leu
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Purification of Isopropanol
JACS 54 1445 (1932)
Note on the Preparation of Absolute Isopropanol
BY LEWIS E. GILSON
During several years of biochemical research the writer has found many instances where isopropanol could be substituted for ethanol in laboratory
work. It is cheap and there are no restrictions governing its use; nor is it likely to be an object of theft. The commercial 91% azeotropic mixture
was used instead of 95% ethanol and found to be fully equal or superior to the latter as a solvent or extracting medium. Absolute isopropanol was used
in place of absolute ethanol.
Absolute isopropanol is easily prepared. The 91% grade is shaken with 10% of its weight of commercial flake sodium hydroxide, separated from the
aqueous layer which forms, then shaken with a little more sodium hydroxide, decanted and distilled. The product obtained mixes with eight volumes of
carbon disulfide, xylene or petroleum ether without the slightest trace of turbidity.
Dilute isopropanol can be concentrated by shaking with dry sodium chloride. Water is removed as a saturated layer of brine. The upper layer contains
about 87% isopropanol and 2-3% of sodium chloride. While distilling, an additional quantity of brine separates. The distillate has so nearly the
composition of the 91% azeotropic mixture that it can be used as such without further treatment. Or, after shaking the dilute isopropanol with sodium
chloride and separating, it can be treated directly with sodium hydroxide and the absolute grade prepared.
Chemistry is our Covalent Bond
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Magpie
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Thanks leu this can potentially save the expense of buying or preparing 95% or absolute ethanol. Especially convenient since 99% isopropanol is
readily and cheaply available at my corner drugstore. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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ordenblitz
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For what it's worth...
Isopropanol usually contains a small amount of ammonia that is difficult if not impossible to remove by distillation.
I usually add a pinch of Sulfamic acid first then distill.
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