Talk:Hygroscopy

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Is this the same as Deliquescent? If not, what's the difference?

  • i am by no means an expert but i would think that the main difference is the phrase "forms a liquid solution" found in the article for "Deliquescent"
    • According to my offline pedia, a deliq.. dissolves in water from the air while a hygro.. just tends to absorb it.

Dililequence should be put in its own seperate article because it is the oppisite of hygroscopicness.

Contents

[edit] cotton fibre

is cotton Hygroscopic because each fibre aborbs water or because the cotton fibres trap air, and in this trapped air water exists as water vapor ? Teeteetee 10:58, 6 February 2006 (UTC)

[edit] Merge from Deliquescence

Even if they're technically different, they are so similar that they would be better presented as one article. —Keenan Pepper 03:25, 29 June 2006 (UTC)

There is a spectrum here. "Deliquescence" refers to hygroscopic substances such as Calcium Chloride that "self-dissolve" in air, and thus can be used as dessicants. However, this phenomenon depends on humidity. Cobalt Chloride will self-dissolve (with a lovely color change) only at quite high humidity and quite warm temperature...the color change is a rough indicator of relative humidity. Under more "comfortable" conditions, it does not so it isn't considered deliquescent. So it is like relative hardness in minerals. One might consider two hygroscopic salts in a sealed chamber; the more hygroscopic one would dessicate the other. A comprehensive article would rank "deliquescent" substances by their critical humidity.--Polymath07 19:34, 7 July 2006 (UTC)

Good point. Let's merge them and add an explanation of that. —Keenan Pepper 02:04, 8 July 2006 (UTC)

I think a merge would be appropriate, esp. as both articles are so short, and don't really need to be much longer to be a complete explanation of two ends of the same spectrum. A few more examples would be helpful but I personally think if larger examples (ie more than just the sentence or two about wood and building materials) are needed there should be a link to them. Jnb 01:43, 2 September 2006 (UTC)

I agree. Merge.

[edit] Merge with Dessication

I agree with the notion of merging this with Deliquescence, but why not merge both with Dessication. Given the relative (small) size of this article, or even the combined articles, and the close relationship of hygroscopic substances - even those so hygroscopic as to be deliquescent - wouldn't the reader be better served by being redirected to that article, and add the appropriate stubs there? —The preceding unsigned comment was added by KnockNrod (talk • contribs) .

Hmm.. I guess that could work. Make an omnibus article, Dessication, hygroscopy, and deliquescence? —Keenan Pepper 20:52, 30 June 2006 (UTC)

I agree the three can be treated together. I think the primary term ought to be Hygroscopy; I see Deliquescence as a subset thereof, and Dessicants/Dessication has a connotation that is more commercial than technical.—Polymath07 19:08, 29 August 2006 (UTC)

I'm not sure that desiccant/Desiccation should be merged into hygroscopy, as desiccation is a technical term for drying, which is not always accomplished via the use of hygroscopic materials. Argyriou 00:12, 6 September 2006 (UTC)
I agree with the last comment -- dessicants should be treated in a separate article from the merged article on hygroscopy & deliquescence. Cgingold 14:19, 23 October 2006 (UTC)

First off, it isn't proper Wikipedia style, as far as I know, to make one article with three different titles as suggested above. Secondly, Dessication has very little to do with Deliquescence, in spite of how many deliquescent materials are use for dessication. Dessication is a process for removing water; Deliquescence is a property of certain molecules. Merging would just provide confusion to viewers of the encyclopedia. Ruff Bark away! 19:07, 27 October 2006 (UTC)

[edit] Question re Biodiesel:

It occurred to me that a comment/question I recently posted on the Biodiesel Talk page ought to be posted here as well, since this article was where it sprang from in the first place. Seeing as I put I good deal of time into writing it, I hope I will be forgiven for simply inserting the entire comment intact, without altering it for this page. So without further ado:

Re: Water contamination
The first line of this section was recently changed (Oct. 3) to state that biodiesel is "hydrophobic". Previously, it had stated that biodiesel is "hydrophilic" -- the opposite of hydrophobic. (This change was made several days after a question was raised in the "To-do list" -- the original statement seems to have gone unchallenged for a considerable period of time.) The change to "hydrophobic" seems to me to be consistent with the statement in the "Description" section that biodiesel "is practically immiscible with water...."
On the other hand, these statements appear to flatly contradict the assertion in the WP article on Hygroscopy, which states that "An example of a hygroscopic substance is biodiesel, which absorbs water to about 1200 parts per million (PPM)." I checked around and found that this claim is repeated widely on numerous websites, but I could not find definitive substantiation -- merely repetition of the same statement. I was hoping this apparent contradiction would be explored here on Wikipedia -- but this specific claim is not addressed anywhere in the Biodiesel article.
This is not a minor point. If biodiesel is indeed hygroscopic -- meaning that it has a strong tendency to pull water molecules out of the atmosphere -- there are serious implications in terms of its use, storage, etc., which would need to be addressed in the article. Currently, the problem of "Water contamination" is stated to arise because "Some of the water present is residual to processing, and some comes from storage tank condensation." But there's no mention of continuing accumulation of water due to its alleged hygroscopic properties.
So I pose the following question: Is it, in fact, possible for a substance be BOTH hydrophobic AND hygroscopic?? In other words, can it, somehow, both repel water molecules and also absorb them? One way or the other, this question needs to be settled.

