Crystalline salts hygroscopicity

Physical and Chemical Properties. Ammonium nitrate is a white, crystalline salt, df = 1.725, that is highly soluble in water, as shown in Table 3 (7). Although it is very hygroscopic, it does not form hydrates. This hygroscopic nature compHcates its usage in explosives, and until about 1940, was a serious impediment to its extensive use in fertilizers. The soHd salt picks up water from air when the vapor pressure of water exceeds the vapor pressure of a saturated aqueous ammonium nitrate solution (see Table 4). 

The potassium salt reacts in the cold with an equi valent amount of hypochlorous acid to form potassium chloraiiiidosid phonate, N1IC1.S03K, which may be isolated by evaporation to small bulk in vacuo and precipitation with alcohol.2 It is a comparatively stable, hygroscopic, crystalline salt, hydrolysed by mineral acids to form ammonium chloride and sulphuric acid. The corresponding bromine compound is similar in properties. Barium forms a less stable chloro-compound. 

CALCIUM CHLORIDE. Calcium chloride. [CAS I004.7-52-4J. CaClj, is a white, crystalline salt that is very soluble in water. Solutions containing 30-45 wl % CaCh are used commercially. Of the alkaline-earth chlorides it is the most soluble in water, h is extremely hygroscopic and liberates large amounts of heat during water absorption and on dissolution. It forms a series of hydrates containing one. two, four, and six moles of water per mole of caJcium chloride (Table I). Another hydrate. CaCl 0.331 I O. has been identified, mol wi 116.98 94.8 wl % CaCl, heat of solution in water to infinite dilution. -71.37 kJ/mol (- 17.06 keal/mol). 

Dimethylhalonium fluoroantimonates such as dimethylbromonium and -iodonium fluoroantimonates can be isolated as crystalline salts. They are stable in a dry atmosphere at room temperature, and some are now commercially available. Dimethylhalonium fluoroantimonate salts are very hygroscopic, and exposure to atmospheric moisture leads to immediate hydrolysis. 

PROP White crystalline powder hygroscopic with a faint salt taste. Sol in... 

Double bromides of the type RjUBre, similar to the corresponding chlorides, have been prepared by passing uranium tetrabromide vapour over the heated alkali bromides. The potassium and sodium salts, KgUBrg and NajUBr, are green crystalline substances, hygroscopic, but less so than uranium tetrabromide. 

Pyridines form crystalline, frequently hygroscopic, salts with most protic acids. Pyridine itself, with p/faH... 

Carboxylic, and arylsulfonic acid halides react rapidly with pyridines generating 1-acyl- and 1-arylsulfonyl-pyridinium salts in solution, and in suitable cases some of these can even be isolated as crystalline, non-hygroscopic sohds. Solutions of these salts, generally in excess pyridine, are commonly used for the preparation of esters and sulfonates from alcohols, and of amides and sulfonamides from amines. 

Sodium salt, C10Hj,N,N O,.S. Inadin, Inaktin, Brevinar-con, Narkothion, Crystalline, slightly hygroscopic solid. Readily sol in water-... 

Pyridines form crystalline, frequently hygroscopic, salts with most protic acids. Pyridine itself, with pATa 5.2 in water, is a much weaker base than saturated aliphatic amines which have pATa values mostly between 9 and 11. Since the gas-phase proton affinity of pyridine is actually very similar to those of aliphatic amines, the observed solution values reflect relatively strong solvation of aliphatic ammonium cations this difference may in turn be related to the mesomerically delocalised charge in pyridinium ions and the consequent reduced requirement for external stabilisation via solvation. 

In a method utilizing the deliquescence of crystalline salts, the salt crystals deliquesce in a space with a vapor pressure that exceeds the vapor pressure of their saturated solution. In this way it is possible to draw from their state conclusions about whether the vapor pressure of the measuring space is actually below or above the limit value. The dry bulb temperature and the dew point temperature of air determine the state of air present in the measuring space and also the partial pressures. The method based on this consists essentially of measuring the dew point of the air. The measurement of the equilibrium vapor tension of the air can be carried out by means of hygroscopic cell. 

