railway Wheels.—The leading and trailing wheels of locomotives, and railway carriage wheels, are commonly hollow cast-iron disc wheels.
The process of annealing adopted in a large manufactory in Philadelphia is as follows:—
