                  TOXIC SUBSTANCES CONTROL ACT

                   INVENTORY REPRESENTATION FOR

           PRODUCTS CONTAINING TWO OR MORE SUBSTANCES:

                FORMULATED AND STATUTORY MIXTURES

I.  Introduction

     This paper explains the conventions that are applied to

listings of certain mixtures for the Chemical Substance Inventory

that is maintained by the U.S. Environmental Protection Agency

(EPA) under the Toxic Substances Control Act (TSCA).  This paper

discusses the Inventory representation of mixtures of substances

that do not react together (i.e., formulated mixtures) as well as

those combinations that are formed during certain manufacturing

activities and are designated as mixtures by the Agency (i.e.,

statutory mixtures).  Complex reaction products are covered in a

separate paper.  The Agency's goal in developing this paper is to

make it easier for the users of the Inventory to interpret

Inventory listings and to understand how new mixtures would be

identified for Inventory inclusion.  

     Fundamental to the Inventory as a whole is the principle

that entries on the Inventory are identified as precisely as

possible for the commercial chemical substance, as reported by

the submitter.  Substances that are chemically indistinguishable,

or even identical, may be listed differently on the Inventory,

depending on the degree of knowledge that the submitters possess

and report about such substances, as well as how submitters

intend to represent the chemical identities to the Agency and to

customers.  Although these chemically indistinguishable

substances are named differently on the Inventory, this is not a

"nomenclature" issue, but an issue of substance representation. 

Submitters should be aware that their choice for substance

representation plays an important role in the Agency's

determination of how the substance will be listed on the

Inventory.  

 

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     NOTICE:  The policies set out in this document are not final

Agency action, but are intended solely as guidance.  They are not

intended, nor can they be relied upon, to create any rights

enforceable by any party in litigation with the United States. 

EPA officials may decide to follow the guidance provided in this

document, or to act at variance with this guidance, based on an

analysis of specific circumstances.

II.  Definition of Terms

     TSCA identifies two types of materials:  (1) chemical

substances and (2) mixtures of chemical substances.  The

Inventory lists only chemical substances.  It does not list

mixtures; however, the individual components of mixtures are

listed separately.  

     "Chemical substance" is defined in section 3 of TSCA (and

in section 710 of the Agency's implementing regulations) by

chemical composition, by source or origin and by identification 

of certain categories of materials that are not considered

"chemical substances":  

          "Chemical substance" means any organic or inorganic

     substance of a particular molecular identity, including --

                    (i) any combination of such substances occurring in

          whole or in part as a result of a chemical reaction or

          occurring in nature, ... .  

          "Chemical substance" does not include:

                    (i) any mixture [710.2(q)], ...

     "Mixture" is defined in section 710.2(q) as:

          any combination of two or more chemical substances if the

     combination does not occur in nature and is not, in whole or

     in part, the result of a chemical reaction; except that

     "mixture" does include:

            (1) Any combination which occurs, in whole or in part, as

     a result of a chemical reaction if the combination could

     have been manufactured for commercial purposes without a

     chemical reaction at the time the chemical substances

     comprising the combination were combined and if, after the

     effective date of premanufacture notification requirements,

     none of the chemical substances comprising the combination

     is a new chemical substance, and 

            (2) Hydrates of a chemical substance or hydrated ions

     formed by association of a chemical substance with water.

III.  Inventory Representations with Illustrative Examples

          A.  Mixtures resulting from blending substances that do not

     react.

     A blend of two or more substances that has been physically

combined without a chemical reaction is considered to be a

mixture.  Such a blend, as a whole entity, is excluded from the

Inventory and premanufacture notification (PMN) requirements for

new chemical substances.  Individual components of such a mixture

are separately reportable for the Inventory, however, and are

considered to be "new substances" if they are not currently

listed on the Inventory.  

     Note, however, that salt formation, the creation of ionic

bonds, is considered to be a chemical reaction.

               1.  Combinations of materials that are physically 

     blended or mixed together and do not themselves result in a

     chemical reaction are always considered to be mixtures.

