21 CFR § 184.1769a - Sodium metasilicate.

---
identifier: "/us/cfr/t21/s184.1769a"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 184.1769a - Sodium metasilicate."
title_number: 21
title_name: "Food and Drugs"
section_number: "184.1769a"
section_name: "Sodium metasilicate."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "B"
subchapter_name: "FOOD FOR HUMAN CONSUMPTION"
part_number: "184"
part_name: "DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "21 U.S.C. 321, 342, 348, 371."
regulatory_source: "42 FR 14653, Mar 15, 1977, unless otherwise noted."
cfr_part: "184"
---


# 184.1769a Sodium metasilicate.

(a) Sodium metasilicate (CAS Reg. No. 6834-92-0) is a strongly alkaline white powder. It does not occur naturally but rather is synthesized by melting sand with sodium carbonate at 1400 °C. The commercially available forms of sodium metasilicate are the anhydrous form (Na<sub>2</sub>SiO<sub>3</sub>), the pentahydrate (Na<sub>2</sub>SiO<sub>3</sub>·5H<sub>2</sub>O), and the nonahydrate (Na<sub>2</sub>SiO<sub>3</sub>·9H<sub>2</sub>O).

(b) The ingredient must be of a purity suitable for its intended use.

(c) In accordance with § 184.1(b)(1), the ingredient is used in food with no limitation other than current good manufacturing practice. The affirmation of this ingredient as generally recognized as safe (GRAS) as a direct human food ingredient is based upon the following current good manufacturing practice conditions of use:

(1) The ingredient is used as a processing aid as defined in § 170.3(o)(24) of this chapter.

(2) The ingredient is used to treat the following foods at levels not to exceed current good manufacturing practice: for use in washing and lye peeling of fruits, vegetables, and nuts when used in accordance with § 173.315 of this chapter; for use as a denuding agent in tripe; for use as a hog scald agent in removing hair; and for use as a corrosion preventative in canned and bottled water when used in accordance with § 165.110 of this chapter.

(d) Prior sanctions for this ingredient different from the uses established in this section do not exist or have been waived.

[50 FR 38781, Sept. 25, 1985; 50 FR 42011, Oct. 17, 1985, as amended at 72 FR 10357, Mar. 8, 2007; 73 FR 8608, Feb. 14, 2008]