Lead Sulphate

Many attempts have been made to utilize the sulphate of lead (PbSO₄) as a pigment. This compound, which is nearly insoluble in water and in dilute acids, is almost, if not entirely, destitute of poisonous properties owing to this insolubility, although as ordinarily prepared it possesses neither the pure whiteness nor the body of white lead. But under the name of Freeman's white lead, or non-poisonous white lead, a paint has been introduced which may prove a rival to ordinary white lead. It is essentially lead sulphate, and is prepared by precipitating lead acetate solution with sulphuric acid. But this precipitate is subjected to a special process of grinding with small quantities of zinc-white and barium sulphate, and acquires thereby a considerable increase of density and opacity, although both the latter compounds are of less specific gravity than the lead sulphate to which they have been added. Being, when ground in oil, not only destitute of the disagreeable smell of white lead, but much less readily darkened by sulphuretted hydrogen, Freeman's white possesses distinct advantages in these respects over the more common paint.

It may be mixed with other permanent pigments without injuring them: it is practically non-poisonous. On the other hand, it does not possess the remarkable hardening and drying powers of white lead.