The purity is too low: the amount of water poured is insufficient when dissolving, and the sodium chloride is only partially dissolved; liquid splashes out when dissolving; liquid splashes out due to the failure to use a glass rod for drainage during filtration; the filtrate does not wait for all the liquid to be filtrated. Take away the beaker when it flows into the beaker; stop heating when it evaporates to dryness; do not use a glass rod to stir during evaporation, causing local overheating and splashing of droplets.

The purity is too high: when weighing the quality of coarse salt, "left and right things"; when dissolving, use salt water instead of distilled water; when filtering, the filter paper leaks and part of the sediment enters the beaker.

Extended information:

When purifying and filtering coarse salt, pay attention to one stick, two low and three stick.

1. "One stick" means that the folding angle of the filter paper should match the diameter of the inner wall of the funnel, so that the wet filter paper is close to the inner wall of the funnel without bubbles, because if there are bubbles, it will affect the filtration speed.

2. "Two lows" means that the edge of the filter paper should be slightly lower than the edge of the funnel. Second, during the entire filtration process, it should always be noted that the liquid level of the filtrate should be lower than the edge of the filter paper. This can prevent impurities from flowing directly into the beaker without filtering. In this way, the unfiltered liquid will be mixed with the filtrate, making the filtrate turbid and failing to achieve the purpose of filtration.

3. "Three supports" means that when the liquid to be filtered is poured into the funnel, the mouth of the beaker containing the liquid to be filtered should rest on the inclined glass rod (glass rod drainage) to prevent the liquid from splashing. and the liquid to be filtered breaks through the filter paper; it means that the lower end of the glass rod should be lightly pressed against the three layers of filter paper to prevent it from breaking the filter paper (one side of the three layers of filter paper is thicker than the other side of the first layer of filter paper, and the three layers of filter paper are not easily broken); refers to the funnel The neck should be close to the inner wall of the receiver that receives the filtrate to prevent liquid from splashing out.

Baidu Encyclopedia - Coarse Salt Purification