Dear all,
Farmer's reducer is an old chemical from the times of black and white
photography. In case of gels it is a solution containing 10 g of potassium
ferricyanide and 16 g of sodium thiosulfate in 1 liter of water. The whole
silver staining protocol with the use of Farmer's reducer is described in
"Current Protocols in Protein Science", chapter 10.5. The only potential
"danger" related to Farmer's reducer is the time and number of water washes
necessary for a complete removal of the reagent from gel. It does take
time and _many_ changes of water. And complete removal of Farmer's reducer
from a gel is critical. Also, ferricyanide may produce HCN when reacted
with acids and for that reason silver stained gels have to be washed with
water prior to the use of Farmer's reducer. Acid-free gel is then
submerged in Farmer's reducer solution for about 5 minutes (or longer -
until all the silver is gone) and then extensively washed with water.
Jacek Mozdzanowski
Bioanalytical Sciences
SmithKline Beecham