Shen ChangHong How to use the BOD tester is a question that we will have when we first use the instrument. With the development of science and technology, the appearance of the BOD tester brings us great convenience in environmental testing. This instrument can quickly determine the BOD of water samples. The following brings us the operation and notes of the BOD tester.
Operation of BOD tester
1、 Preparation of electrolytic cell for BOD tester
1. Inject about 2ml saturated K2SO4 into the liquid filled cavity of the tungsten rod (indicating negative electrode) of the clean and standby electrolytic cell. (about 70mm away from the bottom of quartz core of electrode)
2. About 2ml 3mol / L sulfuric acid solution was injected into the liquid filled cavity of single platinum wire (electrolytic anode).
3. Leave the cell for 10min, observe whether there is obvious leakage in the filling liquid, and make up in time before the experiment if there is any.
4. Place the cell on the mixer on the right side of the main engine.
5. Connect single platinum wire lead terminal (electrolytic anode) with red clamp of electrolytic wire;
6. Connect the double platinum lead terminal (electrolytic cathode) with the Black clamp of the electrolytic wire;
7. Connect single platinum lead terminal (indicating positive pole) with red clamp of signal wire;
8. Connect tungsten rod lead terminal (indicating negative pole) with Black clamp of signal wire.
9. Insert the plugs of the electrolytic line and the signal line into the corresponding sockets on the back of the main engine.
2、 Start operation of BOD tester:
1. Add 45ml distilled water and 17ml concentrated sulfuric acid into the clean digestion cup, cool down, add 7ml ferric sulfate solution, add 1.0ml K2Cr2O7 solution, and put in the stirrer.
2. Place the digestion cup on the mixer concave and connect the electrodes according to the "preparation of electrolytic cell" in the instrument operation steps.
3. Turn on the power, adjust the potentiometer of the agitator, and select the appropriate mixing speed (the electrolyte starts to rotate, but there is no bubble).
4. Press "blank / sample" to make the instrument in the blank position, and select the electrolytic current as "20mA".
5. Press the "start" key, after the automatic potential compensation of the instrument, the indicator light of electrolysis will be on, the instrument will start electrolysis and make a signal time diagram. When it reaches the end point, the buzzer will give an alarm, the electrolysis current will be cut off automatically, and the COD value will be displayed.
6. Add 1ml K2Cr2O7 standard solution into the same digestion cup after * times of data removal for determination, repeat for 3-4 times, the repeatability error is within ± 2%, and the average data is about "40", indicating that the instrument works normally, and the accuracy and reproducibility of the instrument can meet the requirements.
Precautions for BOD tester
1. Glassware should be washed thoroughly. First, wash it with detergent, then with dilute hydrochloric acid, and then wash it with tap water and distilled water in turn.
2. When siphon or pipette is used to take water sample, medicine or diluted water, the nozzle shall be immersed under the liquid level to avoid bubbles during operation and affect the accuracy of measurement.
3. The BOD5 of diluted water for inoculation should be between 0.3? 1.0mg/l, and should be used immediately after preparation.
4. The oxygen consumption of diluted water sample inoculated for five days should be greater than 2mg / L, and the residual dissolved oxygen after five days of culture should be greater than 1mg / L. Generally, 40% - 70% of the original dissolved oxygen consumed in five days is better.
The above is the operation and precautions of BOD tester. BOD tester can facilitate the tedious operation of water environment detection. Now it is the instrument that many testing parties like to use. Here, we recommend Shenzhen Changhong company for good quality assurance.
Key words of this paper: use of BOD tester, precautions of BOD tester: http://www.szchkj.com/show-13-142.html
