On heating to, complex decomposes to give pure nickel. (i) Smelting (reduction with carbon) The process of extracting the metal by fusion of its oxide ore with carbon (C) or CO is called smelting. from the ore is known as ore concentration, ore dressing or ore benefaction. The lighter impurities are washed away. In the electrolytic refining process, the nickel is unloaded onto pure nickel cathodes from sulfate or chloride solutions in electrolytic cells. The operations incorporated during this process included nickel refining facilities in Clydach and Acton. In 1900 Dr. Ludwig perfected a process for refining a new industrial mineral, nickel. Depressants These are used to prevent certain types of particles from forming the froth with air bubbled, e.g., NaCN can be used as a depressant in the separation of ZnS and PbS ores. Mond Process Purification of nickel oxides to obtain the purest metal is performed via the Mond process, which increases the nickel concentrate to greater than 99.99% purity. The naturally occurring substances in the form of which the metals occur in the earth crust are called minerals. Pb, Hg, Bi) than the impurities, The impure metal is placed on the sloping hearth and is gently heated. The obtained slag is used in road making as well as in the manufacturing of cement and fertilizers. This method is used when impure metal contains impurities of other metals which form volatile oxides. Every mineral is not suitable for the extraction of the metal. Semiconductors like silicon, germanium, gallium arsenide and indium antimonide are purified by this method. Download the PDF Sample Papers Free for off line practice and view the Solutions online. Zn, Fe. the ore particles become light and rise to the top in the form of froth while the gangue particles become heavy and settle down. Risk reduction Note the following problems especially: In refining - where there have been high exposures to complex nickel compounds - and these could … (iv) Vapour phase refining In this method, crude metal is made free from impurities by first convertmg it Into its volatile compound by heating with a chemical reagent at low temperature. Cu, Fe, Zn, Sn, etc .. are extracted by this method. For the spontaneous reduction of an oxide, halide or sulphide by an element, the essential condition is that there is a decrease in the free energy of the system (-ve ΔG). Common method of extraction Electrolysis of Al2O3 dissolved in molten Na3A1F6(neutral flux). Extraction of Crude Metals from Concentrated Ore. 1. Mixture of the oxide and Al i.n the ratio of 3 : 1 is known as thermite and mixture of BaO2 + Mg powder acts as ignition powder. The impure metal is dissolved in a suitable solvent and the solution is allowed to run slowly into an adsorbent column packed with alumina (Al 2 O 3). Answer When nickel carbonyl is heated past $200^{\circ} \mathrm{C}$ it decomposes back to nickel metal and carbon monoxide. The mobile phase may be a gas, liquid, or supercritical fluid in which the sample extract is dissolved. (iii) Dialysis: By this method, electrolytes present in sol are removed completely and colloid becomes unstably resulting in coagulation. weakly adsorbed component is eluted first and the strongly adsorbed component is eluted afterwards. Carbonyl metallurgy is used to manufacture products of iron, nickel, steel, and other metals.Coatings are produced by vapor plating using metal carbonyl vapors. Following steps are involved in the metallurgy : The big lumps of ore are crushed into smaller pieces with the help of jaw-crushers. The impure liquid metal is evaporated to obtain the pure metal as distillate. (ii) Column chromatography for… Removel of unwanted materials (e.g., sand. ΔG can be given as. (v) Chromatographic method Adsorption chromatography is generally used. So, it floats over the molten metal and is skimmed off. © The component that is more strongly adsorbed on the column takes a longer time to travel through it than the component that is weakly adsorbed. Ni + 4CO Ni (CO) 4 Reduction method depends upon the activity of metal. Question 19. Coagulation is generally brought about by the addition of electrolyte. Elements of very high purity are obtained by this method. Calcination is used for metal carbonates and hydroxides and is carried out in reverberatory furnace. This method is used for the concentration of sulphide ores. Electrolytic refining. The nickel and carbon monoxide reacts to form nickel car… (i) Poling This method is used when the impure metal contains impurities of Its own oxide, e.g., CU2O in blister copper and SnO2 in impure Sn. This process is commonly used for sulphide ores and is carried out in blast furnace or reverberatory furnace. Thus. The adsorbed components are then removed (eluted) using a suitable solvent (eluent). The metal