Soda Ash (Sodium Carbonate), sold per 1 lb. bag. Soda Ash is used as an alkali fixative for PRO MX Reactive Dyes, setting color permanently (an alternative to PRO Dye Activator). It is recommended you work with good ventilation and use a respirator with Acid Gas cartridges while it is in powder form. This is a Pro Chemical & Dye product; for MSDS sheets, visit www.prochemicalanddye.com.