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Purified Sodium Hydroxide: Caustic Soda Dissolved in Alcohol, Filtered and Dried in Silver

Walkerma (Wikimedia Commons) · Public domain

创建者

Charlie

19. 十月 2026

Purified Sodium Hydroxide: Caustic Soda Dissolved in Alcohol, Filtered and Dried in Silver

Commercial caustic soda carries alumina, carbonates, chlorides, phosphates, silicates and sulphates. For analysis, the British Pharmacopoeia of 1898 (quoted in the 1907 US Dispensatory) purified it with alcohol: sodium hydroxide dissolves in alcohol, most of those salts do not, so they are filtered off and the alcohol is evaporated in a silver dish. The result is free of phosphates and sulphates, nearly free of carbonate, but not quite free of alumina. The source gives no quantities, so none are given here. The picture: sodium hydroxide pellets (Walkerma, Wikimedia Commons, public domain).

中级

A day

说明

Dissolve the caustic soda in alcohol

Put commercial caustic soda in a beaker and stir in alcohol until it has dissolved. Caustic soda burns skin and eyes: wear goggles and gloves.

此步骤所需材料：

烧碱（氢氧化钠）1 as required

所需工具：

乙醇——实验级，95 %

硼硅玻璃烧杯

玻璃搅拌棒

化学防溅护目镜

橡胶手套

Filter off what does not dissolve

Filter the solution. The salts that stay behind on the filter are the impurities.

所需工具：

带颈玻璃漏斗

滤纸

硼硅玻璃烧杯

化学防溅护目镜

橡胶手套

Evaporate to dryness in a silver dish

Evaporate the filtrate to dryness in a silver dish, adding a little distilled water from time to time as it goes. Caustic soda attacks glass and porcelain, hence the silver. Alcohol vapour catches fire: use an electric hot plate, no flame, in a well-aired place.

所需工具：

银皿

电热板

蒸馏水

化学防溅护目镜

橡胶手套

Bottle the purified sodium hydroxide

The residue is purified sodium hydroxide. It draws water from the air (the source calls it deliquescent), so put it at once into well-stoppered bottles of hard glass. It should show no phosphate or sulphate, at most a trace of carbonate, and it is not quite free of alumina.

所需工具：