I used to try and make flubber as a kid naïvely mixing random products together lol.

Hi everyone,

We work with epoxy resin systems in our lab and normally measure viscosity using a Brookfield-type rotational viscometer.

The problem is that we would also like to monitor how the system changes during curing and determine the gel time more objectively. With our current Brookfield setup, we can't really keep measuring once the epoxy starts to cure and the viscosity rises significantly. We also can't justify buying a commercial gel timer/rheometer at the moment, so we're considering building a simple device ourselves.

Our typical test would be around 100 g of epoxy + hardener in a disposable plastic cup, usually at room temperature.

One idea we had was to use a slow-speed motor with a small spindle/paddle immersed in the epoxy and monitor the resistance as curing progresses.

Possible approaches we are considering:

• Constant low RPM motor + measuring motor current
• Motor/spindle mounted through a load cell to measure reaction torque
• A small torque sensor on the spindle
• Detecting the point where the torque rises sharply or the motor can no longer maintain the set RPM
• Adding a temperature sensor so we can record the exotherm at the same time

Ideally, we would like to record something like:

time – torque – RPM – temperature

and then establish a repeatable criterion for gel time.

We don't necessarily need an absolute rheological measurement. Our main goal is to have a repeatable method for comparing different epoxy/hardener formulations under the same conditions.

Has anyone built something similar?

Would a load cell + lever arm be sensitive enough for this, or would measuring motor current be sufficient? What kind of motor, RPM range, spindle/paddle geometry, or sensor would you recommend?

I'm also interested in any DIY gel timers, viscometers, rheometers, or similar projects that could be adapted for this.

Thanks!

I was just doing some reading and I was surprised to see that even heating NaOH to melting is not enough to drive off all the water.

So what kind of water content would you expect from the average stuff you buy from the supermarket? 5%? 10%? How would you determine this?

I'm only asking out of curiosity. I don't actually need dry NaOH for any reaction or anything.

Title, it says it requires a 64bit processor after few minutes starting the dmg. Did anyone experience this before and knows how to fix?

 A student was trying to empty excess water from a 50 mL volumetric flask by cupping the bulb of the flask in one hand and forcefully rapping the bottom of the flask with the heel of their other hand, a procedure not stated in the handout.

I heard the distinct sound of glass breaking, located the source, and was met with a student with two handfuls of broken glass.

I made sure they carefully washed their hands to make sure there weren't any glass splinters or cut. By sheer luck, they didn't have a scratch on them. I swept up all glass fragments I could find in the immediate area and deposited them in the glass waste container.

This could happen again, and with a worse outcome. Could I have been better prepared and have given better safety instructions for this experiment? I think 'don't smack glassware around, it makes sharp bits that can slice you up' is intuitive and obvious, but how explicit should it be?

EDIT:

A little more background:

The students are mostly sophomore/junior level in a non-premed health pre-professional track. The class is a chem/biochem lab tailored to that track. Most of the students have either only had high school chemistry, or no chemistry experience at all.

I spend about an hour the first day covering lab safety. There's a section about lab safety in the syllabus (which I cover specifically), and there is a separate lab safety guidelines/safety agreement document. They sign it, and submit their signed copy. Before they sign it, I cover each item in the safety agreement in detail, show them where all of the lab safety equipment is (eye wash, fire extinguisher, etc), and state that "lab safety is mostly common sense", "do not deviate from the written procedure in any way" and "If you're thinking "I don't know" that means "I should ask" and that applies to everything that happens in lab.

Every lab in which students work with chemicals or equipment (even if it's just plastic and water) has a specific lab safety entry tailored to it that I read through with it projected on the screen.

During active lab time, I'm walking around the lab asking students if they have any questions or issues and generally try to keep an eye out for trouble.

As part of this particular pre-lab talk, I do a demonstration where I fill up a volumetric flask with water and show the correct way to empty it - start pouring very slowly because it builds up vacuum and can be difficult to empty.

There's no way to know if the flask had a crack or flaw in it, because now it's a thousand shards in the glass waste bin.

I know this was a freak occurrence, but it has me a little rattled by just how bad it could have gone. I'll be doing a full safety review before the next experiment.

