Talk:Zinc chloride

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This page has been selected for the release version of Wikipedia and rated B-Class on the assessment scale. It is in the category Natsci.

Zinc chloride was a good article nominee, but did not meet the good article criteria at the time. There are suggestions below for improving the article. Once these are addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake. Reviewed version: March 20, 2007

Contents 1 Solubility 2 Solubility 3 Errors 4 Delisted GA 5 Failed "good article" nomination 6 Toxicity

[edit] Solubility

Is zinc chloride really THIS soluble? Adding 432 grams of dry powder in 100 grams of water, and still say that it dissolves? Wim van Dorst July 8, 2005 19:43 (UTC).

Yes, true, according to the Merck Index and the CRC Handbook. If I get a chance I will check this, but I seem to recall reading something like, "Zinc chloride has the remarkable ability to dissolve in only ...." The solubility in boiling water is even more remarkable, 614g per 100g H2O! And ZnBr2 has similar solubility. Walkerma 19:50, 11 July 2005 (UTC)

[edit] Solubility

I have tried to dissolve 100g in 1 L of H20 at 25 deg C. It doesn't work. I ought to have a pH 5 solution according to the MSDS, but I have a pH 5.5 solution and I estimate just under half the ZnCl2 remaining undissolved. Sigma-Aldrich have suggested lowering the pH of my solution, but I'm convinced the pH of the water wasn't a factor. I'm hoping Chemistry is wrong, and I'm right; so if anyone else would like to check this for themselves...

I went and tested this for myself, I took of zinc chloride from the stockroom, and at 29 °C (it's hot here today!) I got just over 20 g of it to go into 5.0 mL. Our stuff is not dry, as you can see from the picture, but it did give out a significant amount of heat as it dissolved so it's not totally hydrated away either.

I wonder if your problem is related to the fact that ZnCl2 can hydrolyse. This problem is more often seen with tin(II) chloride and bismuth(III) salts, you can see the description of this problem with SnCl2 here. In other words, you may have some zinc oxide or zinc oxychloride present as an insoluble material. You can (a) filter it off (I bet it's a lot less than half, too!) and use the part that's left or (b) add HCl to get it all to dissolve at (hopefully) pH 5, or (c) buy a fresh bottle. Let us know what you find, please! Walkerma 20:40, 13 September 2005 (UTC)

I have added HCl and I have dissolved all the Zinc Chloride. The pH is approximately 5, I think a little insoluble material is still present but that won't matter for what I need it for. Thanks for your help. Karl. 15/09/05.

As an aside, does anybody know why we can't make a 10% solution of zinc chloride using de-ionised water, but we can make a 50% solution using distilled water? Thanks, Karl. 21/09/05.

Have you checked the quality of the deionised water lately? That may indeed be the problem. After all, zinc carbonate is insoluble! For my tests I used distilled water. Cheers, Walkerma 15:49, 21 September 2005 (UTC)

I haven't checked our deionised water, but I also had to make up a calcium chloride solution. I used distilled but just out of interest I made up a small amount with deionised and the solution formed a precipitate, which I'm guessing is calcium carbonate. Karl 22/09/05.

Deonisation normally happens by exchanging cations against H⁺ and anions against OH^-. Either cation exchange is not working anymore and you therefore get a fairly basic solution from your ion exchange columns (check pH). Or both columns are not working, there is a fairly high carbonate content and the tap water passes unchanged. Iridos 22:38, 26 April 2007 (UTC)

[edit] Errors

This makes no sense (a mix of topics) and has no citations: "Typically this flux was prepared by dissolving zinc foil in dilute hydrochloric acid until the liquid ceased to evolve hydrogen, for this reason such flux was known as killed spirits. because of its corrosive nature it is not a suitable flux for situations where any residue cannot be cleaned totally away, such as electronic work. This property also leads to its use in the manufacture of magnesia cements for dental fillings and certain mouthwashes as an active ingredient. "

Yes, this was probably added by someone passing through who was familiar with the use. It seems plausible. Do you know anything about this topic, enough to rewrite it with a citation? Or should we just delete it? When I originally wrote the article, my source only stated that it was used as a flux - no details. Walkerma 20:59, 6 November 2006 (UTC)

This property also leads to its use in the manufacture of magnesia cements for dental fillings and certain mouthwashes as an active ingredient. does not sound plausible - which property exactly leads to its use in mouthwashes?! I suggest to delete it (well, keep it here on the discussion page) until someone comes with a source and it can be rewritten properly. Iridos 22:42, 26 April 2007 (UTC)

[edit] Delisted GA

This article has been removed from the GA list due to a lack of in line citations. Tarret 18:14, 14 March 2007 (UTC)

[edit] Failed "good article" nomination

This article failed good article nomination. This is how the article, as of March 20, 2007, compares against the six good article criteria:

1. Well written?: The grammar and format is good. Unfortunately, it contains too many unexplained technical terms and jargon; a reader would not want to click on every single link to find out what the mentioned word means.

