Although graphite crucible has the characteristics of high bulk density, high temperature resistance, fast heat transfer, acid and alkali corrosion resistance, high temperature strength, high oxidation resistance, etc., for the refining of individual raw materials, the cleaning work after the graphite crucible is used is very troublesome.
The first task of cleaning the graphite crucible is to clean out the chemical substances in the crucible, and then clean it. We need to decide what to use for cleaning based on what is the residual substance in the graphite crucible. Generally, the attachment on the graphite crucible is the residue after inorganic combustion. We can use hydrochloric acid to clean it, most of which can be dissolved. Some carbon-containing residues cannot be dissolved with hydrochloric acid, and nitric acid can be used for cleaning at this time. Because nitric acid has strong oxidizing properties, it can also be heated appropriately during cleaning.
For substances that are still difficult to clean, you can boil them in dilute hydrochloric acid or dilute nitric acid. Note that the hydrochloric acid used must not contain nitric acid, nitrates, halogens and other oxidants. If the dilute nitric acid cannot be cleaned, use potassium pyrosulfate, sodium carbonate or borax to melt and clean.
Graphite crucibles need to be kept clean in order to stay bright inside and out. After a long period of burning, the crucible may appear dull and dull, and it will penetrate deep into the crucible over time, causing the crucible to become fragile and rupture. Therefore, unclean materials must be removed. If there are still stains or the surface is black, use fine sand that has passed 100 mesh without sharp edges and rubbed gently with water to restore the surface gloss.
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