If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Roasting and calcination - extraction of metal

Sulfide ores are roasted and carbonate ores are calcinated to convert them to oxide. Created by Ram Prakash.

Want to join the conversation?

Video transcript

let's talk about how to convert metal sulphides or metal carbonates to metal oxides in a previous video we talked about how to get pure metals from metal ores and we said that these are the four steps for doing it and we also talked about the first step which was enrichment of the ore basically we take a metal ore and we crush it into pieces and then we separate the metal compound from its impurities and if the metal compound is not metal oxide it's so metal sulphide or metal carbonate then first of all we will convert them to metal oxide form and that is because it is easier to separate metal from its oxide and that will happen in the third step reduction to metal and after that we will refine this metal to get pure metal in the fourth step but in this video let's talk about the second step conversion to metal oxide now let's say for example we are dealing with zinc ore we have the zinc ore over here and in the first step enrichment of the ore we crushed it into pieces and we separated the zinc compound from the impurities now this is in compound this happens to be zinc sulphide and now since this compound is not an oxide we will first have to convert this to a metal oxide then we will react this we will heat this with excess of oxygen and that's how zinc sulphide will convert to zinc oxide whereas if we had zinc carbonate then we will heat this in limited supply of oxygen and that's how a carbonate converts to oxide so the thing to remember here is that the compound that we got after enrichment of all if that is a sulfide then we need to heat it in the presence of oxygen and that's how it will get converted to oxide and this makes total sense if we need to remove sulfur and add oxygen we will have to react this with oxygen right now this process is called roasting just like how we roast chicken or vegetable in the presence of oxygen that's how the sulphide ores are roasted in the presence of oxygen now the second thing was if this metal compound is a carbonate then in that case we need to heat it in limited supply of oxygen and that's how we will convert a carbonate to oxide and this also makes sense see carbonate already has an oxygen so we don't need to provide lot more oxygen over here and this process where we heat carbonate in limited supply of oxygen is called calcination and this goes without saying that if the metal compound is already an oxide for example if you had an iron ore and you directly got iron oxide in that case you do not need to convert it to metal oxide it's already in its oxide form right and in case you are dealing with inert metals like gold and platinum then in that case after doing the enrichment of or you would not get metal compound you would not get a compound of gold because it does not form any compound you will get gold in its free State and for that you do not need to convert it to metal oxide and then later reduce it to get the metal you already have the metal with you right so you can directly take the inert metal that you get here to the refining step okay so in the second step we converted the metal compounds that were there in the form of sulfides or carbonates into oxides and for this we used roasting or calcination process now in future videos we will see how we can remove the oxygen out of these metal oxides and reduce them to get metal out of them and after we have got the metal we will see how to refine those metals to get pure metal 99.99% pure metal