Lamy Benitoite-Maybe an Iron Gall Answer

[bunnspecial]

In another thread running now, @InesF through out an idea to me on measuring ink chemistry in reference to another topic that, in experimenting a bit, I think I might have actually hit on another data point to recognize an iron gall ink.

 

Basically, a mention was made in the context of ink pH that a conductivity reading could point to whether or not an ink is buffered to maintain that pH. Inks at relatively low or relatively high pH probably wouldn't benefit from a buffer system as they will tend to be somewhat resistant to a pH change by virtue of their pH in and of itself(that's a really poor explanation, but I hope that it helps the non-chemists, and that the chemists here won't rip me apart )

 

To give a bit of an overview, when ionic compounds(for purposes of this post, a metal in a compound with a non-metal formed by exchange of electrons, and the resulting charged species holding together by the principle of "opposites attract"-again an incomplete explanation) are put in solution, to varying degrees they undergo a process called "dissociation", where essentially the compound separates into its component ions and aligns with water.

 

Ionization also has the effect of making a solution conductive. The more ions present in a solution, the higher its conductivity will be.

 

We can quantitate this to some extent by measuring a parameter called conductivity. Basically we take a two-pole electrode, immerse it in the solution, and measure the resistance of the solution. This resistance is then often reported in a value called siemens, abbreviated capital S. 1S=1/Ω, so a higher value indicates more "stuff" that's ionized to allow a lower resistance for a given distance. Usually the electrode is a fairly precise 1cm, so a typical unit is µS/cm.

 

I did a but of playing and here's what I came up with...

 

We know iron galls to have VERY low pHs. I measured a couple at my immediate disposal and found them to be in the range of 2.12(Montblanc Midnight Blue) to 1.63(Chesterfield Archival Vault, which is claimed to be Diamine Registrars).

 

Conductivity will increase to some degree as pH moves away from 7(in either direction) but I'm not feeling up to calculating what the theoretical conductivity of a strong acid at a given pH would be.

 

With that said, here are some numbers:

 

First of all, Waterman Florida Blue(a bottle actually labeled Florida Blue I bought in ~2012) has a pH of 3.05 and a conductivity of 10,348 µS/cm.

 

The only pigment permanent ink I have on hand(we know that Benitoite is marketed as "Document Proof" or some such language, and pigment is one way to get that) is Montblanc Permanent Blue. It has a pH 6.93 and a conductivity of 932µS/cm. The two super-saturated(but not necessarily permanent) inks I have at work with me are Penman Mocha and Lamy Azurite. Mocha is 4.94 and has a conductivity of 6500µS/cm, and Azurite is 5.32 with a conductivity of 6304 µS/cm. It would be hard to give a universal answer as it would depend on several factors, but I strongly suspect that a heavy dye loading would not generally increase conductivity by itself.

 

Looking at a few other iron galls, though, I'll throw out the "serious business" Diamine Registrars, which we know likely has a whole lot of iron, has a pH of 1.63, and has a conductivity of 31,000µS/cm.

 

To look at a couple more mundane and "normal" ones, though, Montblanc Midnight Blue has a pH of 2.12 and a conductivity of 18,156µS/cm. Pelikan Blue-Black, which is sometimes considered "just barely an iron gall", has a pH of 2.04 and a conductivity of 13,601µS.

 

That brings us to Benitoite, which has a pH of 2.01 and a conductivity of 15,781µS/cm.

 

This is not a definitive answer by any means, and I can think of more definitive ways to test for iron content, but the fact that it bears so many similarities to other iron galls including in measurable parameters, leads me increasingly to think it probably is.

[lapis]

Sounds very interesting. I never thought that that ink (which I use quite often since its issue about a half a year ago) would be an IG ink. Your consideration of measuring its pH and µS values is of course a good idea but I'd prefer to do it in a more old-fashioned (classical) manner by simply spectrophotometrically determining iron (II) with the sodium bromate - crystal violet system in acidic media. But that, too, is IYAM yet another negative effect of me no longer being in my lab all day, every day. Ach, ya. 😒

[bunnspecial]

14 minutes ago, lapis said:

Sounds very interesting. I never thought that that ink (which I use quite often since its issue about a half a year ago) would be an IG ink. Your consideration of measuring its pH and µS values is of course a good idea but I'd prefer to do it in a more old-fashioned (classical) manner by simply spectrophotometrically determining iron (II) with the sodium bromate - crystal violet system in acidic media. But that, too, is IYAM yet another negative effect of me no longer being in my lab all day, every day. Ach, ya. 😒

 

Hmm, I was thinking of doing it electrochemically but spectrophtometry is good as well. I don't have access to a full-spectrum UV-Vis, but can cobble together "close enough" to probably get some idea.

 

Out comes Skoog and Holler again...

[arcfide]

Now this is the kind of content we're all waiting for. Or wait, was it just me? 🙂 Very nice to have some of those numbers! 

