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**To**:**<Aquatic-Plants at actwin_com>****Subject**:**Re: ppm (parts per million)****From**:**"Craig David" <whamajamma at earthlink_net>**- Date: Tue, 26 Jan 1999 20:10:52 -0800

Hello Quek, On Mon, 18 Jan 1999, you wrote: Could some kind soul help me with the above term. I was offered a couple of equivalent for dosage. They are 1mg/lit and 10mg/lit. How do you arrived at the equivalent. Thank you. Dave Lorenzen responded to you and is right in stating for concentrations in water 1mg/L= 1ppm. If you are curious to know more about the derivation please read below : A concentration of one part per million (ppm) corresponds to one part of the substance per one million parts of the gas, liquid or solid mixture in which the substance occurs. In the case of liquids and solids the reference is generally to ppm by weight. (In the case of a gas mixture, the reference is generally ppm by volume). The density of water is 1g/mL. There are 1,000 milligrams (mg) in one gram and 1,000 milliliters (mL) = 1 liter. Therefore, 0.001g(of your substance) in one mL of water (1mg/mL) = one part/thousand, and so it further follows that 1mg/1000mL (1mg/L) = one part per million (1 ppm). 1mg/L = 1ppm and of course 10mg/L would be 10 ppm. Craig David

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