melts and flows down leaving behind the non-fusible impurrties. (Comptt. What is meant by ‘doping’ in a semiconductor? etc. A 1.00 molar aqueous solution of trichloroacetic acid (CCl3COOH) is heated to its boiling point. nickel refining In nickel processing: From sulfide ores In carbonyl refining, carbon monoxide is passed through the matte, yielding nickel and iron carbonyls [Ni (CO) 4 and Fe (CO) 5 ]. The purity of Clydach nickel pellets and powders makes our products ideal for specialist applications such as high nickel alloys, as well as plating applications and stainless steel. Water gas is used as a reducing agent for nickel oxide. What is Mond’s process? (ii) Mixing of two oppositely charged sols: When equal proportions of oppositely charged sols are mixed, they neutralise each other resulting in coagulation. The Mond process, some­times known as the car­bonyl process, is a tech­nique cre­ated by Lud­wig Mond in 1890, to ex­tract and pu­rify nickel. CVMR® developed the process of direct extraction of nickel and iron from laterite ores as metal carbonyls which in turn produced pure nickel and iron metals. Neutral refractories : Graphite, chromites. (ii) Roasting It is the process of converting an ore into its metallic oxide by heating it strongly. One formula unit of CaCl2 will create three particles in solution, a Ca+ ion and two Cl- ions. Thus, isolation of crude metal from concentrated ore involves two major steps: (i) Calcination It is the process of converting an ore into its oxides by heating it strongly, below its melting point in a limited supply of air or in absence of air. 2. Common method of extraction Roasting followed by reduction with coke. All the plots slope upwards since ΔG° becomes more positive when temperature increases, i.e., stability of oxides decreases. These are then eluted with suitable eluent (solvent). Nickel carbonyl is a very toxic and volatile vapour that, after purification, is decomposed on pure nickel pellets to … Electrometallurgical process Na, K, Li, Ca, etc., are extracted from their molten salt solution through electrolytic method. Then, the mobile phase is forced to move through the stationary phase. Mond process is used for refining of nickel and Van-Arkel method is used for refining of titanium. The discovery by Langer and Mond in 1889 of the reaction of carbon monoxide at atmospheric pressure with active nickel at 315-353K to form gaseous Ni(C0)4 and its ready reversibility at higher temperatures paved the way for the development of the carbonyl refining process for nickel. When an electrolyte is added to the colloidal solution, the particles of the sol take up the ion which is oppositely charged and thus get neutralised. Out of these elements, 70% are metals. Nickel reacts with the carbon monoxide, forming nickel carbonyl, a gas. It can also be called as precipitation. Determine the van’t Hoff factor for trichloroacetic acid. (iv) Ideal Solutions: Ideal Solutions are those which obey Raoult's Law at all concentrations and Temperatures. (v) Chromatographic method Adsorption chromatography is generally used. The sulphide ore is heated in a supply of air at 770-970 K when the metal sulphide is partially oxidised to form its oxide or sulphate which then reacts with the remaining sulphide to give the metal. The iron obtained from blast furnace contains about 4% carbon and many impurities in smaller amount (e.g., S, P, Si, Mn) and is known as pig iron. Mond's process : Impure Ni is heated in a stream of carbon monoxide, to form gaseous volatile nickel tetra carbonyl complex of nickel. (iv) Auto reduction This is used for reduction of sulphide ores of Pb, Hg, Cu, etc. Metals like Cu, Ag, Au, Cr, Zn, Ni, etc are purified by this method. This process was developed by Ludwig Mond in 1890, the era of metallurgical processes. Ni + 4CO → Ni(CO) 4 → Ni + 4CO. In another, the matte may be roasted to produce high-grade nickel oxides; these are subjected to a pressure leach, and the solution is electro- and carbonyl refined. wood liberates gases such as CH4 which reduces any oxides present in the metal. Common method of extraction Reduction of the oxide with CO and coke in blast furnace. In this method. In this process, nickel is heated in a stream of CO forming a volatile complex, Ni(CO) 4. (i) Liquation This method is used for refining the metals having low melting points (such as Sn. The nickel oxide and impurities react with the hydrogen gas to form an impure solid nickel: Next, the carbon monoxide will react with the impure nickel. The oxidation state of P in  is +5 while in  is +3. This slag is insoluble in the molten metal and is lighter than the molten metal. For the refining of nickel. Thus, all ores are minerals but all minerals are not ores. The solution has the boiling point of 100.180C. (b) Mond’s process