Caustic Soda Flakes — Frequently Asked Questions

Always caustic to water, never the reverse. Dissolution is strongly exothermic, and adding water to solid caustic concentrates that heat in a small volume of liquid, which can boil violently and spit concentrated alkali. Adding the solid slowly to a large volume of water with agitation spreads the heat through the bulk and keeps it controllable.

Surface area. A thin flake presents far more surface for its mass than a sphere does, and dissolution happens at the surface, so flakes go into solution noticeably faster. That is the advantage of the flake form, and the corresponding disadvantage is that the same surface area generates more dust and takes up atmospheric moisture more readily.

Because they absorb atmospheric moisture and carbon dioxide. The moisture dissolves the surface, which then recrystallises into bridges between flakes, and the carbon dioxide converts some of the caustic to sodium carbonate, reducing assay. Bags should be resealed immediately after part use and stored in a dry area.

Chemical splash goggles or a face shield, alkali-resistant gloves, and protective clothing covering exposed skin. Caustic soda causes severe burns and, unlike acid, gives little immediate pain warning as it penetrates tissue, so contact can be more damaging than it first appears. An eyewash and safety shower should be immediately accessible where it is handled.