Ammonium chloride reaction with calcium

Carbon dioxide and the ammonia recovered by treating the ammonium chloride formed with calcium hydroxide are returned to the process cycle. Ammonia is therefore only a reaction-aid. The overall reaction is ... 

Treatment of the ammonium chloride liquor with calcium hydroxide regenerates ammonia for the use in the first reaction ... 

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. 

Preparation. Hexagonal boron nitride can be prepared by heating boric oxide with ammonia, or by heating boric oxide, boric acid, or its salts with ammonium chloride, alkaU cyanides, or calcium cyanamide at atmospheric pressure. Elemental nitrogen does not react with boric oxide even in the presence of carbon, though it does react with elemental boron at high temperatures. Boron nitride obtained from the reaction of boron trichloride or boron trifluoride with ammonia is easily purified. 

Reactions of the Side Chain. Benzyl chloride is hydrolyzed slowly by boiling water and more rapidly at elevated temperature and pressure in the presence of alkaHes (11). Reaction with aqueous sodium cyanide, preferably in the presence of a quaternary ammonium chloride, produces phenylacetonitrile [140-29-4] in high yield (12). The presence of a lower molecular-weight alcohol gives faster rates and higher yields. In the presence of suitable catalysts benzyl chloride reacts with carbon monoxide to produce phenylacetic acid [103-82-2] (13—15). With different catalyst systems in the presence of calcium hydroxide, double carbonylation to phenylpymvic acid [156-06-9] occurs (16). Benzyl esters are formed by heating benzyl chloride with the sodium salts of acids benzyl ethers by reaction with sodium alkoxides. The ease of ether formation is improved by the use of phase-transfer catalysts (17) (see Catalysis, phase-thansfer). 

The equations that represent the reactions with water support the prediction that NH4NO3 dissolves to form an acidic solution and Na3P04 dissolves to form a basic solution. Calcium chloride is the salt of a strong base-strong acid, so neither ion reacts with water and the solution is neutral. Both ions in ammonium hydrogen carbonate react with water. Because Kt, for HCOs" is greater than for NH4, the salt dissolves to form a weakly basic solution. 

The Solvay process involves a series of partial reactions. The first step is calcination of calcium carbonate to form lime and CO2. Lime is converted to calcium hydroxide. The most crucial step of the process involves reacting brine solution with carbon dioxide and ammonia to produce sodium bicarbonate and ammonium chloride. Sodium bicarbonate converts to sodium carbonate. The calcium hydroxide and ammonium chloride react to form calcium chloride as the by-product. The partial reactions are shown below ... 

An intimate mixture ot 274 grms. of rubidium iron alum, or 260 grms. of rubidium aluminium alum with 100 grms. of calcium carbonate, and 27 grms. of ammonium chloride, is heated in a nickel crucible to a dull red heat until ammonia vapours are no longer evolved, and then the temp, is raised to redness. The product is ground with a litre of cold water for 15 minutes filtered by suction and washed with 400 c.c. of water, added in small portions at a time. The combined sulphuric acid is precipitated by the addition of barium hydroxide, and the filtered liquid boiled while a stream of carbon dioxide is passed through the soln. If the soln. loses its alkaline reaction, and yet retains some calcium, a little rubidium carbonate must be added to precipitate calcium carbonate. The soln. is then treated with hydrochloric acid and evaporated. 

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