Ammonia/ammonium chloride, separations

Dissolve the sample in nitric acid. Separate Pb by extraction with CHC solution of sodium diethyl dithiocarbonate using alkaline cyanide solution to mask interferences. Titrate Pb in an ammonia-ammonium chloride medium at pH =10 using eriochrome black T. 

Codeine may be isolated from opium by the Gregory process [9], in which the concentrated aqueous opium extract is treated with a concentrated solution of calcium chloride, when calcium meconate, lactate, and sulphate are precipitated and removed, when the filtrate on concentration deposits the Gregory salt , a mixture of the hydrochlorides of morphine and codeine. This is purified, dissolved in water, and the morphine precipitated by ammonia, when the codeine remains in solution from which it is extracted by benzene, or the solution concentrated to the point at which a mixture of codeine hydrochloride and ammonium chloride separates. Other procedures for the isolation of codeine are available [7, 8, 10-22 inc.], critical summaries of which are given by Kanewskaja [23] and Barbier [24], Codeine may be separated from neopine (see Chap. VII) through the sulphate [25] and from morphine by chromatography [26-29]. Most of the codeine used commercially is prepared by the methylation of morphine (see below). 

A certain amount of hydrolysis of the original acetamide to acid and ammonia always occurs, and the final amine always contains traces of ammonia. This is separated by extracting the mixed anhydrous hydrochlorides with absolute ethanol, which dissolves the amine hydrochloride but not the ammonium chloride filtration of the hot ethanolic extract removes the ammonium chloride, whilst the amine hydrochloride crystallises readily from the filtrate on cooling. 

Dilute hydrochloric or sulphuric acid finds application in the extraction of basic substances from mixtures or in the removal of basic impurities. The dilute acid converts the base e.g., ammonia, amines, etc.) into a water-soluble salt e.g., ammonium chloride, amine hydrochloride). Thus traces of aniline may be separated from impure acetanilide by shaking with dilute hydrochloric acid the aniline is converted into the soluble salt (aniline hydrochloride) whilst the acetanilide remains unaffected. 

A solution of a-lithiomethoxyallene was prepared from nethoxyal lene and 0.20 mol of ethyllithiurn (note 1) in about 200 ml of diethyl ether (see Chapter II, Exp. 15). The solution was cooled to -50°C and 0.20 mol of ethylene oxide was added immediately. The cooling bath was removed temporarily and the temperature was allowed to rise to -15 c and was kept at this level for 2.5 h. The mixture was then poured into 200 ml of saturated ammonium chloride solution, to which a few millilitres of aqueous ammonia had been added (note 2). After shaking the layers were separated. The aqueous layer was extracted six times with small portions of diethyl ether. The combined ethereal solutions were dried over sodium sulfate and subsequently concentrated in a water-pump vacuum. Distillation of the... 

Several commercial grades are available fine crystals of 99 to 100% purity, large crystals, pressed lumps, rods, and granular material. Double-Decomposition Methods. Double-decomposition processes all iavolve the reaction of sodium chloride, the cheapest chlorine source, with an ammonium salt. The latter may be suppHed directiy, or generated in situ by the reaction of ammonia and a supplementary iagredient. Ammonium chloride and a sodium salt are formed. The sodium salt is typically less soluble and is separated at higher temperatures ammonium chloride is recovered from the filtrate by cooling. 

Sodium bicarbonate precipitates from solution and is recovered by filtration. Ammonium chloride is then crystallised from the filtrate, separated, washed, and dried. The exact proportion of ammonium chloride recovered depends on the relative demands for sodium carbonate and ammonium chloride. If economic conditions requite, part of the ammonia can be recovered and returned to the hrine-ammoniation step by distillation of the ammonium chloride solution ia the presence of lime. The spent calcium chloride Hquor, a final product ia manufacture of sodium carbonate by the ammonia—soda process, can also be used to obtain ammonium chloride. This Hquor is treated with ammonia and carbon dioxide... 

Laudanine, C20H25O4N, was isolated by Hesse. The crude alkaloid is purified by recrj stallisation from dilute alcohol for the removal of small quantities of cryptopine, or it may be dissolved in acetic acid and the solution poured into dilute caustic soda, when this impurity is precipitated and laudanine may be recovered from the filtrate by addition of ammonium chloride. It still contains its isomeride laudanidine, which may be separated by repeated crystallisation of the hydrochlorides, laudanidine accumulating in the aqueous mother liquors. The base crystallises from dilute alcohol, or from a mixture of alcohol and chloroform in rhombic prisms, m.p. 166°, [a]o 0°. It dissolves in solutions of alkali hydroxides, fornung metallic derivatives, which are precipitated by excess of alkali, but is nearly insoluble in solution of ammonia. The salts crystallise well ... 

With stirring, 6 g of ammonium chloride (to decompose excess acetylide) is added and the remaining ammonia is allowed to evaporate. To the residue is added cautiously 50 g of crushed ice followed by 150 ml of water the contents are mixed and steam distilled rapidly to obtain the 1-hexyne. The organic layer is separated, dried (magnesium sulfate), and distilled through a short column. 1-Hexyne has bp 71-72° the yield is about 28 g (68 %). 

During its synthetic use in liquid ammonia, some of the salt separated as a crust owing to evaporation of solvent, and exploded violently. Such salts are stable in solution, but dangerous in the solid state. Evaporation of ammonia must be prevented or made good until unreacted salt has been decomposed by addition of ammonium chloride [1]. An improved preparation of the lithium derivative is available [2],... 

A detailed description of salt mining will be postponed until the next chapter, but it is important to note that soda ash is made from both limestone and salt, the two major raw materials. As outlined in Fig. 5.2, the brine (salt solution) is mixed with ammonia in a large ammonia absorber. A lime kiln, using technology similar to that discussed earlier, serves as the source of carbon dioxide, which is mixed with the salt and ammonia in carbonation towers to form ammonium bicarbonate and finally sodium bicarbonate and ammonium chloride. Filtration separates the less soluble sodium bicarbonate from the ammonium chloride in solution. 

Diammino-zinc Chloride, [Zn(NII3)2]Cl2, is obtained by evaporation of the solution from which the tetrammino-deri vative is separated (see under). It may also be prepared by heating tetrammino-zinc chloride to a temperature of 149° C., or by dissolving zinc in an aqueous solution of ammonium chloride with the aid of metallic copper or silver, or by passing ammonia gas into a concentrated solution of zinc chloride in acetone.1... 

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