Section 186.1374 - Iron oxides(a) Iron oxides (oxides of iron, CAS Reg. No. 1332-37-2) are undefined mixtures of iron (II) oxide (CAS Reg. No. 1345-25-1, black cubic crystals) and iron (III) oxide (CAS Reg. No. 1309-37-1, red-brown to black trigonal crystals).(b) In accordance with § 186.1(b)(1) , the ingredient is used as an indirect human food ingredient with no limitation other than current good manufacturing practice. The affirmation of this ingredient as generally recognized as safe (GRAS) as an indirect human food ingredient is based upon the following current good manufacturing practice conditions of use:(1) The ingredient is used as a constituent of paper and paperboard used for food packaging.(2) The ingredient is used at levels not to exceed current good manufacturing practice.(c) Prior sanctions for this ingredient different from the uses established in this section do not exist or have been waived.53 FR 16867, May 12, 1988; 53 FR 20939, June 7, 1988, as amended at 69 FR 24512 , May 4, 2004