     The exclusion of these mixtures from the Inventory applies

only to the mixture itself and not to the individual chemical

substances of which the mixture is comprised.  Each chemical

substance in a mixture requires a separate Inventory listing. 

This approach affords considerable flexibility to processors, who

are allowed to make many different mixtures of Inventory-listed

substances without submitting PMNs.

               Example 1.  Consider two petroleum streams, each of which
is

          a complex chemical substance.  The two streams are

          mixed, but no reaction occurs.  The Agency considers

          that the combination of the two petroleum streams

          themselves is a mixture; each would be listed

          separately on the Inventory.  A similar example from

          the petroleum industry is a blended gasoline to which a

          non-reactive corrosion inhibitor has been added.

               Example 2.  Solid solutions are treated as mixtures; they

          are found in certain alloys.  For example, gold and

          copper form solid solutions in which some of the copper

          atoms in the lattice are replaced by gold atoms.  In

          general, the gold atoms are distributed at random, and

          a range of gold-copper compositions is possible,

          according to this mixture representation for gold and

          copper.  

               Example 3.  Consider a substance that is encapsulated in
a

          second substance.  If the two substances do not react

          together, they are considered to be a mixture under

          TSCA if they do not constitute an article.  

               Example 4.  A commercial product described as "coating

          material of linseed oil and titanium dioxide," formed

          by the intentional mixing of two or more substances,

          which produces no new substance(s) and results only in

          a combination of the mixed substances, is not itself a

          substance under TSCA.  The component substances of such

          mixtures (e.g., linseed oil and titanium dioxide),

          however, are individually reportable as substances.

               Example 5.  Consider a multi-nutrient "mixed fertilizer"

          that could have been prepared by physically blending

          dry products such as urea, superphosphate and potash or

          by chemical reaction when liquid ammonium phosphate was

          granulated with potash.  The Agency considers this

          "mixed fertilizer" a mixture of urea, superphosphate

          and potash regardless of the method used to make it.  

               Example 6.  If commercially-available pine oil, a
non-ionic

          surfactant, and sodium soap of coconut oil acids are

          mixed, without chemical reaction, a combination is

          produced that is a mixture.  Alternatively, if that

          same combination is prepared by mixing pine oil, the

          non-ionic surfactant, coconut oil acids and sodium

          hydroxide, and carrying out the saponification reaction

          to form the sodium soap of coconut oil acids, the

          combination would be identical to that manufactured by

          mixing the first set of substances without chemical

          reaction.  The three substances in the final

          combination (i.e., pine oil, the surfactant and the

          sodium salt of coconut oil) constitute a mixture and

          each one is subject to Inventory reporting, regardless

          of the method used to manufacture the mixture.  

     In some cases two substances may be physically intertwined

such that they cannot be separated without breaking bonds of one

or the other.  As long as they have not reacted with each other

(i.e., there are no covalent bonds between the two types of

molecules), they are considered to be a mixture.  As an extreme

example, two or more intertwined rings (i.e., concatenated

molecules) that had different chemical compositions would be

considered a mixture under TSCA if, in fact, they had no covalent

bonds connecting them.  

          B.  Combinations that are considered to be statutory

     mixtures under TSCA

                    1.  Certain alloys, inorganic glasses, ceramics,
frits

          and cements, including Portland cement are considered

          to be statutory mixtures by the Agency.  

     Inorganic glasses, ceramics, frits and cements, including

Portland cements, are considered to be statutory mixtures under

TSCA.  Manufacturers of these products are not required to report

them.  When the initial Inventory was being developed, both EPA

and industry recognized that the individual substances comprising

these mixtures are complex solids and would be very difficult to

identify.  Therefore, instead of requiring industry to identify

and report every such substance for the Inventory, several

special categories were created to include the various substances

formed when cement, glass, frit or ceramic are produced.  These

categories were reported during the initial Inventory reporting

period and are currently listed on the TSCA Inventory.  Each

category contains a definition that describes the various

components of that category in terms of the elements and the

various types of chemical substances that may be formed with

these elements.  These categories of substances are:

