In section C, the definitions of groups of chemical elements are as follows: Alkali metals: Li, Na, K, Rb, Cs, Fr Alkaline earth metals: Ca, Sr, Ba, Ra Lanthanides: elements with atomic numbers 57 to 71 inclusive Rare earths: Sc, Y, Lanthanides Actinides: elements with atomic numbers 89 to 103 inclusive Refractory metals: Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W Halogens: F, Cl, Br, I, At Noble gases: He, Ne, Ar, Kr, Xe, Rn Platinum group: Os, Ir, Pt, Ru, Rh, Pd Noble metals: Ag, Au, Platinum group Light metals: alkali metals, alkaline earth metals, Be, Al, Mg Heavy metals: metals other than light metals Iron group: Fe, Co, Ni Non-metals: H, B, C, Si, N, P, O, S, Se, Te, noble gases, halogens Metals: elements other than non-metals Transition elements: elements with atomic numbers 21 to 30 inclusive, 39 to 48 inclusive, 57 to 80 inclusive, 89 upwards Section C covers: pure chemistry, which covers inorganic compounds, organic compounds, macromolecular compounds, and their methods of preparation; applied chemistry, which covers compositions containing the above compounds, such as: glass, ceramics, fertilisers, plastics compositions, paints, products of the petroleum industry. It also covers certain compositions on account of their having particular properties rendering them suitable for certain purposes, as in the case of explosives, dyestuffs, adhesives, lubricants, and detergents; certain marginal industries, such as the manufacture of coke and of solid or gaseous fuels, the production and refining of oils, fats and waxes, the fermentation industry (e.g., brewing and wine-making), the sugar industry; certain operations or treatments, which are either purely mechanical, e.g., the mechanical treatment of leather and skins, or partly mechanical, e.g., the treatment of water or the prevention of corrosion in general; metallurgy, ferrous or non-ferrous alloys. In the case of operations, treatments, products or articles having both a chemical and a non-chemical part or aspect, the general rule is that the chemical part or aspect is covered by section C. In some of these cases, the chemical part or aspect brings with it a non-chemical one, even though purely mechanical, because this latter aspect either is essential to the operation or treatment or constitutes an important element thereof. It has seemed, in fact, more logical not to dissociate the different parts or aspects of a coherent whole. This is the case for applied chemistry and for the industries, operations and treatments mentioned in Notes (1)(c), (d) and (e). For example, furnaces peculiar to the manufacture of glass are covered by class and not by class . There are, however, some exceptions in which the mechanical (or non-chemical) aspect carries with it the chemical aspect, for example: Certain extractive processes, in subclass ; The chemical purification of air, in subclass ; Chemical methods of fire-fighting, in subclass ; Chemical processes and apparatus, in class ; Impregnation of wood, in subclass ; Chemical methods of analysis or testing, in subclass ; Photographic materials and processes, in class , and, generally, the chemical treatment of textiles and the production of cellulose or paper, in section D. In still other cases, the pure chemical aspect is covered by section C and the applied chemical aspect by another section, such as A, B or F, e.g., the use of a substance or composition for: treatment of plants or animals, covered by subclass ; foodstuffs, covered by class ; ammunition or explosives, covered by class . When the chemical and mechanical aspects are so closely interlocked that a neat and simple division is not possible, or when certain mechanical processes follow as a natural or logical continuation of a chemical treatment, section C may cover, in addition to the chemical aspect, a part only of the mechanical aspect, e.g., after-treatment of artificial stone, covered by class . In this latter case, a note or a reference is usually given to make the position clear, even if sometimes the division is rather arbitrary. In this class, the following term is used with the meaning indicated: "preparation" covers purification, separation, stabilisation or use of additives, unless a separate place is provided therefor. Biocidal, pest repellant, pest attractant or plant growth regulatory activity of compounds or preparations is further classified in subclass . In subclasses and within each of theses subclasses, in the absence of an indication to the contrary, and with the exception referred to below, a compound is classified in the last appropriate place. For example, 2-butyl-pyridine, which contains an acyclic chain and a heterocyclic ring, is classified only as a heterocyclic compound, in subclass . In general, and in the absence of an indication to the contrary (such as groups , ), the terms "acyclic" and "aliphatic" are used to describe compounds in which there is no ring; and, if a ring were present, the compound would be taken by the "last place" rule to a later group for cycloaliphatic or aromatic compounds, if such a group exists. Where a compound or an entire group of compounds exists in tautomeric forms, it is classified as though existing in the form which is classified last in the system, unless the other form is specifically mentioned earlier in the system. Chemical compounds and their preparation are classified in the groups for the type of compound prepared. The processes of preparation are also classified in the groups for the types of reaction employed, if of interest. General processes for the