2. Factually accurate?: Inline citations are an issue. Although they are not absolutely required, they are helpful especially in areas with possibly dubious information.

3. Broad in coverage?: "Precautions" is just two short sentences and needs expansion.

4. Neutral point of view?: Follows NPOV.

5. Article stability? Stable.

6. Images?: Good.

When these issues are addressed, the article can be resubmitted for consideration. If you feel that this review is in error, feel free to take it to a GA review. Thank you for your work so far.

King of ♥ ♦ ♣ ♠ 19:49, 20 March 2007 (UTC)

GA review (see here for criteria)

1. It is reasonably well written.

   a (prose): b (MoS):

2. It is factually accurate and verifiable.

   a (references): b (citations to reliable sources): c (OR):

3. It is broad in its coverage.

   a (major aspects): b (focused):

4. It follows the neutral point of view policy.

   a (fair representation): b (all significant views):

5. It is stable.

   

6. It contains images, where possible, to illustrate the topic.

   a (tagged and captioned): b lack of images (does not in itself exclude GA): c (non-free images have fair use rationales):

7. Overall:

   a Pass/Fail:

King of ♥ ♦ ♣ ♠ 19:49, 20 March 2007 (UTC)

Unfortunately, it contains too many unexplained technical terms and jargon;

That seems a little unfair - it is a chemical article. You can't go around and explain what covalent means in every article mentioning covalent bonds. Same goes for Lewis acid, etc. etc.- the only (!!) term I see that could be easily explained would be hygroscopic (attracts water). Everything else would just be to complex//too far away from the topic to explain in here. Perhaps what you complained about has already been fixed (?) - if not, please explain which jargon you see that could be easily explained (or expressed differently without garbling its meaning). Iridos 04:39, 26 April 2007 (UTC)

All too often we get that complaint, though in this article I tried to keep the style readable & accessible. I agree, it's hard to write a thorough chem article without "jargon". I also believe in writing in levels - beginner, medium, expert - and some of the expert may have put off this reviewer. User:KOH is a very experienced reviewer, though, and I'm sure we could make this article much better (as you're doing, Iridos!). Walkerma 05:10, 26 April 2007 (UTC)

I think you didn't do a bad job with this - only the 1st, perhaps the 1st two paragraphs are on non-chemist level, I think. Hardly any non-chemist will be interested in the details about in which synthesis zinc chloride is mainly used... so the complaint about jargon can only mean the first paragraphs. And there I don't see much room for improvement. Let's go through this:

• or its hydrates

or its crystalline forms containing crystal water (hydrates)?

• hygroscopic
• deliquescent

skip hygroscopic, explain deliquescent (attracts enough water from air moisture to form a solution when exposed to air)

alternatively: (forms solutions with water attracted from air moisture)

or explain hygroscopic (attracts water) and link deliquescent as already done

• hexagonal close-packed

don't see how that can be explained further in a few words

• metallurgical fluxes

ditto.

Apropos: Shouldnt it be: is used as metallurgical flux?

• ionic

ditto

• covalent

ditto. Cant explain the concept of covalent bonds here.

• melting point

should be understood by non-chemists?

• solubility

should be understood by non-chemists?

• diethyl ether

should be understood by non-chemists?

Could include the formula - but would that help to understand the article?

• lewis acid

too complex to explain here, I think. Any explanation will only add confusion. Keep the link.

• pH

I expanded that to "[..ZnCl₂ solutions...] are acidic with a pH around 4."

• hydrolized

hm... (reacted with water)

• oxychloride

Well, dunno - could show the formula.

• anhydrous/hydrated (again)
• hydrolysis
• dioxane

Could show formula, but would that help understanding the article?

• precipitate

hm "percipitates or crystallizes" (crystallization being the more common term??)

