Zinc also gives white precipitates with ferrocyanide of potassium and ammonia.
As the last, but adding a mixture of thoroughly dried sulphate of iron and ferrocyanide of potassium.
The product is chemically pure, and equal to fully 10% of the ferrocyanide employed.
Copper:—a. Moisten the suspected bread with a few drops of a solution of ferrocyanide of potassium.
If it be heaped up and kept hot in contact with air, some of the ferrocyanide is also decomposed, with diminution of the product.
Adopting these proportions, 4224 parts of ferrocyanide of potassium yield 81 parts of hydrocyanic acid.
Dip out a little of the Bordeaux mixture in a cup or saucer and drop the ferrocyanide on it.
It is also made by melting the ferrocyanide of potassium with sulphide of potassium.
It is always well to make Bordeaux mixture by using the ferrocyanide of potassium test — Cornell University.
ferrocyanide of potassium gives no precipitate at first, but after a time the whole forms a thick jelly.