 # Arsenic standard solution of 10 ppm

In indian pharmacopoeia they are preparing arsenic standard solution of 10 ppm by taking 330 mg of arsenic trioxide and made up the volume to 250 ml. Further took 1 ml of this solution and made up the volume up to 100 ml.As far as I know it’s a 5 ppm solution. If anyone have any idea how 330 mg of arsenic trioxide weight is converted to 10 ppm arsenic so plz share ur information.

Please note the following calculations & explanation -

The atomic weight of Arsenic is 74.92 (As)
Molecular weight of Arsenic trioxide is 197.84 (AS2O3)
Therefore,
197.84 mg = (2 X 74.92) = 149.84 mg 2As (2 Arsenic atoms)
Hence, 1 g mole of As2O3 = 2 As (2 Atoms of Arsenic)
Hence, 197.84 mg As2O3 = 149.84 mg Arsenic
Hence, 330 mg As2O3 = 249.84 mg Arsenic = 250 mg As
Hence, 330 mg As2O3 OR 250 mg Arsenic is present in 250 ml of solution.
Hence, 1 mg Arsenic (As) is present in 1 ml of the above solution.
This 1 ml is further diluted to 100 ml.
Hence, the diluted Arsenic solution has 1 mg Arsenic in 100 ml
Hence in 1000 ml diluted solution of Arsenic has 10 mg of Arsenic (As).
Hence this is a 10 ppm solution of Arsenic (As).

Please note the important formula is the number of mg (X mg) of solute dissolved in 1 liter of solution is (X) ppm solution.
Similarly, the number of mg (Y mg) of a substance present in 1 kg of material is (Y) ppm concentration.

Hope I have explained this in sufficient detail.

1 Like

It was very helpful information that u shared thanku sir

You are always welcome.

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