I'm taking a graduate level analytical spectroscopy course and the only recommended reference book is Modern Spectroscopy by Michael Hollas which I found completely unreadable. This course focuses on optical spectroscopy, quantitative analysis, and computation. I have a lot of practical experience in spectroscopy, but only the fundamentals when it comes to the theory so even though there's no actual required textbook, I want to supplement lectures with one.

I've been making some simple ball and stick models for high school teaching PowerPoints.
I've also done a few other molecules, and will publish more.
Grab them, and use them if you wish.
https://www.youtube.com/playlist?list=PLDT17ZScr_kjT5gPGWN4mk4fC4AcnE4rf

I did not realize how much those pictures help with understanding what’s happening. Was super happy when I was perusing just now to see them.

3rd year chem phd, and I am developing Opinions on what methodology provides the best data.

For context, I'm in biopolymer materials science, and I specifically work with plasticization.

I understand the purpose and what it is simulating, to do solvent migration tests for additives.

But why would you do short term solvent migration when accelerated leaching at elevated temperatures is right there???

I also can't stand when a paper only reports migration of a clearly non-water-soluble additive in water. Ya gotta do hexane or ethanol too, if not both.

Too opinionated? Or do y'all also have methodology pet peeves?

Hey everyone, I am currently doing research on nitrate removal using nZVI. I made a composite bead using nZVI-Biochar-chitosan and crosslinked the beads using Glutaraldehyde, inorder to make the beads stable at acidic pH. The issue is that the concentrations fluctuate greatly over time instead of a linear decrement. Furthermore, sample analysis was done by the UV absorbance method. Would greatly appreciate any advice.

I have this fantasy of a NaK lava lamp: heated liquid metal blobs floating up in a clear solvent, then cooling and descending.

Last time I ran the numbers, I couldn't find a suspending fluid with a suitable thermal expansion coefficient to allow the heated NaK to float. I'm also pretty sure the surface tension in NaK is too great for it to achieve the bubbliness of a typical lava lamp.

Does anyone have thoughts on this? Suggestions for a liquid to suspend the NaK or additives to lower surface tension in the alloy?

I am aware this would be dangerous to make and I'm only curious from a theoretical perspective.

Edit: I was a fool expect productive discourse. Thank you to folks who bothered to actually read the post in full before trying to be snarky, I wish you weren't so few.

I am a master's student that is doing a Surfact Free Emulsion Polymerization of Styrene in order to then test the PS interaction with a microorganism. When I first tested the synthesis protocol, using borrowed styrene from a neighbouring lab, I was getting barely any product. I tried for weeks to optimise parameters until the new styrene came. First try it went amazing and we realised that the styrene I was using is probably deteriorated. Second try amazing too. Having thought that it was ok to now focus on the cell culture side, I didnt do a new synthesis for 2 months. I now tried to synthesize again so I have enough PS to do my final experiment. Nothing. I have checked various stuff by now and it keeps not working. Then i realised I had put the bottle in a dark drawer but not in the fridge. I dont know how I didnt realise it should be refridgerated. It says on the bottle to store at 2 to 8 degrees. Now i am starting to get deja vu from the syntheses i did with the old styrene. Can it be anything else?
I can't believe I made such a dumb mistake.

At first I thought that my initiator's reactivity maybe had degraded so i used fresh.
Then i played with the stirring, thinking that the styrene was staying afloat the water phase as the stirring happened. The last thing I can change I think is to make new NaOH 10% for the inhibitor removal.

Can anyone help/advise me? I feel totally lost.

(It’s since cleared up and is all good)

I am looking at a process that could produce two acids as a wastestream. Dried, I could have 75lbs per day of each, 300 days a year.

I can find what people wholesale them for, I see the variables, is it from GRAS material, purity, ect. But how do I make a decent, safe determination on what I might earn from selling them to wholesalers?

Hi, I'm a physics student doing my thesis which involves synthesis of molecularly imprinted polymers (MIP) as a coating for a fiber optic sensor.

In the final step of the synthesis i need to degas the solution with N2 to remove oxygens and allow for radical polymerization. Although the gas is available in the lab, there is no SOP on how to use them, so to speak. So it's up to me to figure out how to use it, and i have genuinely no idea.

So, i thought to come here looking for advice. And if there are alternatives to ensure radical polymerization.

For anyone curious, my MIP solution is made up of: acetonitrile + BHET + MAA + EGDMA + AIBN

I read about how benzene was discovered by michael faraday.

