Ions in water - what does ppM actually mean?

In summary, the conversation discusses the use of copper ions in swimming pool ionisers for water cleaning purposes. The amount of copper needed is measured in parts per million and can be converted into molarities using Avogadro's number and the molecular weights of copper and water. The method of measurement can vary, but it is typically based on mass for liquids and volume for gases.
  • #1
bitman
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"A Copper test is performed much as you would test for chlorine residue. A level of copper in the range of 0.15 through 0.20 ppM"

The above is an extract from a page on swimming pool ionisers. The ionisers produce copper ions for water cleaning purposes.

0.2ppM (parts per Million) - I don't understand how you can quantify copper ions in this way. Is this a ratio by weight? or does it man 1 atom of ionised copper per 5 million water atoms.

Any thoughts on the actual meaning of this appreciated.

What I'm really looking for is an idea of how much copper I need to electrolyse to prevent algae growth.

I am attempting to construct a simple ioniser for a small decorative fountain we have. Currently we use chlorine tablets but that kills the surrounding plants which get splashed - and more importantly displeases 'she who must be obeyed'.

Bitman
 
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  • #2
IIRC from high school chemistry, using Avogadro's number you can convert particle numbers into moles. Then you can turn the ppM quantities into molarities.
 
  • #3
I would imagine that this is based on weight (mass). Rarely have I seen it based on number of atoms.

Then, 0.2 g Copper per (10^6) g H2O = (0.2/1000000)= 2*(10^-7) Wt %

MW Cu = 63.5 g/mol
MW H2O = 18

Then, .0000002 * (18/63.5) = 5.67*(10^-8) Mol %
 
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  • #4
The question is not as trivial as it might at first seem. It could be by volume (tricky for gases with changing pressures), by mass, by atoms as I suggested earlier. As any of these will yield different results it seems a pretty arbitrary thing.

Bitman
 
  • #5
Indeed it can be arbitrary, but usually for liquids it is on a mass basis, and for gases it is on a volumetric basis. Personally, I would go with this assumption first because it seems the most reasonable.
 

1. What are ions in water and why are they important?

Ions are electrically charged particles that exist in water. They are important because they play a crucial role in various chemical and biological processes, such as conductivity, pH, and nutrient availability.

2. What does ppM mean and how is it related to ions in water?

ppM stands for parts per million, which is a unit of measurement used to express the concentration of a substance in a solution. In the context of ions in water, ppM is used to measure the amount of dissolved ions in a certain volume of water.

3. How do ions get into water?

Ions can enter water through various processes, such as weathering of rocks and minerals, industrial and agricultural activities, and natural sources like rain and rivers. Additionally, ions can also be introduced through water treatment processes.

4. What are the potential health effects of high levels of ions in water?

The health effects of ions in water largely depend on the specific type and concentration of ions present. Some ions, such as sodium and chloride, are essential for our bodies in small amounts, but can be harmful in high concentrations. Other ions, like lead and mercury, can have toxic effects even in small amounts.

5. How can I reduce the amount of ions in my drinking water?

There are several methods for reducing the amount of ions in drinking water, including filtration, reverse osmosis, and ion exchange. It is important to test your water to determine the types and levels of ions present before choosing a treatment method.

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