Sciencemadness Discussion Board

The novel and uncharacterized compounds thread.

Brain&Force - 7-12-2013 at 21:40

So many compounds lack information that can be found in basic references such as Wikipedia.

If you're looking for something to do in your spare time, why not make and investigate some of these compounds? Many of them can be made easily from lab chemicals and not all of them are dangerous.

The criteria for inclusion in the uncharacterized compounds list includes:

- There's no good reason the compound hasn't been researched thoroughly (i.e. requires no special handling and is not prohibitively expensive, something that can be done in your home/backyard)
- No Wikipedia article, or article marked as stub.
- Its Wikipedia article is about an application rather than the compound's chemistry.
- No research papers on the compound
- Any of this information missing or unknown:
-Color or other appearance information that could be determined with a photo
-Melting/boiling points
-Density
-Solubility in water (if applicable) or other solvents
-Air stability

Here are some compounds that meet this definition and warrant further study.

Iron(II) iodide - The Wikipedia article is a stub.

Chromium dioxide - although its article does exist, and is not a stub, it doesn't have any information about its chemistry; most of the article is about its application in cassette tapes.

Samarium(II) iodide - same as above, though it's used as a reducing agent in labs. Its air stability and density are not known. (This may be harder to work with.)

Most lanthanide compounds.

Compounds without images on Wikimedia Commons cannot be considered uncharacterized, but it would be a good idea to make and submit any images you have of these compounds for article improvement.

I hope this can kickstart some novel research here at ScienceMadness!

Tdep - 8-12-2013 at 04:45

What credibilities must one have to create a wikipedia page or add a picture of a chemical to an existing wikipedia page?

I was planning to make some terbium sulphate some time, and noticed that it didn't have a wikipedia page (although there are some picture of it on the terbium page). Would my experiences with the chemical as an amateur home chemist be any sort of use to write up an article, if I'm not all that trustworthy?

Edit: There's a terbium sulphate article in german, not english. Strange. But the question still remains. Isn't no information better than untrustworthy information, especially when it comes to chemistry?

blogfast25 - 8-12-2013 at 06:06

Quote: Originally posted by Tdep  
What credibilities must one have to create a wikipedia page or add a picture of a chemical to an existing wikipedia page?



I don't know but just because Wiki doesn't provide the information doesn't mean it isn't available somewhere.

Before people go off on wild goose chases, I suggest they familiarise themselves with methods of literature research, as outlined in the guidelines of the forum:

http://www.sciencemadness.org/talk/viewthread.php?tid=19143#...


[Edited on 8-12-2013 by blogfast25]

bismuthate - 8-12-2013 at 06:34

blogfast has a point, not everything is from wiki.
The big problem I see is that the list could be incredibley long. Other than that I love the idea!

Pok - 8-12-2013 at 06:59

Wikipedia is an encyclopedia. And this is nothing but a collection of quotations verified by references (at least it should be so).

It's useless and dangerous to write something in wikipedia about density or solubility that was measured by a home chemist. Dangerous because they are not reliable. Unfortunately the solubility table at wikipedia is not verified by references. This table is nearly completely useless because you can't trust it. In this case wikipedia destroyed knowledge that was reliable in old "real" encyclopedias!

Photos of chemicals would be a good idea. They are difficult to find in the standard literature. But they also don't contain much information that is relevant for a chemist.

blogfast25 - 8-12-2013 at 07:40

Pok:

I disagree somewhat: dismissing Wiki's entire solubility table on the basis of it not being referenced seems wasteful to me. References data aren't necessarily correct either: different authorative sources sometimes present different values too.

Also, densities or solubilities measured by a home chemist aren't by definition unreliable.

As regards photos, why would they be more reliable than any other data presented by home chemists?

kristofvagyok - 8-12-2013 at 08:05

Quote: Originally posted by Pok  
Photos of chemicals would be a good idea. They are difficult to find in the standard literature. But they also don't contain much information that is relevant for a chemist.

