AOAC Official Method 937.09 Salt (Chlorine as Sodium Chloride) in Seafood
First Action 1937
(a) Silver nitrate standard solution.—0.1M. Prepare as in 941.18A (see A.1.11) and standardize against 0.1M NaCl containing 5.844 g of pure dry NaCl/L.
(b) Ammonium thiocyanate standard solution.—0.1M. Prepareas in 941.18D(b) (see A.1.11) and standardize against 0.1M AgNO3.
(c) Ferric indicator.—Saturated solution of FeNH4(SO4)2×12H2O.
(a) Shellfish meats.—Weigh 10 g meats, liquid, or mixed meats and liquid, into 250 mL Erlenmeyer or beaker.
(b) Other fish products.—Use suitable size test sample, depending on NaCl content.
Add known volume 0.1M AgNO3 solution, more than enough to precipitate all Cl as AgCl, and then add 20 mLHNO3. Boil gently on
hot plate or sand bath until all solids except AgCl dissolve (usually 15 min). Cool, add 50 mL H2O and 5 mL indicator, and titrate with 0.1N NH4SCN solution until solution becomes permanent light brown. Subtract mL 0.1M H4SCN used from mL 0.1M AgNO3 added and calculate difference as NaCl. With 10 g test sample each mL 0.1N AgNO3 = 0.058% NaCl.
References: JAOAC 20, 410(1937); 23, 589(1940).
CAS-7647-14-5 (sodium chloride)