Insoluble and porous, Cargille Boiling Stones are excellent as catalyst and reagent carriers for analytical procedures and production processes. Porous grainy structure insures a "myriad of sites for ebullience", not just corners. Large contact area that cannot be worn smooth and light weight promotes stirring action and heat distribution. Cargille Boiling Stones are recommended for Kjeldahl, Folin-Wu and other procedures where superheating may occur. If trace alkalinity is a concern, rinse Boiling Stones a few times in distilled water and dry before using. The lower density also means economy-more pieces per pound. Fused silica grains, 93.4% pure.