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ദ്ദി（• ˕ •マ.ᐟ

In a 5 liter round-bottomed flask, fitted with a stopper holding a condenser set for downward distillation and a thermomether which will extend well into the liquid, are placed 4 kg (3711 ml, 47-53 moles) of technical formaldehyde (35-40 percent; d 1.078 at 20°C) and 2 kg (37 moles) of technical ammonium chloride. The mixture is heated on the steam bath until no more distillate comes over and then over a flame until the temperature of the solution reaches 104°C. The temperature is held at this point until no more distillate comes over (four to six hours). The distillate, which consists of methylal (bp 42-43°C), methylformate and water may be treated with NaOH solution to recover methylal and sodium formate. The contents of the reaction flask are cooled too room temp and the ammonium chloride which separates is filtered off. The mother liquor is concentrated on the steam bath under reduced pressure to 2500 ml, and again cooled to room temp, whereupon a second crop of ammonium chloride separates. The total recovery of ammonium chloride up to this point amounts to 780-815 grams. The mother liquor is again concentrated under reduced pressure until crystals begin to form on the surface of the solution (1400-1500 ml). It is then cooled to room temperature, and a first crop of methylamine hydrochloride, containing some ammonium chloride is obtained by filtering the cold solution. At this point 625-660 grams of crude product is obtained. The mother liquor is now concentrated under reduced pressure to about 1000 ml, and cooled, and a second crop of methylamine hydrochloride (170-190 grams) is then filtered off. This crop of crystals is washed with 250 cc of cold chloroform, and filtered to remove most of the dimethylamine hydrochloride which is present. After the washing, the product weighs 140-150 grams. The original mother liquor is then evaporated under reduced pressure, as far as possible, by heating on a steam bath, and the thick syrupy solution (about 350 ml) which remains is poured into a beaker and allowed to cool, with occasional stirring, in order to prevent the formation of a solid cake, and the crystals obtained are washed with 250 ml of cold chloroform, the solution is filtered yielding 55-65 grams of product. There is no advantage in further concentrating the mother liquor, which contains mostly tetramethylmethylenediamine hydrochloride, but no trimethylamine hydrochloride. The total yield of methylamine hydrochloride is 830-850 grams. The product contains water, ammonium chloride and some dimethylamine hydrochloride. In order to obtain a pure product, the impure methylamine hydrochloride is recrystallized from absolute ethanol (solubility 0.6g/100ml at 15°C), or preferably butyl alcohol (even less soluble). The recovery of ammonium chloride amounts to 100-150 grams, making the total recovery 850-950 grams. The yield of recrystallized methylamine hydrochloride is 600-750 grams (45-51 percent of theory, based on the used up ammonium chloride).

A standard run, from 250 grams ammonium chloride and 500g 37% formaldehyde (containing 15% methanol), gives 100-134 grams methylamine hydrochloride, 27 grams dimethylamine hydrochloride and 81 grams of recovered ammonium chloride. The distillate contains methylal (formaldehyde dimethyl acetal) and methyl formate, which after treatment with NaOH can yield 25g of sodium formate and 30 grams of methylal, as the compound cannot be separated by fractional distillation, neutralization is the way to go. Ammonium chloride is very sparingly soluble in a concentrated solution of methylammonium chloride, making the separation of the compounds pretty sharp.