• sublimation

Just put your comments inside the list (with two '::')... I think it's important not to overdo it, though - else the article stops being readable and nothing is gained.

as for the other issues:

Citations I don't think there 'dubious information' in here (??) so the citaions are no issue?

Anyways, they might become one. Could check here: [1]

Precautions being to short: I expanded it (now it's actually too long and does not only contain precautions, but also health effects).

Iridos 22:28, 26 April 2007 (UTC)

[edit] Toxicity

I was missing this data on toxicity in the article. The LD-50 value gives you a rough estimate of the amounts when a substance will be toxic (like, if you're factor 100 or 1000 away from it it should be non-toxic for a single exposure). Not sure, if all of those should be entered, or only some of them, so I put them here for discussion first. They should probably go in the table in some way. LD50:

• ORL-RAT LD50 350 mg/kg
• IPR-RAT LD50 58 mg/kg
• ORL-MUS LD50 350 mg/kg
• IPR-MUS LD50 24 mg/kg
• SCU-MUS LD50 330 mg/kg
• ORL-GPG LD50 200 mg/kg

Source: http://www.camd.lsu.edu/msds/z/zinc_chloride.htm Iridos 04:15, 26 April 2007 (UTC)

• Please limit the biomedical MSDSy info. One can flood all chemistry article with tons of safety-tox data that is not highly relevant to the technical gist of this project. In special cases, WE-Chem has created articles on specific toxicities, e.g. Arsenic poisoning. Cyanide has an extensive and regularly edited section on its toxicity. These more acute poisons indeed merit attention. Also another problem is that including extensive safety info encourages contributions from individuals that have zero knowledge of chemistry. It is awkward reversing such well intentioned cruft. Many new contributors, kids and students probably, love to paste in safety info. ZnCl2 is not particularly interesting from a toxicology perspective, especially relative to more pressing compounds in the WE-chem project that really need this kind of attention. IMHO. --Smokefoot 22:53, 26 April 2007 (UTC)

It is not? It's a trace mineral, present in many enzymes (e.g. for zinc fingers), absolutely essential for the body and yet, you can be poisoned by it... But anyways, I cant see "flooding" by having a pretty long table. Space for text is not an issue in Wikipedia. Readability and a clear structure are, of course, and that was my concern (else I would have just edited the article). Why is it a problem, when people with small chemical knowledge enter safety data? If it makes them read the article and some related articles, they will probably learn a lot and I'm all for it :) Hm, apropos zero-knowledge - ORL-RAT is pretty clear. SCU is probably subcutane (?) MUS is a weird abbreviation for mouse (?!?) and -duh- IPR means intraperitoneal and I got no clue what GPG should be. Well, that makes the decision which of those to skip quite a lot easier *g*. Apropos cyanide - the cyanide anion doesnt have a very exciting space-fill model, so I would regard that one as cruft :) 199.74.98.127 03:50, 27 April 2007 (UTC)

ZnCl2 does not have particularly interesting toxicology. Zn2+ of course does being so pervasive in enzymology and in natural waters etc. But most of the effects that you will allude to arise from Zn2+, fairly independent of the counter anion. So by all means write an article about the biomedical chem of Zn2+! Great project for you and WE-chem. But it might save your time and that of readers if the information were consolidated, otherwise one would need to include very similar information into dozens of articles describing Zn2+ salts (thousands are known). And each one of these individualised safety blurbs (on the sulfate, bromide, chloride, iodide, carbonate, mixed anion...) would be subjected to independent editing by well meaning individuals who rarely understand even introductory coordination chemistry or the difference between various hydrates and gegenions and the difference between solid state structures and solution structures. But maybe you have some deeper insights and we look forward to reading them. There are four crystalline modifications of anhydrous ZnCl2 and several hydrates. Each has its own MSDS - so how do you decide which one gets the priority??? Ditto for many of the zinc salts. --Smokefoot 12:58, 27 April 2007 (UTC)

Well, this is generally true for ionic substances - only a lack of solubility in water or decompositon in water can change this fact for any salt. Still, ZnCl₂ is one major Zn²⁺ compound... Anyways - 'Four crystalline forms, so-called polymorphs, of ZnCl2 are known,' Is different from 'Four crystalline hydrates of zinc chloride are known' You didnt provide a source there... where's that from?199.74.98.127 15:45, 27 April 2007 (UTC)