A Lousy Paper

Quote: Originally posted by Praxichys

What the heck is with the MP of Co(sal)3? It is listed as "13-215."

This is why its not always a good idea for noob like me TUTFSE! How would I know it was shite?
thats why I ask basic stuff .
Well done for taking time to email them though.

Quote: Originally posted by The Volatile Chemist

Really, DA? Post the conversation so far, I'm curious!

Quote: Originally posted by phlogiston

He is probably just excited that someone read his paper and took up an interest in it, even if it is for a different reason than a shared interest in the scientific content. Good scientist tend to take criticism pretty well, its part of the job (as is criticizing other scientists research/finding the weak spots).

I wouldnt make a good scientist then, I hate criticism!
I have seen your you tube channel Draconic Acid, it made me feel so very much better knowing that at my age you had similar disasters that I do lol.

Nitric acid and sodium bicarb in too small a vessel and too large a quantity WOOSH, also had some copper in, so a lovely blue fountain , I am still cleaning it all up!
Ruined the power supply as acid got in and the copper traces in parts are no more. I also had a run in with what I though was fuming nitric acid and turned out to be something else far more dangerous lol

Quote: Originally posted by Little_Ghost_again

I have seen your you tube channel Draconic Acid, it made me feel so very much better knowing that at my age you had similar disasters that I do lol.

Quote: Originally posted by Little_Ghost_again

Might be your website then, you do have a web site? Yeah I am sure so dont try and hide it lol

Quote: Originally posted by Little_Ghost_again

I also had a run in with what I though was fuming nitric acid and turned out to be something else far more dangerous lol

Quote: Originally posted by Cheddite Cheese

What was it: anhydrous perchloric acid?

i think most probably he ended up collecting nitrogen dioxide(in the liquid state) in the condensing flask
if you use a very strong acid along with a nitrate salt ,that's what happens

[Edited on 21-10-2014 by CuReUS]

Quote: Originally posted by The Volatile Chemist

That's too bad. When was the paper written?

Yep, that's definitely a peer reviewed journal I would consider it a mark against me if I had a paper in a journal like that.

We have discovered that bacteria are inhibited by shitloads of copper!

I read the text before the paper, saw "complexes" and went "Oh NO". It's an extremely common mistake for scientists, especially biologists (note: I'm a microbiologist/geneticist myself, so this is not me throwing shade at another department), who are unfamiliar with the intricacies of the field. If you look into making metal complexes, you'll find some good procedures amongst a heap of "the equation balances so it works! ".

My favourites are the ones who react metal sulphates with a very weak acid, most commonly an amino acid like glycine, and then claim they got the chelate of the weak acid plus sulphuric acid as the side-product. Example below:



(another error - they refer to tryptophan (Trp) in their first para, but in their second para they refer to tyrosine (Tyr), a different amino acid)

This is frustratingly common in horticultural/agricultural research. I recall a paper which attempted to synthesise ferrous "amino acid chelates" by directly reacting FeSO₄ with either glycine, arginine, or histidine. The problem is that the amino groups in all three amino acids would be protonated at pH<9, so they actually obtained adducts where Gly/Arg complexes the iron through monodentate coordination of the carboxylate group to the metal (complex II in the below).


Source: https://doi.org/10.1021/jp054119b

(Histidine is slightly different as it can coordinate to metals through the imidazole ring, and hence can form bidentate chelates even as a neutral zwitterion. However, it would still be an adduct instead of a chelate e.g. ferrous bis-histidinate.)

Stuff like this matters because the adducts are significantly weaker complexes; glycine, for example, has a complex stability constant of K=10^1.09 for its ML complex with calcium but a complex stability constant of just K=10^0.3 under the same temperature + ionic conditions for its protonated M(HL) complex (stability constant calculated as [MHL]/[M][HL]). With iron(III), the same constants are K=10^9.25 for the fully-deprotonated ML, versus K=10^3.7 for M(HL). If anyone's interested in the stability constants of various complexes, someone has made a database explorer for the old NIST stability constant database which has unfortunately been discontinued - this is where I got the above figures.

This even shows up in biological assays; as an example, one study found that ferrous glycine sulphate (the adduct) has a significantly higher rate of adverse events than ferrous bisglycinate (chelate).

Ever since "chelation" became the trendy thing to do to mineral nutrients to make them more available, there's been a whole range of papers by people employing methods which don't stand up to scrutiny to make their "chelates". I should add that I have attempted to and failed to replicate many such methods, because many of them are simple enough that if they did work, they would make metal complex synthesis so much easier.

As an example, this paper claims to have synthesised histidine complexes (with no chloride) by directly reacting the metal chloride with histidine in an aqueous methanol solution. This would be such an easy synthesis method if it worked! Unfortunately, histidine has low solubility in water, and L-histidine has essentially no solubility in methanol (plus, methanol is actually the worst solvent for the stereoisomer D-histidine), so I have no idea if the histidine would even dissolve into the solution. Plus, there's the classic issue of "where does the anion (chloride, in this case) go? The conjugate acid of the anion is too strong...".

Nevertheless, I decided to try and replicate the procedure using manganese chloride, and even after 4 hours of reflux, the primary precipitate was undissolved L-histidine (the L-His I used came in needle-shaped crystals, so I was able to identify its presence in the precipitate). I gave up after about the 5th hour and left the manganese chloride/L-histidine/methanol/water mixture in a tube on a shaker for about a month. When I came back, there was a little bit of light brown precipitate, but most of the L-His crystals remained undissolved, at which point I gave up and tossed the entire tube out.

The procedure didn't make sense theoretically, I spent a little L-His to give it a fair shot anyway, and it didn't work despite me giving it reasonably favourable conditions for success. In my experience, that's how all of these have gone.