Chemical reagents whose quality cannot meet the requirements of the experiment can be purified or refined to reduce its impurity content and increase its purity.
 
Distillation
 
It is suitable for volatile liquid reagents, such as inorganic reagents such as hydrochloric acid, nitric acid and ammonia, and various organic solvents, such as chloroform, carbon tetrachloride, petroleum ether, etc.
 
a. Distilling toxic, corrosive or irritating reagents should be performed in a fume hood.
 
b. When distilling strongly volatile reagents such as ammonia, multiple bottles should be absorbed in series, and the absorption bottles should be cooled with iced saline to increase the concentration of refined reagents.
 
c. When purifying reagents (such as nitric acid) that are easy to decompose at the boiling point temperature, sub-boiling distillation method should be used to slowly evaporate the reagent below its boiling point and absorb after condensation. High boiling point reagents can be purified by vacuum distillation.
 
d. Nitric acid or hydrochloric acid must be distilled using an acid-resistant borosilicate glass or quartz still.
 
e. Flammable reagents such as ether should be kept away from open flames.
 
f. Distilling and refining organic solvents should control the heating temperature, collect distillates within a certain boiling range, and if necessary, fractional purification should be performed to improve the purity of refined products.
 
g. The water-insoluble organic solvent's initial distillation liquid is often opaque because it contains a small amount of water. It can be collected temporarily in a drying container. The distillate should be clarified and then changed to a bottle for formal collection. Agent (such as anhydrous calcium chloride) after treatment and incorporated into the reagent to be distilled

Distill inside.
 
h. Solid reagents that can directly sublimate, such as iodine, can be refined by sublimation. Put a small amount of iodine in the beaker, cover a watch glass with the convex surface facing upward, and heat the iodine with micro-fire to condense on the watch glass to obtain sublimed iodine with higher purity.
 
⑵Isothermal diffusion method
 
(3) Recrystallization method
 
⑷Freezing method
 
Radon extraction
 
Alcohol analysis
 
Other methods:
 
Some reagents can be purified by electrolytic method, chromatography, ion exchange method, activated carbon adsorption method, etc. after preparing the test solution. The purified test solution can be used directly, or the solvent can be separated and stored in a dry state.