Talk:Carbon dioxide

Ratio of densities

I am making reference to the very first sentence in the article, which says that “Carbon dioxide is a colorless gas with a density about 60% higher than that of air (1.225 g/L)”. In my opinion, carbon dioxide has a density about 50% (not 60% !) higher than that of air. Even by taking into account the presence of water vapor in air, and treating both CO2 and air as real gases by means of van der Waals’ equation, the ratio of the two densities turns out to be much closer to 1.5 than 1.6. Therefore, I suggest to replace 60% with 50%.Ekisbares (talk) 14:00, 20 July 2017 (UTC)

After waiting about two months for comments, I decided to make the above suggested replacement. Actually, as regards the sentence in the previous version, stating that carbon dioxide has “a density about 60% higher than that of air (1.225 g/L)”, it is likely that the figure of about 60% has been obtained by dividing the density of CO2 as reported in the side-box of Properties of that substance (“1.977 kg/m3 (gas at 1 atm and 0 °C)”) by that of air as reported at the beginning of the article (1.225 g/L). But the latter figure, which was probably taken from Wikipedia article about the Density of Air, is the density of (dry) air at 1 atm and 15 °C, and obviously that ratio produces a meaningless result. If both gases are compared at 1 atm and 15 °C (this temperature being more representative of the average terrestrial conditions), the ratio is about 1.53. For a more realistic comparison, we have to consider that air always contains a variable amount of water vapor, a fact that decreases its density. But even if we allow for the presence of a 100% of humidity in air at 15 °C, the ratio rises only to 1.54. Ekisbares (talk) 14:33, 17 September 2017 (UTC)

By the ideal gas law the ratio of densities works out to the ratio of molecular weights, or roughly 44.0/29.0 = 1.52. Pressure and temperature are irrelevant. So you're correct that it's closer to 50% than 60%, even though you arrived at the answer in a way that doesn't take into account the fundamental reason. Shock Brigade Harvester Boris (talk) 14:44, 17 September 2017 (UTC)

Together with any elementary-level student of chemistry, I am well aware of the fundamental fact, coming out of Avogadro law, that the ratio of densities of gases is equal to the ratio of their molecular weights (average molecular weight for air), provided the gases are considered as ideal, and the comparison is made at the same temperature and pressure. But in order to provide more realistic data to the average users of Wikipedia, which are supposed not to be specialists in chemistry, I directly took the ratio of the real gases, at a temperature and pressure that might be representative of the average terrestrial conditions (in comparing the densities of real gases, temperature and pressure are not irrelevant); I also took into consideration the presence of water vapour. With respect to considering both gases as ideal, the differences turned out to be minimal. Ekisbares (talk) 16:24, 17 September 2017 (UTC)

Rising CO2 toxic?

DMacks, the other day you reverted an edit I made. I had added a qualifier to a sentence claiming that rising CO2 levels may soon constitute a danger to human health. My qualifier pointed out that human breath contains more than 100 times as much CO2 as the atmosphere. Your comment was, "WP:SYNTH for relevance. The atmosphere is not monolithic, else ground-level ozone would be a good thing".

Please explain. Do you really think CO2 will be dangerous for human health, at a level of, say, 500 ppm, when our breath contains about 5% (50,000 ppm)? What does this have to do with whether the atmosphere is monolithic?

Eric Kvaalen (talk) 07:51, 18 September 2017 (UTC)

The bit about breath sounds like SYN to me, too. OTOH the first ref looks to be self-pub with no particular status (add it back if you think otherwise, or there's some reason why it is a good ref) and the language looked stronger than demanded, so I weakened it William M. Connolley (talk) 13:01, 18 September 2017 (UTC)

@William M. Connolley: I know that some people interpret the policy on "synthesis" as though it means we cannot put anything into an article if it involves using our head a little bit! But I don't think that's how that policy should be interpreted. If a sentence seems stupid, there's nothing wrong with putting in a caveat so that people will see that it's stupid. Frankly I would prefer that the article didn't say anything on the subject of a potential future health risk unless it is that there is none (for the very reason that I have pointed out -- the concentration is much too small). In fact, now that you have taken out the reference, the statement is unsupported, so we may as well remove it completely. Eric Kvaalen (talk) 13:32, 18 September 2017 (UTC)

It may partially depend on your definition of a "health" impact. Studies [1] [2] have pointed to measurable, but mild, declines in cognitive performance when exposed to 1000 ppm. Dragons flight (talk) 14:12, 18 September 2017 (UTC)

Um. To take the first of those links, that's somewhat problematic, because as it says These impacts have been observed at CO2 levels that most Americans — and their children — are routinely exposed to today inside classrooms, offices, homes, planes, and cars. So, meh, if you accept that then the climate change connection disappears: the problems are mostly due to air rebreathing. So I'm not sure what we'd do about that (I mean, in this article) William M. Connolley (talk) 16:06, 18 September 2017 (UTC)

