Thiourea
Description
Shiny, white, crystals that can dissolve salts of silver, gold, and platinum. Thiourea is used in photography for toning and for removing stains on negatives. However, it can also act as a powerful fogging agent and care must be used to prevent cross contamination of thiourea solutions with other processing aids. Thiourea is often an active ingredient in silver dip type tarnish removal solutions. However, when thiourea is incompletely removed from a metal, it can form an insoluble adduct. Thiourea is also used to accelerate the vulcanization of rubber.
Synonyms and Related Terms
thiocarbamide; sulfourea; sulfocarbamide; thiurea
Other Properties
Soluble in water, ethanol, ammonium thiocyanate solutions. Slightly soluble in ether.
| Composition | (NH2)2CS |
|---|---|
| CAS | 62-56-6 |
| Melting Point | 176-172 |
| Density | 1.405 |
| Molecular Weight | mol. wt. = 76.12 |
Hazards and Safety
Suspected carcinogen. Skin contact causes irritation. Should not be used on metals containing more than 7% copper.
Link: International Chemical Safety Card
Authority
- Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
- Marie Svoboda, Conservation Survey Index, unpublished, 1997
- The Merck Index, Susan Budavari (ed.), Merck Research Labs, Whitehouse Station, NJ, 12th Edition, 1996 Comment: entry 9505
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 837
- Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
- Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997