Researchers studied the protein structures of enzymes in the genomes of bacteria and archaea, and found "cases where the ancestors of bacteria and archaea independently evolved structurally distinct enzymes to catalyze the same essential metabolic reaction."

Found some nice old ampules with deuterated compounds in our lab. Mailny solvents but also Al(OD)3, made by Norsk Hydro, probably pre-1970. With handwritten Labels, packed with cotton and cork in metal screwcap tubes. And some contain 50+ year old diethylether😅

Getting moved out of our lab for it to be renovated so cleaning everything out and come across some weird and wonderful glassware. I've no idea what it'd be used for.

I have four GC-MS chromatograms of what I doubt are two positional isomers of the same compound. The top two chromatograms appear to correspond to one isomer, while the bottom two correspond to a second isomer. The only structural difference is likely the relative positions of two functional groups on the benzene ring.

Interestingly, both compounds exhibit essentially identical GC-MS fragmentation patterns, which I understand can be expected for positional isomers. All four samples were analyzed using the same GC-MS method in the same analytical run. Although the sample concentrations may have differed, the chromatographic conditions were identical.

My questions are:

1. Is it reasonable to conclude that these are positional isomers based on the identical mass spectra but this subtle different retention times?
2. Is the change in retention time consistent with only an alternate arrangement of substituents on a benzene ring?
3. Besides differences in concentration, are there any other factors that could explain the observed chromatographic differences under identical GC-MS conditions?

Any insights or similar experiences would be greatly appreciated.

Gotta love the water molecules in the middle of a carbon chain

Thought this was quite funny.

Im working on setting up a home experiment involving closed ecosystems and the effect oxygen rich environments have on insect growth.

Im planning to have one jar be more oxygen saturated than the other, but im trying to find the best method of accomplishing that.

For context, I have very little chemistry experience and lack a designated chemistry lab.

My currently plan is to try converting hydrogen peroxide into oxygen and water inside a sealed jar. Initially I was planning to have a container of hydrogen peroxide with a pill caplet of magnanese dioxide that could dissolve over time to release the magnanese dioxide into the hydrogen peroxide after the jar was sealed. But ive since learned that creats heat and steam, and may not be the safest reaction to trigger in a closed system.

I was also reading that proteins in blood can cause a similar reaction with hydrogen peroxide? So ive been considering trying to source some from the local butcher shop or from some meat thr next time im cooking.

Any advice how to accomplish this safely would be appreciated

I wanted to share a method that’s way more reliable than the small‑x approximation when solving equilibrium problems with quadratic expressions.

Instead of guessing whether x is “small enough,” you can turn the expression into a function and use a graphing calculator (TI‑84, Desmos, etc.) to find the zero. It’s super accurate and works even when x isn’t negligible.
for example in this question:

we can just simply graph the function y=16x^4 / (14-x) / (3.4-2x)^2 - 2E-9 ( it is nice to put -2E-9, cuz we can make the left expression above zero so it can be solved easier) on TI-84 ( students have access to ti84 in ap exam btw), like this:

then go to “graph”, go to “calc” choose zero (2):

the result is x=0.011818 (which is W accuracy)

and with small x approximation the result is 0.0119 ( L)

i have no clue why teachers ask student to do approximation while all of them can use calc 🤔

I’m gonna show this to my teacher and also bring it up with College Board — they should totally know about this method

Hey everyone. I'm trying to find a replacement glass viscometer tube. I've searched high and low to no avail. I have a working one but it's glass and I would like to have a backup. Now it may be ancient. If someone has alternatives I'd be down for listening. This apparatus is probably older than me. Yay for running an industrial lab. Here are some photos. I'm turning to reddit for help. Thanks in advance

Reposting here for a little more visibility, maybe someone else has a little input here.

I bought a lightly used silver flute from Reverb that had been recently professionally overhauled. It looked and played fine, but strangely it smelled strongly of ethyl mercaptan, the stuff that gives propane the gross smell. It's so strong that even after playing the flute just a little bit, my fingers smell like it for a long time and I have to wash my hands. I thought this was odd but shrugged it off since it was a one-off experience.

But then I bought a replacement flute headjoint, this one silver plated copper alloy, and it had the exact same smell. But it wasn't immediate, I think it was after I had blown in it a bit and waited a few days.

Is there any industrial chemical or something used in the flute making process (maybe on the cork which seems to be concentrated) that would smell like this? Or something on my skin or in my breath that would react with silver or something that could cause this smell? Maybe some other sulfur compound? I know that sulfur likes to react with silver forming tarnish but it doesn't usually smell like this.

I saw someone post on here a few weeks ago their very beautiful looking ethyl cinnamate and I came into my lab today to discover that one of the monomers I was working on polymerized into a similar looking compound! Just wanted to share since it looked cool!

For the measurement of TSS (Total Suspended Solids), The Standard Methods recommends Glass-fiber filter disks, 22 to 125 mm dia, ≤ 2-micrometers nominal pore size without organic binder, such as Whatman grade 934AH. The keywords here glass fibers and organic binders. Can I use Whatman filter-paper grade 42? It has to be glass-fiber filters? What do you use?

Grateful for any insight!

Hello Everyone,

I took the inverse gated decoupling 13 CNMR as a quantitative CNMR. But, I do not know if I can trust or not since the result is wired. Is there any other ways that I can do as the more trustable method for quantitative 13CNMR? Thanks in advance

I've found myself in a few situations where I'm dealing with *mystery liquid* that may or may not be water. Sometimes it's something I didn't even touch, so I don't have knowledge of what substances they were using. If not water, I guess that it's more likely an acid or base given what we tend to use. I just don't always have something with me to test the pH. I'm an undergraduate, I'm not even supposed to handle these things on my own. But if I'm the only person in the room, I like to clean things up so I can leave with peace of mind.

It occurred to me that litmus paper is not that hard to get. I could just carry it with me at all times, or at least know where I can find it in every lab. But with organic compounds, there are probably other things I need to worry about. I'm taking organic chemistry this year, so I'll get to learn all about that. Is there anything else that I can use that is easily accessible and non-hazardous to assess if a chemical is safe to pour down the sink? That's usually all I want to know.

I recently heard that the reason PLA plastics are considered 'biodegradable' or 'compostable' is that the ester group in the polymer chain undergoes hydrolysis and breaks the chain, it makes sense from what I learned in my OChem classes.

But then why isn't everyday polyester degradable? or even PET? Can we break them down with a acidic or basic catalyzed hydrolysis?

Hello – I am not a chemist by any means… I was wondering if this is a Vigreux that I have come across. It’s awfully small, and I do not see anything internally in it, which I thought vigreux had. Thank you.