We have several thousand chemicals in the university, if anyone would like to make a photo from them it would be a several month long project and it would be almost totally useless.

Why? Depending on the source, impurities, crystal forms a compound could look really different. A great example 5-bromo-2-carboxyethyl-indole. This was the first chemical what I have made and every time I made it, it looked really different. First it was a brown gunk, just like as they described in the patent what I have worked from (it contained none of the title compound), second turn it was a beautiful orange crystalline solid and third time it was a white foam like crystalline solid. So if I would take a photo from the first product and submit it as "it should look like this", than everyone who makes this and gets a nice crystalline stuff, would be disappointed.

In case of inorganic compounds, what have characteristic colors and crystal form like copper, cobalt ect. containing chemicals, it could be a good idea, but for the 99% of the chemicals, especially at the organics, it is totally useless.

Pok - 8-12-2013 at 08:34

Quote: Originally posted by blogfast25  
I disagree somewhat: dismissing Wiki's entire solubility table on the basis of it not being referenced seems wasteful to me.

This table contains many mistakes. So it can't be used as a reliable source of information. When planning an experiment which depends on the solubility of one substance you can't simply trust these values given there. So you could only use this table as a basis for further research on the solubility. But if no references are given it's not even useful as a basis for literature research! The only useful thing about this table is that you can say that the values for one substance are "correct with a probability of 90 %".

One example: I once wanted to precipitate caesium out of solution. I searched at the table for the least soluble caesium salt which is CsBrO3 (at 0 °C). So I took the expensive sodium bromate to precipitate the Cs. But later I noticed that this value is wrong. It's 10 times higher in reality (which makes absolutely sense if you plot the values against temperature!). Cheap sodium chlorate would have done a similar good job. :mad:

Photos are not per definition more reliable. But you don't need much equipment and knowledge to make a photo. But that's the case for real measurements like density or solubility. That's why it's at least "more probable" that photos made by home chemists show the truth than measurements made by a home chemist.

@kristofvagyok: OK. I agree.

[Edited on 8-12-2013 by Pok]

blogfast25 - 8-12-2013 at 09:36

Pok:

Your opinion may be a little coloured by that bad experience, whereas mine maybe coloured by a recent positive one, where the tabled values were in perfect alignment with my experiment.

Whatever tabled values you find anywhere, caution and scepticism are always good to have at hand.

And I agree with Kristov on the photos: taking good, clear shots of representative samples of reasonably pure compounds is really no sinecure. I think they're more useful as evidence (but not proof) that a reporting experimenter has actually done what he claims. And we all like a good picture...


[Edited on 8-12-2013 by blogfast25]

kristofvagyok - 8-12-2013 at 16:03

Quote: Originally posted by Brain&Force  
So many compounds lack information that can be found in basic references such as Wikipedia.





-sorry for the large image, but this is pretty informative I think(:

Brain&Force - 8-12-2013 at 17:22

Whoa! I did not expect to get a lot of responses. Thanks for the critiques; I'll address them individually.

Tdep: The point I had in mind was not to edit Wikipedia - it's to expand the member publications section (which is painfully lacking) and just start some research. Any information gathered here would be useful for forum users' future reference.

I would like a ScienceMadness wiki, but that's a different thread...

blogfast25: The main intent is to streamline the search process, but there is much to be found in the literature. Also, users can contribute and add more information, especially about reactions which haven't been attempted yet.

Pok: Taking one data point is prone to error, but the idea is to aggregate data points and average. That should give a much better result. If ScienceMadness could store some basic data gathered by members about simple compounds, I'd use it rather than Wikipedia.

kristofvagyok: You do have a point about photos being a big endeavor, especially with organics. But as I mentioned earlier, the point is to aggregate and average. Photos can be essential to certain projects - just look at the neodymium sulfate thread. Images could be uploaded to Wikimedia Commons as well.
Also, I was hoping this project could cover simple inorganic compounds first, then move on to more complex ones as well as organics.
By the way, where did you find the comic? I can't find it in the xkcd archives.

