Use as a Desiccant

Quicklime s high affinity for water has resulted in its use as a desiccant for both gases and organic liquids. In some applications, finely ground quicklime is used. In others, the quicklime is mixed into a paste with an inert organic liquid and possibly other components. The paste is then formed into blocks or granules and the solvent removed by evaporation. 

A high-calcium quicklime is preferred. Reactivity to water does not appear to be particularly important, but, where blocks or granules are produced, the particle size distribution should be such that it gives the required rheological properties. 

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Dimethipin. 2,3-Dihydro-5,6-dimethyl-l,4-dithiin-l,l,4,4-tetraoxide [55290-64-7] (dimethipin, oxidimetbiin, UBI-N252, Harvard) (25) is used as a cotton defoHant and has been used as an experimental desiccant in potato vines. In addition, it defoHates nursery stock, grapes, dry beans, and natural mbber and is used as a desiccant for seed of canola, flax (l lnum usitatlssimum), rice, and sunflower (He/lanthus annuus) (10). The product has been available since the mid-1970s and the experimental work was first reported in 1974 (44). 

Monosodium methanearsonate (MSMA) [2163-80-6] CH AsONaOOH, disodium methanearsonate (DSMA) [144-21-8], CH2AsO(NaO)2, cacodyhc acid [75-60-5], (CH2)2AsOOH, and arsenic acid [7778-39-4], H AsO, are used ia agriculture appHcations (11,12). MSMA, DMSA, and cacodyUc acid are used as herbicides (qv) especially ia cotton (qv) fields for the control of Johnson and nutsedge grass and other weeds. Arsenic acid (13) and cacodyhc acid may be used as a desiccant for the defoHation of the cotton boU prior to harvesting. Calcium arsenate [7778-44-1], Ca2(As0 2> once an important chemical for the control of the boU weevil and cotton worm, has disappeared from appHcation and the use of lead arsenate [7784-40-9], Pb AsO, for fmit crops is currentiy restricted. 

Calcined Anhydrite. Soluble anhydrite, or second-settle stucco, has physical properties similar to those of gypsum plaster. It hydrates to the dihydrate rapidly in water. Its outstanding property is its extreme affinity for any moisture, which makes it a very efficient drying agent (see Desiccants). In ambient moisture-laden air, it readily hydrates to hemihydrate. Soluble anhydrite, under the trade name Drierite, is widely used as a desiccant in the laboratory and in iadustry. A small amount is also used as an insecticide carrier. Small amounts of soluble anhydrite are unintentionally produced in most commercial calciners during hemihydrate production. 

The second most important (3%) use of sodium chlorate in 1990 was as an intermediate in the production of other chlorates and of perchlorates. The use of sodium chlorate as in agricultural appHcation amounted to about 7000 metric tons in 1990. The agricultural use of sodium chlorate is as a herbicide, as a defoHant for cotton (qv). Magnesium chlorate is used as a desiccant for soybeans to remove the leaves prior to mechanical picking (see Desiccants). 

Silica Get for Use as a Desiccant for Packages, BS 2 540 1960, British Standards Institution, London... 

A colloidal solution of silicic acid concentrated until it contains only about 7% water. It has very high absorbent properties and is used as a desiccant. 

When used as a desiccant, the oxide removes water by the reaction... 

As pointed out earlier, all U.S. cotton in commercial production is now harvested by machines. The application of harvest-aid chemicals to cause the plants to shed their leaves (defoliation) or to kill and dry the plant (desiccation) are common practices in many areas. Chlorates and organic phosphates are popular defoliant materials and arsenic acid is commonly used as a desiccant. 

Two principal applications of ammonium thiosulfate are (i) as a fertdizer blend, and (ii) in photography. It is blended with other nitrogenous fertdizers to provide sulfur to the sod. Also, the compound itself is a fertilizer however, such applications are limited. In photography it dissolves undeveloped sdver hahdes from negatives and prints. It is also used as a desiccant and defohant in cotton, rice, soybean and other plants in flue-gas desulfurization and in... 

Calcium chloride has several industrial applications. The major applications of this compound are in deicing of roads, dust control, imparting stability to roads and buildings, and to improve traction in tractor tires. It is mixed with ice to make freezing mixtures. Hexahydrate mixed with crushed ice can lower the temperature of the cooling bath to below -50°C. It also is used as a desiccant for dehydrating gases and liquids. It is added to cement in various proportions to manufacture different types of concrete. Other uses are in adhesives, to lower gel temperatures, and as a calcium source in liquid feed supplements for dairy cattle. Also, the compound is used to control particle size development and reduce coalescence in plastics. 

Arsenic trioxide finds major use in the preparation of other compounds, notably those used in agricultural applications, The compounds monosodium methylarsonate. disodium methylarsonate, methane arsenic acid (cacodylic acid) are used for weed control, while arsenic acid, H3ASO4, is used as a desiccant for the defoliation of cotton crops, Other compounds once widely used in agriculture are calcium arsenate for control of boll weevils, lead arsenate as a pesticide for fruit crops, and sodium arsenite as a herbicide and for cattle and sheep dip. In some areas, arsenilic acid has been used as a feed additive for swine and poultry. Restrictions on these compounds vary from one country and region to the next. 

LiBr finds use as a desiccant in industrial air conditioning systems. 

Zinc bromide, ZnBr2, used as a desiccant Zinc chloride, ZnCl2, used as a dehydrating condensing agent in org synthesis Commercial dehydration operations are best performed on solids by an apparatus that provides air to catty off water vapor on its release Some of the equipment is convertible from heat removal to heat supply by simply changing the temp level of the fluid or air (Ref 3)... 

The anhydrous form of a compound that has a strong tendency to absorb water can be used as a desiccant. Desiccants scavenge the last traces of water from a system. One of the most commonly used desiccants is silica gel (Si02). Addition of water to a desiccant is a reversible process, so hydrated forms of a desiccant can be used as moisturizers. 

Uses herbicides/insecticides pre- or post-emergence control of broadleaf weeds in cereals, maize, lucerne, clover, trefoil, grass leys, potatoes, peas, onions, garlics, peas, leeks, soya beans, orchards, groundnuts, strawberries, vineyards and other crops for control of strawberry runners and raspberry suckers and overwintering forms of insect pests on fruit trees also used as a desiccant for leguminous seed crops destruction of potato haulms as a pre-harvest hop defoliant, etc. 

The compound is a powerful dehydrating agent that is sometimes used as a desiccant, and the reaction with water can be shown as... 

The structural formula of P4O,0. Note that some of the oxygen atoms act as "bridges" between the phosphorus atoms. This compound has a great affinity for water and is often used as a desiccant, or drying agent. 

Anhydrous copper sulphate absorbs moisture strongly, and is also used as a desiccating agent, however it does not become wet. 

Tablet and capsule diluent. The anhydrous form is used as a desiccant.

Paraquat is used as a broad-spectrum herbicide on weeds and grasses in agricultural and nonagricultural areas. It is used as a desiccant on tomatoes, cotton, beans, soybeans, potatoes, sunflowers, and sugar cane to aid in harvesting and to induce resin soaking on pine trees. 

Kjelgest [Thomas], TM for anhydrous granular magnesium perchlorate for use as a desiccant. 

Water vapor permeability (WVP) was determined gravimetrically at 25°C at the relative humidity of 33, 54, and 76% according to ASTM (American Society for Testing Materials) E 96 (ASTM E 96, 2001). Anhydrous CaCl2 of about 50 g (Baker, J.T., Deventer, The Netherlands), was used as a desiccant. WVP was calculated with Equation 24.2 where mass of water is WhjO/... 

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