Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 3, 1802).djvu/94

76&#93; 76] LEA 3t the same time, castor- oil, or other mild laxatives, conjoined with gentle opiates, have greatly- contributed to afl'ord relief. — ^The patient's diet ought to consist of nourishing broths, panada, and gruel, or similar light dishes. In whatever form lead may be introduced into the human body, it is equally deleterious and fatal, ■whether its vapours be inhaled through thelangs, absorbed through the pores of the sl;i;i, or particles of the metal betaken into the stomach. The only efiedtual /.atidotes to this insidious poison are, antimonial emetics; and, after them, the in- ternal use of liver of sulphur, toge- ther with veaetable oils, bolh ex- ternally and internally, should be liberally continued. Red-lead, or Mhuum, is a calx of lead of a lively red colour, which it acquires by slow calcina- tion and reverberation. — Its pre- paration is as follows : A quantity of lead is first burnt in a furnace, till it is converted into a kind of litharge, being stirred continually ^■ith an iron spatula, while it is mfcltinsj : it is then ground in a mill to a fine powder, after which it is again put into the furnace and stirred as before, when it assumes first a blackish hue, then a yellow cast, and at length becomes of a deep red colour. While this ope- ration is performing, the greatest caution is requisite to keep the fire at- a certain height, in order to prevent the matter from adhering, and running together. The bright colour of miniuin would render it a valuable pigment, if it could stand either in oil or in water : but, being apt to become black, it is seldom employed, ex- rr.pt as a ground for vermilion. — - Ihe genuine quality of red-lead LEA may be ascertained by the bright- ness of its colour ; and, as it is fre- quently adulterated, such fraud may be easily detected, by mixing equal quantities of minium and charcoal-dust in a crucible, and placing the whole over a fire suffi- ciently intense to melt lead. When it has continued for soiie time over the flame, it must be removed ; and, when cold, stricken against the ground. Thus, the red-lead will be reduced to its metallic state ; and, when freed from the charcoal, its diminished weight will shew the proj)ortion of adulterated matter. In medicine, red-lead is only employed externally : it obtunds the acrimony of humours ; mitigates inflammations 3 and, if judiciously ai^plied, is of excellent service in cleansing and healing old ulcers. White-Lead, or Cerussa, is prepared by placing a vessel con- taining vinegar in a moderately warm place, and over which thin plates of lead are suspended, so that the vapour arising from the acid may circulate freely round the plates. A white powder settles in the course of two or three weeks, on the surface of the metal, which is now removed into another room, and passed beneath a screen, and pair of rollers, for separating the corroded from the sound part; that is again suspended, till it is wholly- converted into a white calx ; when it is called cerusse, or white-lead. During this operat on, a considerable portion of fine dusty |)artic!es settles on the skin and lungs of the work- men, to whom it is aitemied with the most pernicious consequences. In order to countera6t such inju- rious etFects, Mr. Ward, in the ye,!r 1/95, laid a machine before the Society for the Encouragement of ArlS; Sec. and was consequently rev-'ardeU