Hill indexing system

List of chemical symbols of substances according to the alphabetical order of elements (modified Hill indexing system)... 

Each compound is characterized by its chemical name, net formula and Chemical Abstracts Service Registry Number (in square brackets). The data are ordered by the compound net formula in accordance to the Hill Indexing System [00-hil] (in each formula, carbon atoms are placed first, hydrogen atoms second, and further elements based on an alphabetical sequence). 

The elements of an organic compound are listed in empirical formulas according to the Hill system [8] and the stoichiometry is indicated by index numbers. Hill positioned the carbon and the hydrogen atoms in the first and the second places, with heteroatoms following them in alphabetical order, e.g., C9H11NO2. However, it was recognized that different compounds could have the same empirical formula (see Section 2.8.2, on isomerism). Therefore, fine subdivisions of the empirical... 

The element symbols within each formula are arranged according to a modified Hill system in which the order is metal(s), C, H and then any remaining symbols arranged alphabetically. Compounds containing two (or more) different metals appear twice (or more), being listed under each metal. Common ligand abbreviations which appear in the text have also been used in the index. These include acac (acetylacetone), bipy (2,2 -bipyridyl), diars [o-phenylenebis(dimethyl-arsine)], dien (diethylenetriamine), etc. 

A single unstable compound of known composition is placed in the main first volume and is located on the basis of its empirical molecular formula expressed in the Hill system used by Chemical Abstracts (C and H if present, then all other element symbols alphabetically). The use of this indexing basis permits a compound to be located if its structure can be drawn, irrespective of whether a valid name is known for it. A representation of the structure of each compound is given on the third bold title line while the name of the compound appears as the first bold title line. References to the information source are given, followed by a statement of the observed hazard, with any relevant explanation. Cross-reference to similar compounds, often in a group entry, completes the entry. See Trifluoroacetyl nitrite p. 244. 

Plochere, Plochere Color System , Los Angeles, Calif (1948) 6)Kirk Othmer 4 (1949), 242-51 (Color measurements) 7)E. M.Graves, "Color Fundamentals , McGraw-Hill, NY (1952) 8)Anon, "Color Index , Society of Dyers St Colourists, London and American Association of Textile Chemists Sc Colorists, Durham, NC, 2nd edition in 4 vols (1955 1959) 9)Anon, "Reinhold Color Atlas , Reinhold, NY (1962) 10)D.B.Judd G.Wyszecki, "Color in Business, Science and Industry , Wiley, NY (1963)... 

The Formula Index links the molecular formulae of chemical substances with their CA Index Names, CAS registry numbers, and CA abstract numbers. Molecular formulae are arranged according to the Hill system order (see Section 10.1). 

Although the Hill system is now used almost exclusively, other systems have been used in the past. For example, the early formula indexes to Beilstein used the Richter system, in which the elements are cited in the order C, H, O, N, Cl, Br, I, F, S, R... 

The two major costs associated with evaporators, as with any process equipment, are capital investment and operating costs. The best estimate of the installed cost of evaporation systems is, of course, a firm bid from a vendor. The installed cost, however, can be estimated based on the heat transfer surface area, as in Peters and Timmerhaus. Costs taken from published references must be adjusted for changes subsequent to the time of publication. To do this, one may use an index such as the Marshall and Swift allindustry index. The value of this index is published each month in Chemical Engineering, a McGraw-Hill publication. Further information on the use of this and other cost indices as well as their histories are available, for example, in Peters and Timmerhaus and Ulrich.f Variation of purchased evaporator costs with material of construction and pressure can also be found in Ulrich. ... 

Although these simple considerations help to frame in a general logic the behavior of these bimetallic surface, there are at present no such simple models to explain the more complex mesoscopic reconstructions, such as the pyramids observed on Pt3Sn(100) or the hill and valley structure observed on PtsSnCl 10). These phenomena are obviously related to the tendency of the system to relax in-plane stress, in turn resulting from the different atomic radius of the elements involved in the presence of concentration gradients. This relaxation appears to take place on the (111) oriented plane simply by an outward relaxation of the tin atoms. On the other two low index surfaces, instead, it takes a more complex route leading to reconstruction phenomena (pyramids on the (100) and hill and valley on the (110)) which are so far unique to the Pt-Sn system. 

There are two systems of formula indexing in common use today, the Hill and the Richter systems. 

In the original Hill system (II) formulas are written in strict alphabetic order, omitting water of crystallization, except that with carbon compounds carbon is written first, followed immediately by hydrogen if present—i.e., trichloropropanol, C3H5CI3O. Each compound is arranged in the index by its own formula the sodium salt of propionic acid, C3H5 Na02, is entered as such. 

The Hill system is used in modified form today by Chemical Abstracts and Referativny Zhurnal, Khimiya (17) and indexes both inorganic and organic compounds. Beilsteins Handbuch (2) formula index to the second supplement uses the Hill system. This index covers the original work and two supplements. 

Volumes 28 and 29 of the Second Supplement are, respectively, the subject and formula indexes to the entire "Beilsteins Handbuch the three-part cumulative formula index, arranged by the Hill system, is the only index recording the known formulas of organic compounds from the beginnings of organic chemistry through 1929. (The Chemical Abstracts cumulative formula index extends this period to 1946.)... 

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