Important: Safety Warning
This page contains a formula or preparation using substances now known to be dangerously toxic, such as arsenic, mercury, lead, or cyanide compounds. Exposure to these substances can cause severe poisoning, permanent injury, or death.
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.
Oxalic Acid
This substance exists as binoxalate of potash in common sorrel and the rhubarb plant, which accounts for the acid taste common to those vegetables. As oxalate of soda it is found in the barilla plant, and as oxalate of lime in lichens. It is commonly prepared by the oxidation of sugar or starch with nitric acid: 1 part of sugar is dissolved in 8 parts of nitric acid and gently heated, when intense action ensues, with a copious disengagement of nitrous-acid fumes. The crystals obtained are sour and poisonous, resembling Epsom salts, for which they are often mistaken. Chalk or magnesia suspended in water acts as an antidote in cases of poisoning. This acid is extensively used in calico-printing, and is also employed as a test for the presence of lime. It also removes ink and iron stains from cloth by forming a soluble oxalate of iron, but the fabric suffers injury if the acid be not washed off immediately.