The colorimeter measuring cell may collect sediment or develop a film growth on the inside walls. Cleaning with an acid solution and a cotton swab on a monthly basis is recommended. Depending on sample conditions, it may be necessary to clean the cell more often.
CAUTION: Chemical exposure hazard. The chemicals used in this procedure may be hazardous if inappropriately handled or accidentally misused. Please read all warnings on the reagent labels. Protective eye wear is always recommended when contact with chemicals is possible.
Colorimeter cell cleaning procedure:
1. Press the MENU key, then press the down ARROW key until the MAINT menu appears. Press ENTER .
2. Press the down ARROW key to scroll to the CLEAN option. Press ENTER .
3. Refer to Figure 22 and locate the colorimeter.
4. Remove the rubber plug on the top of the colorimeter assembly.
5. Remove the magnetic stir bar using a bent steel paper clip as a retrieval tool. Refer to Figure 22 .
6. Wait until CLEAN flashes on the status line of the display, then fill the colorimeter with 19.2 N Sulfuric Acid Standard Solution (203832).
Note: Lower normality sulfuric acid will NOT be sufficient for cleaning the colorimeter.
7. Allow the sulfuric acid to stand in the colorimeter for 15 minutes.
8. Insert a wooden or paper cotton-tipped swab into the opening and move it up and down with a gentle scrubbing action, cleaning the interior surfaces of the colorimeter cell. Clean the stir bar with the cotton swab ( Figure 23 ).
9. Install the stir bar.
10. Replace the rubber plug on the top of the colorimeter assembly and make sure the cover is on the viewing port of the colorimeter.
11. Press the EXIT key to immediately return to normal operation; the instrument will return to normal operation automatically after 60 minutes.