Cement, Portland, Chemicals             [65997-15-1* ]

Cement, Alumina, Chemicals              [65997-16-2* ]

Glass, Oxide, Chemicals                 [65997-17-3* ]

Frits, Chemicals                        [65997-18-4* ]

Steel Manufacture, Chemicals            [65997-19-5* ]

Ceramic Materials and Wares, Chemicals  [66402-68-4* ]

     For example, a category such as Ceramic Material and Wares,

Chemicals includes any combination of the elements listed in the

Inventory definition, as oxides, borides, carbides, etc., in

multiple oxidation states, or in more complex compounds.  The

listed elements included in the definition of each of these

categories are not intended to be inclusive.  EPA recognizes that

the list of elements may need to be updated from time to time as

the state of the technology changes.

     Example 7.  Glass, oxide, chemicals (CASRN 65997-17-3* )

               The definition of this substance is as follows:

                    Synonym:  Chemical substances manufactured in the

          production of inorganic glass

                    This category encompasses the various chemical

          substances manufactured in the production of inorganic

          glasses.  For purposes of this category, "glass" is

          defined as an amorphous, inorganic, transparent,

          translucent or opaque material traditionally formed by

          fusion of sources of silica with a flux, such as an

          alkali-metal carbonate, boron oxide, etc. and a

          stabilizer, into a mass which is cooled to a rigid

          condition without crystallization in the case of

          transparent or liquid-phase separated glass or with

          controlled crystallization in the case of glass-

          ceramics.  The category consists of the various

          chemical substances, other than by-products or

          impurities, which are formed during the production of

          various glasses and concurrently incorporated into a

          glass mixture.  All glasses contain one or more of

          these substances, but few, if any, contain all of them. 

          The elements listed below are principally present as

          components of oxide systems but some may also be

          present as halides or chalcogenides, in multiple

          oxidation states, or in more complex compounds.  Trace

          amounts of other oxides or chemical compounds may be

          present.  Oxides of the first seven elements listed*

          comprise more than 95 percent, by weight, of the glass

          produced.  

          Aluminum*                     Lanthanum

          Boron*                        Lead

          Calcium*                      Lithium

          Magnesium*                    Manganese

          Potassium*                    Molybdenum

          Silicon*                      Neodymium

          Sodium*                       Nickel

          Antimony                      Niobium

          Arsenic                       Nitrogen

          Barium                        Phosphorus

          Bismuth                       Praseodymium

          Cadmium                       Rudibium

          Carbon                        Selenium

          Cerium                        Silver

          Cesium                        Strontium

          Chromium                      Sulfur

          Cobalt                        Tellurium

          Copper                        Tin

          Germanium                     Titanium

          Gold                          Tungsten

          Holmium                       Uranium

          Iron                          Vanadium

                                        Zinc

     Definitions such as this may be subject to revision to

reflect changes in the underlying technology.  

     Alloys that are solid or liquid mixtures of two or more

metals or of one or more metals with certain nonmetallic elements

(e.g., certain carbon steels), are considered mixtures and are

not reportable.  However, intermetallic compounds of well-defined

stoichiometry are not considered alloys and should be reported.  

                    2.  Certain combinations of metals, inorganic metal

          compounds and inert supports, which are frequently used

          for commercial purposes, including for use as solid

          phase heterogeneous catalysts, are also considered to

          be mixtures for the purposes of the TSCA Inventory.   

               Example 8.  Consider the following supported catalysts:

          Pt supported on SiO2, Al2O3 or C

          Pd supported on SiO2, Al2O3 or C

          Rh supported on SiO2, Al2O3 or C

          Ni supported on SiO2, Al2O3 or C

                    In supported catalysts, the catalytic ingredient is

          dispersed in the internal porosity of such supports as

          silica gel, alumina or charcoals.  Tiny crystallites of

          such metals as platinum, palladium, rhodium and nickel

          can be formed in the pore structure.  Supported

          catalysts have much larger surface area of the

          catalytic ingredient and are much more resistant to

          coalescence of the catalytic ingredient than are

          powders.  For example, the supported catalyst Pt/C was

          prepared by the reduction of PtCl2 adsorbed on

          charcoal.  Although a reaction was involved in the

          preparation, the resultant catalyst is represented in

          terms of the products formed and is viewed under TSCA

          as a mixture of the two substances, platinum and

          carbon.

