Indirect Calibration by Fluid Standards

Pure liquids can be used for the purpose of calibration to absolute intensity, because their diffuse scattering In (0) = lims, o/f (5) caused from density fluctuations can be computed theoretically. Some examples are in the literature [91,93-95], 

Another fluid standard used in the literature is a suspension of colloidal noble-metal particles in a solvent [96]. The method is explained starting on p. 134. The application of such calibration methods is in particular feasible, if polymer solutions are studied and thus the measurement of a calibration fluid does not require to modify the setup. 

Obviously the slit-smearing causes an additional background be.u w which is a function both of the sample material and the temperature of the sample. Disregarding this background results in a systematic error. 

For benzene - one of the best-suited calibration fluids - the error is 4% at room temperature. For polymers errors of up to 65% (polystyrene at room temperature) have been verified both theoretically and experimentally. 

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