The Power of Apple Cider Vinegar for Rust Removal

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Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals, and in the monohydrate form as crystal carbonate) is the water-soluble sodium salt of carbonic acid.

I guess I should have said per 1 cup because washing soda is powder and ash is flakes and doesn't weigh as much