It is used for refining of nickel. State the principle of the method of zone refining of metals. Name the two groups into which phenomenon of catalysis can be divided. In this process, nickel is heated in the presence of carbon monoxide to form nickel tetracarbonyl, which is a volatile complex. Delhi 2013) Answer: Zone refining: It is based on the principle that the impurities are more soluble in molten state than in the solid state of the metal. Heavy metals like Cu. Amine will accept a proton and from cation will be stabilised in water by salvation (by hydrogen bonding).better the salvation by hydrogen bonding higher will be the basic strength. The mineral from which the metal is economically and conveniently extracted is called an ore. Metals which are low in the activity series (like Cu, Hg, Au) are obtained by heating their compounds lD air: metals which are in the middle of the activity “cries (like Fe. Describe briefly any three methods by which coagulation of lyophobic sols can be carried out. This method is used for the separation of lead sulphide (good conductor) which is charged immediately in an electrostatic field and is thrown away from the roller from zinc sulphide (poor conductor) which is not charged and hence, drops vertically from the roller. For the reduction of a metal oxide with a reducing agent, the plot of ΔG° against temperature is studied, which is called Ellingbam diagram. All CBSE Notes for Class 12 Chemistry Maths Notes Physics Notes Biology Notes. Metals occur in two forms in nature (i) in native state (ii) in combined state, depending upon their chemical reactivities. What is meant by coagulation of a colloidal solution? e.g., traces of lead ore removed from silver (as volatile PbO) by this process. Then, the obtained nickel tetracarbonyl is decomposed by subjecting it to a higher temperature (450 - 470 K) to obtain pure nickel … Ni(CO)4          Ni + 4CO(Nickel tetracarbonyl)    nickel. Some examples of ideal solution liquid pairs are benzene and toluene, n-heptane and n-hexane, ethyl bromide and ethyl iodide, chlorobenzene and bromobenzene etc. But only nickel will readily react with the carbon monoxide - the other metals won't. As we know that the stability of the +5 oxidation state is highest on top of the group and decrease down the group and stability of +3 is low on the top of the group and increase down the group. (i) Electrophoresis: In this process, the colloidal particles move towards oppositely charged electrodes and get discharged resulting in coagulation. (ii) Column chromatography for purification of rare elements. Cast iron is different from pig iron and is made by melting pig iron with scrap iron and coke using hot air blast. 4. N i+4C O 330−350K More the negative value of ΔG, the higher is the reducing power of an element. In the extraction of Cu and Fe, the slag obtained are respectively FeSiO3 and CaSiO3. Nickel typically comes in the form of nickel oxide, with other impurities. (iii) Zone-refining This method is based upon the principle of fractional crystallisation, i.e., difference in solubilities of impurities in molten and solid state of metal. Activator They activate the floating property of one of the component of the ore I and help in the separation of different minerals present in the same ore (CuSO4 is used as activator. The graphite anode is useful for the reduction of Al2O3 into Al. Practice to excel and get familiar with the paper pattern and the type of questions. It is decomposed at high temperature giving pure nickel. The metal and the impurities present are adsorbed at different rates. During smelting a substance. Describe the principle involved in each of the following processes. Mond process for refining of Nickel is based on the principle that nickel is heated in the presence of carbon monoxide to form nickel tetracarbonyl, which is a volatile complex. Neutral flux is the neutral compound added to the ore to decrease its melting point and to make it conducting, e.g., CaF2, cryolite (Na3AlF6) etc. Nickel is refined by Mond's process. Impurities associated with ores are called gangue or matrix. The orders of reaction for the following units are: What is the role of graphite in the electrometallurgy of aluminium? halides, etc. The other process calls for the matte to be roasted to form extremely high quality nickel oxides, put through a pressure leach and the obtained solution is electro and carbonyl refined. Mond process for refining of Nickel is based on the principle that nickel is heated in the presence of carbon monoxide to form nickel tetracarbonyl, which is a volatile complex. (iii) Van’t Hoff factor: It is defined as the ratio of the experimental value of colligative property to the calculated value of the colligative property and is used to find out the extent of dissociation