---
kind: "section"
citation: "21 C.F.R. § 73.3123"
title: "21"
number: "73.3123"
heading: "6-Ethoxy-2-(6-ethoxy-3-oxobenzo[b]thien-2(3H)-ylidene) benzo[b]thiophen-3 (2H)-one."
url: "https://uscodex.org/cfr/21/73.3123"
---

# §73.3123. 6-Ethoxy-2-(6-ethoxy-3-oxobenzo[b]thien-2(3H)-ylidene) benzo[b]thiophen-3 (2H)-one.

- (a) **Identity.** The color additive is 6-ethoxy-2-(6-ethoxy-3-oxobenzo [b]thien-2(3H)-ylidene)benzo[b]thiophen-3(2H)-one (CAS Reg. No. 3263-31-8), Colour Index No. 73335.
- (b) **Uses and restrictions.**
  - (1) The substance listed in [paragraph (a)](#a) of this section may be used as a color additive in contact lenses in amounts not to exceed the minimum reasonably required to accomplish the intended coloring effect.
  - (2) Authorization for this use shall not be construed as waiving any of the requirements of sections [510(k)](/cfr/21/510.md?p=k), [515](/cfr/21/515.md), and [520(g)](/cfr/21/520.md?p=g) of the Federal Food, Drug, and Cosmetic Act with respect to the contact lens in which the color additive is used.
- (c) **Labeling.** The label of the color additive shall conform to the requirements of [§ 70.25](/cfr/21/70.25.md) of this chapter.
- (d) **Exemption from certification.** Certification of this color additive is not necessary for the protection of the public health, and therefore the color additive is exempt from the certification requirements of [section 721(c)](/cfr/21/721.md?p=c) of the act.

## Notes

### Amendments

[51 FR 11436, Apr. 3, 1986]

### Authority

Authority: 21 U.S.C. 321, 341, 342, 343, 348, 351, 352, 355, 361, 362, 371, 379e.

### Source

Source: 42 FR 15643, Mar. 22, 1977, unless otherwise noted.

### Amendments

[51 FR 11436, Apr. 3, 1986]