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Cinnabar decomposition by heating optional method?
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Justin Martinez
Cinnabar decomposition by heating optional method?
Yes, it is possible to fully decompose cinnabar to elemental mercury and sulfur.
What conditions need to be satisfied in the new method?
Before reaching to decomposition temperature, cinnabar phase transitions to a different polymorph. Data from this paper1 indicate that α-HgS (trigonal) → β-HgS (cubic) phase transition occurs at 673 K and is completed at 698 K. The thermal expansion of cinnabar is fairly isotropic. At 744 K, the thermal decomposition of HgS occurs to elemental mercury and sulfur accompanied by a change in mechanism2.
So, is this decomposition technique feasible for producing mercury?
Not really, because you have to achieve very high temperature for cinnabar to fully decompose. Then, you have to separate mercury and sulfur from the mixture which is again additional work.
So, basically roasting process is applied. In this case, crushed cinnabar ore is roasted in rotary furnaces. Pure mercury separates from sulfur in this process and easily evaporates. A condensing column is used to collect the liquid metal, which is most often shipped in iron flasks. If the ore is heated in an atmosphere of oxygen, then mercuric oxide is formed which gets decomposed to mercury (which is deposited below while the gases escape). The other advantages is that the roasting temperature is lower than the decomposition temperature, so it is easy to achieve.
$$\ce{2HgS + 3O2 -> 2HgO + 2SO2 ^}$$
$$\ce{2HgO + HgS -> 3Hg + SO2 ^}$$
$$\ce{2HgO ->[\Delta] 2Hg + O2 ^}$$
Another technique is to heat cinnabar in an atmosphere of hydrogen. The sulfur that is forming quickly reacts with hydrogen to form hydrogen sulfide which escape as a gas. Simultaneously, hydrogen helps in the reduction of cinnabar and the process quickly accelerates to completion.
$$\ce{HgS + H2 ->[\Delta] Hg + H2S ^}$$
References
Ballirano, Paolo & Botticelli, Michela & Maras, Adriana. (2013). Thermal behaviour of cinnabar, α-HgS, and the kinetics of the β-HgS (metacinnabar) → α HgS conversion at room temperature. European Journal of Mineralogy. 25. 957-965. 10.1127/0935-1221/2013/0025-2341.
Baláž, P., Godočiková, E. Thermal Reduction of Mechanically Activated Cinnabar (HgS) and Stibnite (Sb2S3). Journal of Thermal Analysis and Calorimetry 65, 51–57 (2001). https://doi.org/10.1023/A:1011564232088
Yes, it is possible to fully decompose cinnabar to elemental mercury and sulfur.
What conditions need to be satisfied in the new method?
Before reaching to decomposition temperature, cinnabar phase transitions to a different polymorph. Data from this paper1 indicate that α-HgS (trigonal) → β-HgS (cubic) phase transition occurs at 673 K and is completed at 698 K. The thermal expansion of cinnabar is fairly isotropic. At 744 K, the thermal decomposition of HgS occurs to elemental mercury and sulfur accompanied by a change in mechanism2.
So, is this decomposition technique feasible for producing mercury?
Not really, because you have to achieve very high temperature for cinnabar to fully decompose. Then, you have to separate mercury and sulfur from the mixture which is again additional work.
So, basically roasting process is applied. In this case, crushed cinnabar ore is roasted in rotary furnaces. Pure mercury separates from sulfur in this process and easily evaporates. A condensing column is used to collect the liquid metal, which is most often shipped in iron flasks. If the ore is heated in an atmosphere of oxygen, then mercuric oxide is formed which gets decomposed to mercury (which is deposited below while the gases escape). The other advantages is that the roasting temperature is lower than the decomposition temperature, so it is easy to achieve.
$$\ce{2HgS + 3O2 -> 2HgO + 2SO2 ^}$$
$$\ce{2HgO + HgS -> 3Hg + SO2 ^}$$
$$\ce{2HgO ->[\Delta] 2Hg + O2 ^}$$
Another technique is to heat cinnabar in an atmosphere of hydrogen. The sulfur that is forming quickly reacts with hydrogen to form hydrogen sulfide which escape as a gas. Simultaneously, hydrogen helps in the reduction of cinnabar and the process quickly accelerates to completion.
$$\ce{HgS + H2 ->[\Delta] Hg + H2S ^}$$
References
Ballirano, Paolo & Botticelli, Michela & Maras, Adriana. (2013). Thermal behaviour of cinnabar, α-HgS, and the kinetics of the β-HgS (metacinnabar) → α HgS conversion at room temperature. European Journal of Mineralogy. 25. 957-965. 10.1127/0935-1221/2013/0025-2341.
