Gases ammonia

The soda-ammonia process occurs in two main stages. First, brine is saturated with ammonia gas and this ammoniacal brine is then treated with carbon dioxide. The equilibrium... 

The ammonia gas is used again and the only by-product, calcium chloride, is used to melt snow, prevent freezing of coal in transit and as an antidust treatment since it is hygroscopic and forms a solution of low freezing point. 

Ammonia as a reducing agent. Ammonia gas will not burn in air but it does burn in oxygen with a yellowish flame after ignition. A convenient apparatus is shown in Figure 9.3. By reversing the gas supplies it can easily be shown that oxygen will also burn in ammonia. 

Using the apparatus shown in Figure 9.3 it can be shown that ammonia gas will bum in chlorine gas, the ignition being spontaneous in this case ... 

Reactions with electropositive metals. Ammonia gas reacts with strongly electropositive metals to form the amide, for example... 

Liquid ammonia. This can be prepared by compressing ammonia gas. It has a boiling point of 240 K and is an excellent solvent for many inorganic and organic substances as well as for the alkali metals. Liquid ammonia is slightly ionised. ... 

The process is as follows ammonia gas (made by the Haber process) is liquefied under pressure, to freeze out any water, and the anhydrous gas is then passed together with dust-free air through a... 

Formamide. Commercial formamide may contain excess of formic acid. It is purified by passing ammonia gas into the mixture until a slight alkaline reaction is obtained. The ammonium formate thus formed is precipitated by the addition of acetone the filtrate, after drying over anhydrous magnesium sulphate, is distilled under reduced pressure. Pure formamide has b.p. IO571I mm. 

Alternatively, dissolve or suspend the acid chloride in 5-10 ml. of dry ether or dry benzene, and pass in dry ammonia gas. If no solid separates, evaporate the solvent. Recrystallise the amide from water or dilute alcohol. 

Cool the solution in ice while the alkali hydroxide is dissolving some ammonia gas is evolved. When the potassium hydroxide has dissolved, separate the amine, and dry it for 24 hours over sodium hydroxide pellets. Filter into a Claisen flask and distil. Collect the di-n-butylamine at 157-160°. The yield is 31 g. 

Cupferron, the ammonium salt of the N-nitroso derivative of phenylhydr-oxylamine, is prepared by passing ammonia gas into an ethereal solution of phenylhydroxylamine and n butyl nitrite ... 

Ammonium Carbamate. Ammonium carbamate is a white crystalline soHd which is soluble ia water (2). It forms at room temperature by passiag ammonia gas over dry ice. In an aqueous solution at room temperature, it is slowly converted to ammonium carbonate, (NH2 2C02, by the... 

This carbon dioxide-free solution is usually treated in an external, weU-agitated liming tank called a "prelimer." Then the ammonium chloride reacts with milk of lime and the resultant ammonia gas is vented back to the distiller. Hot calcium chloride solution, containing residual ammonia in the form of ammonium hydroxide, flows back to a lower section of the distiller. Low pressure steam sweeps practically all of the ammonia out of the limed solution. The final solution, known as "distiller waste," contains calcium chloride, unreacted sodium chloride, and excess lime. It is diluted by the condensed steam and the water in which the lime was conveyed to the reaction. Distiller waste also contains inert soHds brought in with the lime. In some plants, calcium chloride [10045-52-4], CaCl, is recovered from part of this solution. Close control of the distillation process is requited in order to thoroughly strip carbon dioxide, avoid waste of lime, and achieve nearly complete ammonia recovery. The hot (56°C) mixture of wet ammonia and carbon dioxide leaving the top of the distiller is cooled to remove water vapor before being sent back to the ammonia absorber. 

Ammonia—Gas-Cured Flame Retardants. The first flame-retardant process based on curing with ammonia gas, ie, THPC—amide—NH, consisted of padding cotton with a solution containing THPC, TMM, and urea. The fabric was dried and then cured with either gaseous ammonia or ammonium hydroxide (96). There was Httle or no reaction with cellulose. A very stable polymer was deposited in situ in the cellulose matrix. Because the fire-retardant finish did not actually react with the cellulose matrix, there was generally Httle loss in fabric strength. However, the finish was very effective and quite durable to laundering. 

Phosphonium Salt—Urea Precondensate. A combination approach for producing flame-retardant cotton-synthetic blends has been developed based on the use of a phosphonium salt—urea precondensate (145). The precondensate is appUed to the blend fabric from aqueous solution. The fabric is dried, cured with ammonia gas, and then oxidized. This forms a flame-resistant polymer on and in the cotton fibers of the component. The synthetic component is then treated with either a cycUc phosphonate ester such as Antiblaze 19/ 19T, or hexabromocyclododecane. The result is a blended textile with good flame resistance. Another patent has appeared in which various modifications of the original process have been claimed (146). Although a few finishers have begun to use this process on blended textiles, it is too early to judge its impact on the industry. 