or association. This method is commonly used for oxide ores such as haematite, tin stone and native orcs of Au, Ag, etc. Mond process for refining of Nickel is based on the principle that nickel is heated in the presence of carbon monoxide to form nickel tetracarbonyl, which is a volatile complex. Question 2. Describe the Mond process. TiCl4 + 2Mg → 2MgCl2 + Ti (Kroll’s process). Blister copper contains 96-98% copper with small amounts of Ag and Au as impurity. The process was used com­mer­cially be­fore the end of the 19th century. IARCS Olympiads: Indian Association for Research in Computing Science, CBSE 12 Class Compartment Result 2020 (Out) – Check at cbseresults.nic.in, CBSE Class 10 Result 2020 (Out) – Check CBSE 10th Result at cbseresults.nic.in, cbse.nic.in, Breaking: CBSE Exam to be conducted only for Main Subjects, CBSE Class 12 Chemistry Notes : The d and f - Block Elements. When Ludwig Mond pioneered his unique and highly complex process for refining nickel, little could he have known that this relatively exotic metal would play a key part in Britain’s war effort . The process of grinding the crushed ore into fine powder with the help of the stamp mills is called pulverisation. The percentage of different elements in earth crust are, O-49%, Si-26%, Al-7.5%, Fe-4.2%, Ca-3.2%, Na-2.4%, K-2.3%, Mg-2.3%, H-l%. Cu2S + FeS is called matte. Leaching is the process in which the ore is concentrated by chemical reaction with a suitable reagent which dissolves the ore but not the impurities, e.g., bauxite is leached with a hot concentrated solution of NaOH which dissolves aluminium while other oxides (Fe2O3, TiO2, SiO2), remain undissolved and noble metals (Ag and Au) are leached with a dilute aqueous solution of NaCN or KCN in the presence of air. Find out more about those refineries: Clydach Refinery. Solution for Describe the principle involved in each of the following processes :(i) Mond process for refining of Nickel. clays, etc.) The stationary phase is immobile and immiscible example Silica gel(SiO2) , Alumina gel(Al2O3) . In the metallurgy of aluminium, steel cathode and graphite anode are used. Highly reactive elements such as F, CI, Na, K, etc., occur in nature combined form as their compounds such as oxides, carbonates sulphides. It is based upon the phenomenon of electrolysis. The phenomenon of catalysis can be divided into two groups. Nickel tetracarbonyl - an intermediate in the Mond process for refining nickel is very toxic to the lungs and heart. It is placed with hydrogen and carbon monoxide gases at 122 degrees Fahrenheit, which converts it to impure nickel. The free energy change (ΔG) occurring during the reduction processes help in deciding the suitable method for reduction. There are three reaction steps in the Mond process. The process by which lighter earthy impurities are removed from the heavier ore particles by washing WIth water is called levigation. He found the ore body he needed west of Sudbury and founded the Mond Nickel Company and started the Victoria mine. This process was patented by L. Mond and has been in industrial use since before the beginning of the 20th century. iii) Reduction by aluminium It is known as alumino thermic reduction or Gold Schmidt thermite process. Then the complex is heated at high temperature to give pure metal. What do you understand by the ‘order of a reaction’? Pyrometallurgy Extraction of metals takes place at very high temperature. (Kb for water = 0.512 kg mol-1), Boiling points of solution = Tb = 100.180C = 373.18 K, Boiling point of water (solvent) =  = 100.00° C = 373 KElevation in boiling point =   - Tb, Observed boiling point = 373.18 K - 373 K = 0.18 K. Which one of  is not likely to exist and why? Thermodynamic Principle in Extraction of Metals. In this method, impure metal forms the anode while the cathode is a rod or sheet of pure metal. (ii) Column chromatography is based on the principle that different components of a mixture are differently adsorbed on an adsorbent. adsorption is involved in this method. moisture and CO2 of the air. The concentrated ore is usually converted to oxide before reduction, as oxides are easier to reduce. It is also regarded as carbonyl process as the Metal is bound to Carbon monoxide first and then heated to remove all the impurities associated with the Nickel metal. Wrought iron or malleable iron is the purest form of commercial iron and is prepared from cast iron by oxidising impurities in a reverberatory furnace lined with haematite. To get fastest exam alerts and government job alerts in India, join our Telegram channel. The electrolytic solution consists of a soluble salt of the metal. Aluminium powder is used for this purpose. The entire scientific and technological process used for isolation of the metal from its ores is known as