Baláž, P., Godočiková, E. Thermal Reduction of Mechanically Activated Cinnabar (HgS) and Stibnite (Sb2S3). Journal of Thermal Analysis and Calorimetry 65, 51–57 (2001). https://doi.org/10.1023/A:1011564232088
Yes, it is possible to fully decompose cinnabar to elemental mercury and sulfur.
Before reaching to decomposition temperature, cinnabar phase transitions to a different polymorph. Data from this paper1 indicate that α-HgS (trigonal) → β-HgS (cubic) phase transition occurs at 673 K and is completed at 698 K. The thermal expansion of cinnabar is fairly isotropic. At 744 K, the thermal decomposition of HgS occurs to elemental mercury and sulfur accompanied by a change in mechanism2.
Not really, because you have to achieve very high temperature for cinnabar to fully decompose. Then, you have to separate mercury and sulfur from the mixture which is again additional work.
So, basically roasting process is applied. In this case, crushed cinnabar ore is roasted in rotary furnaces. Pure mercury separates from sulfur in this process and easily evaporates. A condensing column is used to collect the liquid metal, which is most often shipped in iron flasks. If the ore is heated in an atmosphere of oxygen, then mercuric oxide is formed which gets decomposed to mercury (which is deposited below while the gases escape). The other advantages is that the roasting temperature is lower than the decomposition temperature, so it is easy to achieve.
$$\ce{2HgS + 3O2 -> 2HgO + 2SO2 ^}$$
$$\ce{2HgO + HgS -> 3Hg + SO2 ^}$$
$$\ce{2HgO ->[\Delta] 2Hg + O2 ^}$$
Another technique is to heat cinnabar in an atmosphere of hydrogen. The sulfur that is forming quickly reacts with hydrogen to form hydrogen sulfide which escape as a gas. Simultaneously, hydrogen helps in the reduction of cinnabar and the process quickly accelerates to completion.
$$\ce{HgS + H2 ->[\Delta] Hg + H2S ^}$$
References
Yes, it is possible to fully decompose cinnabar to elemental mercury and sulfur.
Before reaching to decomposition temperature, cinnabar phase transitions to a different polymorph. Data from this paper1 indicate that α-HgS (trigonal) → β-HgS (cubic) phase transition occurs at 673 K and is completed at 698 K. The thermal expansion of cinnabar is fairly isotropic. At 744 K, the thermal decomposition of HgS occurs to elemental mercury and sulfur accompanied by a change in mechanism2.
Not really, because you have to achieve very high temperature for cinnabar to fully decompose. Then, you have to separate mercury and sulfur from the mixture which is again additional work.
So, basically roasting process is applied. In this case, crushed cinnabar ore is roasted in rotary furnaces. Pure mercury separates from sulfur in this process and easily evaporates. A condensing column is used to collect the liquid metal, which is most often shipped in iron flasks. If the ore is heated in an atmosphere of oxygen, then mercuric oxide is formed which gets decomposed to mercury (which is deposited below while the gases escape). The other advantages is that the roasting temperature is lower than the decomposition temperature, so it is easy to achieve.
$$\ce{2HgS + 3O2 -> 2HgO + 2SO2 ^}$$
$$\ce{2HgO + HgS -> 3Hg + SO2 ^}$$
$$\ce{2HgO ->[\Delta] 2Hg + O2 ^}$$
Another technique is to heat cinnabar in an atmosphere of hydrogen. The sulfur that is forming quickly reacts with hydrogen to form hydrogen sulfide which escape as a gas. Simultaneously, hydrogen helps in the reduction of cinnabar and the process quickly accelerates to completion.
$$\ce{HgS + H2 ->[\Delta] Hg + H2S ^}$$
References
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