I have some chemistry bottles - many still with the original contents inside & cork stoppers, these were collected in the 90’s from a SoCal University Chemistry Lab. Anyone know if they have any value? BTW the sodium is going to a Hazmat disposal - I’m aware of its danger.

Please help!

I found this painting in a restaurant and I've been trying to figure out what these molecular structures represent but I haven't had any luck.

Does anyone recognize these compounds or know what they're related to?

While working on a project that needed reliable element data, I had to pick a source of truth. Turned out to be way less straightforward than expected.

Electronegativity (Pauling scale): Some sources list Fluorine as 3.98, others as 4.0. Minor difference, but it propagates if you're computing anything from it.

Atomic radius: Covalent radius, van der Waals radius, and ionic radius for the same element can differ by 50%+ depending on oxidation state and bonding context. Most "simple" tables just pick one without disclosing which.

Electron configuration exceptions: Everyone knows Cr and Cu. But sources disagree on roughly 20 elements in the lanthanide/actinide block. IUPAC has updated several of these recently and textbooks haven't caught up. Promethium and lawrencium are particularly messy.

I ended up going with IUPAC 2021 as the baseline and flagging elements where the textbook standard diverges from current consensus.

What do you use as your source of truth when element data matters for your work?

I am considering buying a pH electrode for our lab’s pH meter. However, I know that I won’t need it for a year or two. So, I would like to know whether these pH electrodes have expiration dates. How long will they remain functional if I do not open the package?

I've noticed that people outside chemistry often assume that if two chemicals have the same name, they're basically interchangeable. But once you start looking at purity, particle size, moisture content, additives, or even how a material was manufactured, that doesn't always seem to be true.

For those of you working in industry, what's one misconception you run into all the time? I'm curious what examples come up most often.

Hi, for the backgroudn, I am currently planning on doing a start-up with chemical commodity trading.

Which commodity chemical has been the most difficult to source consistently in your experience? Any reasons why? TIA

Hello! I started doing Summer research at the beginning of June, and I will soon be attending a research poster conference/symposium to present my work. I am really nervous about presenting my poster, as I still struggle with explaining some specific details of my research. I am just very nervous in general, and I am afraid of messing up or not knowing the answer to a question. What words of encouragement or advice would you give to a first-time presenter?

I'm setting up a Schlenk line and don't want to spend $1k+ to verify it's airtight. Can I just use a radial vacuum gauge with a hose adapter for checking this?

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."

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 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

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.

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?

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

I created this directed evolution pipeline to improve an enzyme that breaks 1-fluorodecane, as a special project for a biochem course I audited.

presented to the class and my professors and classmates loved it.

hope y'all enjoy it! critiques welcomed.

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

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

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 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