1, burette, a volumetric instrument for measuring the volume of added titrant, is a slender, uniform and precisely calibrated glass tube with a sharp mouth at the lower end and a cut-off door to control the dropping speed of solution. According to the different structure of the door, it can be divided into acid type and alkali type.
2, volumetric flask, used to prepare standard solution or diluted solution, is a measuring instrument. When the full-scale solution is poured out of the volumetric flask, the solution will adhere to the bottle wall. The volume to be poured out must be smaller than the indicated volume, so a pipette and burette should be used to quantitatively transfer the solution instead of a volumetric flask.
3. Pipette: When transferring liquid, firstly suck out the solution above the marking line with ear washing ball, block the upper opening with index finger, then adjust the lower edge of the meniscus of the solution to make it tangent to the marking line, and then put the pipette into the receiving container, so that its tip contacts the inner wall of the container, the container is slightly inclined and the test tube is upright. Loosen the index finger and take out the pipette after the solution flows freely 15 seconds.
4, instrument calibration instrument, instrument calibration is accurate, will directly affect the accuracy of capacity analysis. Different levels of instruments are allowed to have different errors, for example, the allowable error of a first-class 25 ml pipette is 0.04 ml.
Extended data
When using the measuring tool, don't pile it up with tools, files and other tools, turning tools, drill bits, etc. to avoid colliding with the measuring tool. Don't put it on the machine tool casually, so as not to damage the measuring tool due to the vibration of the machine tool. After use, put it flat in a special box to avoid deformation of the ruler. Measuring tools are measuring tools and can never replace other tools, such as marking lines with calipers and cleaning up debris with steel rulers.
Temperature has a great influence on the measurement results, so the precise measurement of parts must make both parts and measuring tools measure at 20 degrees Celsius. Measurement can generally be carried out at room temperature, but the temperature of the workpiece and the measuring tool must be the same. Otherwise, due to the characteristics of thermal expansion and cold contraction of metal materials, the measurement results are inaccurate.
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