The filter with the holmium perchlorate solution is placed into the beam path of the measuring instrument. The smallest slit width has to be used for this measuring (e.g. 1 nm). The smoothing (damping) has to be adjusted to a relatively high level. Alternatively the average of several measurements can be calculated to avoid evaluation errors. The precise peak positions at 241.15 nm, 287.15 nm, 361.5 nm and 536.3 nm are measured and compared with the values given in the certificate. Deviation should not be more than ±1 nm in the ultraviolet range or more than ±3 nm in the visible range. If available the reference filter 667-UV14 filled with perchloric acid can be placed in the reference beam path.
This suppresses the background of the spectrum without influencing the peak position. Ideally the measurement is performed with the slit width specified in the certificate. If this is not possible, choose the smallest possible slit width.