ASTM D6696-10
(Guide)Standard Guide for Understanding Cyanide Species
Standard Guide for Understanding Cyanide Species
SIGNIFICANCE AND USE
This guide provides standard terminology for use in identifying and describing the different chemical forms of cyanide. The complex nature of cyanide chemistry, existence of numerous distinct chemical forms as well as the various regulatory distinctions that may be made can lead to confusion in technical discussions on cyanide and in the selection of appropriate methods for its analysis. This guide is intended to provide clarification and a common framework of terms and definitions to facilitate discussions and referencing different cyanide chemical species and groups of cyanide compounds.
The use of such common terminology is particularly important from an environmental perspective because certain forms of cyanide are considered to be toxic. Therefore, their release into the environment is regulated by federal and state agencies. Thus a general understanding of cyanide chemistry and species definitions is needed for proper wastewater management and testing.
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.
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Designation: D6696 − 10
StandardGuide for
1
Understanding Cyanide Species
This standard is issued under the fixed designation D6696; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope* agencies. Thus a general understanding of cyanide chemistry
and species definitions is needed for proper wastewater man-
1.1 This guide defines standard terminology used for the
agement and testing.
classification of the various chemical forms of cyanide. It is
intended to provide a general understanding of the chemical
5. Cyanide Species Terms and Definitions
nature of distinct cyanide species as related to chemical
5.1 Chemistry Related Terms and Definitions:
analysis and environmental fate and transport.
5.1.1 Cyanide Ion—The term used to describe a negatively
charged ion comprised of one carbon atom and one nitrogen
2. Referenced Documents
-
atom triply bonded to each other (C≡N ). The cyanide ion is
2
2.1 ASTM Standards:
reactive and readily forms neutral compounds or anionic
D1129 Terminology Relating to Water
complexes with most metals.
D7237 Test Method for Free Cyanide with Flow Injection
5.1.2 Free Cyanide—The form of cyanide that is bioavail-
Analysis (FIA) Utilizing Gas Diffusion Separation and
able and known for its toxic effect on organisms (1). Free
Amperometric Detection
cyanide refers to the sum of molecular hydrogen cyanide
-
(HCN)andcyanideion(CN ).Hydrogencyanideisacolorless,
3. Terminology
poisonous gas having an odor of bitter almonds (mp = -13.4°C,
3.1 Definitions—For a definition of terms used in this guide,
bp = 25.6°C). It is readily soluble in water existing as HCN or
-
refer to Terminology D1129.
CN , or both, depending on the pH conditions (pK = 9.36).At
a
a pH of 7 or less in water, free cyanide is present entirely as
4. Significance and Use
HCN; the opposite is true at pH 11 or greater. Because of its
4.1 This guide provides standard terminology for use in toxicity, free cyanide is regulated in environmental wastewater
identifying and describing the different chemical forms of
discharges.
cyanide. The complex nature of cyanide chemistry, existence 5.1.2.1 In Test Method D7237, sum of the free cyanide
-
of numerous distinct chemical forms as well as the various
(HCN and CN ) and cyanide bound in the metal-cyanide
regulatory distinctions that may be made can lead to confusion complexes that are easily dissociated into free cyanide under
in technical discussions on cyanide and in the selection of
thetestconditionsdescribedinTestMethodD7237atpH6and
appropriate methods for its analysis. This guide is intended to room temperature.
provide clarification and a common framework of terms and
5.1.3 Aquatic Free Cyanide—In Test Method D7237, free
definitions to facilitate discussions and referencing different cyanidemeasuredwhenthebufferortemperatureisadjustedto
cyanide chemical species and groups of cyanide compounds.
mimic the receiving water environment.