Feel free to add in more compounds that you think are worthy of investigation. Here are some others I have thought of:

Lower vanadium oxides (specifically VO and VO2)
Selenium trioxide
Permanganates of heavier alkali/alkaline earth elements

bismuthate - 8-12-2013 at 17:44

copper permanganate
pretty much every
(PH4)- compound
many azides also remain unresearched
I could iust keep on going for pages upon pages.

ScienceSquirrel - 8-12-2013 at 17:54

I have done several crystallisations using the Wikipedia solubility table data and found that they worked OK.
There are lots of mistakes everywhere.
Last week I read a recipe that said to boil potatoes for 5 minutes, the writer meant 25 minutes at least. Potatoes boiled for 5 minutes are still very hard.
Scepticism is required when reading everything.

blogfast25 - 9-12-2013 at 05:01

Quote: Originally posted by ScienceSquirrel  
I have done several crystallisations using the Wikipedia solubility table data and found that they worked OK.


I've noticed that occasionally the values in the table and the values in the compound entries are very different, indicating multiple editors consulting different sources. But that happens outside of Wikipedia too.

[Edited on 9-12-2013 by blogfast25]

learningChem - 9-12-2013 at 18:24

Quote:
Wikipedia is an encyclopedia. And this is nothing but a collection of quotations verified by references (at least it should be so).



I wonder where you got that idea?

http://www.merriam-webster.com/dictionary/encyclopedia

" a work that contains information on all branches of knowledge or treats comprehensively a particular branch of knowledge usually in articles arranged alphabetically often by subject "

"Medieval Latin encyclopaedia course of general education, from Greek enkyklios + paideia education"



[Edited on 10-12-2013 by learningChem]

bfesser - 10-12-2013 at 06:11

Why not let <a href="http://en.wikipedia.org/wiki/Wikipedia" target="_blank">Wikipedia</a> <img src="../scipics/_wiki.png" /> tell you what it is?

learningChem - 11-12-2013 at 12:35

I don't care what 'wkipedia' says about 'wikipedia'. I'm commenting on what an encyclopedia is.

blogfast25 - 11-12-2013 at 12:42

Quote: Originally posted by learningChem  
I don't care what 'wkipedia' says about 'wikipedia'. I'm commenting on what an encyclopedia is.



Yawn.

Wikipedia is an encyclopedia, really not too different from most others. The fact that you don't seem to like it much doesn't change that fact.

bfesser - 11-12-2013 at 13:35

<strong>learningChem</strong>, close-mindedness is certainly not a good trait for a scientist, and is quite unbecoming of a science hobbyist. (Besides, I wasn't particularly meaning to address your reply, but the topic as a whole.) Lighten up; you'll live longer, and you might just learn something along the way.

learningChem - 14-12-2013 at 15:37

I'm pointing out that an encyclopedia is not a collection of 'sourced quotes' - encyclopedias can have and do have original content. I'm not sure how pointing this (admitedly off-topic) fact shows that I'm close minded.

But thanks for the friendly advice anyway.

smaerd - 15-12-2013 at 08:34

Wikipedia does use web-sites for references. Those tend to be the more scrupulous things. As much as I trust my fellow scientists doing work at home it would only seem fair that any data gathered and shared on wikipedia were cataloged and referenced in the form of a prepublication or similar. So a reader can see the method, any criticism from fellows, and maybe even join SciMad to ask further questions or share their results. In that clause I feel that adding amateur experimental data to wikipedia would actually be far more informative then a published article. So much is left out in papers and publications that isn't on message boards. In a lot of ways I feel amateur experimentalism is science at it's purest when done correctly.

