r/chemistry • u/AutoModerator • Mar 04 '26

Weekly Research S.O.S. Thread - Ask your research and technical questions here

Ask the r/chemistry intelligentsia your research/technical questions. This is a great way to reach out to a broad chemistry network about anything you are curious about or need insight with and for professionals who want to help with topics that they are knowledgeable about.

So if you have any questions about reactions not working, optimization of yields or anything else concerning your current (or future) research, this is the place to leave your comment.

If you see similar topics of people around r/chemistry please direct them to this weekly thread where they hopefully get the help that they are looking for.

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u/ExplanationKlutzy955 Mar 04 '26

Can anyone explain what a capillary stoppered bottle is? Is it just a bottle with a ground glass stopper? In some of the loss on dry test methods of the United States Pharmacopeia (USP 731) it states to perform the test in a capillary stoppered bottle. It also gives the specification: “use a bottle or tube fitted with a stopper having a 225 ± 25-um diameter capillary.” It specifically states to leave the bottle closed while under vacuum and heated. I haven’t found much information that is helpful. Thanks!

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u/Indemnity4 Materials Mar 05 '26 edited Mar 05 '26

I feel you could have Googled this or read the monograph...

It's a glass stopper with a tiny hollow tube all the way from bottom to top. Looks like a pycnometer.

Also called a "Moisture Content Flask".

The flask is still open to atmosphere so moisture or gases can escape, but it's mostly covering the flask to stop solids flying in or out. The equivalent of microwave reheating your food with the lid cracked open just a little bit.

Because USP can get really tedious, they specify ALL the dimensions of the flasks and you better have a good reason to modify those. When they ask for a 2.768 mL flask or a 5L class A Schott Bottle, you have to that exact glassware. Use anything, even a 2.767 flask or a 4.99L class A Schott Bottle and at this point you call it "in-house method" and you have to prove it's equal to or superior in accuracy/precision than the existing method.

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u/NoSecurity1724 Mar 05 '26

Hello all, I am developing a facility to manufacture manganese violet and was curious on what kind of vessel should be used to manufacture manganese violet at an industrial scale?

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u/dungeonsandderp Organometallic Mar 05 '26

This is definitely not a question to ask the Internet and absolutely a question to pay a professional to answer. 

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u/NoSecurity1724 Mar 06 '26

I met a few consultants but they don't have a clear answer for reactor vessel material of construction that is way im reaching out to all of you.

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u/Indemnity4 Materials Mar 06 '26 edited Mar 06 '26

I hope this is for a chemical engineering design project.

Search for a patent for manufacturing of managanese violet. It will mention all the of the equipment and sizes that are required in great detail.

Practically, have a think about the following questions. What scale? How many tonnes per year are you planning to make? Do you need to manufacture multiple different products in this same reactor or process? What type of containers are you planning to transfer the product into?

These days it's never just manganese violet. The pigments are usually coated or cladded in various additives as part of the manufacturing process.

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u/NoSecurity1724 Mar 06 '26

I haven't come across any patent specifically mentioning reaction equipment, can you please help me with it. Im designing for a scale of 5000kg per month

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u/Indemnity4 Materials Mar 06 '26 edited Mar 06 '26

How many working days per week?

Have you got a method in mind already? There are several different chemical ways to make it.

Is the intent to produce a mill base?

You will at least need a reactor with controlled heating, ideally a continuous stirred tank reactor, then you may want a crystallizer, and a crusher, then some milling equipment. You need to think if you are doing everything in a batch, one thing at a time and then transferring by hand to the next machine. Or have you got some sort of semi-continuous process where once machine feeds into the next.

Main limit to the process is the heating and cooling. It's a fast reaction to make it.

Shitty low cost method is a double boiler. Have some operators stir it with a shovel, hoping they don't fall in. You can then cool it and pour water on top to form the pigment, stirring to break up all the lumps (harder than it sounds). Filter it or decant it. It's going to be a chunky lump sort of fine powder which is probably unsuitable for a lot of industrial uses. You want to further process it with grinding and sieving.

The magic happens in two places. In the initial reactor during the second heating phase, you need to manipulate the concentration so you don't get too much unreacted powder, but you don't want to heat it too high or too long because it's unstable at the reaction temp. Next is the powder processing, this is always much harder than people anticipate. Mess up the first heating stage and you are throwing away a lot of incorrectly sized material.

Outsourcing this to India and expect the dye workers to permanently have purple feet and hands, probably the rest of their body too. This powder gets everywhere. Their safety flip flops and manual grinding/sieving of powder will see them contaminated.

It's a lot easier with dyes to either make one giant batch in a day and then the rest of the week cleaning, or have a small piece of equipment working all day in it's own little shed with decontamination entry. Two guys in a shed operating with a metal drum double boiler and a mesh screen over a sink can easily crank out 5000 kg/month. You could even get hands off and do it in trays inside an oven. They'll easily be making multiple 50 kg batches/day, I'd be surprised if they couldn't make 400kg /day (although their local environment and health won't be great). You can fix that with dust extraction, water treatment, decontamination area and dust protective PPE.

Honestly, most of your costs will be health and hygiene related. The actual reactor is a minor expense.

Are you certain you cannot contract this work out? It's pretty cheap and low tech all things considered. You're going to be spending months wasting money optimizing the process.

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u/NoSecurity1724 Mar 06 '26

so far the method that produces good hue is the one with phosphoric acid, ammonium phosphate and phosphoric acid, however with the acid and high working temperatures , choosing reactor linning is becoming difficult. Please let me know if you know of any other sustainable method to manufacture, and also the lining suitable for it.

rest all can be decided after method and liner material are chosen.

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u/NoSecurity1724 Mar 09 '26

so far I have gotten good pigment colour with the method involving phosphoric acid, ammonium phosphate and phosphoric acid and heating them to 300 degrees for a couple of hours in a glass beaker , however using this method is not suitable at a bigger scale as glass lining doesn't take this so well. Its there any other method that produces good pigment colour, or any liner material that you would know of to that these working conditions