5.1.4 Simple Cyanide—A neutral compound comprised of
4.2 The use of such common terminology is particularly
an alkali metal, alkaline earth metal or ammonium cation
important from an environmental perspective because certain
bound to cyanide. Simple cyanides are so named because of
forms of cyanide are considered to be toxic. Therefore, their
their structural simplicity and their ability to completely
release into the environment is regulated by federal and state
dissolve and dissociate in water to produce free cyanide and a
cation according to the following reaction:
1 1 2
This guide is under the jurisdiction of ASTM Committee D19 on Water and is
ACN→A 1CN (1)
the direct responsibility of Subcommittee D19.06 on Methods for Analysis for
Organic Substances in Water.
where:
CurrenteditionapprovedJune1,2010.PublishedJuly2010.Originallyapproved
A = alkali metal, alkaline earth metal or ammonium cation.
´1
in 2001. Last previous edition approved in 2005 as D6696 – 05 . DOI: 10.1520/
D6696-10.
Examples of simple cyanides include sodium cyanide
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
(NaCN) and potassium cyanide (KCN).
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.1.5 Metal Cyanide Complex—A negatively charged ionic
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. complex consisting of several cyanide ions bound to a single
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation:D6696–05 Designation:D6696–10
Standard Guide for
1
Understanding Cyanide Species
This standard is issued under the fixed designation D6696; 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 (´) indicates an editorial change since the last revision or reapproval.
1
´ NOTE—Table 2 was corrected editorially in January 2006.
1. 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D1129 Terminology Relating to Water Terminology Relating to Water
D7237 TestMethodforFreeCyanidewithFlowInjectionAnalysis(FIA)UtilizingGasDiffusionSeparationandAmperometric
Detection
3. Terminology
3.1 Definitions—For a definition of terms used in this guide, refer to Terminology D1129.
4. Significance and Use
4.1 This guide provides standard terminology for use in identifying and describing the different chemical forms of cyanide.The
complex nature of cyanide chemistry, existence of numerous distinct chemical forms as well as the various regulatory distinctions
that may be made can lead to confusion in technical discussions on cyanide and in the selection of appropriate methods for its
analysis. This guide is intended to provide clarification and a common framework of terms and definitions from which to facilitate
discussions and referencereferencing different cyanide chemical species and groups of cyanide compounds.
4.2 The use of such common terminology is particularly important from an environmental perspective because certain forms
of cyanide are considered to be toxic.Therefore, their release into the environment is regulated by federal and state agencies.Thus
a general understanding of cyanide chemistry and species definitions is needed for proper wastewater management and testing.
5. Cyanide Species Terms and Definitions
5.1 Chemistry Related Terms and Definitions:
5.1.1 Cyanide Ion—The term used to describe a negatively charged ion comprised of one carbon atom and one nitrogen atom
-
triply bonded to each other (C[N ). The cyanide ion is reactive and readily forms neutral compounds or anionic complexes with
most metals.
5.1.2 Free Cyanide—The form of cyanide that is bioavailable and known for its toxic effect on organisms (1). Free cyanide
-
refers to the sum of molecular hydrogen cyanide (HCN) and cyanide ion (CN ). Hydrogen cyanide is a colorless, poisonous gas
having an odor of bitter almonds (mp = -13.4°C, bp = 25.6°C). It is readily soluble in water partitioning itselfexisting as 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 present entirely as HCN;
a
the opposite is true at pH 11 or greater. Because of its toxicity, free cyanide is regulated in environmental wastewater discharges.
-
5.1.2.1 InTest Method D7237, sum of the free cyanide (HCN and CN ) and cyanide bound in the metal-cyanide complexes that
are easily dissociated into free cyanide under the test conditions described in Test Method D7237 at pH 6 and room temperature.
5.1.3 Aquatic Free Cyanide—In Test Method D7237, free cyanide measured when the buffer or temperature is adjusted to
mimic the receiving water environment.
1
This guide is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.06 on Organic Constituents in Water.
Current edition approved July 1, 2005. Published July 2005. Originally approved in 2001. Last previous edition approved in 2001 as D6696–01. DOI:
10.1520/D6696-05E01.on Methods for Analysis for Organic Substances in Water.
e1
Current edition approved June 1, 2010. Published July 2010. Originally approved in 2001. Last previous edition approved in 2005 as D6696 – 05 . DOI:
10.1520/D6696-10.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM 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.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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