mg/kg to ppm

Thanks, John S. OK, last one for me: if you have %V/V = .05, doesn't that equal to 500PPM?

[JohnS]

Originally Posted by Unregistered

Thanks, John S. OK, last one for me: if you have %V/V = .05, doesn't that equal to 500PPM?

Yes. But recognize that ppm is ambiguous. It can be figured as weight/weight, volume/volume, molar ratios, or even weight/volume. These generally give different ppm answers so you have to know which ratio is meant.

[QUOTE=JohnS;63751]

Originally Posted by Unregistered

Parts per million can be computed on either a mass/mass, volume/volume, or moles/moles ratio. If mass/mass, 2mg/kg IS 2 ppm as milligrams and kilograms are 10^6 apart.

On a volume or mole fraction ratio, we have insufficient info.

Actually, because it is clear that it is a mass ratio, 2 mg/kg is the preferred form, rather than 2 ppm, which is ambiguous.

Both mg/kg (1/1.000) and ppm (1/1.000.000) are ratios, and ppm is not always equal mg/kg, only when it is the same matter. As mike said "mg/kg is not equal to ppm. The conversion depends on the density of both substances. In other words, mg/kg is not mg of water to kg of water, it is mg of x in kg of y". It also depends on the temperature, because diferrent matter have different physical properties.

so yes you can roughly say mg/kg = ppm. But it is not correct. F.ex. when you calculate formaldehyde you use a ratio of 1ppm = 1.2mg/kg. (reference: the danish, Erhvervs- og Byggestyrelsens rapport ”Helbredseffekter og gener ved udsættelse for formaldehyd”, 1988)

[JohnS]

Originally Posted by Unregistered

Both mg/kg (1/1.000) and ppm (1/1.000.000) are ratios, and ppm is not always equal mg/kg, only when it is the same matter. As mike said "mg/kg is not equal to ppm. The conversion depends on the density of both substances. In other words, mg/kg is not mg of water to kg of water, it is mg of x in kg of y". It also depends on the temperature, because diferrent matter have different physical properties.

so yes you can roughly say mg/kg = ppm. But it is not correct. F.ex. when you calculate formaldehyde you use a ratio of 1ppm = 1.2mg/kg. (reference: the danish, Erhvervs- og Byggestyrelsens rapport ”Helbredseffekter og gener ved udsættelse for formaldehyd”, 1988)

"The same matter" is ALWAYS 1 million parts per million. The concept only makes sense for mixtures. Note that the ratio between milligrams and kilograms is one million, hence mg/kg is ppm w/w.

Gas mixtures are normally specified on a µmol/mol basis, so if you have w/w data, it needs to be corrected by molecular weights (molar masses).

Why such complex answers? The conversion factor is "1". Therefore 1mg/kg = 1ppm

Originally Posted by Unregistered

Convert lead concentrations in ash from mg/kg to ppm

69mg/kg P2O5 in soil to ppm

Im I right in saying:
101 mg/kg = 0.101/1000 = 101/1,000,000 = 101 PPM?

[mader0007]

Am I right in saying:
101 mg/kg =
0.101/1000 =
101/1,000,000 =
101 PPM

[JohnS]

Originally Posted by mader0007

Am I right in saying:
101 mg/kg =
0.101/1000 =
101/1,000,000 =
101 PPM

1 kg = 1 million milligrams, so, yes.

Originally Posted by Unregistered

Convert lead concentrations in ash from mg/kg to ppm

am I right to quote =

200 mg/kg =
200/1000000=0,0002
=0.02%