Sciencemadness Discussion Board

Parts per notation

Wrecking Bereserker - 3-4-2019 at 07:59

I know what it is and how to do calculations with it
But whenever i read say 10ppm is the chlorine lethal dosage level im unable to process it in a real life scenery or understand what should it mean to someone producing the gas for example if someone says 1 liter i imagine a 1liter bottle filled with it but what about ppm?

MrHomeScientist - 3-4-2019 at 08:11

Well ppm is 10-6, so for your 1 liter bottle example you'd have 1 mL of contaminant in that volume.
So then your "lethal bottle" of chlorine would have 10 mL of pure chlorine mixed in there with the 1 L of air. Catching a whiff of the contents won't kill you, but inhaling the whole bottle might. Either way it'll definitely be unpleasant.

mayko - 3-4-2019 at 08:41

(a millionth of a liter is a microliter, uL :cool: )

Sulaiman - 3-4-2019 at 08:52

Quote: Originally posted by MrHomeScientist  
Well ppm is 10-6, so for your 1 liter bottle example you'd have 1 mL of contaminant in that volume.
So then your "lethal bottle" of chlorine would have 10 mL of pure chlorine mixed in there with the 1 L of air. Catching a whiff of the contents won't kill you, but inhaling the whole bottle might. Either way it'll definitely be unpleasant.


1ppm = 1 litre / 1,000,000 = 1 ul
if 1 ppm = 1ml then the total volume is 1000 litres, one cubic metre.

10ml @ 1ppm = 10 m3 = room size

Wrecking Bereserker - 3-4-2019 at 09:07

Quote: Originally posted by Sulaiman  
Quote: Originally posted by MrHomeScientist  
Well ppm is 10-6, so for your 1 liter bottle example you'd have 1 mL of contaminant in that volume.
So then your "lethal bottle" of chlorine would have 10 mL of pure chlorine mixed in there with the 1 L of air. Catching a whiff of the contents won't kill you, but inhaling the whole bottle might. Either way it'll definitely be unpleasant.


1ppm = 1 litre / 1,000,000 = 1 ul
if 1 ppm = 1ml then the total volume is 1000 litres, one cubic metre.

10ml @ 1ppm = 10 m3 = room size


So that means if i were to take 1litre bottle then 10 ppm will be 0.01ml right?

Metacelsus - 3-4-2019 at 09:45

Yes.

MrHomeScientist - 3-4-2019 at 09:59

Damn, that's what I get for blindly copying Wikipedia: "The quantity “1 ppm” can be used for a mass fraction if a water-borne pollutant is present at one-millionth of a gram per gram of sample solution. When working with aqueous solutions, it is common to assume that the density of water is 1.00 g/mL. Therefore, it is common to equate 1 kilogram of water with 1 L of water. Consequently, 1 ppm corresponds to 1 mg/L and 1 ppb corresponds to 1 μg/L."

wg48temp9 - 3-4-2019 at 10:10

Quote: Originally posted by Wrecking Bereserker  
I know what it is and how to do calculations with it
But whenever i read say 10ppm is the chlorine lethal dosage level im unable to process it in a real life scenery or understand what should it mean to someone producing the gas for example if someone says 1 liter i imagine a 1liter bottle filled with it but what about ppm?


As usual or frequently you need to look at the context or additional info of any number. See the pararaph below for example, taken from wiki https://en.wikipedia.org/wiki/Chlorine_gas_poisoning.

"Dose toxicity
Humans can smell chlorine gas at ranges from 0.1–0.3 ppm. According to a review from 2010: "At 1–3 ppm, there is mild mucus membrane irritation that can usually be tolerated for about an hour. At 5–15 ppm, there is moderate mucus membrane irritation. At 30 ppm and beyond, there is immediate chest pain, shortness of breath, and cough. At approximately 40–60 ppm, a toxic pneumonitis and/or acute pulmonary edema can develop.... Concentrations of about 400 ppm and beyond are generally fatal over 30 minutes, and at 1,000 ppm and above, fatality ensues within only a few minutes."

As you can see the ppm refers to the concentration in inhaled air for a particular amount of time.

happyfooddance - 4-4-2019 at 10:01

Quote: Originally posted by MrHomeScientist  
Damn, that's what I get for blindly copying Wikipedia: "The quantity “1 ppm” can be used for a mass fraction if a water-borne pollutant...


But we are talking about concentrations of gas, if we were to assume the rest of the liter is filled with water this calculation would be correct. 1 liter of water weighs 1kg, but 1 liter of air weighs far less.

Gasses are sometimes measured in mass fraction and sometimes in mol fraction, sometimes in mass/volume, depending on your use... And you may need to convert between and will need to apply partial pressures and universal gas constant, etc...

[Edited on 4-4-2019 by happyfooddance]