The glazing of the common cream-coloured earthen ware, which is composed of an oxide of lead, readily yields to the action of vinegar and saline compounds; and therefore jars and pots of this kind of stone ware, are wholly unfit to contain jellies of fruits, marmalade, and similar conserves. Pickles should in no case be deposited in cream-coloured glazed earthenware.
The custom which still prevails in some parts of this country of keeping milk in leaden vessels for the use of the dairy, is very improper.
"In Lancashire[121] the dairies are furnished with milk-pans made of lead: and when Mr. Parks expostulated with some individuals on the danger of this practice, he was told that leaden milk-pans throw up the cream much better than vessels of any other kind.
"In some parts of the north of England it is customary for the inn-keepers to prepare mint-salad by bruising and grinding the vegetable in a large wooden bowl with a ball of lead of twelve or fourteen pounds weight. In this operation the mint is cut, and portions of the lead are ground off at every revolution of the ponderous instrument. In the same county, it is a common practice to have brewing-coppers constructed with the bottom of copper and the whole sides of lead."
The baking of fruit tarts in cream-coloured earthenware, and the salting and preserving of meat in leaden pans, are no less objectionable. All kinds of food which contain free vegetable acids, or saline preparations, attack utensils covered with a glaze, in the composition of which lead enters as a component part. The leaden beds of presses for squeezing the fruit in cyder countries, have produced incalculable mischief. These consequences never follow, when the lead is combined with tin; because this metal, being more eager for oxidation, prevents the solution of the lead.
When we consider the various unsuspected means by which the poisons of lead and copper gain admittance into the human body, a very common but dangerous instance presents itself: namely, the practice of painting toys, made for the amusement of children, with poisonous substances, viz. red lead, verdigris, &c. Children are apt to put every thing, especially what gives them pleasure, into their mouths; the painting of toys with colouring substances that are poisonous, ought therefore to be abolished; a practice which lies the more open to censure, as it is of no real utility.
FOOTNOTES:
[121] Park's Chemical Essays, vol. v. p. 193.