Potassium Dichromate in Sulphuric Acid
| Description | Potassium dichromate filter, liquid filter, certified Assessment of photometric accuracy (absorbance) |
| Use | in the UV range (235 nm up to 350 nm) with a spectral bandwidth of 2 nm or less |
| Material | 0.006% Potassium dichromate dissolved in sulphuric acid, sealed in Hellma precision cells made from quartz SUPRASIL® |
667-UV7 Potassium dichromate dissolved in sulphuric acid
is a highly suitable method to check for photometric accuracy (absorbance) in the UV region. Potassium dichromate gives a spectral scan containing characteristic peak maxima at 257 nm and 350 nm and minima at 235 nm and 313 nm. The potassium dichromate solution is sealed in an airtight sealed quartz precision cell with 10 mm light path. The absorbance values of the filter are determined at the wavelengths 235 nm, 257 nm, 313 nm, and 350 nm and are specified in the certificate. It should be noted that the measurements are carried out with the filter 667-UV8 (0.01 N sulphuric acid) in the reference beam path. Measured values of the reference filter are separately displayed in the certificate.
The individually measured absorbance values are free from any systematic errors in the preparation of the solution and in the light path. Since the maxima and minima in the absorbance spectrum are relatively wide, you should measure them with a correspondingly large band width, e.g. 2 nm. In this way the influence of the noise on the measured values is minimised.
| Catalogue-No. | Substance | Wavelength nm | |
| 667.300-UV | 667-UV7 Potassium Dichromate in Sulphuric Acid 667-UV17 Potassium Dichromate in Sulphuric Acid (430 nm) 667-UV8 Sulphuric Acid (Blank) | 235, 257, 313, 350 | also available individually |
Also available:
Calibration set 667.301-UV, consisting of filter 667-UV13 potassium dichromate in perchloric acid and filter 667-UV14 perchloric acid blank.
According to European Pharmacopeia checking of the photometric accuracy (absorbance) is described as follows:
“Check the absorbance using suitable filters or a solution of potassium dichromate R at the wavelength indicated in the table which gives for each wavelength the exact values and the permitted limits of the specific absorbance. The tolerance for the absorbance is ±0.01. For the control of absorbance, use solutions of potassium dichromate R [...] in sulphuric acid [...].”
Typical spectrum of a 0.006 % potassium dichromate solution
| Wavelength (nm) | Specific Absorption A 1 %1 cm | Maximum Tolerance A 1 %1 cm |
| 235 | 124,5 | 122,9 to 126,2 |
| 257 | 144,5 | 142,8 to 146,2 |
| 313 | 48,6 | 47,0 to 50,3 |
| 350 | 107,3 | 105,6 to 109,0 |