AOAC Official Method 939.01 Thallous Sulfate in Rodenticide Formulations
First Action 1939
Final Action
Weigh test portion containing 0.1–0.15 g Tl2SO4 (usually 10 g), transfer to 800mLKjeldahl flask, and add 25mLH2SO4 followed by 5–10 mL HNO3. After first violent reaction ceases, heat until white fumes of H2SO4 appear. Add few drops fuming HNO3 and continue heating and adding HNO3 until organic matter is destroyed, as shown by colorless or light yellow solution. Cool, add 10–15 mL H2O, again cool, and wash contents of flask into 400 mL beaker,continuing washing until volume is 60–70 mL. Boil several min to remove allHNO3, cool, and filter into 400mLbeaker. Wash with hot
H2O until volume in beaker is 175 mL, neutralize with NH4OH, and then slightly acidify with H2SO4 (1 + 4). Add 1 g NaHSO3 to ensure reduction of thallic to thallous state. Heat to bp, add 50 mL 10% KI solution (w/v), stir, and let stand overnight. Filter through tight Gooch containing 2 disks S&S 589 white ribbon paper covered by medium pad of glass wool. Wash 4 or 5 times with 10 mL portions 1% KI solution (w/v), and finally with absolute alcohol. Dry to constant weight at 105°C (1–1.5 h), and weigh as TlI.
Tl2SO4, % =g TlI g test portion ´0.7619 ´100
References: JAOAC 22, 411(1939); 25, 79(1942); 28, 72(1945).
CAS 7446-18-6 (thallous sulfate)
