Nitrites, solubility

Fig. 1. Sodium nitrite solubility in water where (--) represents solid-phase boundaries (1,2,4,5).

Reddish-brown gas with an acrid, pungent odor liquefies under pressure to a brown fuming liquid, which is a mixture of nitrogen dioxide and colorless nitrogen tetroxide, N2O4 density of gas 1.58 (air = 1), liquid 1.448 at 20°C (68°F) 1 L of gas weighs 3.3 g at 21°C (69.8°F) liquefies at 21°C (69.8°F), solidifies at -9.3°C (15.26°F) reacts with water to form nitric acid and nitric oxide, reacts with alkalies to form nitrates and nitrites soluble in nitric and sulfuric acids. 

Nitrates are prepared by the action of nitric acid on a metal or its oxide, hydroxide or carbonate. All nitrates are soluble in water. On heating, the nitrates of the alkali metals yield only oxygen and the nitrite ... 

Dissolve 36 g. of p-toluidine in 85 ml. of concentrated hydrochloric acid and 85 ml. of water contained in a 750 ml. conical flask or beaker. Cool the mixture to 0° in an ice-salt bath with vigorous stirring or shaking and the addition of a httle crushed ice. The salt, p-toluidine hydrochloride, will separate as a finely-divided crystalline precipitate. Add during 10-15 minutes a solution of 24 g. of sodium nitrite in 50 ml. of water (1) shake or stir the solution well during the diazotisation, and keep the mixture at a temperature of 0-5° by the addition of a httle crushed ice from time to time. The hydrochloride wUl dissolve as the very soluble diazonium salt is formed when ah the nitrite solution has been introduced, the solution should contain a trace of free nitrous acid. Test with potassium iodide - starch paper (see Section IV,60). 

Hitec Heat-Transfer Salt. Hitec heat-transfer salt, manufactured by Coastal Chemical Co., is an eutectic mixture of water-soluble inorganic salts potassium nitrate (53%), sodium nitrite (40%), and sodium nitrate (7%). It is suitable for Hquid-phase heat transfer at temperatures of 150—540°C. 

Quality of Product. Ammonium nitrate, commonly made from pure synthetic raw materials, is itself of high purity. If the product is intended for use in explosives, it should be at least 99% ammonium nitrate and contain no more than 0.15% water. It should contain only small amounts of water-insoluble and ether-soluble material, sulfates and chlorides, and should not contain nitrites. The soHd product ought to be free from alkalinity, but be only slightly acidic. 

Only three simple silver salts, ie, the fluoride, nitrate, and perchlorate, are soluble to the extent of at least one mole per Hter. Silver acetate, chlorate, nitrite, and sulfate are considered to be moderately soluble. AH other silver salts are, at most, spatingly soluble the sulfide is one of the most iasoluble salts known. SHver(I) also forms stable complexes with excess ammonia, cyanide, thiosulfate, and the haUdes. Complex formation often results ia the solubilization of otherwise iasoluble salts. Silver bromide and iodide are colored, although the respective ions are colorless. This is considered to be evidence of the partially covalent nature of these salts. 

Silver Nitrite. Silver nitrite, AgN02, is prepared from silver nitrate and a soluble nitrite, or silver sulfate and barium nitrite. 

Table 1. Solubility of Sodium Nitrite in Nonaqueous Solvents ...

Several derivatives of cellulose, including cellulose acetate, can be prepared in solution in dimethylacetamide—lithium chloride (65). Reportedly, this combination does not react with the hydroxy groups, thus leaving them free for esterification or etherification reactions. In another homogeneous-solution method, cellulose is treated with dinitrogen tetroxide in DMF to form the soluble cellulose nitrite ester this is then ester-interchanged with acetic anhydride (66). With pyridine as the catalyst, this method yields cellulose acetate with DS < 2.0. 

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

The sparingly soluble AgN02 can be obtained by metathesis, and simple variants yield the other stable nitrites, e.g. ... 

The mechanism of cyclization of diaminopyrimidines by nitrous acid appears not to have been studied in detail. For the preparative procedure an aqueous solution of alkaline nitrite is treated with the diaminopyrimidine either in the form of a salt or with simultaneous addition of hydrochloric or acetic acid. The first phase of the reaction is usually carried out at 0°C, in some cases the reaction being terminated by heating to 50-60°C. With diaminopyrimidines which are sparingly soluble in water, the reaction was carried out in an organic solvent using amylnitrite. Excess nitrous acid can possibly attack the amino groups present. This was employed in some cases for the preparation of the hydroxy derivatives. ... 

The separation of the physical isomerides is effected in the following manner the mixed nitrites are dissolved in acetone and precipitated by the addition of water, the mixture being cooled to 0°. This process is repeated several times, when eventually the more soluble or /3-nitrite is separated from the less soluble or a-variety. 

Dicyclohexylammonium nitrite s (DCHN) has a solubility of 3-9g in 100 g of aqueous solution at 25°C, giving a solution pH of about 6-8. Its vapour pressure at 25°C appears to be about 1-3 x 10 N/m but the value for commercial materials depends markedly on purity. It may attack lead, magnesium, copper and their alloys and may discolour some dyes and plastics. Cyclohexylammonium cyclohexyl carbamate (the reaction product of cyclohexylamine and carbon dioxide, usually described as cyclo-hexylamine carbonate or CHC)" is much more volatile than DCHN (vapour pressure 53 N/m at 25°C), and much more soluble in water (55 g in 100cm of solution at 25°C, giving a pH of 10-2). It may attack magnesium, copper, and their alloys, discolour plastics, and attack nitrocellulose and cork. It is said to protect cast iron better than DCHN, and to protect rather better in the presence of moderate concentrations of aggressive salts. 

Locomotive diesels As larger volumes of coolant are required in railway locomotives than in road vehicles, the cost of inhibition is proportionally greater. An additional factor is the possibility of cavitation attack of cylinder liners. These considerations place a restriction on the choice of inhibitors. In the past, chromates have been used at concentrations of up to 0-4%, but their use presents handling and disposal problems. Chromates cannot be used with ethanediol antifreeze solutions. A IS I borate-metasilicate at a concentration of 1 % has been used in the UK. Nitrate is added to this to improve inhibition of aluminium alloy corrosion. Tannins and soluble oils are also used, but probably to a lesser extent than in the past. The benzoate-nitrite formulation (formerly BS 3151) is effective and has been used by continental railways . ... 

Determination of nitrate as nitron nitrate Discussion. The mono-acid base nitron, C20H16N4, forms a fairly insoluble crystalline nitrate, C20H 16N4,HN03 (solubility is 0.099 g L 1 at about 20 °C), which can be used for the quantitative determination of nitrates [see Section 11.11(E)]. The sulphate and acetate are soluble so that precipitation may be made in sulphuric or acetic (ethanoic) acid solution. Perchlorates (0.08 g), iodides (0.17 g), thiocyanates (0.4 g), chromates (0.6 g), chlorates (1.2g), nitrites (1.9 g), bromides (6.1 g), hexacyanoferrate(II), hexacyanoferrate(III), oxalates, and considerable quantities of chlorides interfere, and should be absent. The figures in parentheses are the approximate solubilities of the nitron salts in g L-1 at about 20 °C. 

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