Crude Glycerol: Candle-Works Sweet Water Neutralised and Steam-Concentrated to 28° Bé (Thorpe, 1912)

'Saponification crude' or 'candle crude' glycerin, the best grade of crude glycerin: the sweet water from autoclave saponification, holding 6 to 16 per cent of glycerol, is neutralised, filtered and boiled down by steam until it holds 85 to 90 per cent glycerol (sp. gr. 1.240 to 1.242, sold as 28° Bé). It is yellow to dark brown and sweet, with up to 0.3 per cent ash, mostly calcium, magnesium or zinc sulphate. Refined with charcoal it gives 'refined' glycerin. Unknown: what the metallic oxides in the sweet water are neutralised with. Thorpe does not say. Source: T. E. Thorpe, Dictionary of Applied Chemistry vol. II (1912), pp. 762-763. Picture: Fig. 1, a Wetzel pan.