---
kind: "section"
citation: "40 C.F.R. § 425.02"
title: "40"
number: "425.02"
heading: "General definitions."
url: "https://uscodex.org/cfr/40/425.02"
---

# §425.02. General definitions.


In addition to the definitions set forth in [40 CFR part 401](/cfr/40/part401.md), the following definitions apply to this part:

- (a) “Sulfide” shall mean total sulfide as measured by the potassium ferricyanide titration method described in appendix A or the modified Monier-Williams method described in appendix B.
- (b) “Hide” means any animal pelt or skin as received by a tannery as raw material to be processed.
- (c) “Retan-wet finish” means the final processing steps performed on a tanned hide including, but not limited to, the following wet processes: retan, bleach, color, and fatliquor.
- (d) “Hair pulp” means the removal of hair by chemical dissolution.
- (e) “Hair save” means the physical or mechanical removal of hair which has not been chemically dissolved, and either selling the hair as a by-product or disposing of it as a solid waste.
- (f) “Chrome tan” means the process of converting hide into leather using a form of chromium.
- (g) “Vegetable tan” means the process of converting hides into leather using chemicals either derived from vegetable matter or synthesized to produce effects similar to those chemicals.
- (h) “Raw material” means the hides received by the tannery except for facilities covered by subpart D and subpart I where “raw material” means the hide or split in the condition in which it is first placed into a wet process.
- (i) “Monthly average” means the arithmetic average of eight (8) individual data points from effluent sampling and analysis during any calendar month.
- (j) “Interference” means the discharge of sulfides in quantities which can result in human health hazards and/or risks to human life, and an inhibition or disruption of POTW as defined in [40 CFR 403.3(i)](/cfr/40/403.3.md?p=i).

## Notes

### Amendments

[47 FR 52870, Nov. 23, 1982, as amended at 53 FR 9181, Mar. 21, 1988]

### Authority

Authority: 33 U.S.C. 1311, 1314 (b), (c), (e) and (g), 1316 (b) and (c), 1317 (b) and (c), 1318 and 1361.

### Source

Source: 47 FR 52870, Nov. 23, 1982, unless otherwise noted.

### Amendments

[47 FR 52870, Nov. 23, 1982, as amended at 53 FR 9181, Mar. 21, 1988]