Field method for the determination of molybdenum in plants

Fresh plant material is ashed directly by heating in nickel or platinum dishes over a "flame. An acid solution of 25 milligrams of ash is treated with stannous chloride and potassium thiocyanate. The amber-colored molybdenum thiocyanate complex ion is extracted with isopropyl ether, and the intensity of the color of the ether layer over a sample solution is compared with the ether layer over standard molybdenum solutions treated similarly. Field determinations can be made quickly and the method requires no special equipment. As little as 0.25 microgram or 0.001 percent molybdenum can be determined in plant ash.