By the U.S, National Institute of Standards and Technology (NIST), the SRD provides information on the physical properties of substances, through a series of open access databases such as Thermochemical Tables, Photoelectron Spectroscopy database, Stability Constants of Metal Complexes, Ceramics, etc.
SRD means data that is–
(A) either–
quantitative information related to a measurable physical, or chemical, or biological property of a substance or system of substances of known composition and structure;
measurable characteristics of a physical artifact or artifacts;
engineering properties or performance characteristics of a system; or
one or more digital data objects that serve–
to calibrate or characterize the performance of a detection or measurement system; or
to interpolate or extrapolate, or both, data described in 1-3; and
(B) that is critically evaluated as to its reliability under section 290b of the 1968 Standard Reference Data Act