Question

How will you test pure chloroform?

Answer 1

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.

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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.