[peroride]

2 hours ago, bunnspecial said:

would be hard to give a universal answer as it would depend on several factors

 

Thank you for your insight work; I too enjoy this thread of discoveries with measurement 🤯

 

While I enjoy IG inks marketed as such, there are some more iron gall-y than others, say compare Platinum Classic ink to mentioned Diamine Registrars) Looks like the pattern is low pH to high EC = really iron gallish

 

I follow this YouTuber, An Ink Guy and he discusses properties such as water resistance and viscosity. Knowing pH and EC maybe a game changer to help understand some of these ink properties.

 

I barely passed biochem so bear with my naivete incompetence.😩 I tried holding a magnet next to the bottle to test fer the irons! 🤣

 

Would more EC measurements or even this arbitrary ratio of pH to EC across brands or specific suspect IG inks be helpful toward a benchmark of latent iron gallness identification as was done with Lamy Benitoite?

 

It would be cool to see how other inks fare on a plot of this data.

[LizEF]

2 hours ago, arcfide said:

Now this is the kind of content we're all waiting for. Or wait, was it just me? 🙂 Very nice to have some of those numbers! 

  Nope, not just you.  But I confess, I put off starting this thread until after I'd had a milkshake to fortify me...

 

Thanks for the additional scientificy observations, @bunnspecial!  I'm thoroughly enjoying these explorations into the inky depths.  (If you spot a kraken, please try to get a photo! )

[InesF]

Thank you @bunnspecial for opening a new science thread!

In the World of fountain pens and inks (and papers) are still so many myths around, so many facts in the dark and causalities are estimated instead of measured - my thumbs up for your effort!

 

Yes, your explanation about the iron gall ink properties is convincing. An ink must have a high conductivity if it is a 'true' IG, because of iron sulfate (or acetate) addition to the organic acids and minerals which are deriving extracted from the plant material. Some of the inks are brought to pH around 2 with sodium hydroxide. All those inputs add up.

 

The usual colorimetric or photometric iron detection methods may fail miserably because of the inks own colour and also because of unpredictable reactions with other ink ingredients. A not so quick but reliable method would be to set the pH of an ink sample to above 9.5 (with ammonia!), either let it settle or centrifuge, discard the supernatant and re-solve the precipitate in 1 or 2 M HCl. The iron detection is more reliable from such a solution. While the phenanthroline or the rhodanide reaction are specific (and both are toxic), you may, this is really funny, add an aqueous solution of tannin and watch for the new formation of iron gall!

 

I'm afraid, only a successful specific iron detection will be the final proof. Some organic dyes will need strong acidic environment with salt(s) added to keep them dissociated and in solution. The dyes can be organometallic compounds, containing more or less exotic metals, but may not be iron gall. 

 

Herewith, I book a seat in the front row to follow your measurement work - butty and thermos flask are at hand! 

[khalameet]

Lamy said themselves that Benitoite is an IG-ink somewhere. I think it was on their Instagram page? I don't know the source for sure since I don't use social media.

 

Otherwise, being an electrical engineer, this is a thread to my liking

[inkstainedruth]

Interesting thread.  I have a bottle of Benetoite and I'll have to see if the tests I did the first time I used it have oxidized.

Ruth Morrisson aka inkstainedruth

[arcfide]

I think one of the things I'd love to to see is if we can gain a quantifiable measurement of the amount of IG in any given ink. It would be interesting to see the relative levels of IG ink various inks rather than guessing as we do now. 

[khalameet]

Isn't it possible to let the ink precipitate until all of the iron component solidified?

[lapis]

No, you can't. You could possibly make it precipitate, but it'd be difficult to do so to make only the iron (iron II or ferrous component) precipitate. That is, you're considering "how much IG is in that ink?". Also, otherwise organic parts in the dyes used can be bound and/or precipitated, which could interfere with the quantitative analysis. And then what do you want to do with the precipitate? A better decision would be to lyophilize it (the ink) to concentrate it for better results and then measure the iron (as iron II). Then you could say "now, we see that there is so and so many µg or mg of iron per ml" and so forth.

[bunnspecial]

TBH, the best way in my head to check would be probably to do cyclic voltammetry and look for a peak at the correct reduction potential. You could also quantitate it pretty easily by anodic stripping. I don't have a potentiostat now so can't do that.

 

Ion chromatography or capillary electrophoresis would be options I think too.

[lapis]

13 hours ago, bunnspecial said:

Ion chromatography or capillary electrophoresis would be options I think too.

I was thinking of doing that, too (honestly)... and to be specific, using IMAC (immobilized metal ion affinity chromatography). As a simple example, I once worked out a hand-held operation using a syringe and a chelating column to separate iron in cytochrome c variants in tuna, horse and yeast samples. But then, again, that needed a manual analysis using a spectrophotometer, which I don't have access to anymore. Worse yet, I'd better inform myself first, whether that would work (or not) with an IG ink because I'm not sure if its iron (II) ion presence is equatable to the mode of binding between an iron atom and heme.

 

Whew (II)