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Testing Gypsum Purity

This document outlines three methods to test the purity of gypsum: 1. Determine the percentages of SO3 and CaO, calculate the theoretical LOI, and multiply by 1.25 to get purity if the SO4 and Ca percentages add up correctly. 2. If the SO4 and Ca do not add up, calculate purity from the sulfate content alone since some calcium may be present as CaCO3. 3. Purity can be calculated by dividing the sulfur percentage by 0.186, with sulfur determined through acid digestion and ICP analysis against a standard. An alternative method is provided if combined water content and moisture data are available.

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Japhet Charles Japhet Munnah
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2K views1 page

Testing Gypsum Purity

This document outlines three methods to test the purity of gypsum: 1. Determine the percentages of SO3 and CaO, calculate the theoretical LOI, and multiply by 1.25 to get purity if the SO4 and Ca percentages add up correctly. 2. If the SO4 and Ca do not add up, calculate purity from the sulfate content alone since some calcium may be present as CaCO3. 3. Purity can be calculated by dividing the sulfur percentage by 0.186, with sulfur determined through acid digestion and ICP analysis against a standard. An alternative method is provided if combined water content and moisture data are available.

Uploaded by

Japhet Charles Japhet Munnah
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Testing gypsum purity

Steps to test gypsum purity:

1. Determine SO3 and then divide by 0.8333 to get SO4,


2. Determine CaO and then divide by 1.4 to get Ca,
3. After checking that % SO4 x 40/96 = % Ca then:
a. Add % SO4 and % Ca
b. Divide by 4 to get theoretical LOI.
c. Multiply by 1.25 to give gypsum, Calcium Sulphate (CaSO4.2H2O) purity.

If line 3 doesn’t add up then calculate gypsum purity from Sulphate content (not calcium as some
of it is likely to present as CaCO3).

Other purity methods of testing:


a) Purity of gypsum is calculated by dividing Sulphur % by 0.186 (i.e. pure gypsum is 18.6%
Sulphur). Sulphur is determined by the method specified in the report , that is by addition of
hydrochloric acid and water then boiled for 30 minutes. Concentration of Sulphur is then
determined using ICP against Standard.
b) if the product is of high quality virgin mined product with out organics in it and you have
results moisture content for free and combined moisture, and

c) If the max theoretical amount of Combined water present in the sample is < 20.93, you can
calculate the Purity % using the following formula, c) % Purity = (% Combined
water/20.93)×100

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