Section 186.1797 - Sodium sulfate(a) Sodium sulfate (Na2SO4, CAS Reg. No. 7757-82-6), also known as Glauber's salt, occurs naturally and exists as colorless crystals or as a fine, white crystalline powder. It is prepared by the neutralization of sulfuric acid with sodium hydroxide.(b) The ingredient is used as a constituent of paper and paperboard used for food packaging, and cotton and cotton fabric used for dry food packaging.(c) The ingredient is used at levels not to exceed good manufacturing practice in accordance with § 186.1(b)(1) .(d) Prior sanctions for this ingredient different from the uses established in this section do not exist or have been waived.45 FR 6086, Jan. 25, 1980