Hello! I'm trying to lower the DO saturation of 200 mL's worth of DI water by boiling it for 30 minutes, and then purging it with Argon bubbling. I need to make two solutions: one DI solution with a 1.5% DO saturation, and another anoxic saturation of as close to 0% DO saturation as possible.

A research article (link) recommended 30-40 minutes of N2 bubbling (or Ar, I'm assuming?) at a flow rate of 25 mL/second to purge 1 liter of DI, but this is in a closed system with a sintered gas bubbler.

I've been purging DI in an Erlenmeyer enclosed with a rubber stopper, which is being pierced with a needle for Ar input and another needle for O2 output. Going from 98% DO to 5% DO takes me 30 minutes, but going from 5% to 2% takes several hrs and I'm not sure why...?

I use DO probe to monitor the % saturation of DO, but it requires me to open the stopper and expose the system to air for prolonged periods. (can take anywhere from 1-4 minutes for probe to calibrate). Some oxygen might be getting re-introduced back into the solution. Once 2% DO is reached, it seems like I can't get the saturation any lower, no matter how long I let the Ar bubble.

I am looking for a way to make this purging process faster and more efficient without buying expensive equipment. Any advice would be greatly appreciated. Thank you so much!

Classically delta U=q+w but in combustion (like a campfire) the internal energy change caused by breaking CH bonds is lost as heat and light (which doesn’t do work). How is all of the internal energy change supposedly accounted for by heat and work when some energy leaves the system as light? I’m sure I’m missing something here.

I'm looking to conduct a microscale ester synthesis lab for senior high school chemistry students (16-18 year olds). Following http://www.chemistrylabmanual.com/uploads/2/5/6/1/25614215/experiment_5_synthesis_of_wintergreen_oil.pdf

It's 0.25 salicylic acid with 4 mL of methanol + 8 drops of concentrated sulfuric acid. I am also modifying the procedure as to use ethyl acetate instead of DCM.

I am curious as to what concentration would be safe for high school students to handle.

I have inherited a stock bottle and also a bottle of 1M H2SO4

I am thinking of either diluting the stock H2SO4 to 6M and putting it into eyedropper bottles so they never have to be pouring it in any way.

I feel like the 1 M would be too dilute and they might not be able to isolate any product at all but I'm wary of any accidents.

My gut tells me that it will be fine as we have safety shower and many sinks in the classroom and my students are well behaved and careful but I thought I'd ask!

Hi there!

I’m an artist, not a chemist, and I’ve built a custom-engineered glove box to work with materials I’m allergic to. I had the acrylic box manufactured and custom designed the airflow system myself (I am a mechanical engineer). It’s been working great for about nine months! When I use these materials without the box I sneeze and have all sorts of bad reactions, yet using my box it's been wonderful and well worth having to have a barrier there since I can use whatever materials I want now!

However, I’ve been using polyethylene gloves, which tear too often to be practical, requiring replacements every three hours. Since I can’t find thicker PE gloves that meet my specs, I’m considering upgrading to a drybox glove system. This would let me work uninterrupted, turn the gloves inside out between uses to dry, and wash them periodically (I wear cotton liners inside).

Most drybox gloves are made of Butyl or Butadyl, materials I’m unfamiliar with. My main question is: Are these gloves safe for long-term use? Lab workers typically use them for short periods with very dangerous substances - but my application is much different. I’m curious if extended exposure (hours at a time) poses any risks. Specifically, are they inert for prolonged skin contact and safe to be around for hours (including any potential off-gassing up-close)?

Thanks in advance for any insights!

Was hoping for some salary insights from people in the field. Currently, I work as an environmental chemist for a consulting company (who is contracted by the govt) that performs environmental remediation at a superfund site in NJ. I have been with this company since before graduating college, always with the intent that I would receive my degree and eventually replace the senior chemist I currently am supervised by. I’ve since received my degree 3 years ago and that eventually has arrived, and I am at the point of a performance review to discuss promotions and compensations. If you’ve gotten this far, my question is for those that are in a similar role: how much do you make and how many years of experience do you have? I am trying to find comparable roles with their salaries to base my compensation adjustment. For reference I am looking at requesting 70-80k with 4 years of experience. Thanks!

