The other procedures listed in this section for iron determination are good activities but may require equipment or chemicals not available in your lab. There is a less complex, but a bit less accurate method for the determination of iron in food. It consists of burning the food in a crucible, dissolving the residue in water or dilute hydrochloric acid, mixing with thiocyanate ion and comparing to a standard set of solutions visually or with a spectrophotometer. The text ChemCom: Chemistry in the Community by the American Chemical Society has a procedure in the foods unit that works reasonably well.
The following is the outline of a simple procedure that works with raisins,dates, cereal, and spinach.
iron III chloride (hexahydrate)
evaporating dishes, beakers, 100 mL grad., small test tubes
10 ml pipet
burner and ringstand
Testing food for iron:
The orange-red color of the iron thiocyanate complex is not totally stable and is an equilibrium condition. If standard solutions are prepared in advance, it would be best to add the KSCN the day of the lab. A simple visual comparison is enough to get the range of iron in different foods.
The use of a light box and looking down the tubes length will increase the sensitivity as long as the tubes are all the same diameter and the same total volume is used in each tube.