George S. Klinger; Randall D. Scheele; Marilyn J. Steele
Chemical & Engineering News (8 Jan 1996) Vol. 74, No. 2, pp. 2.
In our laboratory recently, Tollens' reagent was used as a semiquantitative test for formaldehyde in water. While disposing of a small quantity of unused Tollens' reagent, there was an unexpected explosion. This happened as a glass vial containing a small quantity of two-day-old reagent was rinsed with deionized water from a plastic laboratory squeeze bottle. Because we used a fume hood, no injury to staff or damage to equipment occurred.
Apparently, a shock-sensitive precipitate is formed from this alkaline ammoniacal silver solution after a relatively short period of time. A literature search revealed some speculation about the formation of silver azide, silver amide, and silver nitride from Tollens' reagent. Literature concerning the preparation of silver nitride from ammoniacal silver solution suggests that formation of silver nitride is responsible for this reagent's instability. Letters to various publications warning of the hazards of ammoniacal silver solutions were also found, but most were quite dated.
The potential hazards associated with Tollens' reagent are omitted from most organic chemistry texts that describe the simple test for aldehydes that we used. Some references state that the solution should be prepared just prior to use, which implies only a loss of effectiveness, not instability. A reference that does describe the potential hazards is "Handbook of Reactive Chemical Hazards," by L. Bretherick, London, Butterworths, 1979.
We hope this information is valuable to other chemists considering
the use of Tollens' reagent.
page last revised December 7, 1998