Desiccants

chemical preparations for drying standing crops. Many contact herbicides (DINOC, dinitro-sec-butyl-phenol, pentachlorophenol, and pentachlorophenates of alkali metals) are used as desiccants. Inorganic compounds that can be used as desiccants include sulfuric acid, arsenous acid, and sodium, magnesium, and calcium chlorates. Because of the danger of explosion, sodium chlorate is usually used in a mixture with sodium pentabromate, and magnesium chlorate is used in a mixture with sodium chloride. Thiocyanates , ethyl and isopropyl xanthates of alkali metals, bis-(ethylxanthogen)-di-, tri-, and tetrasulfides, and calcium cyanamide are also used. Other good desiccants are a mixture of endotal and ammonium sulfate, sodium cis-β-chlo- roacrylate, sodium 2,3,4,5,5-pentachloropenta-2,4-dienate, potassium and sodium cyanates, and the preparations dikvat and parakvat.

For partial drying of plants, most desiccants are used in the form of aqueous solutions or emulsions. The most widely used are chlorates, parakvat, dikvat, and salts of chloroacrylic acid. The standard consumption of chlorates is 10-20 kg per hectare, or kg/ha (in terms of chlorate), and 0.3-2.5 kg/ha for parakvat and dikvat. The last two preparations are highly toxic to animals (LD₅₀ for rats is 17-50 mg/kg).