ASTM D6696-05
(Guide)Standard Guide for Understanding Cyanide Species
Standard Guide for Understanding Cyanide Species
SCOPE
1.1 This guide defines standard terminology used for the classification of the various chemical forms of cyanide. It is intended to provide a general understanding of the chemical nature of distinct cyanide species as related to chemical analysis and environmental fate and transport.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
An American National Standard
Designation:D6696–05
Standard Guide for
1
Understanding Cyanide Species
This standard is issued under the fixed designation D 6696; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 5.1.1 Cyanide Ion—The term used to describe a negatively
charged ion comprised of one carbon atom and one nitrogen
1.1 This guide defines standard terminology used for the
-
atom triply bonded to each other (C[N ). The cyanide ion is
classification of the various chemical forms of cyanide. It is
reactive and readily forms neutral compounds or anionic
intended to provide a general understanding of the chemical
complexes with most metals.
nature of distinct cyanide species as related to chemical
5.1.2 Free Cyanide—The form of cyanide that is bioavail-
analysis and environmental fate and transport.
able and known for its toxic effect on organisms (1). Free
2. Referenced Documents cyanide refers to the sum of molecular hydrogen cyanide
-
2
(HCN)andcyanideion(CN ).Hydrogencyanideisacolorless,
2.1 ASTM Standards:
poisonous gas having an odor of bitter almonds (mp = -13.4°C,
D 1129 Terminology Relating to Water
bp = 25.6°C). It is readily soluble in water partitioning itself as
-
3. Terminology
HCN or CN , or both, depending on the pH conditions
(pK = 9.36). At a pH of 7 or less in water, free cyanide is
3.1 Definitions—Foradefinitionoftermsusedinthisguide, a
present entirely as HCN; the opposite is true at pH 11 or
refer to Terminology D 1129.
greater. Because of its toxicity, free cyanide is regulated in
4. Significance and Use
environmental wastewater discharges.
5.1.3 Simple Cyanide—A neutral compound comprised of
4.1 This guide provides standard terminology for use in
an alkali metal, alkaline earth metal or ammonium cation
identifying and describing the different chemical forms of
bound to cyanide. Simple cyanides are so named because of
cyanide. The complex nature of cyanide chemistry, existence
their structural simplicity and their ability to completely
of numerous distinct chemical forms as well as the various
dissolve and dissociate in water to produce free cyanide and a
regulatory distinctions that may be made can lead to confusion
cation according to the following reaction:
in technical discussions on cyanide and in the selection of
appropriate methods for its analysis. This guide is intended to 1 2
ACN→ A 1 CN (1)
provide clarification and a common framework of terms and
where:
definitions from which to discuss and reference different
A = alkali metal, alkaline earth metal or ammonium cation.
cyanide chemical species and groups of cyanide compounds.
Examples of simple cyanides include sodium cyanide
4.2 The use of such common terminology is particularly
(NaCN) and potassium cyanide (KCN).
important from an environmental perspective because certain
5.1.4 Metal Cyanide Complex—A negatively charged ionic
forms of cyanide are considered to be toxic. Therefore, their
complex consisting of several cyanide ions bound to a single
release into the environment is regulated by federal and state
transition metal cation. Also referred to as “metal-complexed
agencies. Thus a general understanding of cyanide chemistry
cyanides,” “metal cyano-complexes” or “transition metal cya-
and species definitions is needed for proper wastewater man-
nides,” these species have the general formula:
agement and testing.
x2
@M~CN! # (2)
b
5. Cyanide Species Terms and Definitions
5.1 Chemistry Related Terms and Definitions: where:
M = transition metal cation,
b = number of cyanide groups, and
1
This guide is under the jurisdiction of ASTM Committee D19 on Water and is
x = ionic charge of the transition metal complex.
the direct responsibility of Subcommittee D19.06 on Organic Constituents inWater.
Metal cyanide complexes are represented by the following
Current edition approved July 1, 2005. Published July 2005. Originally approved
equilibrium in aqueous solution:
in 2001. Last previous edition approved in 2001 as D 6696 – 01.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
x2 n1 2
@M~CN! # ⇔ M 1 bCN (3)
b
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 ----------------------
D6696–05
TABLE 2 Selected Strong Metal Cyanide Complexes (2, 3)
where:
Cyanide Complex Stability Constant (log K at 25°C)
M = transition metal cati
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.