The pursuit of new scientific knowledge requires a foundation of accepted and highly accurate measurements. Scientists cannot constantly re-determine the fundamental properties of every substance or reaction. This is where the concept of a standardized value becomes necessary for comparison and validation. The term “literature value” defines this accepted, published, and reliable standard for a chemical or physical property. This established figure acts as a universal reference point, allowing researchers around the world to communicate and compare their findings effectively.
Defining Literature Value
A literature value is a known, extensively verified constant or physical property derived from rigorous, repeated experimentation and calculation. These numbers are not arbitrary; they have been confirmed over time and are considered the most accurate representation of a property under specified conditions. For instance, the boiling point of pure water at standard atmospheric pressure is accepted as 100 degrees Celsius, a classic example of a physical constant used as a literature value. The authoritative nature of these values comes from a process of standardization, often involving meticulous peer-review and international agreement among scientific bodies. This ensures that the value is both precise (highly reproducible) and accurate (closely reflecting the true magnitude of the property). Other common examples include the molar mass of an element or Planck’s constant, which are used routinely in both theoretical and practical chemistry.
Sources for Standardized Chemical Data
Finding a literature value requires consulting highly reliable and curated reference materials that compile chemical and physical data. The most traditional and comprehensive source is the CRC Handbook of Chemistry and Physics, a large-volume reference that lists properties like melting points, boiling points, and densities for thousands of compounds. Chemical handbooks like this are routinely updated to reflect the most current and accepted measurements. In the digital age, recognized scientific databases offer easy access to this standardized information.
Key Data Sources
The National Institute of Standards and Technology (NIST) Chemistry WebBook provides thermochemical, thermophysical, and ion energetics data compiled by the U.S. government’s standards agency. International bodies like the International Union of Pure and Applied Chemistry (IUPAC) publish definitive nomenclature and data, which are adopted as global standards. Open-access resources like PubChem and CAS Common Chemistry are also used to search for chemical and physical properties from large collections of curated data.
The Role of Literature Value in Error Analysis
In a laboratory setting, the primary practical use of a literature value is in the assessment of experimental accuracy through error analysis. An experimental result is compared directly to the accepted literature value to determine the quality of the measurement and the technique used. This comparison is often quantified using metrics like percent error, which mathematically expresses the deviation between the measured value and the known standard. A low percent error indicates that the experimental result closely matches the accepted literature value, suggesting the experiment was performed with a high degree of accuracy. The literature value acts as the known value in the percent error calculation, which is essential for validating the findings of the experiment. This process is used by students to verify their technique and by professional chemists to validate new methods, confirm compound identity, or assess product purity by comparing properties like the melting point.