S 1668 (OTTO) Sodium azide, GR 99% Cas 26628-22-8 - used for the preparation of other azide compounds. It is an ionic substance, is highly soluble in water, and is very acutely toxic. S 1668 (OTTO) Sodium azide, GR 99% Cas 26628-22-8 used for the preparation of other azide compounds. It is an ionic substance, is highly soluble in water, and is very acutely toxic.