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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: schuheric on February 25, 2020, 10:44:32 AM

Title: Percent to PPM
Post by: schuheric on February 25, 2020, 10:44:32 AM

Hello,

I have a simple question. I am trying to make a 3% chlorine solution. What would be the equivalent ppm of that solution? 30,000ppm no?

Thanks

Title: Re: Percent to PPM
Post by: billnotgatez on February 25, 2020, 11:20:08 AM

I did GOOGLE on

Quote

convert percent to ppm

Title: Re: Percent to PPM
Post by: AWK on February 25, 2020, 12:00:38 PM

Yes, the conversion factor from % to ppm is 10⁴.

Title: Re: Percent to PPM
Post by: pcm81 on March 14, 2020, 05:28:53 PM

The problem with % to ppm conversions is that % content is not a unique measure, while ppm is very specific. For example, vodka is 40% by volume ethanol, which is not the same as 40% by mass and it is not the same as 400,000ppm.
PPM is very specific since it is molecular fraction, hence the molar mass is irrelevant or accounted for. The percent composition can be by mass, by volume or by molar fraction...

Title: Re: Percent to PPM
Post by: chenbeier on March 14, 2020, 05:40:47 PM

ppm is defined as 1 part per 1 million.

So it could be 1 mg per 1 kg in case of mass.  But as already mentioned also if Volume is meant   
1 μl per 1 liter.

In case of the chlorine solution its difficult, because a gas is dissolved in water. The percentage is also not correct. So need to have the mass of the chlorine in mass solution.

Title: Re: Percent to PPM
Post by: Borek on March 14, 2020, 07:33:27 PM

Quote from: pcm81 on March 14, 2020, 05:28:53 PM

ppm is very specific

Sadly, it is not. It can be mass parts (most common) but it can also be volume, atoms per atoms, or mg per L (whatever the mass of the L is). It is generally not better than %.