Numerical Data for Scientists

Stephen R. Heller
Lewis H. Gevantman

The scientific community is currently undergoing phenomenal changes in the way it produces, compiles, and disseminates scientific information and data. Much of it can now be managed by computer. Similarly, bibliographic literature searching has become routine using a variety of on-line systems (see box).

A newer activity that is starting to make its presence felt in the scientific community is that of providing the scientist with access to numerical data through a variety of automated mechanisms. Several numerical data bases have emerged and are now being used. However most of these data bases remain unique--some have search and retrieval capabilities, but for the mostpart they remain free-standing bodies of numerical data without connection to one another.

A decade ago the idea of combining related numerical data bases for the environmental science community (1) was activated first at the National Institutes of Health and subsequently by the EPA. Coordination with other government agencies led to a system of 22 data bases and software analysis programs entitled Chemical Information System (CIS). This system, which is under private operation, is available to the environmental scientist. However, some of the newer computer capabilities and improved data management designs are not available in the system.

A numerical data base is defined as a collection or compilation of numerical data that describes either singular or multiple physical parameters of a specified chemical substance. Generally, the number of parameters and substances are limited. The data base may have simply a listing of numbers or it may have search and retrieval software for extracting the desired data value. Some come with calculational capability for extrapolating or interpolating values based on theoretical or empirical grounds. Most of these data bases are free-standing and each may require the use of a unique approach for extraction of the information contained in the data base. This makes for the investment of considerable time and effort on the part of the user to learn and manipulate each data base. In addition, the data contained in such data bases are culled from the scientific literature and other sources with minimal attempt to evaluate the quality of the data. Also, some data bases are created with little or no regard for adding to or updating their capability. This tends to render the data less useful with the passage of time

On-line dissemination

A better approach to on-line numerical data dissemination for environmental scientists has been initiated by Technical Database Services, Inc., (TDS, see box) in their Numerica system. In contrast to the individual free-standing bodies of data bases available to users, the Numerica system is one of a cluster of experimental data bases, each of which has been scrutinized and accepted by the data base developer for quality and timeliness. Although each data base comes from a different source, inconsistencies between data bases (primarily in the area of nomenclature) are resolved by the use of Chemical Abstracts Service (CAS) registry numbers. Furthermore, each part or data base is closely related to the, other so that the data can be checked for consistency within all data bases. Programs are available to round out an compare calculational versus expert mental values with further opportunity to extend the data into areas where no data exist. The search and retrieve strategies for accessing the data bases are also rendered in a consistent manner, so there is no need to learn how to use each data base. Consequently, the buildup of data bases clustered about a centralized theme such as environmental science presents a highly useful systems concept.

Highlights of how the Numerica system searches for specific chemical properties data illustrate the system's utility in meeting the needs of the environmental scientist. For example, the chemical 1,l'-biphenyl (molecular formula C12.H10) has been assigned CAS registry number 92-544. Access to the Numerica on-line system is achieved in the usual manner through a dial-up telephone network, in this case Telenet.

What data base to use

Before beginning a search of Numerica data bases, one must check to see which, if any, data base contains data on the chemical of interest. This can be done by using SYNDEX, which contains an index of CAS registry numbers, chemical names, synonyms, and TDS data base tags. This allows the user to save both time and money by avoiding systems that do not contain the needed data. The results of the search show that numerical data on l,l'-biphenyl can be found in the Thermodynamic Research Center Database, the Carcinogenic Information Database for Environmental Substances (CIDES) (see box), the Environmental Fate Database (EFDB) (2), and the Log P and Related Parameters Database (3). Illustrative excerpts from three of these data bases are shown in Table 1. In performing a search for data and information on 1,1'-biphenyl, the first type of data to be searched is environmental fate data.

Yet another data base, CHEMEST, can be used to calculate many of the parameters described in Table 1. CHEMEST shows property relationships and fills in for missing data.

It is hoped that the searches and displays shown have conveyed the value of having high-quality data that are easily searched in an on-line system. Numerica is a simple system to use, and having the SYNDEX data base as a front end allows one to perform a quick and efficient search of available data before even going into a specific data base. Lastly, the ability or potential to compare experimental and calculated data (e.g., in the TRC Datafile) is a valuable resource.

Looking ahead

The future direction for Numerica is twofold. First, there is the need to bring other useful and important data bases into the present cluster. By integrating the new data with the present files, an ever-increasing numerical data capability is available to the user with a minimum investment of time and effort. Second. the cluster of environmental data permits the formation of other clusters of numerical data that may relate or be completely independent of the environmental data. The option to select the theme of the next cluster is obviously predicated upon the availability of data bases and the ability of such data bases to serve a need expressed by the user community.

For example, a new cluster aimed at chemical engineering, chemical manufacture, and data that embrace chemical and pharmaceutical concerns is a natural extension of the Numerica system. Obvious relationships to the Physical Properties Data System and other data bases would then promote the use of both data clusters because of the need to satisfy data requirements of a mutual nature. Similarly, a biologically oriented cluster would again have implications for relating the contents of the new set of data bases to the existing cluster. The flexibility and advantages described for constructing clustered data bases are believed to be clearly superior mechanisms for producing online systems in the future.


(1) Heller, S. R.; Milne, G. W. A. Environ. Sci. Technol. 1979 13,798-803.

(2) Howard, P. H.; et al. J. Chem. Inf. Comp.Sci. 1982 22 38-44.

(3) Leo, A. J. J. Chem. Soc. Perkins Trans. 11, 1983,825-38.

Stephen R. Heller is a research leader in the model and data base coordination laboratory of the Department of Agriculture, Beltsville, Md.

Lewis H. Gevantman is a guest researcher at the National Bureau of Standards in Gaithersburg, Md. He retired from federal service after 17 years as program manager in the NBS Office of Standard Reference Data.