What Is a Melting Crucible?

Crucible is an important part of chemical instruments. It is a container for melting and refining metal liquids and solid-liquid heating and reaction. It is the basis for ensuring the smooth progress of chemical reactions.

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Crucible is

Crucible iron crucible

Iron crucibles are used when melting strongly alkaline substances such as NaOH. However, due to problems such as susceptibility to rust and oxidation, they are not widely used. Inactive metal crucibles are still used.

Iron crucible ^[1]

Crucible cast iron crucible

Cast iron crucibles are cast from cast iron. They are used to melt aluminum, zinc, lead, tin, antimony and other metals. They are more durable than iron crucibles.

Cast iron crucible ^[1]

Crucible quartz crucible

1. Quartz crucibles can be used below 1650 degrees, and are divided into transparent and opaque. The semi-transparent quartz crucible made by the arc method is a large-diameter single-crystal silicon, which is an essential basic material for the development of large-scale integrated circuits. Today, the developed countries of the semiconductor industry in the world have replaced this small transparent quartz crucible with this crucible. It has the advantages of high purity, strong temperature resistance, large size, high precision, good thermal insulation, energy saving, and stable quality.

2, can not contact with HF, at high temperatures, it is easy to react with caustic alkali and alkali metal carbonate.

3 The quartz crucible is suitable to use K2S2O7, KHSO4 as the flux to melt the sample and Na2S207 (to be dried at 212 degrees) as the flux to treat the sample.

4 Quartz is brittle and fragile. Pay attention when using it.

5. In addition to HF, common dilute inorganic acids can be used as cleaning liquids.

Quartz Crucible ^[1]

Crucible porcelain crucible

Main ingredients: alumina (45-55%), silica

1. Can withstand heat around 1200 degrees

2. Suitable for melting samples of acidic materials such as K2S2O7.

3 Generally cannot be used for melting with alkaline substances such as NaOH, Na2O2, Na2CO3, etc., so as not to corrode the porcelain crucible. Porcelain crucibles should not come into contact with hydrofluoric acid.

4 Porcelain crucibles can usually be washed by dilute hydrochloric acid.

Porcelain crucible ^[1]

Crucible Corundum Crucible

Main article: Corundum crucible

Crucibles with an alumina content of more than 95% are called corundum crucibles.

1. Corundum crucible is composed of porous fused alumina, which is firm and refractory.

2. Corundum crucibles are suitable for melting samples with some weakly alkaline substances such as anhydrous Na2C03, and not suitable for melting samples with strongly alkaline substances such as Na 202, NaOH and acidic substances (such as K2S 207, etc.).

Another: In Japanese, the crucible (RUTUBO) means "dilemma", and it is translated as "vortex" or "mud" in anime works. (It's misread here. In fact, the crucible Japanese Roman sound should be written as Rutsubo.)

Crucible graphite crucible

Main article: Graphite crucible

The main raw material of graphite crucible is crystalline natural graphite. Therefore, it maintains the original physical and chemical properties of natural graphite.

The graphite crucible has good thermal conductivity and high temperature resistance. In the process of high temperature use, the thermal expansion coefficient is small, and it has certain strain resistance to rapid heating and cooling. It has strong corrosion resistance to acids and alkaline solutions and has excellent chemical stability.

Graphite crucible

Graphite crucibles are widely used in the smelting of alloy tool steels and the smelting of non-ferrous metals and their alloys in the metallurgical, foundry, machinery, chemical and other industrial sectors due to their excellent properties. And has good technical and economic effects.

Crucible silicon carbide crucible

The silicon carbide crucible is a ceramic deep-bottomed bowl-shaped container. When solids are to be heated by high fire, crucibles must be used. Because it can withstand higher temperatures than glassware. When the crucible is used, the molten material is usually not filled too much to prevent the heated object from jumping out, and to allow air to come in and out freely for possible oxidation reactions. The crucible has a small bottom, so it usually needs to be mounted on the mud triangle to be directly heated by fire. The crucible can be placed upright or obliquely on an iron tripod. It can be placed by itself according to the needs of the experiment. Do not place the crucible on a cold metal table immediately after it has been heated to avoid it from bursting due to rapid cooling. Do not place it on a wooden table immediately to avoid scalding the table or causing a fire. The correct way is to leave it on an iron tripod to cool it naturally, or put it on an asbestos net and let it cool down slowly. Please refer to the crucible tongs for the use of the crucible.

Quartz crucible

Crucible platinum crucible

Made of metallic platinum, it is a spare part of a differential thermal analyzer for heating non-metallic materials. Such as; glass fiber production, glass drawing and so on.

Inaccessible: solid K2O, Na2O, KNO3, NaNO3, KCN, NaCN, Na2O2, Ba (OH) 2, LiOH, etc .;

aqua regia, halogen solution or solution capable of generating halogen;

Compounds of easily reduced metals and these metals;

Carbonate-containing silicates, phosphorus, arsenic, sulfur and their compounds.

Crucible nickel crucible

The melting point of nickel is 1455 degrees Celsius, and the melting temperature of a nickel crucible should not exceed 700 ° C, because nickel is easily oxidized at high temperatures.

Nickel has strong alkali resistance and corrosion resistance, so nickel crucibles are often used for molten iron alloys, slag, clay, refractories and so on. Nickel crucibles are suitable for melting samples of NaOH, Na2O2, NaCO3, and alkaline fluxes containing KNO3. KHSO4, NaHSO4, K2S2O7, or Na2S2O7 and sulfur-containing alkaline sulfide fluxes cannot be used for melting samples.

Molten metal salts such as Al, Zn, Pb, Sn, and Hg can make the nickel crucible brittle. Nickel crucibles cannot be used for the ignition of precipitation. Borax cannot be melted in a nickel crucible.

Nickel crucibles often contain trace amounts of chromium, and care should be taken when using them. The new nickel crucible should first be burned to bluish purple in a muffle furnace to remove the oil on the surface, then boil it with 1:20 (volume ratio) hydrochloric acid for a while, and then rinse it with water.

Nickel crucible ^[1]

Crucible gold crucible

Gold is also a precious metal and has a strong corrosion resistance, but its low melting point (1063 ° C) limits its use. The molten alkali metal hydroxide does not corrode gold, and it is better to make such a gold crucible for melting.

Ancient crucible

Note: Gold will melt when heated on a high-temperature gas lamp (never allow gold to contact aqua regia)

Crucible silver crucible

Silver is cheaper than gold, it is not attacked by potassium hydroxide or sodium, and only slightly affects the edge near the air in the molten state. However, the melting point of silver is 960 ° C, which cannot be directly heated on fire. After the silver is heated, a layer of silver oxide is formed on the surface. The silver oxide is unstable at high temperatures and stable below 200 ° C. Silver easily interacts with sulfur to form silver sulfide. It is not allowed to decompose and burn sulfur-containing substances in silver crucibles. Alkali vulcanization flux is not allowed. In the molten state, metal salts such as aluminum, zinc, tin, lead, and mercury can make the silver crucible brittle. The silver crucible cannot be used for melting borax, and no acid can be used when leaching the melt, especially the concentrated acid. The quality of the silver crucible will change after burning, so it is not suitable for weighing of precipitation.