21 CFR §182.1745

1. (a)Product. Sodium carboxymethylcellulose is the sodium salt of carboxymethylcellulose not less than 99.5 percent on a dry-weight basis, with maximum substitution of 0.95 carboxymethyl groups per anhydroglucose unit, and with a minimum viscosity of 25 centipoises for 2 percent by weight aqueous solution at 25 °C.
2. (b)Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing practice.