I am trying to calculate the correct dose of a chemical that has the
following active ingredients:
Active ingredients: Formaldehyde 1031 g/l
Malachite green 19.1 g/l
Recommended dose rate on the label is 1 millilitre per 76 litres.
However the suggested scientific ppm level for effective treatment is:
Formaldehyde 25 ppm,
Malachite green 0.5 ppm.
(a) To find the delivered ppm at the manufacturers dose rate, the formula is:
ppm = Solute x % of active ingredients divide by Solution x 1,000,000
Calculation is then: (for formaldehyde)
=1 mil x 103.1% divide by 76 litres x 1,000,000
=1 x 1.031 divide by 76,000 x 1,000,000
=1.031divide by 76,000 x 1,000,000
=0.0000135 x 1,000,000
=13.5 ppm (a little over half the required dose rate)
(b) To calculate a dose rate of 25 ppm, the formula is:
Dose rate = required ppm x volume of water divide by (% of active
ingredient x 1,000,000)
=25 ppm x 76 litres divide by (103.1% x 1,000,000)
=25 x 76,000 mil divide by (1.031 x 1,000,000)
=1,900,000 divide by 1031000
=1.8428709 mil
=1.84 mil per 76 litres. (almost double the recommended rate)
I just wanted to know if I was doing the calculation correctly?
Adrian.
Adrian R. Tappin
"Home of the Rainbowfish"
http://www.ecn.net.au/~atappin/home.htm