Ferric subsulfate solution is a styptic or hemostatic agent used once superficial skin biopsies have been completed. Ferric subsulfate solution is also known as basic ferric sulfate solution or Monsel’s solution. United States Pharmacopeia 29 has published its recognized formula. Ferric subsulfate solution is made from nitric acid, ferrous sulfate, and sulfuric acid. It contains, per 100 mL, basic ferric sulfate equivalent to not less than 20g and not more than 22g of iron. Ferric subsulfate solution should be stored within airtight containers at a temperature above 22 degrees Celsius. If stored below temperatures of 22, it is possible and likely for crystallization to occur. The crystals may redissolve by warming the solution. The solution should be stored where it will be protected from and kept out of light. Leon Monsel invented ferric subsulfate solution in the late 1840’s. His invention quickly became a French Corps standard and saved many lives during battle.