               Example 9.  Zeolites are considered for TSCA purposes to
be

          mixtures of the substances used to manufacture them. 

          The individual reactant materials used to produce

          zeolites are required to be listed separately on the

          Inventory.  The application of EPA's guidance is not

          affected by the chemical composition of the zeolite

          under consideration.  

     EPA recognizes zeolites as a family of aluminosilicates

manufactured from a number of commercial processes and techniques

that utilize different proportions of alumina, silica and a

variety of sources of different inorganic and organic cations. 

The final zeolites are characterized by covalently linked AlO4

and SiO4 tetrahedra.  Zeolites as a class of substances are

considered mixtures under TSCA regardless of the commercial

manufacturing processes and reactants utilized to achieve the

desired chemical composition of the final zeolite structure.  

               Example 10.  Consider a cobalt oxide-aluminum oxide

          catalyst.  A mixed hydroxide precipitate formed by the

          reaction of sodium hydroxide and an aqueous solution of

          cobalt (II) nitrate and aluminum nitrate is heated in

          air to produce a mixed oxide catalyst.  Some of the

          cobalt is known to be oxidized to Co(III) in the

          process.  In this case, cobalt (II) oxide, cobalt (III)

          oxide and aluminum oxide would each be reported for the

          Inventory.  More complex compounds of cobalt and/or

          aluminum which may be formed incidentally in the

          manufacture of the catalyst mixture are not reported.  

          C.  Hydrates of a chemical substance or hydrated ions formed

     by association of a chemical substance with water are

     considered to be mixtures of the anhydrous form of the

     chemical substance and water.

     Hydrated forms of chemical substances are exempt from the

Inventory as mixtures; the anhydrous chemical substances,

however, are reportable for the Inventory.  Thus the manufacturer

of hydrated copper sulfate, CuSO4.(H2O)x, would use the anhydrous

form, CuSO4, for Inventory purposes.  

               Example 11.  Na2CO3.10H2O is a mixture of Na2CO3 and H2O;

          CuSO4.5H2O is a mixture of CuSO4 and H2O.  The anhydrous

          forms, Na2CO3 and CuSO4, are subject to reporting under

          TSCA.

     This provision does not apply to the product of discrete

chemical reactions in which either water or a solvent is a

reactant.  For example, hydrates are not formed when water reacts

with an ester to form an acid and an alcohol; likewise,

substances with Chemical Abstracts (CA) names containing the term

"hydrolyzed" are not hydrates.  Similarly, metal hydroxides

formed by the reactions of metal oxides with water are not

considered to be hydrates for TSCA Inventory purposes.

               Example 12.  A stable, hydrated complex of two substances

          and water is considered to be a mixture of the three

          chemicals.  In this case, the only chemical interaction

          between the three entities is hydrogen bonding, which

          EPA does not recognize as bonding for purposes of

          chemical identification under TSCA.  

     Hydrogen bonding does not result in the formation of a new

chemical substance for the purposes of TSCA, even though it has

significant effects on physical properties.  For example, the

hydrogen of the chloroform molecule, Cl3CH, forms hydrogen bonds

with an electron pair of the oxygen of the acetone molecule,

Cl3CH   O=C(CH3)2, and chloroform-acetone mixtures have higher

boiling points than either pure component.  This type of

interaction between two molecules is caused by the

electronegative atoms (such as fluorine, nitrogen or oxygen) in

one molecule and hydrogen atoms bound to electronegative atoms in

another molecule.  The hydrogen-bonded materials are considered

to be mixtures for the purposes of TSCA.  

               Example 13.  Consider the reaction of calcium oxide (CaO)

          (CASRN 1305-78-8) with water (CASRN 7732-18-5) to form

          calcium hydroxide (Ca(OH)2) (CASRN 1305-62-0).  The

          calcium hydroxide is not a hydrate with water and thus

          would require its own Inventory listing.  