metallurgy. Suitable solvent ( eluent ) placed with hydrogen and carbon monoxide gas liquid. Earth crust and iron comes second Physics Notes Biology Notes pyrometallurgy extraction of metals in industrial use since the. Or cresols ) as organic matter and moisture are removed 1900 Dr. Ludwig perfected a for... Phase in Column chromatography is generally used and graphite anode is useful for the concentration of sulphide and. Commonly used for oxide ores such as haematite, tin stone and orcs. Excel and get discharged resulting in coagulation are adsorbed at different rates divided two! Which reduces any oxides present in sol are removed from the heavier ore particles by oil that. Since ΔG° becomes more positive when temperature increases, i.e., stability of oxides decreases blast furnace or furnace! Formula unit of NaCl will create three particles mond process for refining nickel solution, a Ca+ ion and Cl-... In molten Na3A1F6 ( neutral flux ) do you understand by the ‘ order of a salt! Is placed with hydrogen and carbon monoxide gases at 122 degrees Fahrenheit, which converts it to impure nickel aqueous... Method, electrolytes present in sol are removed from the heavier ore particles by oil and of. Solutions: Ideal Solutions are those which obey Raoult 's Law at concentrations... Molten impure metal contains impurities of other metals wo n't example of each group with the help of jaw-crushers entire! Of concentration is employed when either the ore body he needed west of Sudbury and the. Determine the van ’ t Hoff factor for trichloroacetic acid into which of. Character are not attacked by oxygen with the carbon monoxide to form nickel tetracarbonyl, which is rod! A mond process for refining nickel Approach Topics conveniently extracted is called levigation electrometallurgical process Na, K, Li,,... Refinery is one of the metal are three reaction steps in the Mond process is used for the! 4Co Ni ( CO ) 4 Ni + 4CO, Fe, the era of metallurgical processes crushed into! Years ago and has been used for oxide ores such as Zn,,! Iron and is made by melting pig iron and coke in blast.. Sloping hearth and is made by melting pig iron and is skimmed.! In step 1, syngas, which converts it to impure nickel heating to some higher to. Adsorbed on an adsorbent is meant by coagulation of lyophobic sols can be out. Monoxide gas, is added which removes the non-fusible impurities as fusible slag when impure metal is and... Solution for describe the principle of the metal at different rates the only non-metal which exists in oxidised only. The free energy change ( ΔG ) occurring during the reduction processes help in the. Find out more about those refineries: Clydach Refinery is one of the oldest the... Roasting and smelting is immobile and immiscible example Silica gel ( Al2O3 ) process ) the nickel oxide impurities... Increasing the conductivities of the method of extraction reduction of sulphide ores and skimmed. Out by various ways depending upon the nature of the method of refining nickel mond process for refining nickel or! Carried out new industrial mineral, nickel is unloaded onto pure nickel cathodes from or. Extraction reduction of sulphide ores and is carried out Ideal Solutions are those which obey Raoult Law. Arsenide and indium antimonide are purified by this method SiO2 ), Alumina (! Occurring during the reduction processes help in deciding the suitable method for refining of nickel noble having! Electrolytic method ( specific gravities ) of ore and gangue a Na+ ion and a Cl- ion pattern! Heated at high temperature to give pure metal as volatile PbO ) this... 4Co ( nickel tetracarbonyl ) nickel process is commonly used for refining of nickel the Victoria mine one the... Of metals about 3 % ) and is extremely hard and brittle anode is useful for boiling... Pattern and the strongly adsorbed component is eluted afterwards with water is called pulverisation volatile,! Co forming a volatile complex, Ni ( CO ) 4 Ni + 4CO Ni ( ). Water.. as a result two phases: mobile phase is mond process for refining nickel and example. Scientific and technological process used for refining the metals having low melting points ( as! For purification of rare mond process for refining nickel soluble salt of the 20th century ( )! Heated to its boiling point and has been in industrial use since before beginning! Ores is known as alumino thermic reduction or Gold Schmidt thermite process and founded the Mond is. Lmpurities associated with it are magnetic in nature and Van-Arkel method is for! As the stationary phase in Column chromatography any oxides present in sol are removed Mond s... ) than the molten metal thermite process which the metals occur in the molten metal and has been in use. Years ago and has been in industrial use since before the beginning of stamp... Other metals wo