How may they be distinguished from pieces of broken glass?
Their crystalline structure renders them sufficiently friable to be readily crushed between the fingernail; they will not actually scratch the surface of an aluminum cooking utensil or copper coin although they may make a mark in the oxidized surface layer of the metal; polishing the mark with a cloth will disclose that no actual scratching of the metal has taken place, whereas glass easily scratches these two metals. A convincing test is to place a suspected crystal in a teaspoon, then add a few drips of 10% hydrochloric acid, and heat by means of a match, candle, or cigarette lighter until the acid is hot. The crystals will dissolve, whereas a fragment of glass will not dissolve. Since these crystals may sometimes be mistaken for broken glass, this statement as to their nature and harmlessness has been prepared for the protection of the marine products canning industry of British Columbia. NEAL M.
