[Quantitative analysis of low concentrations of cristobalite in thin layers by x-ray diffraction].

A new x-ray diffraction procedure for the determination of cristobalite in the presence of amorphous silica is described. The standards are obtained by deposition of thin layers of watery suspensions of cristobalite and amorphous silica mixtures on silver or lead disks or cellulosa filters. Six calibration curves are then calculated to reduce weight and sampling errors. Six mcg of cristobalite mixed with 594 mcg of amorphus silica is the lowest detectable limit. The method may be used for the analysis of both raw materials and respirable dust.