Does anyone now if there are any other medical gases that smell similarly to isoflurane? My medical facility has a persistent very strong smelling odor of what seems like isoflurane but all anesthetic machines have been triple-checked and no leaks. We do not have a central anesthetic gas supply and it seems super odd that our waste gas system would continue to release an isoflurane smell.

Any ideas on what other odors could be mistaken for isoflurane? Feel free to redirect me to a more appropriate group if needed!

https://preview.redd.it/ph5drotx9i4e1.jpg?width=1280&format=pjpg&auto=webp&s=e0322625baaa9a0d2db5fe0e08fd79bcafd4c7ac

I’m currently working on starting my own company specializing in plasmonic nanoparticles synthesis for biosensing and chemical sensing applications, and I’d love to get my particles into the hands of researchers, developers, or anyone interested in testing them out.

I produce gold-plated silver nanoparticles (or other metals) tuned across the visible spectrum, with sensitivities upwards of 400 nm/RIU for LSPR (Localized Surface Plasmon Resonance) technology. These nanoparticles are ideal for applications in biochemistry, nanotechnology, or sensor prototyping.

Types of Nanoparticles Available:

• Gold-Plated Silver Particles: Optimized for high sensitivity and stability.
• Custom Sizes/Tunings: Let me know if you have specific requirements.

Why I’m Doing This:

I’m passionate about advancing LSPR technology and helping others explore its potential. By offering free samples, I hope to gain exposure, feedback, and connect with like-minded researchers or industry professionals.

How to Get Some:

• Send me an email salmansha8821@outlook.com
• Tell me what you’ll use the nanoparticles for and if you have any specific needs.
• Just cover the shipping cost, and I’ll handle the rest

Let’s collaborate and explore the possibilities of plasmonic nanotechnology together

Hey everyone. I have a mercury refining operation and am doing some cleaning and maintenance. We use this condenser to cool and condense mercury coming from still.

It’s proving very difficult to clean the pipes. I am considering getting a new condenser but I can’t seem to find anyone that sells anything similar for replacement. Does anyone know the proper name of the pictured condenser and know where I could buy a new one?

(We only use the front set of pipes on the condenser)

I have been struggling to find a vendor for bulk 100um silica gel. Best I can find is 1 - 3 mm. Can anyone point me in the right direction?

My mother has noticed that she need to use much less salt in Mexico City than she uses in Washington, DC to cook the same dish. She estimates the ratio to be around 1 : 4/3. I cannot make sense of this. Any ideas? Is it something in the salt, or maybe something in the water?

To be a little more precise: she this happens with all dishes involving water and salt, such as soups, broths, and stews.

Thanks!

Hi, I'm sending my samples abroad and I have to use dry ice. However, this is the first time I will be sending dry ice package. How do I prevent explosion? I'm using styrofoam container with thick walls. Can CO2 penetrate styrofoam? Otherwise how the excess gas will escape from the box?

Hey everyone,

I really need the refractive index of ethanol vapor. I've searched a lot now, and there appear to be no websites and no research paper. They all show the refractive index at usually 20°C. I need it at vapor liquid equilibrium. Can anyone give me a citation or source for that?

I can buy ammonium carbonate and would need to have it in a liquid form soaked in some material and reacting with the air to ammonia NH3. Any help would be greatly appreciated!

This is a dedicated weekly thread for you to seek and provide advice concerning education and careers in chemistry.

If you need to make an important decision regarding your future or want to know what your options, then this is the place to leave a comment.

If you see similar topics in r/chemistry, please politely inform them of this weekly feature.