                     CaO  +  H2O     Ca(OH)2

               Example 14.  Consider the reaction of acetyl chloride

          (CASRN 75-36-5) with water (CASRN 7732-18-5) to form

          acetic acid (CASRN 64-19-7) and hydrochloric acid

          (CASRN 7647-01-0).  Both products of this reaction

          would require Inventory listing.  

             CH3-COCl  +  H2O     CH3-COOH  +  HCl

          D.  Surface Treatment

     With this term the Agency generally means the process of

chemically treating the surface of a substance, the substrate,

with another substance so as to enhance some physical property of

the surface of the substrate or to impart chemical reactivity to

the surface (i.e., to functionalize the surface chemically).  The

surface-treating substance adheres to the surface by van der

Waal's forces, ionic bonds or covalent bonds.  If the substance

only alters a physical characteristic, the combination of the

surface treatment substance and the substrate is considered to be

a mixture of two substances, each requiring its own Inventory

listing.  If, however, the surface treatment is intended to

impart chemical reactivity, the reaction product is required to

be on the Inventory.  

     Example 15.  Consider the following reaction:  

            º                                        º   Me

            º                                        º    

            º-OH                                     º-O-SiC10H21

     silica º     +  ClSiMe2C10H21    ---->   silica º    

            º-OH                                     º   Me

     silica surface                            hydrophobic silica

                    In this example, the silica surface was modified by
a

          chemical reaction to introduce a material onto the

          outermost layer of the silica, contributing the

          property of hydrophobicity to the silica without

          changing the bulk properties of the silica.  This type

          of reaction is usually not stoichiometric and would not

          be reportable under TSCA.  

               Example 16.  On the other hand, if the surface of the

          substrate is functionalized, the reaction product

          formed upon reaction of the substrate and surface

          treating substance is considered to be a reportable

          substance, as illustrated below:

           º                                      º    

           º-OH                                   º-O-Si(CH2)3NH2

     glass º    + (EtO)3Si(CH2)3NH2 ----> glass   º    

           º-OH                                   º

     glass surface       silane              coupling agent

                                             chemically bonded to

                                             surface, providing

                                             amine functionality

                    The glass filler (particles, spheres, flakes and

          fibers) is coated with an organofunctional silane. 

          Chemical modification of the filler through treatment

          with the silane is necessary to promote interfacial

          adhesion between the filler and a polymer in making

          polymer blends, which allows for uniform dispersion of

          the filler in the polymer blend.  Such functionalized

          glasses, which are formed by chemical reactions, are

          reportable substances and not considered mixtures under

          TSCA.  Generally, when the surface of glass or silica

          is modified to incorporate certain functional group(s)

          intended to react with other chemical substance(s), the

          Agency considers the surface modified glass or silica

          to be a chemical substance.    

               Example 17.  If a functionalized glass sphere is coated
with

          a polymer having reactive sites capable of reaction

          with the functionalized glass, the functionalized

          glass-polymer reaction product is not reportable.  This

          type of substance is generally a combination of two or

          more materials present as separate phases and combined

          to form desired structures that take advantage of

          certain desirable mechanical/physical properties of

          each component.  Chemical reactions merely take place

          over the interface region of the polymeric matrix and

          the dispersed particulate (filler) phases.  The Agency

          considers such combinations comprising separate phases

          in the polymer blend to be, for purposes of TSCA, the

          same as a physical suspension of the functionalized

          filler in the polymer.  Consequently, this type of

          material is considered to be a mixture of the

          suspending filler(s) and polymer(s), even though a

          reaction was involved.  

      º                                    º    

      º-O-Si(CH2)3NH2                      º-O-Si(CH2)3NHCO/\/\/

glass º                       ---> glass   º    

      º         + HO2C/\/\/\               º

      º-O                                  º

Functionalized    Polyester                The linking moiety at

Glass             molecule with            the interface between

                  its acid end             polyester and glass    

                  group