For example, puffs of higher concentration exhaled are not the same as long-term exposure via inhalation. WP:SYN is exactly a problem when you draw your own conclusions, especially with regards to effects of raw biochemical data. DMacks (talk) 14:38, 18 September 2017 (UTC)

But we're not talking about puffs of exhaled air. The air in our lungs is always around 5% CO₂ (unless you hyperventilate). Again, I think we should just get rid of the sentence. It now has no reference! Eric Kvaalen (talk) 14:47, 18 September 2017 (UTC)

"It occurs naturally at a concentration of 400ppm"

Shouldn't this be a little controversial? Arguably, it occurs naturally [at least, in this geological era] at concentrations of 280ish ppm and we've boosted it to 400+ppm since then...

Yes, I think it is worded in a way that is potentially misleading. The first part of the phrase, "It occurs naturally in Earth's atmosphere as a trace gas", is of course correct, but the rest of the phrase, "at a concentration of about 0.04 percent (400 ppm) by volume" implies that the current concentration is natural. It is not until 4 paragraphs later that the fact of increasing CO₂ concentrations in the industrial era is introduced. I think separating the two parts of the sentence could avoid giving the misleading impression. Perhaps, "It occurs naturally in Earth's atmosphere as a trace gas. The current concentration is about 0.04 percent (400 ppm) by volume, having risen from pre-industrial levels of 280 ppm." — Preceding unsigned comment added by Edgar181 (talk • contribs) 15:46, 23 January 2018 (UTC)

(edit conflict) Was going to say pretty much the same thing about splitting the two ideas, and Edgar's wording is at least as good as what I was going to write. DMacks (talk) 16:03, 23 January 2018 (UTC)

this statement is really stupid because it naturally occurs all the way up to 7000ppm, depending on how far back in time you go. It should specify that it occurs at 280 or 400ppm at this point in time, but has been known to fluctuate drastically over millions of years — Preceding unsigned comment added by 24.194.170.120 (talk) 09:27, 20 March 2018 (UTC)

Carbon dioxide in Earth's atmosphere seems to cover the historical perspective well. Here, we are mostly talking about now. DMacks (talk) 15:01, 20 March 2018 (UTC)

Also this article has a section In Earth's atmosphere, which includes the sentence Five hundred million years ago the carbon dioxide concentration was 20 times greater than today, decreasing to 4–5 times during the Jurassic period and then slowly declining with a particularly swift reduction occurring 49 million years ago. So the information is there. Dirac66 (talk) 18:55, 20 March 2018 (UTC)

Industrial CO2 production

There seems to be a scarcity regarding how it works (there are some mention on how it does not) and no statistics in production and utilization and percentage of contribution to annual atmospherics increase/decrease or why on how it can't be turned into a cycle linked to sequestration. --109.49.141.100 (talk) 20:47, 21 June 2018 (UTC)

That's a lot of topics, and some of them may be too specific for this article. I think some of what you want is in other articles already, such as Carbon dioxide in Earth's atmosphere. --OuroborosCobra (talk) 18:44, 26 June 2018 (UTC)

That was my point there is lot of information missing (even a link to another article that covers it would work)...

No information on industrial CO2 production besides some mentions, no numbers on what is produced what is used by industry and again what impact it has on atmospheric levels and how or why not it isn't done in conjunction with sequestration efforts (in place of producing it from stable repositories of CO2).

Will check the link you prodded but I don't think that it will cover this subjects (the article topic is more restricted there) (It doesn't, as expected) --109.49.141.100 (talk) 03:50, 8 July 2018 (UTC)

There isn't all that much besides burning fuel and producing cement which is mentioned in the article. After that you're into things like extracting it from natural gas and or using it in dry ice but that doesn't contribute anything very relevant to climate change. Dmcq (talk) 09:41, 8 July 2018 (UTC)

I was not referring to CO2 as an industrial by-product but on intentional creation for industrial processes, like beverage gasification and other uses. How much is produced and the reasons why it can't be re-purposed from those sources you mentioned or even re-captured from the atmosphere (in place of other more stable repositories). That was what I was after, and percentages comparison about human sources that included intentional production of CO2. --109.49.141.100 (talk) 18:07, 22 July 2018 (UTC)

Incorrect info

. It is an unwanted byproduct in many large scale oxidation processes, for example, in the production of acrylic acid (over 5 million tons/year).[6][7][8][9]

The sources do not verify the claim at all, neither does Acrylic acid. Please remove or correct.5.198.10.236 (talk) 07:48, 1 July 2018 (UTC)