How to use the burette
In general, the burettes used in chemical laboratories mainly include non-plug burettes, seat burettes, three-way piston burettes, plug burettes, and side piston burettes. Among them, the advantages of the plugless burette and the stopper with the plug burette are most prominent.
1. Selection principle
From the perspective of capacity tolerance and outflow time, the A-stage burette is only one-half of the B-stage burette. Therefore, when conducting chemical analysis experiments with high accuracy of measurement and analysis, the relevant measurement personnel should try to use the A-grade burette. In addition, according to relevant experiments, if the nominal capacity of the burette under the same level exceeds the quota reference, the capacity tolerance that occurs will become more obvious.
Therefore, in order to reduce the occurrence of chemical analysis measurement errors, the experimenter should select the appropriate burette in strict accordance with the national titration solution volume standard.
At the same time, the reasonable selection of the burette can also be confirmed according to the nature of the solution. Generally, it is not suitable to inject a large alkaline solution in a plug burette; a plugless burette repels a solution that reacts with rubber, such as potassium permanganate, acid, iodine, and silver nitrate.
Based on the limitations of this selection, at present, Chinese researchers have developed a PTFE plastic piston burette that can adapt to both acid and alkali liquids and has played a great role in many experimental projects. In addition, if chemical analysis is performed on those solutions that are easily decomposed by light, a brown glass plug burette should be used as much as possible.
2. How to use
1 It should be thoroughly cleaned in the early stage of use. It can be soaked with a professional lotion, then thoroughly cleaned and dried until the inner wall is not hanged, and the measuring liquid can be injected into the inside.
2 It is necessary to carefully check the water leakage. If there is no water leakage in the burette, the glass beads and latex tubes in the tube should be inspected and replaced if necessary.
3 The piston of the three burettes and the nozzle of the non-plug burette must be uniformly matched, and the tightness and flexibility of the piston must be consistent with the corresponding normative standards. If the piston is found to be leaky or inflexible during the experiment, remove the piston and dry it, then apply a little Vaseline or silicone grease to the surface.
4 During the use of 4 plug burettes, it is forbidden to pull the piston outward or pull the piston inward, because these two ways of use will lead to liquid leakage, which will affect the final measurement accuracy. When using a plugless burette, the staff should also hold the glass beads in one hand and slowly pull the latex tube outwards in one hand to try to make the liquid flow out from the gap beside the glass beads.
5 Regardless of the type of burette, it must be thoroughly cleaned before injecting the liquid, and the piston or latex tube should be pulled out during the cleaning process to ensure the quality of the cleaning inside the tube.
6 When zeroing the measurement count of the burette, first check the flow port of the burette to see if there is air bubble, and control the elevation of the liquid surface so that it is below the marked line to avoid contamination of the non-metering part of the tube. To the liquid, causing a certain measurement error.
7 When using the burette glass measuring device, it is necessary to fully understand the counting of the outer surface of the tube, and then take the correct observation method for reading. In addition, in order to improve the clarity of the meniscus of the burette, the staff also set a corresponding light-shielding belt 1mm below the meniscus to facilitate the observation of the reading.
8 Under normal circumstances, the nominal capacity of common glass gauges will only be confirmed at standard temperature. If the outside temperature changes greatly, the temperature value of the gauge should be corrected first.
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