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Temporary hardness differs from permanent hardness in that it

  • A.affects only the dyeing stage of the process
  • B.is removed by boiling the water
  • C.cannot be removed by any treatment at all
  • D.is caused by the sodium salts present

Answer: B

Bicarbonates decompose on heating and deposit as carbonate scale, which is why kettles fur. Sulphates and chlorides of the same metals persist through boiling and make up the permanent part. Both kinds must be dealt with in a mill.

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