# Is there a difference between ppm and mg/l?



## kakkoii (Jan 18, 2008)

Is there a difference between ppm (parts per million) and mg/l (milligrams per liter)? Everywhere I have looked said they equal the same amount. Is this true?


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## cfreeman (Mar 19, 2008)

If you are dealing with water (as most on this forum presumable do!), they are equivalent. The reason is that 1 liter of water weighs 1 kilogram. So, when you have 1 milligram of a substance dissolved in water (weight of 1,000 grams or 1,000,000 milligrams) it is the same as 1 part per million. For other liquids this does not work out so neatly because they have different weights. This is the beauty of the metric system.


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## kakkoii (Jan 18, 2008)

Thank you!


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