copper benzoate

[Fred]

Thank you for correction, ist`s my fault. Yes, one need 2 moles of potassium benzoate for 1 mole of copper sulfate like its correctly indicated at Pyroguide.

 

The formula for Copper benzoate might not be very important, if the mass off the reagents is correct. What`s the accurate formula for copper benzoate?

 

Could you describe the right procedure to avoid copper benzoate di- and trihydrate?

[Mumbles]

You can't avoid the hydrates, but you can heat it at an elevated temperature, 100-150C. It turns a darker shade of teal IIRC when anhydrous.

 

The molecule actually exists as a dimer. It's not really that important for stoichiometry(unless you start getting polymeric crap), but it explains the hydration pattern. It adopts the chinese lantern structure like the following:

 

http://upload.wikimedia.org/wikipedia/comm...te-3D-balls.png

 

I don't know why they show a metal-metal bond though. The distance is too far the last time I checked.

[AdmiralDonSnider]

Sorry for the obvious misinformation on Pyroguide; we are trying to verify the contents - unfortunately I don´t know enough about chemistry to do so in this special case.

 

So the 2 to 1 mole turn out to be 1,28:1 parts by weight, right? How is the sulphate removed best? How much washings will be necessary? Thanks!

[Mumbles]

It's approximately 1.28:1. You end up about a gram short on a full molar ratio from round off errors, but I think as long as you have the molar masses on there it should not be a problem. I don't know how many washings it takes to remove the sulfate. Just go until the washings are negative for sulfate.

[FrankRizzo]

It's approximately 1.28:1. You end up about a gram short on a full molar ratio from round off errors, but I think as long as you have the molar masses on there it should not be a problem. I don't know how many washings it takes to remove the sulfate. Just go until the washings are negative for sulfate.

 

As long as you use potassium benzoate in the synthessis, a minimal amount of potassium sulfate doesn't seem to make much difference in the color produced.

[Ventsi]

Anybody here who has ACTUALLY made some, please help me out. I have a about 150g of CuBenz that I dehydrated to a nice teal color. Next problem is , how the hell do I get it down to a fine powder? Even anhydrous the stuff is waxy and horribly clumpy, I'm guessing milling is not an option. Plus I don't have a jar that I can dedicate to copper salts.

 

I intend to use it in the "New Blue" formula which uses AP and I assume I need it finely powdered. Any info is appreciated, thanks.

Edited May 12, 2010 by Ventsi

[Mumbles]

The little I made, while waxy and clumpy, it precipitated as a fine powder. Screening into compositions was quite sufficient.

[boblangdon]

Hello,

Here is how I have made it for years, but I am not the creator of the process, just an avid user of it.

You will need the following items:

1) Benxoic Acid

2) Copper Carbonate

3) Adjustable electric heat source

4) Very Large Pot for process, teflon coated or ceramic (No exposed metal)

5) Plastic stirring Spoon

6) Scale (electronic is perfect)

7) Coffee filters

8) Jar that the coffee filters fit in. (I use an older type coffee maker where the filter fits into a removable holder.)

9) Distilled Water

A) Misc other items I forgot to mention.

 

1st) Weigh out by weight 12 parts of Benzoic Acid & 6 Part by weight of Copper Carbonate.

 

2nd) Fill up your Very Large Pot with distilled Water about 50 - 75 parts by weight.

 

3rd) Place pot with water on your adjustable heat source & bring water to just under a boil.

 

4th) Once you have reached almost the water boiling point add in your 12 parts by weight & stir vigorously.

 

5th) Now add in 1/3 of your copper carbonate by weight & stir vigorously. Within a few seconds the reaction starts.

 

6th) The mixture with darken & start releasing small bubbles but lots & lots of them. In fact it will try to overflow you

container which is why it is mixed in small amounts. Anyway as long as you keep stirring the carbon dioxide will

be released from the bubbles & the whole mixture will stop it's growth once all of the copper carbonate has

reacted with the benzoic acid. Now once your mixture has stopped the generation of bubbles (CO2) go on to the

next step.

 

7th) repeat steps 5 & 6 until you have finished off the copper carbonate & there is no more release of CO2.

