Crystal Cake Washing: Impurity Displacement Can Also Dissolve Product

Define the Phase or Process Boundary

Shahid and colleagues' primary washing study discusses displacing impurity-bearing mother liquor while limiting dissolution of product crystals. Product already dissolved in the retained liquid must also be distinguished from product lost from the crystalline solid.

Review a Hypothetical Comparison

Assume an invented complete wash boundary initially contains 100 g crystalline product plus mother liquor holding 2 g dissolved product. At the end, suppose all liquid has been collected and assayed and it contains 3 g product, while the recovered crystal inventory is 99 g. Total product closes as 102 g initially and 102 g finally. Of the 3 g in collected liquid, 2 g came from the initial dissolved inventory and 1 g from the crystalline inventory. Calling all 3 g crystal loss would overstate the assigned loss.

Keep the Evidence with the Decision

Retain initial solid and dissolved inventories separately, with complete collected-liquid and final-solid evidence. Include liquid remaining in the cake and any precipitation if those are present. A wash-solvent choice should address impurity removal and changes in product phase inventory; clarity of filtrate alone does not establish either result.

All masses and complete collection are hypothetical. No solvent, wash temperature or product recovery target is recommended, and a real imbalance does not automatically prove dissolution.

What evidence accounts separately for displaced mother liquor and dissolved solid product?

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Shahid and colleagues' primary washing study
• Reference from hmpharmamachines.com