Crude salt decontamination: add sodium hydroxide can remove magnesium ions, and then add barium chloride can remove the sulfate ions, and then add sodium carbonate can remove calcium ions and more than the barium ions. Filter, then add hydrochloric acid can remove excess hydroxide ions and carbonate ions.
Filtering details:
To do "one stick, two low, three lean". (see figure)
Filter cloth bag
One sticking
Even if the filter paper is wetted, close to the inner wall of the funnel, no residual air bubbles.
(Prevents air bubbles from slowing down the filtration speed.) Two low
1. The edge of the filter paper is slightly lower than the edge of the funnel.
2. The liquid level is lower than the edge of the filter paper.
(Prevent the liquid from being filtered out.) Three leans
1. The beaker cup should be poured with the mouth of the beaker close to the glass rod.
2. The lower end of the glass rod rests against the three layers of filter paper.
3. The spout on the long side of the lower end of the funnel is pressed against the inside wall of the beaker.
Details of evaporation:
1. The amount of liquid in the evaporation dish must not exceed 2/3 of the volume.
2. The evaporation process must be stirred constantly with a glass rod to heat the liquid evenly to prevent localized high temperatures from splashing the liquid.
3. When heated to (a large number of) solid appear, should stop heating to use the residual heat evaporation.
4. hot evaporation dish can not be placed directly on the laboratory bench, should be padded with asbestos mesh.
5. Crucible tongs are used to hold the evaporating dish.
Dishes should not be more liquid to prevent splashing to stir.
More solid precipitation, remove the wine lamp natural steam.
Related explanations
1, the liquid in the dish should not be more to prevent splashing to stir: "dish" refers to the evaporation dish. Means that the liquid added to the evaporation dish should not be too much (generally should not exceed 2/3 of the volume of the evaporation dish), in the heating process, to use a glass rod to stir constantly, to prevent due to the local temperature is too high, resulting in droplet splashing.
2, more solid precipitation, remove the alcohol lamp natural steam: means when the evaporation dish appears more solid, should immediately remove the alcohol lamp to stop heating, the use of the residual heat of the evaporation dish so that the liquid naturally evaporate.
Sulfate test: add an excess of BaCl solution, wait until a precipitate is produced and then drop 1 to 2 drops of HCL solution, no bubbles will be produced.
Please adopt it