 

8th) Using the coffee filters, filter the contents of the pot but this will take multiple coffee filters if you used 12oz & 6oz

worth of benzoic acid & copper carbonate. I have used up to 6-10 filters depending on how full I let them get.

 

9th) Allow the water to evaporate naturally or use a vacum system to draw the water out of the coffee filters leaving a

blue powder tha's still a bit wet.

 

10th) Dump all the copper benzoate out of the dried coffee filters onto a non stick cookie sheet & place in your oven

thats pre heated to 225 degree's F. Make sure you have some form of air circilation in the oven as it's needed.

(As a note the oven I use is a temp chamber that goes hot or cold but the real deal is that it has air circilation

which is required & does speed up the process.)

 

11th) Once it has completely dried out take it and run it through a 200-325 mesh screen to break up any of the lumps

that may have, will have formed. Once it's been screened place it in a platic bag then into airtight containers until

you need to use it.

 

Now this method appeared in the American Firework New #119 issue in 1991. Since then I have for many years made 3-5 pounds up & sold it to others for use until this year when I decided to get out of the game & leave it to the younger guys. Hence my reason for selling my last batch to a newbie on Ebay & also having him help me make these past four years, he thought I was training a helper but I trained a replacement. Anyway it is not that hard to make but if care is not taken you will get a @#$#^&*% of blue goo with lots of bubbles rising out of the pot oh so very very fast all over you & your clean work area so do not rush & after you do it enough times you know what quantities you can work with at one time. NEVER MIX IN THE WHOLE 6 PARTS OF THE METALIC CARBONATE AT ONE TIME, UNLESS YOU ARE JUST WORKING IN GRAMS & NOT OUNCES!

 

Chemical sources;

1) Benzoic Acid (Firefox)

2) Copper Carbonate (Skylighter) * (Firefox) * (Ebay) * (Bentspoonmaterials)

3) Distilled Water (Grocery Store) One's outside of a lot of stores are only just filtered tap water which is a NO NO! Use

Distilled water only

4) Copper Benzoate (Skylighter) * (Ebay)

 

Mis equipment sources;

1) Large glass, ceramic, or non stick metal pot (Grocery Store) * (Lab Equipment Supply House) * (Ebay)

2) Heating Element (Grocery Store) * (Ebay) * (Lab Equipment Supply House)

3) Coffee Filters, Large Plastic Spoon, Resealable Jars, Sieve (Local Grocery Store)

4) Electronic Scales, is cheap & perfect for this use. (Ebay) * (Grocery Store) * (Post Office) * (Office Supply Store)

4) Back issue of AFN #119 (American Firework News Website)

 

Good luck & remember that Copper Benzoate is just one of MANY metalic Benzoates you can mnf using this simple process, others include; Calcium Benzoate, Barium Benzoate, & Strontium Benzoate

 

That's my favorite process. Seems more cost-effective than starting with K-benzoate.

CHEAPER yet, start with copper sulfate and make your own carbonate.

 

@ < $2 a lb for Copper sulphate, 1 lb will cost you about $5 to make (counting a few cents for the soda ash), whereas I pay $8+ a pound for "store-bought" copper carbonate.

:-)

[Powderman]

I was thinking creating copper benzoate thread and then I found this... At the moment I am running experiment to see if it would be beneficial to grow nice Cu benzoate crystals from CuSO4 and Na benzoate. The idea is having crystals that are easy to wash and filtrate to get rid of Na contamination... I hope it will not embedd itself into the crystals.

I have the chems and they are both easy to obtain and cheap here. And I have not seen such crystals on web so why not create it :-) It is growing as I type and tomorrow the blue solution should be colorless and crystals ready to test.

[Powderman]

Here are pictures how it went and a video of this CuBenz burning with AP

 

www.amateurpyro.com/forums/gallery/album/533-copper-benzoate-preparation

 

Edited February 21, 2023 by Powderman

[Crazy Swede]

I was thinking creating copper benzoate thread and then I found this... At the moment I am running experiment to see if it would be beneficial to grow nice Cu benzoate crystals from CuSO4 and Na benzoate. The idea is having crystals that are easy to wash and filtrate to get rid of Na contamination... I hope it will not embedd itself into the crystals.

