[Closed] Any chemistry experts in the house?

/me waves...

hey there Saccades, here's what we're having problems with - the interpretation of the modern analysis hinges on the presence of Fe3O4, which was a predominant phase seen in scanning electron microscope. (the material concerned is metallurgical slag)

One of the 1860's analyses lists ferrous oxide (FeO ?) and ferric oxide (Fe2O3 and/or Fe3O4 ?). I'm assuming the historic analyses used classic 'wet' techniques, but I just wasn't sure how accurately they'd have been for identifying & quantifying different oxides of iron.

Do you know how they'd have worked out the amount of various iron oxides?

I'm an organic chemist, so not really up to speed on old timey gravimetric analysis. What they will have done, though, is something along the lines of a chemical test for iron(II), which will be quanitified by a titration reading for example.

They'll then oxidise the whole show to iron (III), and use a different test for that. By difference, they can then know the partitioning between ferrous and ferric.

Gravimetric analysis can be very accurate. Even from metallurgical slag, which will contain all sorts of metals and counterions, there will have been empirical methods for dealing with it.
One problem for the case at hand, though, is keeping the Fe(II) at the right oxidation level during analysis. It oxidises in air - I don't know how good the old timers would have been at controlling this.

Thanks for the info Garry. Hmm...I thought there might be potential for some of these historic analyses to be accurate, but wasn't 100% sure - I hadn't thought about the problem of oxidation levels.

Another fly in the ointment is that I've also noticed that, in the historical table, each column of results (representing samples from different furnaces) were presented by different companies. It looks like a representative from the Institute of Mines & Metals (or similar) collected data from different private companies - which IMO just adds to potentail variables.

We're currently in contact with a couple of museums to see if we can scrounge any archive samples of the material, so that we can do some comparative stuff.

Thanks again for the info.

Ah Gravimetric analysis... how I hated it.

it's hard to answer your question properly (ie you sent samples for modern analysis but are hoping to get old samples that have been analysed to do modern analysis if I've read your posts correctly?). I'm intrigued that a museum would consider metallic slag important enough to keep samples of.

However, if your wanting to hang your hat on a set of results, go for consistancy. A set of results from a modern lab tested at the same time with the same methodology should be precise if not accurate, allowing you to compare like for like. I presume your testing lab uses validated methods.

Taking results from different companies using potentially different methods (sample point, prep and analysis) introduces too many variables. Modern methods of analysis would allow 2% RSD and expect ~0.2% actual RSD, in older wet chem methods (we still use them a lot, even a modern titrator can only do so much though) we get much closer to 8% RSD and that's with heavy training (it's just that a lot of endpoints are subjective.

Go with the new stuff.

I'm intrigued that a museum would consider metallic slag important enough to keep samples of.

You haven't heard the best yet - there is something rather grandly called the 'National Slag Collection' at Ironbridge Gorge Museum (people usually look at me in disbelief when I tell 'em....don't know why 😆 ). Last time I heard, the reality of the Collection is that it's a rather mottly collection of 'historic slags' that were donated by late or retired metallurgists/academics etc. Allegedly, there are quite a few bits of unusual slag relating to metallurgical processes that are no longer used.

The author of the 1860's book was, at the time, a famous engineer/metallurgist and he left a collection of 'stuff', which is in the Science Museum archives - tho' we've just been told it's mainly bits of iron & steel (things like very early alloy steels & wotnot).

I guess it's a very long shot, but if we can turn up any of this old coal-fired reheating furnace slag, we're going to drop it in at one of the local labs with a sample of the stuff that we had the SEM-EDS analysis done on.

P.s. glad I ran the question by, because the fella that I've been working with has been pretty insistant that it's OK to use the old data for direct comparison - and I've been getting a bit concerned.
Thanks for the feedback.

tbh mate your colleague still sounds like he's talking pish. Why would he have any reason to query the SEM data? Agree it would be interesting to run a comparison though - get a wee paper out of it if you fancied it.

Anyhow, thanks for the info on the Ironbridge gorge 'National Slag Collection'. I'm through Ironbridge semi-regularly - I might drop in and see this collection of slags. The museum is in Coalbrookdale is it not?

Yes, it's the museum in Coalbrookdale. Not sure if the collection is open to the public - last time I asked, you had to write/email the curator to get access, my guess is because it lurks in boxes in a dark corner of the site. Just thought, I think there's an on-line catalogue of the collection - I'll send you the link when I can find it.

The fella that I've had to work with on the project is a bit odd, and has a bit of a reputation. I gather he's from an arts (historian) rather than science background, so he's got a different perspective to me. (I've come close to wringing his neck once or twice!)

I didnt know there was such a thing as Fe3O4??

i love the idea of a historical slag museum..... i chuckled lots.

"I gather he's from an arts (historian) rather than science background"

ah, he probably would have preferred something aristotle calculated then....

<Organic Chemist>

I'd assume that given correct stoichiometry the wet chemistry would be reasonably accurate, at best comparable to modern analytical techniques.

</Organic Chemist>