Things such as solubility data are not as known as I wish they were, especially for solvents outside of water. Color isn't something I'm terribly fond of for many reasons (isomorphs, hydrates, contamination, poor characterization). Density, sure but be mindful of significant figures. Solubility is fine, most people only need a ball-park anyways (except maybe physical chemists...), so long as the experiment is conducted properly. pKa's why not, just include information about the resolution with replication. Melting-point range can't really go too wrong there... Pictures, who doesn't love a good picture :D?

I like the idea, I've tried adding things to wikipedia articles before but my submissions were rejected because I couldn't figure out how they did their referencing... There are thousands of compounds that are rich in literature which don't have wiki pages. I find it a bit annoying because wikipedia can be a cursory launch point for research.

[Edited on 15-12-2013 by smaerd]

Bezaleel - 16-12-2013 at 05:20

Quote: Originally posted by smaerd  
Wikipedia does use web-sites for references. Those tend to be the more scrupulous things. As much as I trust my fellow scientists doing work at home it would only seem fair that any data gathered and shared on wikipedia were cataloged and referenced in the form of a prepublication or similar. So a reader can see the method, any criticism from fellows, and maybe even join SciMad to ask further questions or share their results. In that clause I feel that adding amateur experimental data to wikipedia would actually be far more informative then a published article. So much is left out in papers and publications that isn't on message boards. In a lot of ways I feel amateur experimentalism is science at it's purest when done correctly.

I feel very similar. I've had many thoughts on how practical data for home experimentors would need to be compiled, but I haven't found an answer yet.

On solubility data
Take the solubility data from wiki as an example. When I added the values from Gmelin for praseodymium sulphate, the first thing I was confronted with was that I had two lists: one for the anhydrous substance, and some for hydrated species. I decided to focus only on the hydrated species, and only on that hydrate which you obtain after crystallisation from solution under standard conditions.

Next are the values. The CRC handbook, for example, lists the solubilities as grams of the zero-hydrate per 100 grams of water, also for the hydrated species. That's the first reason I decided to explicitly add the crystal water as part of the formula for my entry.

Secondly, some water-free compounds have a lower solubility than the hydrated salt (per gram of water free substance, soluble in 100g of water), or the other way around. I then realised that this is one big reason for differences and potential misunderstanding of solubility data.

My conlcusion was that wiki's solubility table had simply not been set up with all these complications in mind. And for that reason, the data contained in it should be used with caution.
Quote: Originally posted by smaerd  
Things such as solubility data are not as known as I wish they were, especially for solvents outside of water. Color isn't something I'm terribly fond of for many reasons (isomorphs, hydrates, contamination, poor characterization). Density, sure but be mindful of significant figures. Solubility is fine, most people only need a ball-park anyways (except maybe physical chemists...), so long as the experiment is conducted properly. pKa's why not, just include information about the resolution with replication. Melting-point range can't really go too wrong there... Pictures, who doesn't love a good picture :D?
[Edited on 15-12-2013 by smaerd]


Agreed, especially the first point you mention here. And I often have great difficulty finding these data. Even big works like my favorite Gmelin are incomplete. For example, I couldn't find any solubility data on [Ni(en)3]OH2 in it, whereas I can hardly believe it hasn't been researched.

In short, I'd very much like to have data pages composed by a mixture of literature data and amateur scientists' results.

Besides, a good initiative started a few months back, was bfesser's creation of the topical compendium. This gives at the very least an overview of what experimenting has been done and posted here on the forum, categorised per compound.

blogfast25 - 16-12-2013 at 06:19

Quote: Originally posted by Bezaleel  
My conlcusion was that wiki's solubility table had simply not been set up with all these complications in mind. And for that reason, the data contained in it should be used with caution.



The 'complications' exist largely in your mind only. Solubility should always be expressed as the anhydrous salt: in solution what matters only is the mole fraction of salt and the mole fraction of water because you can't distinguish between the solute and the solvent, it's one phase. And if you actually want to use solubility data for practical purposes it's mole fractions that matter to calculate crystallisation yields and such like (although it can be done on a mass basis also).