I have the chems and they are both easy to obtain and cheap here. And I have not seen such crystals on web so why not create it :-) It is growing as I type and tomorrow the blue solution should be colorless and crystals ready to test.

It is often hard not to end up with anything but extremely small sized crystals when making copper benzoate. How will you approach this to allow them to grow slow and big?

 

One method I think could work would be to use gels and low concentrations of copper and benzoate salts in respective gel. I've done this once with oxalates. The principle is to cast one gel in the bottom containing one of the ions you want to make crystals of (say copper sulfate), then you cast a layer of clean gel (just water and agar-agar) and let that solidify until the last gel layer is cast containing to other ion (preferably potassium benzoate or benzoic acid). The crystals will slowly start to form in the middle gel layer and it might take weeks since the transport of ions is diffusion related. (Sorry for improper explanation, I'm in a hurry!)

[Powderman]

Cu benzoate is not as insoluble as one might think. It just have low solubility. Water from washing the crystals is definitely slightly blue.

I have done this by using low concentrations and I have added a bit of acetic acid to adjust PH - my water is not distilled, it is from old reverse osmosis filter. With distilled water it might or might not be needed...

 

Solution on my photos consisted of 1,7g CuSO4.5H2O in 100ml + 2,13g C6H5COONa in 100ml. Few minutes after adding the solutions together crystals start to appear and it takes several hours to finish. Best to let it overnight. Filtering and washing was a piece of cake :-)

This might not be ideal setup, other concentrations should be tested and also the need/amount of aicd.

 

Low concentration of salts and nicely formed crystals resulted in usable product without the need of excessive washing - that was my goal. And I finally saw how those crystals look. Google found none.

[Crazy Swede]

...Low concentration of salts and nicely formed crystals resulted in usable product without the need of excessive washing - that was my goal. And I finally saw how those crystals look. Google found none.

Cool, I thought the material would crash out of solution immediately. That was how I remembered it the times I tried to prepare copper benzoate way back when.

 

Can you upload pictures of the crystals? It would be interesting to see!

[Powderman]

Photos are in gallery- link is over the video I posted...

[Crazy Swede]

Ah, I missed that. Thanks!

 

Im very surprised, I did not think that was possible.

 

On the other hand, neutralising benzoic acid with malachite is a completely different process where no bigger crystals have a chance to form.

 

Did you dry your finished product to release the co-ordinated water?

[Powderman]

Yes, it is written in photo descriptions - the last one is dark blue because it is dry.

[Powderman]

I have decided to try the benzoic acid route, I do not have any nor can buy it here, only Na benzoate is easily available here. The plus is that I can get rid of the sodium easily because benzoic acid is easy to purify (solubility 1,7g/L at 0°C and 56g/L at 100°C). The crystals are easy to filter and rinse with cold water. Test run was:

Dissolve 50g of Na benzoate in 1L of water, add HCl until the PH drops to acidic (42,2g of 30% HCl was calculated, it was old so a bit more was needed). Heat it to dissolve all benzoic acid - let the clear solution cool down slowly and after it gets to room temp cool it further in refrigerator. Filter and rinse it, add to 1L of water and repeat heating/crystallization/filtration/rinsing... Reaction makes 42,4g of benzoic acid, yield would be few grams less. My was 39g dry product.

[rellim]

Wikipedia gives the following for the double displacement reaction:

4 C₆H₅CO₂K + 2 CuSO₄·5H₂O → Cu₂(C₆H₅CO₂)₄(H₂O)₂ + 2 K₂SO₄ + 8 H₂O

If my calculations are correct, the product contains 5.5% water. However, when I dried the copper benzoate that I made with the above reaction in the oven, it lost 15% of the original weight.  

I am wondering if the included water of crystallization is accounted for in star formulas and will anhydrous copper benzoate re-hydrate when used to make dextrin bound stars.

[Powderman]

The formed pale blue solid seems to be trihydrate. There is also a monohydrate which is darker and dry benzoate which I would say is a small bit lighter in color. At higher temps and concentrations monohydrate forms from reaction - in contact with excess water it converts to trihydrate. You can tell by the color change.