ChemFinder.Com > About ChemFinder.Com > ChemFinder & ChemINDEX > Glossary ACX Number The ACX Number is a unique identifier and registry number for substances in ChemACX, ChemFinder.Com, and submitted via Open Chemistry. ACX Numbers can also be extended to point to physical material, and may contain information relating to the vendor, quality, and package size. ChemFinder.Com displays the substance portion of the ACX Number, which is an abstract representation of the physical substance. CAS Number see CAS Registry Number CAS Registry Number A unique accession number assigned by the Chemical Abstracts Service, a division of the American Chemical Society. Other than being guaranteed unique to a given compound, this number has no particular meaning. CAS Registry Numbers are assigned to every uniquely-identifiable substance, so 'cis-2-hexene', 'trans-2-hexene', and '2-hexene' (a mixture with unspecified cis/trans composition) are all assigned separate CAS Numbers. CAS RN see CAS Registry Number DOT Number Codes for use in the commercial transportation of hazardous materials, as mandaetd by 49 CFR 172 and the U.S. Department of Transportation. A single substance may have multiple codes, depending on its concentration, physical state, etc. Evaporation Rate The rate of evaporation for a liquid, in unitless values relative to butyl acetate, which is assigned an evaporation rate of 1. EPA Code 4-character codes used by the U.S. Environmental Protection Agency to designate regulated contaminants in waste. A single substance may have multiple codes, depending on its concentration, physical state, etc. Flash Point The temperature at which the vapor of a liquid can be made to ignite in air. Listed in Celsius degrees on the ChemFinder WebServer. Melting Point The temperature at which a solid substance becomes a liquid, or at which a liquid substance solidifies. Listed in Celsius degrees on the ChemFinder WebServer. Assumed to be at standard pressure unless otherwise indicated. Sometimes present as a temperature range if an exact value is unavailable. Sometimes accompanied by a note such as dec (decomposes) or subl (sublimes). The NFPA Fire Diamond The NFPA Fire Diamond is divided into four parts listing the health hazards, flammability concerns, and reactivity of a compound, along with recommended protective equipment. Each section is rated on a scale of 0 (minimal hazard) to 4 (extreme). More information is available from the University of Kentucky. RTECS A substance's identification number on the U.S. Registry of Toxic Effects of Chemical Substances, a database compiled, maintained, and updated by the National Institute for Occupational Safety and Health (NIOSH). More information is available at the RTECS home page at NIOSH. Density The ratio of the mass of a substance to the mass of an equal volume of distilled water at 4 degrees celsius. A unitless quantity. Since the mass of one ml of water at 4 degrees celsius is exactly 1 gram, the specific gravity (unitless) is numerically equivalent to its density (in grams per ml). Refractive Index The refractive index (n) of a substance is defined as: n = Vv / V Where Vv is the velocity of light in a vacuum, and V is the velocity of light in the substance. Vapor Density The ratio of the mass of a substance to the mass of an equal volume of air, both at standard temperature and pressure. A unitless quantity. Vapor Pressure The pressure which exists over every liquid (or solid). In a closed vessel, given sufficient time, equilibrium is attained, in which as many molecules leave the liquid surface to form vapor as return to it from the vapor phase to form liquid. The pressure of vapor above any liquid or solid at any temperature, when equilibrium exists, is the vapor pressure of the liquid or solid at that temperature. Numbers are given as kPa in many cases. However, we are in the process of data integrity checking at this point, we do not gurantee accuracy of these data. If you see any number is inconsistant with other data sources you have, please report to us by click 'Add or change property' link on search result page. Evaporation Rate The rate of evaporation for a liquid, in unitless values relative to butyl acetate, which is assigned an evaporation rate of 1. Water Solubility An indication of the solubility in a substance, sometimes listed in relative terms (very soluble); sometimes listed quantitatively (5 mg/ml). ©2004 CambridgeSoft Corporation. All Rights Reserved. Privacy Statement Email   / Tel  1 800 315-7300 / 1 617 588-9300     Fax  1 617 588-9390     EU Tel  00 800 875 20000 / +44 1223 464900     EU Fax  +44 1223 464990     Germany Tel  +49 69 2222 2280     France Tel  +33 1 70 71 98 80 CambridgeSoft Corporation, 100 CambridgePark Drive, Cambridge, MA 02140 USA CambridgeSoft Corporation, 1 Signet Court, Swann's Road, Cambridge CB5 8LA UK All trademarks are the property of their respective holders.