Important: Safety Warning
This page recommends pest-control substances such as arsenic compounds, strychnine, or cyanide — in some cases applied to food crops. These substances are lethal to humans and animals, and their use is now banned or strictly controlled.
In addition, this page describes trade processes that use dangerously toxic materials such as cyanide solutions, mercury amalgams, or strong acids. These processes require training, equipment, and precautions far beyond what the text describes.
This information has been left in for historical purposes but should not be acted upon.
Sulphuric Acid
or OIL OF VITRIOL. In horticulture, this substance is of little use; for, though weak solutions (one part in fifty of water) have been used for syringing plants to destroy insect pests, it can be employed with safety only for hardy subjects; and there are various solutions preferable for use in this way. Sulphuric Acid is largely used in the preparation of soluble phosphates for manure. The sulphates, or compounds of Sulphuric Acid, are of considerable value. Solutions of Sulphate of Copper (Blue Vitriol) and of Sulphate of Soda are employed as washes for seeds of Oats, Barley, and other Cereals, to cleanse them from spores of the Smut Fungus (Ustilago segetum), and also against Bunt (Tilletia caries) in Wheat and in Barley. In like manner, Sulphate of Copper solution (one ounce to a gallon of water) is a valuable insecticide when syringed on plants.
Sulphates are often used as manures. Sulphate of Ammonia, prepared from gas-liquor, by the addition of Sulphuric Acid to it, or to the Ammonia that is removed from the liquor when steam is forced through it, has been found to add largely to crops when given as manure. It supplies Nitrogen in a form readily taken up by plants; but the amount should not exceed 1cwt. per acre. In the South of England, Sulphate of Lime, or Gypsum, is frequently used, in quantities of from 2cwt. to 10cwt. per acre, for Beans, Peas, and other leguminous plants, for which it is especially valuable, and with which it gives excellent results. In Germany, it is used for pastures, and also, to a less amount, for other produce. It is mostly burned and reduced to powder before being applied.