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Concentration units: parts per part?

Concentration units: parts per part?

Concentration units: parts per part?

(OP)
I need concentration as an input to a calculation. This is a gas mixture, so I already have to distinguish clearly between volume ratio and mass ratio (users seem to assume one or the other, without thinking). But I need also to make it clear what the basis of the concentration is. Users seem split between "parts per million", which is universally abreviated to "PPM" and just a straight fraction, which would be "parts per part" or "PPP". But I've not seen those terms used much, if at all. Is there a better term for this that I'm missing? (Nobody seems bothered about percent for this application, which would be easy to handle).



Steve

RE: Concentration units: parts per part?

Steve,

Just started in the electronics gas industry (6 months) and I feel your pain. Here's what I have observed, in order of decreasing concentration, always as a volume concentration:

% purity (for the product)
PPT (part per thousand)
PPM (part per million)
PPB (part per billion)

Hope this helps!

Matt

Quality, quantity, cost. Pick two.

RE: Concentration units: parts per part?

Isn't that simply a ratio?

3 parts A to 5 parts B.

By mass, or volume, as appropriate.

RE: Concentration units: parts per part?

SomptingGuy,

If it is not obvious that you are using either mass or volume, I would explicitly state units. Cubic furlongs per cubic furlong?

--
JHG

RE: Concentration units: parts per part?

"Mass fraction" and "volume fraction" are terms I recall using in chemistry class, and I have since seen ppmv and ppmm (sometimes with the final letter subscripted) used, with definitions of the abbreviation in the units list in a paper. I do like it when the writer specifies which convention he is using.

We recently started upgrading the way we report flow rate measurements, with users overseas split between liters/second and liters/minute (our current software only reports l/s, so the production manager and I had to hack it to get it to report l/min). The IT guy and I had a discussion about the metric system and the silliness of gallons per minute, and decided we needed to include kBl f.q. as an option in the new software. That stands for kilo-Buttloads per fortnight (a butt being 126 US gallons), according to impeccable internet sources.

RE: Concentration units: parts per part?

(OP)
For clarification...

I need to be able to accept mass fraction or volume fraction and have that fraction PPM or PPP (all 4 combinations). I'm just trying to decide on labelling of the input field(s) and don't like "PPP". Having a four-way option menu PPPM|PPPV|PPMM|PPMV is just asking for confusion and errors.

Steve

RE: Concentration units: parts per part?

Steve, are you limited to four characters? If not, then why not PPMm || PPMv || Vfrac || Massfrac

RE: Concentration units: parts per part?

If it's a gas, I would think molar ratio would be the best.

RE: Concentration units: parts per part?

For most gases molar ratio and volume ratio are the same, which is why ppmv or volume fraction are generally used, depending on whether the concentration is low or high.

RE: Concentration units: parts per part?

(OP)
I like that btrueblood. Thanks. It makes the distinction quite clear and precise.

Steve

RE: Concentration units: parts per part?

btrueblood's nomenclature makes a lot of sense. The big problem in Oil & Gas is upstream uses ppm to mean Parts per Million by volume (which is taken as the same as molar for the gases we most often deal with). In downstream they use ppm to mean Parts per Million by mass. When I was writing computer systems (that were often generated by upstream to send to downstream) I always insisted on PPMv, PPMm, PPBv, PPBm, MoleFraction, or MassFraction. I did not allow mass percent or mole percent because too many programs mess it up (i.e., I often see 0.96 in a column labeled "Mole PerCent" which is just under 1% when they mean 96%). It turns out that PPMv gets confused less often than mole per cent.

Introducing PPPv would just cause no end of confusion, parts per part doesn't mean much and is better represented as Mole Fraction, Volume Fraction, or Mass Fraction.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

RE: Concentration units: parts per part?

I agree with mintjulip when dealing with vapors, gases, fumes, and solids but the exception is with fibers. Concentrations expressed as PPT, PPM,PPB should be appended with either(V)or(W) for volume or weight.

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