EFFECTS OF SEA AIR.
Those who frequent the sea-coast are not long in discovering that their best dyed black hats become of a rusty brown; and similar effects are produced on some other colours. The brown is, in fact, rust. Most, if not all, the usual black colours have iron for a basis, the black oxide of which is developed by galls, logwood, or other substances containing gallic acid. Now the sea-air contains a proportion of the muriates over which it is wafted; and these coming in contact with any thing dyed black, part with their hydrochloric (muriatic) acid, and form brown hydrochlorate of iron, or contribute to form the brown or red oxide, called rust. The gallic acid, indeed, from its superior affinity, has the strongest hold of the iron; but the incessant action of the sea-air, loaded with muriates, partially overcomes this, in the same way as any acid, even of inferior affinity to the gallic, when put upon black stuff, will turn it brown.—Ibid.