---
kind: "section"
citation: "21 C.F.R. § 73.3115"
title: "21"
number: "73.3115"
heading: "2-[[2,5-Diethoxy-4-[(4-methylphenyl)thiol]phenyl]azo]-1,3,5-benzenetriol."
url: "https://uscodex.org/cfr/21/73.3115"
---

# §73.3115. 2-[[2,5-Diethoxy-4-[(4-methylphenyl)thiol]phenyl]azo]-1,3,5-benzenetriol.

- (a) **Identity.** The color additive2-[[2,5-diethoxy-4-[(4-methylphenyl)thio]phenyl]azo]-1,3,5-benzenetriol is formed in situ in soft (hydrophilic) contact lenses.
- (b) **Uses and restrictions.** The color additive 2-[[2,5-diethoxy-4-[(4-methylphenyl)thio]phenyl]azo]-1,3,5-benzenetriol may be safely used to mark soft (hydrophilic) contact lenses with the letter R or the letter L for identification purposes subject to the following restrictions:
  - (1) The quantity of the color additive does not exceed 1.1 × 10−7 grams in a soft (hydrophilic) contact lens.
  - (2) When used as specified in the labeling, there is no measurable migration of the color additive from the contact lens to the surrounding ocular tissue.
  - (3) Authorization for this use shall not be construed as waiving any of the requirements of section [510(k)](/cfr/21/510.md?p=k) and [515](/cfr/21/515.md) 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

[48 FR 22706, May 20, 1983]

### 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

[48 FR 22706, May 20, 1983]