preparation of a class of compounds falling into more than one main group are classified in the groups for the processes employed, when such groups exist. The compounds prepared are also classified in the groups for the types of compound prepared, if of interest. In this class, in the absence of an indication to the contrary, the compounds containing carboxyl or thiocarboxyl groups are classified as the relevant carboxylic or thiocarboxylic acids, unless the "last place rule" (see Note (3), above) dictates otherwise; a carboxyl group being a carbon atom having three bonds, and no more than three, to hetero atoms, other than nitrogen atoms of nitro or nitroso groups, with at least one multiple bond to the same hetero atom and a thiocarboxyl group being a carboxyl group having at least one bond to a sulfur atom, e.g. amides or nitriles of carboxylic acids, are classified with the corresponding acids. Salts of a compound, unless specifically provided for, are classified as that compound, e.g. aniline hydrochloride is classified as containing carbon, hydrogen and nitrogen only (in group ), sodium malonate is classified as malonic acid (in ), and a mercaptide is classified as the mercaptan. Metal chelates are dealt with in the same way. Similarly, metal alcoholates and metal phenates are classified in subclass and not in subclass , the alcoholates in groups and the phenates as the corresponding phenols in group or . Salts, adducts or complexes formed between two or more organic compounds are classified according to all compounds forming the salts, adducts or complexes. This subclass does not cover compounds containing saccharide radicals (as defined in Note (3) following the title of subclass ), which are covered by subclass . In this subclass, in compounds containing a hetero ring covered by group and at least one other hetero ring, the hetero ring covered by group is considered as an acyclic chain containing nitrogen atoms. In this subclass, the following terms or expressions are used with the meanings indicated: "hetero ring" is a ring having at least one halogen, nitrogen, oxygen, sulfur, selenium, or tellurium atom as a ring member; "bridged" means the presence of at least one fusion other than ortho, peri or spiro; two rings are "condensed" if they share at least one ring member, i.e. "spiro" and "bridged" are considered as condensed; "condensed ring system" is a ring system in which all rings are condensed among themselves; "number of relevant rings" in a condensed ring system equals the number of scissions necessary to convert the ring system into one acyclic chain; "relevant rings" in a condensed ring system, i.e. the rings which taken together describe all the links between every atom of the ring system, are chosen according to the following criteria consecutively: lowest number of ring members; highest number of hetero atoms as ring members; lowest number of members shared with other rings; last place in the classification scheme. Attention is drawn to Note (3) after class , which defines the last place priority rule applied in the range of subclasses and within these subclasses. Therapeutic activity of compounds is further classified in subclass . In this subclass, in the absence of an indication to the contrary: compounds having only one hetero ring are classified in the last appropriate place in one of the groups . The same applies for compounds having more hetero rings covered by the same main group, neither condensed among themselves nor condensed with a common carbocyclic ring system; compounds having two or more hetero rings covered by different main groups neither condensed among themselves nor condensed with a common carbocyclic ring system are classified in the last appropriate place in one of the groups ; compounds having two or more relevant hetero rings, covered by the same or by different main groups, which are condensed among themselves or condensed with a common carbocyclic ring system, are classified in the last appropriate place in one of the groups . In this subclass: where a compound may exist in tautomeric forms, it is classified as though existing in the form which is classified last in the system. Therefore, double bonds between ring members and non-ring members and double bonds between ring members themselves are considered equivalent in determining the degree of hydrogenation of the ring. Formulae are considered to be written in Kekule form; hydrocarbon radicals containing a carbocyclic ring and an acyclic chain by which it is linked to the hetero ring and being substituted on both the carbocyclic ring and the acyclic chain by hetero atoms or by carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, are classified according to the substituents on the acyclic chain. For example, the compound is classified in group , and the compound is classified in groups and , where X NH₂, NHCOCH₃, or COOCH₃. Individual components of heterocyclic compounds, such as essential substituents, single hetero rings and single condensed systems, which are considered to represent information of interest for search, may also be classified according to Note (6). This can, for example, be the case when it is considered of interest to enable searching of heterocyclic compounds using a combination of classification symbols. Such non-obligatory classification should be given as "additional information". COMPOUNDS CONTAINING ONE HETERO RING HAVING NITROGEN AS RING HETERO ATOM only nitrogen atoms one nitrogen atom Polymethyleneimine Preparation of lactams three-membered ring four-membered ring