Washing Spice

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Washing Spice

The purpose of washing is to disperse impurities off of the product or out of a solution containing the product and into an intermediate solvent.

Alkaline Solution Washing of Impurities

Most of the impurities that plague yields tend to be quite soluble in both alkaline aqueous solutions and non-polar solvents. To remove these impurities, an imbalance in equilibrium must be created between these two types of solutions, causing the impurities to disperse into a disposable solution from the solution containing the product. This procedure is commonly used for purifying product from extractions that utilize naphtha or heptane to obtain a whiter product.

Washing Spice of Oxidization and Inactive Impurities Using Alkaline Solution

Saturate a solution of warm water with a weak base such as sodium bicarbonate (baking soda) or sodium carbonate (washing soda) to render an alkaline solution. sodium bicarbonate can be converted to sodium carbonate. Dissolve product in an NPS of preference. Add alkaline solution to the NPS at a ratio of about 1:4 and mix thoroughly. Remove and collect the top NPS layer, and proceed to recrystallization procedure of preference.

Solvent Washing and Isolation of Impurities

Some product may contain undesirable active or inactive impurities with solubility properties differing greatly from the more desirable components.

Washing Fumarate Spice of Fumaric Acid and Residual Solvent Using Water

Add a small amount of water in slight excess of completely submerging the product. Stir mixture to dissolve the active fumarate component. Decant solution off, leaving solids behind. Repeat process until no more color change is observed in the solution, but perform once more with a minimal amount of water for good measure. the solids remaining should be mainly composed of the excess fumaric acid from the starting material. Evaporate the solution with or without heat and airflow to achieve purified crystalline fumarate product. reduction of the solution by heat and airflow is generally always beneficial, but slow evaporation in the later stages may result in a more uniform and attractive crystalline product.