Ammonium fluoride is a white, deflquescent, crystalline salt. It tends to lose ammonia gas to revert to the more stable ammonium bifluoride. Its solubiUty in water is 45.3 g/100 g of H2O at 25°C and its heat of formation is —466.9 kJ/mol ( — 116 kcal/mol). Ammonium fluoride is available principally as a laboratory reagent. If it is needed in large quantities, one mole of aqueous ammonia can be mixed with one mole of the more readily available ammonium bifluoride (1). 

A newer approach developed for producing commercial quantities of high purity AP (8,36) involves the electrolytic conversion of chloric acid [7790-93 ] to perchloric acid, which is neutralized by using ammonia gas ... 

Lauramide has been prepared by passing ammonia gas through lauric acid in the presence of metallic oxides, specifically a complex mixture of Si02—AI2O2—Fe202—CaO—SO in the ratio of 24 16 3 47 10. The oxides, which are hydrated during amidation, can be regenerated by calcination (12,13). 

Ammonia is readily absorbed ia water to make ammonia liquor. Figure 2 summarizes the vapor—Hquid equiUbria of aqueous ammonia solutions and Figure 3 shows the solution vapor pressures. Additional thermodynamic properties may be found ia the Hterature (1,2). Considerable heat is evolved duriag the solution of ammonia ia water approximately 2180 kJ (520 kcal) of heat is evolved upon the dissolution of 1 kg of ammonia gas. 

Phosphoms trichloride and pentachloride form sodium chloride and sodium phosphide, respectively, in the presence of sodium. Phosphoms oxychloride, POCl, when heated with sodium, explodes. Carbon disulfide reacts violendy, forming sodium sulfide. Sodium amide (sodamide), NaNH2, is formed by the reaction of ammonia gas with Hquid sodium. SoHd sodium reacts only superficially with Hquid sulfur dioxide but molten sodium and gaseous... 

The route to 3-bromothiophene utilises a variation of the halogen dance technology (17). Preferably, 2,5-dibromothiophene [3141-27-3] is added to a solution of sodamide in thiophene containing the catalyst tris(2-(2-methoxyethoxy)ethyl)amine (l DA-1) (33) at temperatures marginally below reflux. On completion, quenching exothermically Hberates ammonia gas the organic phase is separated, washed, and distilled, and foremnning thiophene is recycled. Material of 97—98% purity is isolated. 

Beryllium Nitride. BeryUium nitride [1304-54-7], Be N2, is prepared by the reaction of metaUic beryUium and ammonia gas at 1100°C. It is a white crystalline material melting at 2200°C with decomposition. The sublimation rate becomes appreciable in a vacuum at 2000°C. Be2N2 is rapidly oxidized by air at 600°C and like the carbide is hydrolyzed by moisture. The oxide forms on beryllium metal in air at elevated temperatures, but in the absence of oxygen, beryllium reacts with nitrogen to form the nitride. When hot pressing mixtures of beryUium nitride and sUicon nitride, Si N, at 1700°C, beryllium sUicon nitride [12265-44-0], BeSiN2, is obtained. BeSiN2 may have appHcation as a ceramic material. 

In this dry process, ammonia gas passes into a molten mixture of potassium carbonate and charcoal. Although purity of the product is high, this process became obsolete because of the lower costs of the neutralization process. 

Phthalocyanines. Phthalocyanine is the only novel chromogen of commercial importance discovered siace the nineteenth century. It was discovered accidendy ia 1928, when duriag the routine manufacture of phthalimide from phthaUc anhydride and ammonia it was found that the product contained a blue contaminant. Chemists of Scottish Dyes Ltd, now part of Zeneca, carried out an iadependent synthesis of the blue material by passiag ammonia gas iato molten phthaUc anhydride containing iron filings. The importance of the colorant was realized (it was iatensely colored and very stable), and a patent appHcation was filed ia the same year. 

To minimize the loss of nitrogen in the form of ammonia gas, pH should not rise above about 8.5. 

Kamisako et al., 1988) or alternatively, an addition of ammonia gas leads to a different route for achieving the same product by die photolysis of arnmonia to produce hydrogen atoms... 

Ammonia (aqueous) [7664-41-7] M 17.0 + H2O, d 0.90 (satd, 27% w/v, 14.3 N), pK 9.25. Obtained metal-free by saturating distilled water, in a cooling bath, with ammonia (from tank) gas. Alternatively, can use isothermal distn by placing a dish of cone aq ammonia and a dish of pure water in an empty desiccator and leaving for several days. AMMONIA (gas, liquid or aq soln) is very irritating and should not be inhaled in large volumes as it can lead to olfactory paralysis (temporary and partially permanent). 

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