How to check the purity of lime


Lime must have a purity of at least 70% by weight of CaO when tested as follows:


  1. Take one gram of lime powder, properly weighed, in a platinum crucible. It is 105 + 2. put in the oven0c until, upon cooling and weighing, a constant mass is obtained.
  2. Heat the crucible slowly first and then 1000 . ignite in a muffle furnace0 Cool the crucible in a desiccator and weigh until a stable mass.
  3. Pour the burnt lime into a beaker, add 50 ml of water and mix well. Add 10 to 15 ml of concentrated hydrochloric acid and boil for 15 minutes. Filter, wash with hot water, ignite and weigh down to a stable mass.
  4. To the filtrate, if necessary, add a sufficient amount of concentrated hydrochloric acid, making the total volume equal to 10 to 15 ml of concentrated hydrochloric acid. Add a few drops of nitric acid and boil. Dilute to 200-250 ml. Add a small amount of ammonium hydroxide and keep just below the boiling point until the smell of ammonia is barely perceptible. Filter the iron and aluminum hydroxide when heated, collect the filtrate in a 250 ml volumetric flask. Wash off with warm water. Ignite the residue in a platinum crucible, detonate, cool in a desiccators and weigh as aluminum oxide and ferric oxide. Filter it and make 250 ml.
  5. Pipette 50 mL of the filtrate into a beaker and dilute to 100 mL. Heat to boiling and slowly add about 35 ml of boiling ammonium oxalate solution. Continue to boil for 2 or 3 minutes and allow the precipitated calcium oxalate to solidify for half an hour.
  6. Filter the precipitated calcium oxalate with a filter paper. Wash thoroughly with small portions of dilute ammonium hydroxide (1N) and then warm water until the wash paints a solution of dilute potassium permanganate heated in the presence of dilute sulfuric acid.
  7. Puncture the filter paper and transfer the precipitate with a fine jet of hot water to the beaker already used for precipitation. Add about 50 ml of dilute sulfuric acid, 60 . heat up to0Titrate with constant stirring with C and standard potassium permanganate solution. At the end of the titration, put the filter paper used for filtration in the titration vessel and titrate until the end point is reached.
  8. Remove a blank with all reagents following the procedure outlined for this method. In the case of magnesium lime, through a filter paper, re-dissolve calcium oxalate in the beaker and again with dilute hydrochloric acid in the filter paper four times with hot water and finally with dilute ammonium hydroxide (5 N). ) wash off. A little more and proceed as before. For the second filtration, use the same filter paper that was used before.
  9. If it is desired to complete the analysis in as short a time as possible, a portion of 50 ml of the filtrate from the ferric and aluminum oxide determinations should be precipitated in the usual manner with an excess of ammonium oxalate. Boil for about 5 minutes and let the calcium oxalate run away. Filter through a qualitative filter paper and cool the filtrate (with ice water if possible). Add more quantity of diammonium hydrogen phosphate solution and 5 to 10 ml of ammonium hydroxide solution. Shake vigorously with the rubber ‘copper’. From the amount of the precipitate thus formed, it can be inferred whether there is enough magnesium oxide in the lime to require a double precipitate. For precision work, if there is more than a small amount of magnesium oxide, a double precipitation should be performed using a fresh 50 ml aliquot.


Calcium Oxide in Lyme Test Formula


v1 = volume of standard potassium permanganate solution used for the test, in ml;

v2 = volume, used for blanks in milliliters of standard potassium permanganate solution;

n = normality of standard potassium permanganate solution; And

M = mass, in g, of the material taken for the test


IS: 1514 – 1990

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.