# Chemistry math question.

#### joelbegt

##### New member
Can someone please give the math equation to figure out the following.

If I add .725ml of A to 1022L how may ppm of A do I have assuming 100% purity in A.

#### DonR

##### New member
Parts per million are usually expressed as weight per volume, e.g., milligrams per liter. But assuming A has a specific gravity of 1.0, you have 725 milligrams of A per 1022 liters, or 0.71 mg/l (ppm) of A.

Cheers,

Don

#### toothybugs

##### New member
What are you actually doing? Products, etc.

I get Don's math to be correct, btw.

#### bertoni

For our purposes, ppm is the same as mg/dL, so you can compute from there if you'd like. It's about 2% off, with 1 ppm being more like 1.023 mg/dL, if you'd like more digits. ppm is defined as a ratio of weights, so you'd need to give us precise weights to do the exact computation. The weight of the 1022 liters of water is easy. What does A weigh?

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#### joelbegt

##### New member
What are you actually doing? Products, etc.

I get Don's math to be correct, btw.

Trying to get an equation more so than the answer for future reference sake for dosing trace amounts of minerals or elements. Wasn't sure if it was a simple or complex thing.

#### DonR

##### New member
Trying to get an equation more so than the answer for future reference sake for dosing trace amounts of minerals or elements. Wasn't sure if it was a simple or complex thing.

It's really simple. For aqueous solutions, ppm is practically the same as milligrams per liter. So:

ppm = milligrams of solute / liters of solution

In the case of a liquid solute like your solute "A", whose volume you know, you need to convert the volume to weight. One milliliter of water weighs one gram (1000 milligrams) at standard temperature. Other liquids may weigh more or less per milliliter, but if "A" is an aqueous solution, you can safely use one gram per milliliter for its weight. If "A" is not aqueous (like alcohol, for example), you need to multiply the volume times the specific gravity.

So in your example, 0.725 milliliters of "A" in 1022 liters of water, assuming A is an aqueous solution, has a concentration of:

725 / 1022 = 0.71 ppm

If "A" were ethyl alcohol, it would have a specific gravity of 0.79. So the concentration of A would be:

(725 * 0.79) / 1022 = 0.56 ppm

#### DonR

##### New member
If, however, you are trying to determine how much of some component of "A", like a mineral or trace element, you are adding, you need to know the concentration of the component in the solution "A".

For example, if "A" contains five percent of component "Z", multiply the results of the previous calculation by five percent (0.05). So the concentration of component Z would be:

725 / 1022 * 0.05 = 0.035 ppm

#### disc1

##### -RT * ln(k)
If, however, you are trying to determine how much of some component of "A", like a mineral or trace element, you are adding, you need to know the concentration of the component in the solution "A".

For example, if "A" contains five percent of component "Z", multiply the results of the previous calculation by five percent (0.05). So the concentration of component Z would be:

725 / 1022 * 0.05 = 0.035 ppm

Right. The question is confusing as there is almost nothing that goes into our tanks that is a pure liquid. It is almost all some salt dissolved at some concentration in water.

#### joelbegt

##### New member
Yeah I didn't think that through lol. Thank you for the help!

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