I added solutions of various metals to gold nanoparticles to see which will cause aggregation. Some do, but others don’t. In particular, some of the metals that didn’t cause aggregation (Hg2+, Pb2+) increased the absorbance at lambda max instead. Was wondering why this happened? Thank you in advance.

Oxygen is in the same group as sulfur and selenium. There are sulfuric (H2SO4) and selenic (H2SeO4) acids. Why isn't there "oxygenic acid" (H2OO4) or (H2O5) with the same structure?

I know there is pentaoxydane (H2O5), but this has completely different structure and I'm not sure if it's an acid at all.

I also know that hydrogen peroxide H2O2 is a very weak acid... and no one even calls it an acid.

For example, if i had 100ml of water at 20c, i could dissolve 200g of sucrose and 36g of sodium chloride. If i dissolved the sucrose first, could i dissolve more than 36g of sodium chloride in the solution?

What resources(books/websites/youtube) did you find useful to understand the mathematical parts? What topics should I actually learn to get through this course?

I'm wondering if anyone knows of cheap (under $300, eg $150 USD) Chem courses for chemistry at uni regarding the "living world".

I've started a degree that requires the majority of premed papers, but i really fail at the chemistry parts as they just confuse me without a foundation knowledge (i didnt do science at highschool) & I need to pass a paper well that even students with highschool chem find hard.

I don't want a free course because ADHD & no outside incentive to study doesn't work for me, I've tried for 2 summers & never get anywhere

I'm trying to fathom how to calculate the pka of compounds using quantum calculations.

I'm using psi4 and have tried various levels of accuracy (currently using PCM, 6-31+G(d,p), solvent water, and ensuring the structure/frequency is optimised using SCF for both).

I've come across the direct method for quantifying pka and there's three calculations shown in the attached link: https://pubs.acs.org/doi/10.1021/acs.jpca.0c08283

However, when I input the values I have from psi4 I'm getting nonsense for the calculated gibbs free energy of the proton in aqueous solution. (See below)

Neutral / kcal/mol Ionised / kcal/mol Proton (Calculated) / kcal/mol

Formic Acid: -188.7765641 -188.3239526 19513.97494

Methanol: -115.0282684 -114.5246625 86378.07892

Methanethiol: -437.6916336 -437.23016592 97971.82600

I understand that this method is reasonably inaccurate for calculating pka and certainly is inaccurate for getting an accurate gibbs free energy of the solvated proton but literature sources seem to place the gibbs free energy of a proton ~260 kcal/mol which I'm not even close to.

The reproducibility of the gibbs free energy of the solvated proton is also changing depending on the functional group which I thought should be constant for a given basis set etc.. This means when I'm using the gibbs free energy of the solvated proton (calculated from formic acid for example) for calculating the pka of the other two functional groups (methanol and methanthiol in this case) then I get horrendous pka values.

My questions are:

Am I misunderstanding this and employing the direct method incorrectly?

If I am employing this correctly, why are my calculations so far out?

If this is just how the inaccurate the direct method is, what other viable alternatives are there? I saw something about the isodesmic method, how would this be calculated?

Is this more a problem with psi4 producing incorrect values and my calculations are actually correct?

Is everything actually correct and I should be comparing 'similar' functional groups? i.e. formic acid's gibbs free energy of solvated proton to other carboxylic acids, and methylamines gibbs free energy of solvated proton to other amines.

If everything is correct but this is generally just a terrible method for calculated pka. What are my other options for calculating/obtaining theoretical pka values?

Thanks for your help

Im trying to use a Chinese 220v heating mantle in the US. Does this mean I need to plug the Mantle->220v input variac->step down converter-> outlet?

I’m having the hardest time finding a 220v input variac. Is there an easier way for me to use this Chinese mantle in the US?

How the hell am I supposed to get rid of this. What even is this? Common solvents like acetone, alcohol don’t work. Tried soaking in dilute HCl. Nothing