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Before using the volumetric flask, which two checks should be carried out

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The volumetric flask is a thin-necked pear-shaped flat-bottomed volumetric vessel with a ground glass stopper. There is a marking on the neck, which means that the volume of the solution is exactly when the liquid meniscus is tangent to the marking of the neck at the specified temperature. Equal to the volume marked on the bottle. Marked with: temperature, capacity, scale line.
Before using, you must first check the following two:
1) Whether the volume of the volumetric flask is consistent with the requirement.
2) To check whether the stopper is tight and does not leak water. Put water in the bottle near the marking line, close the bottle stopper, make it stand upside down for 2 minutes, and check with a dry filter paper along the seam of the bottle mouth to see if there is any water droplets oozing out. If there is no leakage, turn the stopper 180° again, plug it tightly, turn it upside down, and test for leakage in this direction. It is necessary to do two inspections, because sometimes the stopper and the bottle mouth are not close at any position.
The suitable bottle stopper must be properly protected. Use a rope to tie it to the neck of the bottle to prevent it from falling or being confused with other volumetric flasks.
When preparing the standard solution, first put the weighed sample in a small beaker, add a small amount of solvent, and stir to dissolve it (if it is difficult to dissolve, you can cover it with a watch and heat it slightly, but it must be cooled before transferring). Move the solution quantitatively into the washed volumetric flask with the operation of transferring the sediment along the stir bar, then use the washing bottle to flush the wall of the beaker 5-6 times, and transfer it into the volumetric flask in the same way. When the solution is added to 2/3 of the bottle, shake it horizontally for a few weeks (do not turn it upside down) to make the solution roughly mixed. Then, put it flat on the table, slowly add water to about 1cm from the marking line, wait for 1-2 minutes to allow the solution adhering to the inner wall of the bottleneck to flow down, use a dropper to reach the bottleneck close to the liquid level, and look straight at the marking line. , Add water until the lower part of the meniscus is tangent to the marking line. Cover the bottle stopper immediately, hold the bottle stopper with the index finger of one hand, and hold the bottom of the bottle with the finger of the other hand. Be careful not to hold the bottle with your hands, so as not to cause the body temperature to expand the liquid and affect the accuracy of the volume. Then turn it upside down to make the bubbles rise to the top, at which point the bottle can be shaken several times. Turn it upside down and still make the bubbles rise to the top. Repeat this more than 10 times to mix evenly.
The volumetric flask cannot store the solution for a long time, especially the alkaline solution will corrode the wall of the bottle and make the stopper stick and cannot be opened. It cannot be heated.