The natural gypsum, or plaster of commerce, consists of
| Water, | 21 | per cent. | |
| Lime, | 33 | " | |
| Sulphuric acid, | 46 | " | |
| 100 | |||
Plaster was used as a fertilizer by the early Roman and British farmers. It was introduced into America in 1772. It may here be worthy of notice, that when Dr. Franklin desired to exhibit its utility to his unbelieving countrymen, he sowed upon a field near Washington, in large letters, with pulverized gypsum, the following words: “This has been plastered.”
The result is supposed to have been highly convincing. But this was as a manure. Dr. Franklin did not recommend it as a condiment.
You may know children who have been sown with plaster—though that plaster was modified by the smaller admixture of sugar—by their pale, puny, weakly appearance. Sugar has a tendency to increase the fatty and warming matter of the system; gypsum, or terra alba, to destroy it.
Gypsum is used in confectionery without being calcined. Calcined plaster, after being wet, readily “sets,” or hardens. Heating gypsum deprives it of the percentage of water, when it is known to commerce as “plaster of Paris.” It is cheap as manure; hence it is used instead of sugar.
Terra alba taken into the system absorbs the moisture essential to health, and disposes the child to weakness of the joints and spinal column, to rickets, marasmus, and consumption. There are other diseases to which its habitual use exposes the user; but if parents will not heed the above warning, it is useless to multiply reasons for not feeding children upon cheap or adulterated confectionery.
To detect Mineral Substance.
Take no man’s ipse dixit when the health or lives of your precious ones are at stake. “Prove all things.”
To detect mineral substances in candy, put a quantity—particularly of lozenges, peppermints, or cream candy—into a bowl, pour on sufficient hot water to cover it well. Sugar is soluble in boiling water to any extent. Terra alba is not. The sugar will all disappear; the plaster, sand, etc., will settle to the bottom; the coloring matter will mix in or rise to the top of the water. Pure candies leave no sediment when dissolved in hot water.