Particular molecular identity

As used in the act, the term chemical substance means any organic or inorganic substance of a particular molecular identity, including any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature and any element or uncombined radical. Items not considered chemical substances are listed in the definition section of the act. The term mixture means 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 such term does include any combination that occurs, in whole or in part, as a result of a chemical reaction if none of the chemical substances comprising the combination is a new chemical substance and 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. 

TSCA coverage extends to chemical substances and mixtures used in a wide range of industrial, commercial and consumer applications. As defined in section 3(2) of the Act a "chemical substance" is "any organic or inorganic substance of a particular molecular identity, including...any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature..."... 

When examining the products of biotechnology, such as recombinant DNA and RNA, for example, it can be seen that they are organic chemical substances of particular molecular identities and... 

On 23 January 2008, the EPA published a general approach to determining if a particular substance, including nano-substances, is present on the TSCA Inventory [1]. As a general matter, under the TSCA, the EPA regulates substances of a particular molecular identity, traditionally stating that particle size and shape are not factors in this definition. 

TSCA Section 3(2)(A) defines the term chemical substance to mean any organic or inorganic substance of a particular molecular identity. .. [3]. Thus, in determining whether a chemical substance is a new chemical for purposes of TSCA Section 5, or instead is an existing chemical, the EPA determines if the chemical substance has... 

Under the Toxic Substances Control Act (TSCA), numerous nomenclature issues have arisen over the years, some of which have been discussed in this book. There will undoubtedly be new nomenclature issues to be resolved, nanoparticles being a current case in point. Issues of the past have often arisen out of administrative and sometimes arbitrary naming conventions, but risks associated with chemical substances do not depend on how they are named. Nanoparticles present different issues in the sense that the Environmental Protection Agency (EPA) stated that the TSCA regulates chemical substances of a particular molecular identity, without regard to physical properties such as size and shape. Potential for significant risk due to nanoparticles clearly exists exactly due to those physical properties. Regulators and interpreters of the TSCA must address potential risks such substances may pose even if their non-nano counterparts do not, and even if their newness does not meet the current definition of substances with different molecular identities. 

Chemical substance is defined in 3(2) of the statute to include any organic or inorganic substance of a particular molecular identity, including... 

Products subject to positive certification are chemical substances, mixtures, or articles containing a chemical substance or mixture as those terms are defined under TSCA, which are either on the TSCA Inventory, or are not on the TSCA Inventory but are being imported in compliance with TSCA. A chemical substance is any organic or inorganic substance of a particular molecular identity including (i) any combination of such substances... 

It is often possible to obtain similar or identical results from statistical mechanics and from thermodynamics, and the assumption that a system will be in a state of maximal probability in equilibrium is equivalent to the law of entropy. The major difference between the two approaches is that thermodynamics starts with macroscopic laws of great generality and its results are independent of any particular molecular model of the system, while statistical methods always depend on some such model. 

Suppose that G is the group of symmetry operations of a polyhedron or polygon, with vertices corresponding to the atomic positions in a particular molecular structure. The division of the structure into orbits, as sets of vertices equivalent under the actions of the group symmetry operations and the calculation of associated permutation representations/characters were described in Chapter 2. In this chapter, the identity between the permutation representa-tion/character on the labels of the vertices of an orbit and the a representation/character on sets of local s-orbitals or a-oriented local functions is exploited to constmct the characters of the representations that follow from the transformation properties of higher order local functions. 

In dealing with the manufacture of materials, a number of physical and chemical properties of materials or streams of materials are of particular interest. These properties include the molecular identity of the material the amount involved the composition or purity of the material its thermodynamic phase its... 

The formulation of complexes as salt-like species containing well-defined cations or anions should be approached with a certain amount of caution. This is particularly well illustrated with xenon difluoride adducts which span the gamut of complexes from salt-like species such as [XeF]+[Sb2Fn] to covalent adducts like XeF2 XeOF4, In the latter the components preserve their molecular identities and dimensions and the adduct is clearly a covalent adduct, but even in the former the relative short Xe F distance between the [XeF]+ cation and the [Sb2Fu] anion (2.34 A) implies considerable covalent character. 

A.26.15 (a) Mass spectrometry uses the mass-to-charge ratio (m/z) of the gaseous ionized molecular ions. Its separation results in a plot that shows the abundance of a particular molecular fragment as a function of its m/z ratio, (b) The compounds could have identical masses and charges. One compound could be a multiple of the mass of the other compound, e.g. 2 1, and have die same ratio in charge. The researcher could have mistakenly used the same compound for both tests. Because of the last possibility, the researcher should repeat her experiment to make certain the result is reproducible. 

Some consequences were discussed in Section I. If a pair of chemically identical (d-d) or nonidentical molecules ( f-D) are packed together, and this packing compared with the corresponding d-l or d-L pair, each for minimum total energy, there is no relation between the pair structures to enable them to be treated in a systematic way. Each case depends on the particular molecular composition and the particular atomic non-bonded radii which collectively are responsible for the surface shape of the molecule conceived as bounded by a hard surface. For each case it is of course possible to make calculations of packing energy and of optimum structure in the way now commonly followed for the packing in molecular crystals. Such calculations have not been reported so far as we are aware. 

If we consider all the symmetry operations which are associated with a particular molecular geometry, these operations form a point group and all these operations have the property of permuting atoms in identical environments in the molecule. However, if a set of identical Cartesian basis functions is placed on each symmetry-equivalent atom then, in addition to the permutation of symmetry-equivalent basis functions, some of the symmetry operations will send these basis functions into linear combinations of themselves (it is only necessary to think of the action of a three- or five-fold rotation on a set of p basis functions to see this). 

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