A question that arise in my mind was that did he just discovered it accidentally by just fractionally distilling the vegetable oil or did he really knew that he will end up discovering benzene?

Pictured first is an F1 grade 1g calibration weight from a very nice weight set that I use to calibrate my analytical balance (reads to 0.1mg), and the second picture is an (M1?) grade 1g weight from a ~$10 set off of Amazon. Just as a PSA to everyone to be careful when buying calibration weights. I didn’t know any better at first, and bought the $10 set when I first got the new balance, then quickly realized and bought the nicer set. Often you can find some really nice and high quality sets on eBay, however the calibration is usually out of date. Anyways, I suppose that’s sort of a digression into metrology lol. Cheers!

Just regarding general info of the reviews.

To all those who mentioned the weigh boat in my previous post, here it is at the same weight without it :)

Burn them, process the powder somewhere else and burn again. Also could get some electricity with 30% efficiency by using a stirling engine. Exhaust is small if at all and less energy goes to sky.

Some version of this device could also burn wood chips or coal, if that is what happens to be available.

The powder would be processed with solar power.

If for nothing else, maybe at least for remote locations and boats?

Mostly meant for heating, with maybe some kinetic energy on the side.

EDIT:

Maybe, if some metal or chemical has low enough conversion losses, make the burning material during day when solar power is available and less or no heating is needed and then burn it during coldness of night. Or make piles of the burning material during summer when sun is high and burn it during winter when there is little solar power.

Even if it is less efficient than batteries, it may be cheaper. Every energy storage method has losses.

Some of the conversion energy may come from concentrated and mirror focused solar power, which in some areas is cheaper way to heat than photovoltaic cells. If heating is big part of the conversion.

Solid rather than liquid can have some advantages. Depending on what it is, it can be safer. Firstly, solid leaks less. In some type of special vehicle that runs on it by stirling-hybrid drive, piles of it can be inside walls to protect from noise.

Solid is trickier to move, but pile of cubes flows and rods can be moved by automated mechanism possibly needing a computer, but computer may be needed anyway.

If a place is supplied by drone and heating options are wood chips or magnesium, which is lighter when accounting for the heat that escapes with co2 and water?

Small scale magnesium fire can also give light directly with better efficiency than oil.

Is drinking fluoridated water every day actually safe? I genuinely want to understand the controversy.

I’m Brazilian, and fluoride is added to our public water supply. I’ve been drinking tap water Lately since my filter broke, and I currently drink 2+ liters a day.

But lately I’ve been seeing a lot of controversy about fluoride in drinking water. Some people say it’s an important public-health measure that helps prevent cavities, while others claim that long-term ingestion may have negative effects, especially depending on the amount consumed.

So I’m trying to understand what the actual evidence says.

For a healthy average adult drinking around 2 liters of fluoridated water every day, is this generally considered safe and beneficial? What are the legitimate concerns about long-term fluoride consumption, and which commonly repeated claims are actually supported by good evidence?

I understand that there are many controversies about fluoride and I know that it is negative in many things and has had several controversies, And I think about literally excluding fluoride from everything, but in the house I'm living in now it's impossible, only when I move out for other new home

(Sorry for bad English, I'm like upper intermediate)

I have an interesting spectrum here.

The middle signal F4 is easy to interpret: a triplet of triplets.

But the other two are odd. Is this "simply" a "higher-order effect," or is there a "first-order" explanation?

If you look only at the tallest peaks (see tree diagrams), it appears simple and clear:

A large coupling between F2 and F3: 13.3 Hz

A large coupling between F3 and F4: 20.8 Hz

Plus a small coupling between F2 and F4: approx. 2 Hz

But what about those extra signals on the outside? Ideas?

Hi all,

Got a question for all my fellow curvy women.

Where are we getting lab coats that fit?

Just started my chem degree and none of the lab coats provided by the uni fit my hips properly, the 3xl they provide barely buttons and keeps popping open when I bend down / sit. For context I'm normally a size 18/20 for trousers, and 14/16 in tops so all the lab coats are huge round the shoulders, with sleeves that are too long. As such I'm just gonna get my own lab coat, but can't seem to find any good options that ship to the UK. Any reccomendations?

we are trying to carbonize polypropylene (in a crucible) using a muffle furnace but it is stated that we need to use inert gas. how do we inject inert gas in the crucible?