If we wish to select a striking example of a culmination on the plus side, we again find it in the coloured steel, which attains the bright red acme, and can be arrested at this point.
Were we here to employ the terminology before proposed, we should say that the first oxydation produces yellow, the hyper-oxydation yellow-red; that here a kind of maximum exists, and that then an ab-oxydation, and lastly a de-oxydation takes place.
High degrees of oxydation produce a bright red. Gold in solution, precipitated by a solution of tin, appears bright red: oxyde of arsenic, in combination, with sulphur, produces a ruby colour.
How far, however, a kind of sub-oxydation may co-operate in some culminations, is matter for inquiry; for an influence of alkalis on yellow-red also appears to produce the culmination; the colour reaching the acme by being forced towards the minus side.
The Dutch prepare a colour known by the name of vermilion, from the best Hungarian cinnabar, which exhibits the brightest yellow-red. This vermilion is still only a cinnabar, which, however, approximates the pure red, and it may be conjectured that alkalis are used to bring it nearer to the culminating point.