Salt form melting point

Salt form Melting point of salt (°C) Aqueous solubility (mg/mL)... 

A mixture of DMF and magnesium nitrate hexahydrate decomposed violently when it was heated above the salt s melting point. It was thought that in those conditions, nitric acid had formed and oxidised DMF. 

The ability of many drugs to form salts affords the formulation scientist increased scope to optimize drug product performance. The formation of a drug salt can alter physicochemical properties such as physical and chemical stability, solid state characteristics such as crystal form, melting point, enthalpy, solvation, hygroscopicity, which in turn impact on processability, dissolution rate, and bioavailability, without... 

Salt Hydration Form Melting point CC) Aqueous solubility (mg/ml) 10 20 Weight change(%) Relative humidity (%) 40 60 70 93... 

Room temperature ionic liquids (RTILs) are molten salts whose melting points are below room temperature. RTILs are formed when the constituent ions are sterically mismatched, thereby hindering crystal formation [17]. As polar solvents, RTILs have unique applications as tunable and environmentally benign solvents with very low volatility, high fire resistance, excellent chemical and thermal stability and wide liquid temperature range and electrochemical windows [17-19]. Solvent applications of RTILs include, for example, organic synthesis [17,20, 21], separations [22, 23], storage and transportation of hazardous chemicals [24], polymeric electrolytes [25, 26], dissolution of natural products [27] and synthesis of hollow metal oxide microspheres [28]. 

Table 14.2 shows that all three elements have remarkably low melting points and boiling points—an indication of the weak metallic bonding, especially notable in mercury. The low heat of atomisation of the latter element compensates to some extent its higher ionisation energies, so that, in practice, all the elements of this group can form cations in aqueous solution or in hydrated salts anhydrous mercuryfll) compounds are generally covalent. 

Note that the amino-acids, because of their salt-like nature, usually decompose on heating, and therefore seldom have sharp melting-points. Furthermore, all naturally occurring amino-acids are a-amino-acids, and consequently, with the exception of glycine, can exist in optically active forms. 

The table below gives the lowest temperature that can be obtained from a mixture of the inorganic salt with finely shaved dry ice. With the organic substances, dry ice (—78°C) in small lumps can be added to the solvent until a slight excess of dry ice remains or liquid nitrogen (—196°C) can be poured into the solvent until a slush is formed that consists of the solid-liquid mixture at its melting point. 

Molten cryohte dissolves many salts and oxides, forming solutions of melting point lower than the components. Figure 1 combines the melting point diagrams for cryolite—A1F. and for cryohte—NaF. Cryohte systems ate of great importance in the HaH-Heroult electrolysis process for the manufacture of aluminum (see Aluminumand ALUMINUM alloys). Table 5 Hsts the additional examples of cryohte as a component in minimum melting compositions. 

Rea.ctlons, When free (R-R, R -tartaric acid (4) is heated above its melting point, amorphous anhydrides are formed which, on boiling with water, regenerate the acid. Further heating causes simultaneous formation of pymvic acid, CH COCOOH pyrotartaric acid, HOOCCH2CH(CH2)COOH and, finally, a black, charred residue. In the presence of a ferrous salt and hydrogen peroxide, dihydroxymaleic acid [526-84-1] (7) is formed. Nitrating the acid yields a dinitro ester which, on hydrolysis, is converted to dihydroxytartaric acid [617 8-1] (8), which upon further oxidation yields tartronic acid [80-69-3] (9). 

Sorbic acid and its salts are highly refined to obtain the necessary purity for use in foods. The quaUty requirements are defined by the Food Chemicals Codex (Table 3). Codistillation or recrystaUization from water, alcohoHc solutions, or acetone is used to obtain sorbic acid and potassium sorbate of a purity that passes not only the Codex requirements but is sufficient for long-term storage. Measurement of the peroxide content and heat stabiUty can further determine the presence of low amounts of impurities. The presence of isomers, other than the trans,trans form, causes instabiUty and affects the melting point. 

Strontium bromide [10476-81 -0] SrBr2, forms white, needle-like crystals, which are very soluble in water (222.5 g in 100 mL water at 100°C) and soluble in alcohol. The anhydrous salt has a specific gravity of 4.216 and a melting point of 643°C. 

Strontium chloride [10476-85-4] SrCl2, is similar to calcium chloride but is less soluble in water (100.8 g in 100 mL water at 100°C). The anhydrous salt forms colorless cubic crystals with a specific gravity of 3.052 and a melting point of 873°C. Strontium chloride is used in toothpaste formulations (see... 

The heavy metal salts, ia contrast to the alkah metal salts, have lower melting points and are more soluble ia organic solvents, eg, methylene chloride, chloroform, tetrahydrofiiran, and benzene. They are slightly soluble ia water, alcohol, ahphatic hydrocarbons, and ethyl ether (18). Their thermal decompositions have been extensively studied by dta and tga (thermal gravimetric analysis) methods. They decompose to the metal sulfides and gaseous products, which are primarily carbonyl sulfide and carbon disulfide ia varying ratios. In some cases, the dialkyl xanthate forms. Solvent extraction studies of a large number of elements as their xanthate salts have been reported (19). 

The purity of (/-a-phenylethylamine-/-malate is not readily determined by its melting point or specific rotation, but rather by its massive crystalline form and solubility. The acid and neutral /-base-/-acid salts are much more soluble, and usually do not crystallize at all. 

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. 

This table shows that the similarity of the two aglycones is most marked in their salts, but they do not appear to be dimorphic forms giving identical salts, for the melting-points of the bases are unchanged after sublimation, the rotations of the two bases in solution are different, though those of the two hydrochlorides are identical within the limits of experimental error, and all attempts at interconversion of the two bases... 

The acetyl group in aconitine may be eliminated in two other ways (a) by heating aconitine in sealed tubes with methyl alcohol, when methylbenzoylaconine, m.p. 210-1°, is formed, or (b) by heating the alkaloid at its melting-point, when pyraconitine, C32H43O9N, m.p. 167-5° (171°, Schulze), [a] ° — 112-2° (EtOH), is formed. The latter yields crystalline, laevorotatory salts, and on hydrolysis by alkalis affords benzoic acid and pyraconine, C2sH3gOgN, amorphous, [a]n — 91° (HgO), but yields a crystalline hydrochloride, B. HCl. 2-5H20, m.p. 154° (135°, Schulze), Md - 102° (HgO) (- 124-6°, Schulze). ... 

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