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How will you test pure chloroform?


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Test of Purity of Chloroform:

  • Chloroform has transparent and colorless, neutral to test paper, non-irritating when inhaled, and should evaporate entirely, leaving no residue or smell on a glass surface. Pure chloroform has a boiling point of 61-620C.

Physical Purity: CHCl3 is a colorless liquid having a boiling point of 62°C. Pure chloroform is boiled & distilled at 62°C. If any impurities are mixed with it, its boiling point also varies-chloroform boils at a higher temperature than 620C.

Chemical Purity: To assure the purity of chloroform. AgNO3 is used. In presence of O2, chloroform produces phosgene gas and HCl. AgNO3 reacts with HCl and produces a white precipitant of AgCl.

  • Chloroform should have a particular gravity of from 1.491 to 1.525, be enormously transparent and colorless, unbiased to test paper, non-irritating when inhaled, and should evaporate completely, leaving no residue or smell on a glass surface.
  • To test the purity of chloroform, shake some of it in a well Stoppard bottle along with oil of vitriol (colorless).
  • Pure chloroform has a boiling point of 61-620C.
  • If any trace of oils is present, the acid becomes more or less yellow, when allowed to stand; a darker line appears at the connection of the liquids.
  • When the yellow color appears, after being shaken and eminence still for a little time, the chloroform is poured off into another vial, where it is shaken anew, with another and a lesser segment of vitriol.
  • If after some time, this appears colorless, the chloroform might be measured as pure.
  • This is because in the presence of air chloroform is oxidized to phosgene.
  • To prevent the formation of phosgene, they are stored in dark-colored bottles. CHCl3 + ½ O2 → HCl + COCl2. Phosgene is represented as COCl2. This is toxic.

Use of Chloroform:

  1. It is used as an anesthetic in surgery. But it has harmful effects on the liver & excessive use of it may threaten the patient’s life—because the difference between an anesthetic dose & a lethal dose of it is very less. So, at present, it is not widely used in anesthesia.
  2. As an excellent solvent, it is used in wax, fats oils, resin & alkaloid industries.
  3. It is used as an anti-rodent agent.
  4. In a laboratory, it is used as a reagent & solvent.
  5. Used as raw material for chloropicrin & in aromatization of foul-smelling drugs.

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