So, what is ppm? And how can something called "parts per million" be represented by mg/L? Parts per million indicates the number of "parts" of something in a million "parts" of something else. The "part" can be any unit, but when mixing solutions, ppm will usually represent weight units. In this context, ppm tells you how many grams of a solute are for each million grams of solvent (e.g., water). Then we divide mL by 1000 to convert mL to L:īy dividing both units by 1000, the ratio becomes: Therefore, we can rewrite the relationship as follows: When dealing with water at room temperature, it is common to assume that the density of water is 1 g/mL. Therefore, you can say that 1 mg in 1 L water is the same as 1 mg in 1,000,000 mg water, or 1 part per million (assuming both room temperature and an atmospheric pressure of 1 atm). If your solvent is not water, you should use the Advanced mode in the ppm to molarity calculator to adjust the solvent's density. You have a stock solution of 1 molar NaOH. Then, divide the result by 1000 to get g/L: How do you go about creating a 1 L solution of 200 ppm NaOH? NaOH has a molar mass of 39.997 g/mol. To calculate the dilution, we use the dilution equation: Next, divide 0.2 g/L by the molar mass of NaOH to get the molarity:Ġ.2 g/L divided by 39.997 g/mol = 0.005 mol/Lįrom step 1, we know the target molarity is 0.005 mol/L. m₁ is the concentration of stock solution.m₂ is the concentration of diluted solution.V₁ is the volume of stock solution and.
We can fill in the numbers for all the variables except for the volume of stock solution:īy rearranging the equation, we will find the volume of stock solution required: Therefore, we need to dilute 0.005 L (or 5 mL) of stock solution to a final volume of 1 L to get a 200 ppm NaOH solution.Ppm means parts-per-million. But what parts? The amount of particles in a suspension can be expressed as the total volume OR total mass of particles in a unit volume of water AND THESE TWO NUMBERS WILL ONLY BE THE SAME IF THE DENSITY OF THE PARTICLES IS 1 g/cm3. If ppm is expressed as THE VOLUME of particles to a unit volume of water, then ppm BY VOLUME is equal to µl/l.
However, if ppm is expressed as THE MASS of particles in a unit volume of water, then ppm BY MASS is equal to mg/l. To convert from ppm by volume to ppm by mass, multiply by the density of the particles. For example, a sample with a volume concentration of 25 µl/l will have a mass concentration of 25*2.65 = 66 mg/l.įor mineral grains (clay, silt and sand sizes), this will typically be 2.65 g/cm3. To convert from ppm by mass to ppm by volume, divide by the density of the particles. For example, a sample with a mass concentration of 100 mg/l will have a volume concentration of 38 µl/l.
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