To test it for yourself, just taste it. It should taste bitter, like soap. Criteria for Success You will have already passed the potash quiz when you bring your potash for evaluation. Your potash must be grey or white, with no obvious contamination. A wet pH test paper should turn blue when touched to your potash.
Sodium carbonate is sold as washing soda .
Other synonyms are soda ash and soda . You can buy washing soda in some grocery stores, on the laundry detergent aisle, next to the borax. It is used to remove calcium from hard water by forming an insoluble precipitate of calcium carbonate. Sodium bicarbonate , a much milder alkali than sodium carbonate, is sold as baking soda. It is also called sodium hydrogen carbonate.