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Units of Measure
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Volume

What is parts per million PPM?

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May 06, 2017 6:50AM

Parts per million

Parts per million (ppm) measures the mass of the substance in the solution divided by the total mass of the solution times one million. For example, if you have 1g of NaCl in 1000g of water, what is the PPM?

1g NaCl/1000g H20 (1,000,000)

0.001 x 1,000,000

1000 ppm is your answer.

In other words, ppm measures the concentration of a chemical in very low quantity. For example, seawater has 0.5 ppm of pure gold, while human blood contains 20 ppm of iron oxide. This unit is used when other units like % and fractions are too big to denote the quantity. Since a percent is one part in a hundred, you can image how small ppm is compared to %.

8 milligrams of mercury in 100 grams of fish would result in a mercury concentration of 0.8 ppm.

Portable Pixmap

PPM could also be an abbreviation for Portable Pixmap. This is a common image format used in Unix systems due to the simplicity of the format. The format is as follows:

Where width, height, and maxval are in ASCII decimal for the width, height, and maximum sample value of the image, respectively. The header portion can also include human-readable comments by using the # character followed by a comment. The image data is just a bunch of uncompressed bytes containing the red, green, and blue sample values of each pixel. There are similar formats called Portable Greymap (PGM) and Portable Bitmap (PBM), and they are defined and treated similarly.

There are many tools for transforming and converting files of these types to other formats. Search for Netpbm for more information.