Commercial crystalline salts frequently exhibit hygroscopy at atmospheric humidities lower than those given for the pure salts in Table 93. Usually impurities present in the product cause the trouble. For example, traces of calcium chloride in sodium chloride would render the crystals damp at very low atmospheric humidities. Removal of the hygroscopic impurity would be the answer, but this is not always economical. Coating of the crystals with a fine inert dust will often prevent the mass becoming damp table salt, for instanee, can be coated with magnesium carbonate or calcium aluminium silicate. 

Sodium thiosulfate (1885) n. NaaSaOs. A hygroscopic crystalline salt used as a photographioc fixing agent and a reducing or bleaching agent. 

By exchange of the gegenion of the hygroscopic chlorides to tetrafluorobo-rates or hexafluorophosphates, crystalline, non hygroscopic salts were obtained. 

Properties—It is a colorless, bitter-tasting, water- soluble white syrup that takes up water rapidly on exposure to air (hygroscopic) and readily forms more stable crystalline salts with acids such eis choline chloride or choline bitartrate. It is fairly stable to heat and storage, but unstable to strong alkali. It exists in all foods in which phospholipids occur liberally. 

Sulphonic acids are frequently crystalline solids, readily soluble in water and often hygroscopic. Because of the difficulty of isolation of the free acids, they are usually encountered as the alkah metal salts. 

Nitronium salts are colourless, crystalline and very hygroscopic nitronium perchlorate and sulphate are unstable and liable to spontaneous decomposition, whereas nitronium tetrafluoroborate and other complex fluoro-salts are relatively stable. 

Lewis Acid Complexes. Sulfolane complexes with Lewis acids, such as boron trifluoride or phosphoms pentafluoride (17). For example, at room temperature, sulfolane and boron trifluoride combine in a 1 1 mole ratio with the evolution of heat to give a white, hygroscopic soHd which melts at 37°C. The reaction of sulfolane with methyl fluoride and antimony pentafluoride inhquid sulfur dioxide gives crystalline tetrahydro-l-methoxythiophenium-l-oxidehexafluoroantimonate, the first example of an alkoxysulfoxonium salt (18). 

Cesium perchlorate [13454-84-7], CsClO, mol wt 232.35 and theoretical cesium content hi.25/q, is a crystalline powder that decomposes at 250°C Cesium fluoride [13400-13-0], CsF, mol wt 151.90, theoretical cesium content 87.49%, has a melting point of 682—703°C and a boiling point of 1253°C. Cesium fluoride is an extremely hygroscopic, colorless, crystalline soUd it has a solubUity of 3.665 kg/L of water at 18°C. Cesium fluoride is made by exactly neutrali2ing cesium hydroxide with hydrofluoric acid and evaporating the resultant solution to dryness at 400°C. Excess HE results in a bifluoride salt that does not decompose at 400°C, and carbonate in the starting material gives an alkaline product. 

Melamine, a non-hygroscopic, white crystalline solid, melts with decomposition above 347°C and sublimes at temperatures below the melting point. It is only slightly soluble in water 100 ml of water dissolve 0.38 g at 20°C and 3.7 g at 90°C. It is weakly basic and forms well-defined salts with acids. 

Nitrites are white, crystalline hygroscopic salts that are very soluble in water. When heated in the absence of air they disproportionate ... 

Salts are obtained by direct neutralization of the acid with appropriate oxides, hydroxides, or carbonates. Sulfamic acid is a diy, non-volatile, non-hygroscopic, colourless, white, crystalline solid of considerable stability. It melts at 205°, begins to decompose at 210°, and at 260° rapidly gives a mixture of SO2, SO3, N2, H2O, etc. It is a strong acid (dissociation constant 1.01 x 10 at 25° solubility 25gper 100g H2O) and, because of its physical form and stability, is a convenient standard for acidimetry. Over 50000 tonnes are manufactured annually and its principal applications are in formulations for metal cleaners, scale removers, detergents and stabilizers for chlorine in aqueous solution. 

This is a hygroscopic crystalline powder and should be used immediately after drying. There is a report2 regarding an explosion of the dry dipotassium salt prepared by another method. There is no evidence that this procedure produces the same unstable impurities. 

The resulting alkoxydlazenium fluorosulfonates are stable, highly hygroscopic, crystalline solids, which are freely soluble in organic solvents, such as dichloromethane (in contrast, the fluoroborate salts are relatively insoluble). 

Crystalline solid. Bromide salt is a hygroscopic white solid. Various other salts have been reported. 

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