JAIC 1986, Volume 25, Number 2, Article 2 (pp. 73 to 81)
JAIC online
Journal of the American Institute for Conservation
JAIC 1986, Volume 25, Number 2, Article 2 (pp. 73 to 81)

TREATMENT OF A SILVER DRAGON FOR THE REMOVAL OF SILVER CYANIDE AND CHALCONATRONITE

Donna K. Strahan



4 HAZARDS OF CYANIDE CLEANING

USING SILVER OBJECTS cleaned or replated in a cyanide bath can be a hazard because of the presence of cyanide salts trapped in a spout, handle, grill, a soldered join or the intricate pattern of a design. Hollow handles which have been slush cast may be thin in some areas and contain tiny holes which could allow the handles to fill up with cyanide solution during the electroplating or cleaning process. In addition, intentional vent holes in two-piece soldered silver alloy sections are potential areas for the entrapment of silver cyanide. Trapped residues could seep out slowly over time.

Cyanide reacts with the silver, producing silver cyanide (AgCN), an extremely poisonous grayish-white odorless powder which darkens when exposed to light. Although it is not readily absorbed through the skin, it is deadly by inhalation or ingestion. Acids readily react with it to break down the complexed metal salt, producing highly poisonous hydrogen cyanide gas which has the characteristic odor of bitter almonds. Cyanide is one of the fastest acting of all known poisons and both the TLV (Threshold Limit Value) and the OSHA PEL (Permissible Exposure Limit) are 5 mg/m3 over an eight hour time period.8 Acids may be present in silver cleaning solutions, such as silver dips and others, or in foods.


Copyright 1986 American Institute for Conservation of Historic and Artistic Works