Washing soda (Sodium Carbonate) is manufactured by Arm & Hammer, the same company that makes baking soda and many other cleaning products. The box says Super Washing Soda Detergent Booster. There are, also, generic brands.
It can be found in some grocery stores, often in the same section as other laundry additives, like fabric softeners and stain treatments. It may be more easily found at stores that sell organic & natural products, since it is considered more enviromentally-friendly than chemical cleaners.
