The problem of lead in mexican pottery.

Much public attention has been focused in the United States on utilitarian Mexican pottery as a source of lead poisoning. Our work demonstrates that, if a firing temperature of at least 1150 degrees is used, lead-glazed earthenware is made safe for the storage and preparation of foods. Examination by d.c. arc emission spectroscopy and X-ray diffraction shows that the lead then remains in crystalline form. An exchange-equilibrium for lead between solutions and earthenware material is postulated.

Wet ashing of coal with perchloric acid mixed with periodic acid for the determination of sulphur and certain other constituents.

A method is described for the determination of sulphur and some other inorganic constituents of coal. Organic matter is destroyed by wet combustion with perchloric acid and periodic acid. The method is rapid and efficient. Silica and sulphur are determined gravimetrically, iron, aluminium, vanadium, titanium, phosphorus, and arsenic spectrophotometrically, and calcium and magnesium volumetrically. No loss occurred by volatilisation. The complete analysis scheme devised was applied to a bituminous coal of Iowa origin.