five-membered ring , six-membered ring , , , , , seven-membered ring Other compounds , two nitrogen atoms four-membered ring five-membered ring , , six-membered ring , , Piperazine seven-membered ring Other compounds , three nitrogen atoms five-membered ring six-membered ring , Other compounds four or more nitrogen atoms , nitrogen and oxygen atoms five-membered ring , , six-membered ring , morpholine Other compounds , , nitrogen and sulfur atoms five-membered ring , , six-membered ring , Thiomorpholine Other compounds , , nitrogen, oxygen, and sulfur atoms HAVING OXYGEN AS RING HETERO ATOM only oxygen atoms one oxygen atom three-membered ring , four-membered ring five-membered ring six-membered ring , Other compounds , two oxygen atoms five-membered ring six-membered ring Other compounds three or more oxygen atoms Other compounds oxygen and nitrogen atoms five-membered ring , , six-membered ring , Morpholine Other compounds , , oxygen and sulfur atoms oxygen, nitrogen and sulfur atoms HAVING SULFUR AS RING HETERO ATOM only sulfur atoms one sulfur atom five-membered ring six-membered ring Other compounds , two or more sulfur atoms , sulfur and nitrogen atoms five-membered ring , , six-membered ring , Thiomorpholine Other compounds , , sulfur and oxygen atoms sulfur, nitrogen, and oxygen atoms HAVING SELENIUM OR TELLURIUM AS RING HETERO ATOM only selenium or tellurium atoms together with nitrogen atoms together with oxygen atoms together with sulfur atoms HAVING HALOGEN AS RING HETERO ATOM COMPOUNDS CONTAINING TWO OR MORE HETERO RINGS IN THE SAME RING SYSTEM HAVING NITROGEN AS RING HETERO ATOM only nitrogen at least one six-membered ring with one nitrogen atom Tropane, granatane Quinine, quinuclidine, isoquinuclidine Emetine, berberine Lysergic acid, ergot alkaloids Yohimbine Vincamine Carbacephalosporins Other compounds , , Purine Pteridine Thienamycin nitrogen and oxygen , , Morphine Oxapenicillins Oxacephalosporins nitrogen and sulfur , Penicillins Cephalosporins nitrogen, oxygen, and sulfur , HAVING OXYGEN AS RING HETERO ATOM only oxygen oxygen and nitrogen , , Morphine Oxapenicillins Oxacephalosporins oxygen and sulfur oxygen, nitrogen, and sulfur , HAVING SULFUR AS RING HETERO ATOM only sulfur in a particular ring sulfur and oxygen sulfur, nitrogen, and oxygen , HAVING SELENIUM, TELLURIUM, OR HALOGEN AS RING HETERO ATOM IN DIFFERENT RING SYSTEMS, EACH CONTAINING ONLY ONE HETERO RING HAVING NITROGEN AS RING HETERO ATOM only nitrogen at least one six-membered ring with one nitrogen atom Other compounds nitrogen and oxygen , nitrogen and sulfur thiamine nitrogen, oxygen, and sulfur HAVING OXYGEN AS RING HETERO ATOM only oxygen oxygen and nitrogen , oxygen and sulfur oxygen, nitrogen, and sulfur HAVING SULFUR AS RING HETERO ATOM only sulfur in a particular ring sulfur and nitrogen thiamine sulfur and oxygen sulfur, nitrogen, and oxygen HAVING SELENIUM, TELLURIUM, OR HALOGEN AS RING HETERO ATOM COMPOUNDS CONTAINING TWO OR MORE RING SYSTEMS, HAVING EACH TWO OR MORE HETERO RINGS ALKALOIDS Emetine Ergot , Granatanine Morphine Nicotine Papaverine Quinine Strychnine Tropane CEPHALOSPORIN PENICILLIN PTERIDINE THIENAMYCIN PURINE THIAMINE COMPOUNDS CONTAINING UNSPECIFIED HETERO RINGS Pyrrolidines having only hydrogen atoms attached to the ring carbon atoms are classified in group . In this group, the following term is used with the meaning indicated: "hydrogenated" means having less than three double bonds between ring members or between ring members and non-ring members. Piperidines having only hydrogen atoms attached to ring carbon atoms are classified in group . Hexamethylene imines or 3-azabicyclo [3.2.2] nonanes, having only hydrogen atoms attached to the ring carbon atoms, are classified in group . Polymethyleneimines with at least five ring members and having only hydrogen atoms attached to the ring carbon atoms are classified in group . Polymethyleneimines with at least five ring members and having only hydrogen atoms attached to the ring carbon atoms are classified in group . Piperazines with only hydrogen atoms directly attached to ring carbon atoms are classified in group . Morpholines having only hydrogen atoms attached to the ring carbon atoms are classified in group . Thiomorpholines having only hydrogen atoms attached to the ring carbon atoms are classified in group . Groups cover compounds containing two or more relevant hetero rings at least two of which are covered by different main groups of groups , neither condensed among themselves nor condensed with a common carbocyclic ring or ring system. Groups cover compounds containing one system of two or more relevant hetero rings condensed among themselves or condensed with a common carbocyclic ring system, with or without other non-condensed hetero rings. For the purpose of classification in groups , the degree of hydrogenation of the ring system is not taken into consideration. For the purpose of classification in groups , , , , the wording of the groups has to be understood, in the absence of an indication to the contrary, as including ring systems further condensed with carbocyclic rings or ring systems, but excluding ring systems further condensed with other hetero rings, either directly or through a common carbocyclic ring system, e.g. sparteine is classified in group , not in group . In groups , , or , the subdivision is based on the number of relevant hetero rings. The numbering may be different according to the RING INDEX and given by the formula: . The numbering may be different according to the RING INDEX and given by the formula: .