Calcium hydroxide is a fine white powder with a density of 224g cm3, heated to 580 will lose water to become calcium oxide, and in the air, it is easy to absorb CO2 and become calcium carbonate. It is soluble in acids, glycerol, insoluble in water, and insoluble in alcohol. At present, there is no more accurate method for the determination of calcium hydroxide content, in this paper, calcium hydroxide is converted into calcium chloride with hydrochloric acid, under the condition of pH value of about 13, calcium carboxylic acid is used as an indicator, and titration is titrated with disodium ethylenediaminetetraacetic acid standard titration solution.
Tests for calcium hydroxide content
a) Principle. Calcium hydroxide is converted to calcium chloride with hydrochloric acid. A small amount of Fe3+, Al3+, Mn2+ plasma was masked with triethanolamine, and calcium was titrated with calcium carboxylic acid as an indicator with a standard titration solution of disodium ethylenediaminetetraacetic acid under the condition that the pH value of the test solution was about 13.
2) Instruments and reagents.
500ml volumetric flask;250 ml Erlenmeyer flask;50 ml pipette;50 ml burette, triethanolamine solution: 1+3;Sodium hydroxide solution: 15%;Hydrochloric acid: 20%;EDTA standard titration solution: 01mol/l；
Calcicarboxylic acid indicator: weigh 1g of calcarboxylic acid indicator (or sodium calcicarboxylate), mix it with 100g of sodium chloride, grind it finely, and store it in a closed manner.
iii) Analytical steps.
Weigh about 20g (accurate to 0.)0002) sample, put it in a 250ml beaker, add a little water to moisten, add dilute hydrochloric acid solution dropwise until the sample is all dissolved, filter and wash it with medium-speed filter paper into a 500ml volumetric flask, dilute it with water to the scale, and shake well. This solution is solution A and is used for related determinations.
Use a pipette to transfer 50ml of test deep solution A, add an appropriate amount of triethanolamine solution, adjust with sodium hydroxide solution until white and turbid, and overdose of 2ml. After heating the sample solution to the appropriate temperature, add a small amount (about 0.).1g) Calcarboxylic acid indicator, titrated to pure blue with EDTA standard titration solution as the endpoint. At the same time, a blank test is done.
4) Calculations. The content of calcium hydroxide is measured as a percentage of calcium by mass
v-v0)×c×m×500
x=---100
m 50 where:
V--- volume of EDTA standard titration solution consumed by titration test solution, ml;
V0--- volume of EDTA standard titration solution consumed by titration blank, ml;
C--- Concentration of EDTA standard titration solution, mol l;
m -- with 100 ml EDTA standard titration solution [C(C10H14O8N2Na2)=1.]000mol l] is equivalent to the calcium mass of calcium hydroxide expressed in grams. （m=0.0401）
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