Abstract: A colorimetric method for the determination of antimony in the range 0.1 to 3.0μg per milliliter blood is described. The time needed for the destruction of organic matter is shortened to 8—12 minutes. The proposed method is as follows: Accurately transfer 1 ml of blood sample to a hard glass test tube (25×150 mm.), to which 1 ml of conc. HNO₃ is then added. Heat gently with a small flame till the solution changes to amber color. Add 0.5 ml conc. H₂SO₄ and heat again carefully until dense white fume is evolved. If the solution is not clear, add a few more drops of HNO₃ and heat repeatedly till a clear colorless solution is obtained. Cool, add 1 ml NaCl solution and 0.5 ml NaNO₂ solution, shake for 2 minutes, then add 1 ml of urea solution. Transfer the mixture to a separatory funnel containing 10.0 ml benzene. Wash the test tube with three portions (5 ml) of distilled water, add 10 drops of malachite green reagent solution and shake the mixture immediately for 5 minutes. Separate the benzene layer in a centrifuge tube and centrifuge 3 minutes to separate the suspended droplets of water. Transfer the benzene solution into a 10 cm cell and measure the extinction with an Ilford 607 filter, using benzene as blank.