So far I've had no response on the Biodiesel Talk page -- hopefully someone on this page will have something to say. Cgingold 14:34, 23 October 2006 (UTC)

Re: Biodiesel; hygroscopic vs. hydrophobic

I'll try to sort this out from my perspective as a chemist. Biodiesel, or any other fuel, is mainly made up of hydrocarbons, e.g. for standard gasoline these would be heptane and octane, among others. These are hydrophobic solvents, if you mix them with water and leave them to stand, the mixture will separate into two layers of water and solvent again. Nonetheless, the organic solvent will now contain some water, and the water some organic solvent, albeit a pretty small amount. The organic solvent will often appear opaque at this point. Hydrophilic solvents, on the other hand, form a uniform mixture with water, often in any ratio of the two. This is true for ethanol (drinking alcohol) for example. If left to stand exposed to air, a hygroscopic substance "draws in" water. If this is true for Biodiesel I don't know, but if so it would absorb some water over time. In this sense, a substance can be both hydrophobic and hygroscopic. Uh, hope this doesn't simply add to the confusion...

Jzimmer 12:54, 31 October 2006

Thanks for your attempt to sort things out. This turns out to be a surprisingly complex (and fascinating) question. I've also had a response on the Biodiesel Talk page which I'm going to re-post here, as it sheds additional light on the subject. I'm including my reply, which brings the discussion back to the bottom-line question (which still needs an answer):
Re: Water contamination
As to your question a to whether a hydrophobic compound can also be hygroscopic, the simple answer is "yes to a point." Organic compounds can elicit both behaviors simultaneously when they have varying functional groups with a wide enough separation. BioDiesel is an ester with a very short side and a long side, the short side can exhibit polar qualities due to the presence of oxygen while the long chain exhibits nonpolar qualities. The polar side is what attracts the water, while the long chain repels the water. Cells of living organisms utilize a similar method to control the amount of materials crossing the membrane. I hope this explanation helps. Das Nerd 20:08, 28 October 2006 (UTC)
Thank you! I think your explanation may well get us "half way there", so to speak. As I said, it's widely stated elsewhere that biodiesel "absorbs water to about 1200 PPM" -- something which is not mentioned at all in the "Water contamination" section. If this is indeed a scientifically verified fact, then it needs to be included here, along with the other two reasons that are given. Again, none of the websites I consulted cited a source for the claim -- my impression was that they were all simply repeating a statement originally made by a single person or publication, which I was unable to locate. Do you have any idea where to find scientific validation (or lack thereof) for this assertion? Or, given your reply to my question, do you at least find it credible enough to include here without further confirmation? Cgingold 21:10, 28 October 2006 (UTC)
Any idea how to settle this? Cgingold 04:04, 1 November 2006 (UTC)

[edit] Word

Is "hygroscopy" a word?


[edit] Etymology

Seeing as how many people mistake hydroscopy with hygroscopy, it would be useful to have the etymology for both words available here. Can someone supply? —Preceding unsigned comment added by 198.212.208.14 (talk) 17:47, 2 October 2007 (UTC)

[edit] Splitting rocks?

Does "It's possible to split a rock by inserting a piece of wood into a fissure and adding water. As it absorbs water the wood's volume increases and pushes the sections of rock apart, increasing the fissure." really belong in this article? It seems off-topic, as it involves pouring water onto wood (as opposed to general absorption from the air), and more anecdotal than informative. 208.67.176.98 16:30, 26 March 2007 (UTC)


Is Washing soda a hygroscopic substance?

[edit] Hydroscopic vs Hygroscopic

I don't think that the one-liner in the article sufficiently covers the misuse of the two words: "The similar sounding but unrelated word hydroscopic is sometimes used in error for hygroscopic." I'm no chemist, and I'm trying to learn the differences between the two words so could someone that knows please flesh that out a bit more? Thanks. Also, is 'hydroscopic' even the correct word? Shouldn't it be 'hydrophilic'? --TheJalAbides (talk) 20:53, 18 January 2008 (UTC)