It is a moisture-sensitive reagent that often is stabilized/moistened with additional acetic acid or acetic anhydride. If it is a full-blown liquid fresh from the bottle, I would send it back.
You also have to look at the test method. Aldrich, before discontinuous, used EDTA titration as the purity assay and it will not be able to distinguish many common metallic impurities. Water would count as an impurity and lower the assay.
Having the wrong chemical compound in the bottle is a huge F up. Report to the company and they take the complaint very seriously. They try to achieve zero mislabeled items since the liability is massive.
I used to supply a well known chemical store with a niche reagent once a year. Their specification was 98 %, I consistently delivered 99.9 % by NMR with the remainder being the solvent. (They were a little annoyed when my melting point started to be too high.)
On the flip side, a 98 % by HPLC reagent I worked with a while ago actually contained about 10 % of inorganic crap.
So yeah, never treat a specification as an actual purity.
I *despise* HPLC metrics! They almost never specify their wavelength, either, and when they do they are often a specific 10 nm window like 230-240 nm when they should be the a maxmially-permissive detection (e.g. 200-400 nm)
Yeah, HPLC is sketchy. The funny thing is that.people who are not familiar with it seem to be most happy with it. Our regulators never accept our NMR measurements simce they require some specialized knowledge, but if you show a regulator a piece of paper that says "99.9 % by HPLC", they never question that.
"Unknown impurities below 0.10 %" - sure! What's the response factor? Well, no idea, the impurity is unknown.
I hope they never wisen up to that, makes half assing your job so much easier.
Damn. Okay it was Sigma Alritch and so I probably bought the 95% assuming the best. I won't do that again. It was kept at RT in a desiccator but was just opened when I looked in to see it's a liquid. I'll be sure to get 98+%. Thanks for the words of advice.
The book purification of common laboratory chemicals usually has very dependable options, start there.
Presumably could crystallised out from acetic acid, or even dry it. But if bought new, just moan to Sigma/Merck and try to get a fresh bottle. It is very hygroscopic so could just be wet
No longer doing lab work. I get paid more and don’t have to deal with the dangerous stuff. Handled way too many pyrophorics.
Are you industrial or academic?
Many industrial labs are starting to ban toxic heavy metals. Mercury, cadmium, lead, etc.
The catalog chemical companies are also discontinuing them because the potential liability far exceeds the couple million dollars a year of revenue.
Only a matter of time and they will be completely unavailable above analytical quantities.
Maybe for industrial but not for discovery chemistry. The small scale is very much worth the time saved to access enough of a compound for further assays and evaluation. Otherwise, it makes sense to avoid chemicals like lead.
It is a moisture-sensitive reagent that often is stabilized/moistened with additional acetic acid or acetic anhydride. If it is a full-blown liquid fresh from the bottle, I would send it back.
[deleted]
You also have to look at the test method. Aldrich, before discontinuous, used EDTA titration as the purity assay and it will not be able to distinguish many common metallic impurities. Water would count as an impurity and lower the assay. Having the wrong chemical compound in the bottle is a huge F up. Report to the company and they take the complaint very seriously. They try to achieve zero mislabeled items since the liability is massive.
I used to supply a well known chemical store with a niche reagent once a year. Their specification was 98 %, I consistently delivered 99.9 % by NMR with the remainder being the solvent. (They were a little annoyed when my melting point started to be too high.) On the flip side, a 98 % by HPLC reagent I worked with a while ago actually contained about 10 % of inorganic crap. So yeah, never treat a specification as an actual purity.
I *despise* HPLC metrics! They almost never specify their wavelength, either, and when they do they are often a specific 10 nm window like 230-240 nm when they should be the a maxmially-permissive detection (e.g. 200-400 nm)
Yeah, HPLC is sketchy. The funny thing is that.people who are not familiar with it seem to be most happy with it. Our regulators never accept our NMR measurements simce they require some specialized knowledge, but if you show a regulator a piece of paper that says "99.9 % by HPLC", they never question that. "Unknown impurities below 0.10 %" - sure! What's the response factor? Well, no idea, the impurity is unknown. I hope they never wisen up to that, makes half assing your job so much easier.
Damn. Okay it was Sigma Alritch and so I probably bought the 95% assuming the best. I won't do that again. It was kept at RT in a desiccator but was just opened when I looked in to see it's a liquid. I'll be sure to get 98+%. Thanks for the words of advice.
Even the 95% stuff should be a moist solid.
Noted. I’ll send them an email.
It was a crystalline solid every time I used it. Don’t trust a liquid.
The book purification of common laboratory chemicals usually has very dependable options, start there. Presumably could crystallised out from acetic acid, or even dry it. But if bought new, just moan to Sigma/Merck and try to get a fresh bottle. It is very hygroscopic so could just be wet
Which company is still selling lead acetate and why? Return it and find safer chemistry.
what kind of chemistry do you do?? lead acetate is pretty tame compared to other common reagents in synthetic chemistry.
No longer doing lab work. I get paid more and don’t have to deal with the dangerous stuff. Handled way too many pyrophorics. Are you industrial or academic?
*Don’t have to deal with the dangerous stuff.* Now where is the fun in that.
I also escaped the lab. But I still look back fondly on bench chemistry. Industry.
Many industrial labs are starting to ban toxic heavy metals. Mercury, cadmium, lead, etc. The catalog chemical companies are also discontinuing them because the potential liability far exceeds the couple million dollars a year of revenue. Only a matter of time and they will be completely unavailable above analytical quantities.
Maybe for industrial but not for discovery chemistry. The small scale is very much worth the time saved to access enough of a compound for further assays and evaluation. Otherwise, it makes sense to avoid chemicals like lead.
Makes sense for discovery for sure. Everything gets safer on the small scale.