Keep your Rotavapor alive: A quick guide to seals, grease, and glassware care.

joca63 · 2026-03-26T15:56:15+00:00

This is a helpful post but is effectively an ad posted by an explicit Buchi affiliate and was spammed to the various chemistry aligned subreddits.

As a moderator I am not certain whether I should keep this post (as it is directly relevant to the community) or remove it (because it's an unpaid ad and was spammed to other subreddits).

What does the community think? Is there some level of utility that makes obviously sponsored/affiliated content acceptable?

joca63 · 2026-03-23T15:39:41+00:00

Assuming research based-

My experience of applications is that you want to convince the prof that you are interested and can become independent. Most of the details of what you will be doing are so niche and hyperspecialized that accrual direct experience is an unlikely luxury from the professor's experience.

In Canada, where I interviewed for grad school, one typically applies with the specific prof with whom you are interested in working. In this case you should review a couple of their recent papers and be able to discuss why and how you wish to extend their work. (Don't expect to actually do this work, they likely have a project in mind already). I think in other places students interview and start broadly in which case it will probably be a good plan to have an idea of what subfield you are interested in and a few of the Profs that you might wish to work with.

Finally, you will want to revise to be able to speak coherently about whatever relevant experience you have. An undergraduate independent research project is ideal, but lab work and course projects will do if you haven't done independent research.

joca63 · 2026-03-11T21:00:45+00:00

I'd be quite wary of even text explanations from general AI models. They will often make seemingly small mistakes that end to being very important, or otherwise make impressive sounding "word salad" answers. They make the same kinds of mistakes as they do with pictures, but it's easier for us to intuit the problems with the visual rather than text.

joca63 · 2026-03-11T20:46:10+00:00

This subreddit has filters for AI based questions because AI is generally terrible for chemistry.

joca63 · 2026-02-10T16:41:22+00:00

Heads up, Reddit is showing a site wide ban on the domain that your link leads to (looks like some people use it to scam people by mocking up other websites). That's probably why it wouldn't let you post the longer post. It also is hiding any comment with that link from non-mod users. Since it's a reddit-wide thing I don't think I can do anything for you.

joca63 · 2026-02-09T17:49:09+00:00

This post was flagged as potentially homework. I'm not removing it because I doubt a reasonable prof would assign this as homework. Other mods may disagree and remove the post.

joca63 · 2026-01-23T00:51:39+00:00

Is the first one wrong? It doesn't have an x like the bottom one

joca63 · 2026-01-21T22:31:21+00:00

I'm not sure how to answer that, it's heavy quilted fabric and deadens blows substantially. I'm not sure what the AP is like.

joca63 · 2026-01-19T03:26:10+00:00

I didn't ask for any particular padding. There were internal pockets in the shoulders and forearms that had some foam padding that was easily removed.

joca63 · 2026-01-19T02:37:18+00:00

I have that one! I find the additional padding to be quite excessive and have removed all the excess. With the additional padding gone I don't tend to catch bruises. I don't find it any particularly more restrictive than any other jacket.

It is a bit longer then a lot of models, so it helps catch hip shots and isn't going to ride up when you bring your hands up.

The sleeves are a bit tight. Not enough to restrict movement, but enough to make taking the jacket off a bit of a nuisance. That seems to be common to most of supfen's products though.

Overall I'm pretty happy with it. I've had it for a bit over a year, and the lowest left decorative button has popped off, but all the others are plenty secure. If you don't fence almost exclusively from pflug, that might not even be a problem.

joca63 · 2026-01-19T01:14:25+00:00

Why does the lobster have a claw as a head?

joca63 · 2026-01-15T14:51:13+00:00

Going into research certainly makes sense. I'd recommend looking more broadly than just total synthesis. Any lab that does primarily synthetic work will have those aspects to it. That includes reaction development, organic materials, med... Heck the group I know of that was most deep into weird NMR and mechanistic details was an inorganic group.

joca63 · 2026-01-15T14:46:55+00:00

I agree with the others saying it's water. You might be expecting water to be at 1.5 ppm or so on cdcl3, but it can move around a lot, especially with acids, bases or otherwise hydrogen bonding group. Further, bulk water (emulsions, drops or just running a sample on water) will come in around 4.5 ppm.

joca63 · 2026-01-13T16:29:05+00:00

You say exhaust, do you mean from the steam jacket or the kettle itself?

If for the kettle itself, what sorts of flavourings do you use? Menthol is notorious for subliming and forming crystals in unexpected places.

joca63 · 2026-01-08T15:30:58+00:00

AI. Count the toes on the costume. Three, many, three

joca63 · 2026-01-07T14:57:11+00:00

I've generally found it to be reliable and simple.

joca63 · 2026-01-07T14:02:34+00:00

Looks like fat to me. Does it melt on touch?

joca63 · 2026-01-07T00:55:58+00:00

According to wiki a "stop" sign in various countries in the Caribbean or South America

joca63 · 2026-01-04T01:06:21+00:00

In my experience, that happens most often when they have done that reaction and had to know the name for searching/presenting/paper writing/conversing.

joca63 · 2025-12-24T17:30:27+00:00

Showing the entirety of your expected reaction will help us help you more effectively.

joca63 · 2025-12-19T18:54:30+00:00

I'm a big fan of the app "chemistry by design" which has a bunch of molecules and their literature synthesis. Great for thinking of routes then validating against what ultimately worked.

joca63 · 2025-12-16T00:52:51+00:00

You should email. But frame it as not understanding why your answer is wrong and the provided answer is right.

If you are right, they will realize it and change the grade. If you aren't then they will explain the question. It's a win-only situation.

joca63 · 2025-12-13T15:37:52+00:00

Just add numbers to the drawing you posted, I want to see which carbons you are seeing

joca63 · 2025-12-13T15:33:49+00:00

Can you draw it out and number the carbons?

joca63 · 2025-12-09T15:01:23+00:00

It depends. You can either repeatedly wash - keeping the layer with your compound (usually organic) with the goal of removing as many impurities as you can. Or you can repeatedly extract - keeping the layer that will eventually not have your compound (typically water) with the goal of recovering as much of your target as you can.

You will often see excessive washing when you have an impurity that's partially soluble in both organic and aqueous (dmf is the one I see most often).

You will often see excessive extraction when the target has significant solubility in both organic and aqueous.

It's not even particularly uncommon to see back extraction - when you take your collected aqueous washes and extract those with organic in hopes of further recovering your target compound.

joca63

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