Using the hydrate as a basis really complicates matters needlessly. For starters: which hydrate? Look at sodium carbonate e.g.: a whole raft of different hydrates.

I think you don't understand very well how two phase systems like these work and shouldn't be let near any published solubility table.

[Edited on 16-12-2013 by blogfast25]

woelen - 16-12-2013 at 07:16

I agree that using hydrated salts needs precise specification of which hydrate, but I do not agree that every thing needs to be renormalized to anhydrous form. Sometimes the anhydrous form does not even exist or it is completely insoluble, because of the totally different structure. An example is anhydrous VOSO4. This compound is totally insoluble and does not react with water, not even with water which contains a lot of strong acid. Anhydrous VOSO4 is some grey inert polymeric and covalent compound, while VOSO4.5H2O is a blue salt and easily dissolves in water.

blogfast25 - 16-12-2013 at 07:29

Quote: Originally posted by woelen  
Sometimes the anhydrous form does not even exist or it is completely insoluble, because of the totally different structure.


Whether the anhydrous form actually exists or is stable is irrelevant here. Many of these compounds don't have stable anhydrates. For solubility/crystallisation calculations that has no consequences.

Nor is this a 'renormalisation' in any sense of the word.

The two phase/temperature system is what it is: it dictates which hydrate is in equilibrium with which saturated solution of which mole fractions of solute and solvent.

In some instances listing solubility of a specific hydrate can be useful, if temperature is specified.

Re. stability, lots of hydrates aren't very stable either: cases of efflorescence or deliquiesence galore!

[Edited on 16-12-2013 by blogfast25]

Bezaleel - 16-12-2013 at 08:23

Quote: Originally posted by blogfast25  
Using the hydrate as a basis really complicates matters needlessly.

Tell Gmelin whose data and notation I quoted without modification.
Quote: Originally posted by blogfast25  
I think you don't understand very well how two phase systems like these work and shouldn't be let near any published solubility table.
[Edited on 16-12-2013 by blogfast25]

Maybe you care to explain how you inferred that?

Edit:
Quote: Originally posted by blogfast25  
Re. stability, lots of hydrates aren't very stable either: cases of efflorescence or deliquiesence galore!
[Edited on 16-12-2013 by blogfast25]

Right.

And in addition, there are compounds that seem to reach an equilibrium hydrate with their environment or crystallise in a (seemingly) non-stoichiometrical hydrate. Cobalt sulphate, to mention an example.

Getting back on topic, this is why I think the home experimentalist's observations are valuable. What do we, amateur experimenters, find in practise? (I seem to remember something close to a 6.5 hydrate on two dehydration experiments I did for cobalt sulphate.)

[Edited on 16-12-2013 by Bezaleel]

blogfast25 - 16-12-2013 at 13:49

Quote: Originally posted by Bezaleel  
Getting back on topic, this is why I think the home experimentalist's observations are valuable. What do we, amateur experimenters, find in practise? (I seem to remember something close to a 6.5 hydrate on two dehydration experiments I did for cobalt sulphate.)


The home experimentalist's observations have very little value for a project like Wikipedia, if the science isn't peer reviewed. It's a recipe for disaster to count on every Dick, Tom and Harry to provide unchecked data for any public data project.

Your '6.5 hydrate' for CoSO4 is a case in point. What was the methodology used? How and what did you measure and with what precision? What about repeatability? And so on. Most home experimentalists wouldn't have the answers to those questions (others wouldn't understand them), making their claims about this hydrate or that hydrate extremely doubtful and of little scientific value.

I love also that qualifier 'in practice', as if we're somehow capable of sorting the wheat from the chaff by our 'practice'. In some cases that may even be true but for most of us it simply isn't so...

[Edited on 16-12-2013 by blogfast25]

[Edited on 16-12-2013 by blogfast25]