Make a saturated solution of salt in water.

First wash the plate with clear water; then immerse it in the saline solution, when it should be agitated, and the coating will soon disappear.

Another process with a salt solution of half the strength of the above is very interesting and effectual.

The plate having been dipped into cold water, is placed in a solution of common salt, of moderate strength; it lies without being acted upon at all; but if it be now touched on one corner with a piece of zinc, which has been scraped bright, the yellow coat of iodine moves off like a wave and disappears.

It is a very pretty process.