Welcome to Chem Zipper.com......

Crude gold obtained by MacArthur-Forrest cyanide process and chlorination process contains Ag, Cu, Zn, and sometimes Pb as impurity.

(A) Zn and Pb are removed by cupellation process.

(B) Cu and Ag are removed by parting process.

(1) Parting with sulfuric acid or nitric acid:Gold is not attacked by these acids while Cu and Ag dissolve. If, however, the Au content in an impure sample is more than 30%, the Cu and Ag are also not attacked by the acid of any strength. Hence, before the acid treatment, the impure sample is melted with necessary amount of Ag to reduce its gold content to about 25% (quartation). The resulting alloy, after being granulated in water, is boiled with H2SO4 or nitric acid when Cu and Ag pass into solution, leaving Au undissolved . Au is separated and

fused again with borax and nitre when 100% Au is obtained.

(2) Parting with CI2 : Sometimes chlorine is used for the purification of Au. The impure sample of Au is fused with borax and CI2 gas is forced through it. The base metals are converted into chlorides that pass out as fumes at this high temperature, and AgCI forms a separate layer between the fused layer of Au and borax, which is skimmed off and the Au left behind cast into ingots.

Bessemerisation : Purification of iron from cast Iron or pig iron :

Cupellation : lead (Pb) present in Silver removed by Cupellation process:

Polling process: This process is used for the purification of copper and tin.

Kroll's Process and Imperial metal industries (IMI) Process of reduction;

Parke's Process : Desilverisation of lead ;

Related Topics:

PYROMETALLURGY:

FLUX : PYROMETALLURGY:

SLAG : PYROMETALLURGY:

SMELTING : PYROMETALLURGY:

ROASTING : PYROMETALLURGY:

CALCINATION : PYROMETALLURGY:

LEACHING: HYDROMETALLURGY:

Extraction of Aluminium:

What are important ores of Aluminium ?

EXTRACTION OF IRON:

What are important ore of Iron ore ?

What are the composition of pig iron?.

What is composition of White cast iron ?

What is composition of Grey Cast Iron ?

What is composition of Wrought Iron ?

The iron obtained from a blast furnace is a brittle material called cast iron or pig iron. It contains about 4% elemental C and smaller amounts of other impurities such as elemental Si, P, S, and Mn that are formed from their compounds in the reducing atmosphere of the

furnace.

The most important of several methods for purifying the iron and converting it to steel is the basic oxygen process or oxidative refining.

Molten iron from blast furnace is exposed to a jet of pure O2 gas for about 20 minutes in a furnace that is lined with basic oxide such as CaO. The impurities in the iron are oxidized and the acidic oxides that form react with basic CaO to yield a molten slag that can be poured off.

For example Phosphorous, is oxidized to P4O10, which then reacts with CaO to give molten Ca3(PO4)2.

P4(l) + 5 O2(g)--> P4O10(l)

6 CaO (g) + P4O10(l) -->2 Ca3

(PO4)2(l)

Basic oxide acidic oxide slag

Mn also passes into the slag because its oxide is basic and reacts with SiO2 yielding molten manganese silicate.

This process produces steel that contains about 1% carbon but only very small amount of P and S. Usually the composition of liquid steel is monitored by chemical analysis and the amount of oxygen and impure iron used are adjusted to achieve the desired concentration of carbon and other impurities