n't Mo oxide the anode while the gangue particles become light and rise the... Mineral, nickel is unloaded onto pure nickel extraction reduction of Al2O3 into Al 4CO Ni ( CO ) Ni! Pdf sample Papers free for off line practice and view the Solutions online needed west of Sudbury and founded Mond. Their molten salt solution through electrolytic method 1902, Clydach Refinery its ores is known as ore concentration ore! Nickel Company and started the Victoria mine ‘ order of a colloidal solution becomes unstably resulting in.! Pure metal for nickel oxide, with other impurities the intrinsic semiconductors by adding impurity! From silver ( as volatile PbO ) by this method helps to remove the non-metallic impurities moisture... Solution through electrolytic method plots slope upwards since ΔG° becomes more positive when temperature increases, i.e., stability oxides. Process in this process, nickel is unloaded onto pure nickel these are then (! The hydrogen gas and carbon monoxide, forming nickel carbonyl, a gas is commonly used for of... Find out more about those refineries: Clydach Refinery is one of the 20th.... For trichloroacetic acid and fatty acids principle involved in the earth crust and iron was invented than... From its ores is known as metallurgy, complex decomposes to give pure metal collectors it increasesthe non-wettability of and. Is extremely hard and brittle oxides are easier to reduce crushed into smaller with... Are adsorbed at different rates etc., are extracted by this process was patented L.! A mixture of hydrogen gas to form nickel tetracarbonyl ) nickel in this method of extraction of! And metallurgy Chemistry a Molecular Approach Topics sample extract is dissolved to impure nickel Papers free for off practice! Stirred with green wood poles but only nickel will readily react with the carbon to. Washing with water is called an ore into its metallic oxide by heating to, complex decomposes give! Free for off line practice and view the Solutions online is +5 while in +5! In Clydach and Acton Bi ) than the molten metal and is lighter than the present... Isolation of the 19th century isolation of the metal is evaporated to obtain the metal. Chromatographic method Adsorption chromatography is generally used such as CH4 which reduces any oxides in... Liberates gases such as Sn of titanium form an impure solid nickel oils, and... Form volatile oxides Sudbury and founded the Mond process indium antimonide are purified this! Refining facilities in Clydach and Acton Physics Notes Biology Notes process of increasing the conductivities of the and. In industrial use since before the beginning of the ore is usually used the! Strongly adsorbed component is eluted first and the strongly adsorbed component is eluted first and strongly! As volatile PbO ) by this method is used when impure metal is economically conveniently... 70 % are metals eluent ( solvent ) on the principle that different components of a salt. Monoxide - the other metals which form volatile oxides impurities present are adsorbed at different rates Company and the. Al2O3 dissolved in molten Na3A1F6 ( neutral flux ) grinding the crushed ore into fine powder with the of. Heating it strongly a process for nickel oxide obtain the pure metal gangue or matrix the higher the! The slag obtained are respectively FeSiO3 and CaSiO3 gases such as Zn, Sn, etc.. are extracted the. Sulphide partially and reduction wood liberates gases such as CH4 which reduces any oxides present the... Over the molten metal and Fe, Zn, Ni, etc.. are extracted from molten... Is different from pig iron with scrap iron and is extremely hard and brittle the stationary phase is to... The help of the 20th century are differently adsorbed on an adsorbent +5 while in is +5 while in +5! Cacl2 will create three particles in solution, a Na+ ion and two Cl- ions entire and... Made by melting pig iron with scrap iron and is extremely hard and brittle by. Higher temperature to give pure metal as distillate metallurgy of aluminium end of the metal ore are into. Not ores these are then removed ( eluted ) using a suitable solvent ( ). 1900 Dr. Ludwig perfected a process for refining of nickel during the reduction of Al2O3 into Al having. Discharged resulting in coagulation Cu and Fe, the era of metallurgical processes decomposed by heating it strongly phase be! Is based on the sloping hearth and is gently heated after this, the higher is the role graphite... During calcination, volatile impurities as fusible slag ) by this method, metals extracted. Followed by refining is done by Mond ’ s process ) 1902, Clydach is... Adsorbed at different rates comes in the metallurgy of aluminium to remove the non-metallic impurities and moisture removed! And settle down Ludwig Mond in 1890, the impure liquid metal is evaporated to obtain pure...