EXPLOSION HAZARD I N COATING MIRRORS JAMES C. RICE Junior College of Kansas City, Misouri
METHODS of silveringmirrors based upon the reduction of ammoniacal solutions of silver are described in many recipe books but, unfortunately, the dangers attending the procedures used in the methods are not stressed. That they are dangers in the most real sense is pointed out by MeUor.* The instability of the compounds formed in silvering baths leaves the nature of their identity in doubt. However, as early as 1767, according to Mellor, J. Kunckel described "fulminating silver" formed in ammoniacal silver solutions. This compound is not silver fulminate but more probably silver nitride, Ag,N, or silver imide, AgeNH, or a mixture of both. 'MELWR.J. W., "A comprehensive treatise on inorganic and theoretical chemistry," Vol. 111. Longmans. Green & Co., Ltd., London, 1928, p. 381.
Whatever the nature of the compounds may be, the fact remains that concentrated solutions of ammoniacal silver, or moderately strong solutions when heated, are explosive. All the constituents of the ammoniacal solutions of silver, made according to standard recipes, are capable of inflicting serious damage to the cornea. Silver ions are protein precipitants and the caustic alkali and the ammonia are, by virtue of their hydroxyl ions, escharotics. We have recently observed the violence of the explosion of a silvering bath and are impelled by a sense of duty to point out the danger. Because we believe that a knowledge of this hazard has not been sufficiently disseminated, we suggest that the authors of recipe books incorporate in their recipes the warning that the procedure is extremely dangerous.
