Distillation, formaldehyde solutions Atmospheric pressure

Four milliliters of 1 AT aqueous sodium hydroxide solution is added to a mixture of 300 g. (5.2 moles) of acetone and 100 g. (0.86 mole) of aqueous 35% formaldehyde solution. The mixture is held at room temperature for 3-4 hours and then neutralized with 4 ml. oi 1 N hydrochloric acid. The excess acetone is distilled off on a water bath heated to 80-85°, and 2-4 g. of anhydrous zinc chloride is added to the residue. The mixture is distilled on an oil bath, and the distillate is collected as long as it comes over colorless. The distillate is treated with potassium carbonate, and the organic material is separated and dried over sodium sulfate. Distillation at 130 mm. pressure gives a 25-35% yield of methyl vinyl ketone boiling at 33-34°. Some decomposition occurs if the distillation is carried out at atmospheric pressure, where the product boils at 80°. 

Since formaldehyde is known to be a catalyst poison it was removed from the reagent mixture prior to hydrogenation by distillation. In order to prevent oligomerization of formaldehyde [14], water was gradually added to the mixture during distillation. The water feeding was adjusted in order to maintain a constant liquid volume in the distillation flask. Distillation was performed imder atmospheric pressure and at 100 °C using a total batch volume of 400 ml (200 ml of aldolization product mixed with 200 ml of distilled water). As the first distilled droplets from the condenser were observed, the addition of extra water was commenced. In this way, the formaldehyde content of the solution was easily suppressed below 0.5 wt.%. 

Tetra-(chloromethyl)-phosphonium chloride (5 g) in 20 mL water was treated with 8 g sodium bicarbonate. The solution became milky and gave a strong formaldehyde reaction with fusion reagent. The phosphine was shaken out with carbon bisulfide, dried over sodium sulfate, and distilled under diminished pressure b.p. 100°C (7 mmHg). While heated at atmospheric pressure, tri-(chloromethyl)phosphine decomposes. It is a colorless, mobile liquid with a powerful, benumbing odor and with slight solubility in water. 

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