Acids

• Boric Acid (H₃BO₃)

  • Molecular Weight: 61.83
  • Purity: Contains 99.5% to 100.5% H₃BO₃ (dried basis)
• Boric Acid

  From Borax:

  • A hot concentrated solution of borax is treated with sulfuric acid or HCl.
  • After decomposition, the hot liquid is filtered and allowed to crystallize.
  • Crystals of boric acid are collected, washed free of sulfate, and dried at room temperature.

  From Colemanite:

  • Colemanite (calcium borate, Ca₂B₆O₁₁•5H₂O) is powdered and suspended in boiling water.
  • SO₂ gas is passed through the suspension, forming boric acid, which crystallizes upon cooling.
• Boric Acid

  Physical Form: Pearly, lamellar, triclinic crystals.

  Solubility: Soluble in 25 parts cold water, 4 parts glycerol.

  Flame Test: Igniting boric acid in methanol with a few drops of sulfuric acid produces a flame with a green border due to methyl ortho-borate formation.

  pH Test: A dilute solution (30g in 90ml boiling distilled water) cools to a faintly acidic solution with pH 3.8 to 4.8.

  • Changes litmus red but has no effect on methyl orange.
• Hydrochloric Acid (HCl)

  • Molecular Weight: 36.46
  • Also known as chlorhydric acid, muriatic acid, spirit of sea salt.
  • Purity: Contains 35.0% to 38.0% w/w HCL
• HCL

  From Sodium Chloride:

  • React concentrated sulfuric acid with sodium chloride.
  • Hydrogen chloride gas is evolved when the mixture is heated.

  From Hydrogen and Chlorine Gases:

  • Burn chlorine in the presence of hydrogen in large silica tubes.
  • Hydrogen chloride formed is absorbed in water to yield pure hydrochloric acid
• HCL

  Potassium Permanganate Test:

  • Adding HCl to potassium permanganate produces chlorine gas (due to oxidation of HCl by potassium permanganate).

  Chloride Reaction Test:

  • HCl precipitates metal ions (Ag, Pb, Hg) as insoluble chlorides.
  • Reacting HCl with potassium dichromate and sulfuric acid evolves chromyl chloride, turning diphenyl carbazide solution on a strip violet-red.