Making MBDCG- is there substitute for Potassium chromate?
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JohnFP
Making MBDCG- is there substitute for Potassium chromate?
Or what about a dye that absorbs the wavelength being used and some GLycerine with a lot of exposure energy?
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a_k
Making MBDCG- is there substitute for Potassium chromate?
The problem with dye alone is not only the huge amount of exposure energy needed (>2J/cm2 with MB) but also the low DE one gets.
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koliaco
Making MBDCG- is there substitute for Potassium chromate?
Thanks you so much Ahmet for all your support, I dont know how would have managed this without your help!
I found HCl (muriatic acid) in the "Warehouse" in NZ. But will give the electrolysis try first since its simpler with chemicals. I think the cooper PCB board would be a great source for cathode as well, its just thin, and hopefully only copper oxide will chemically react. but first will try with 1cent coin - luckily one of my workmates has plenty of them probably since 90s.
I found HCl (muriatic acid) in the "Warehouse" in NZ. But will give the electrolysis try first since its simpler with chemicals. I think the cooper PCB board would be a great source for cathode as well, its just thin, and hopefully only copper oxide will chemically react. but first will try with 1cent coin - luckily one of my workmates has plenty of them probably since 90s.
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a_k
Making MBDCG- is there substitute for Potassium chromate?
Hello Kolia
It's great that you found HCl. Any small copper coin will work just fine. As it is the cathode it won't be eaten as much as the anode, if at all.
Since i had no luck with using NaOH solution as electrolyte with my 18/10 steel spoon, i tried a different route and it seemed to work well. It uses the same materials ( Cu coin, some metal containing chrome, HCl, NaOH or KOH) + H2O2 (hydrogen peroxide)
I used a 5% HCl solution, the said spoon as anode and a copper coin as cathode. The solution quickly started getting a lovely green color which got more intense with time. I stopped the electrolyse when the coin was covered with a thick black layer and the resistance of the cell did increase a lot. The voltage needed to pass 0.7A through the solution had changed from 2V to 7V at this point and the liquid was dark blue. The exact amount of current is not really important.
The dark blue liquid was filtered and a 40% solution of NaOH added. A dark green/bluish precipitate did form, which was filtered out and the filter cake washed twice to remove water soluble impurities.
After that H2O2 was added very slowly, as the solution does heat up and a violent bubble formation is observed. The color of the filtrate is a very intense yellow, which indicates that sodium chromate was formed.
I then added HCl until the solution was neutral. Adding more HCl would have converted the sodium chromate to sodium dichromate.
I'll let the liquid sit in a crystallisation dish till tomorrow so the amount of water will be reduced. NaCl should crystallise out then and will be filtered off. After that KCl can be added to convert the sodium chromate to potassium chromate. And finally the chromate or dichromate crystals can be recrystallised if one wants to get a purer product.
I've prepared an illustrated guide for this reaction. Unfortunately it got 11MB. I'll see to compress its size. If you don't mind waiting 2 minutes or so you can download it here: http://a2.no-ip.org/holo/doc/chemistry/ ... thesis.pdf
Ahmet
It's great that you found HCl. Any small copper coin will work just fine. As it is the cathode it won't be eaten as much as the anode, if at all.
Since i had no luck with using NaOH solution as electrolyte with my 18/10 steel spoon, i tried a different route and it seemed to work well. It uses the same materials ( Cu coin, some metal containing chrome, HCl, NaOH or KOH) + H2O2 (hydrogen peroxide)
I used a 5% HCl solution, the said spoon as anode and a copper coin as cathode. The solution quickly started getting a lovely green color which got more intense with time. I stopped the electrolyse when the coin was covered with a thick black layer and the resistance of the cell did increase a lot. The voltage needed to pass 0.7A through the solution had changed from 2V to 7V at this point and the liquid was dark blue. The exact amount of current is not really important.
The dark blue liquid was filtered and a 40% solution of NaOH added. A dark green/bluish precipitate did form, which was filtered out and the filter cake washed twice to remove water soluble impurities.
After that H2O2 was added very slowly, as the solution does heat up and a violent bubble formation is observed. The color of the filtrate is a very intense yellow, which indicates that sodium chromate was formed.
I then added HCl until the solution was neutral. Adding more HCl would have converted the sodium chromate to sodium dichromate.
I'll let the liquid sit in a crystallisation dish till tomorrow so the amount of water will be reduced. NaCl should crystallise out then and will be filtered off. After that KCl can be added to convert the sodium chromate to potassium chromate. And finally the chromate or dichromate crystals can be recrystallised if one wants to get a purer product.
I've prepared an illustrated guide for this reaction. Unfortunately it got 11MB. I'll see to compress its size. If you don't mind waiting 2 minutes or so you can download it here: http://a2.no-ip.org/holo/doc/chemistry/ ... thesis.pdf
Ahmet
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koliaco
Making MBDCG- is there substitute for Potassium chromate?
Hi Ahmet,koliaco wrote:Unfortunately it got 11MB
I have downloaded your PDF and its very clear with illustrated images. only, it takes a while to move between pages- possibly because of image sizes.
what is the format of these images?
Can you please elaborate on this a little bit? I dont mean asking to retype things here, but is there an article that can be referred to?a_k wrote:There some simple ways for making ammonium/potassium/sodium chromate/dichromate which start with Cr2O3
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koliaco
Making MBDCG- is there substitute for Potassium chromate?
No problem. My apology as well for calling you a_k the first time on another post.a_k wrote:Sorry for misspelling your name
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koliaco
Making MBDCG- is there substitute for Potassium chromate?
Hi Ahmet,
on your last step of adding HCl, does it have to be pure? the muriatic solvent I found actually contains only 70% HCl and rest is Ammonia . would this still be usable?
on your last step of adding HCl, does it have to be pure? the muriatic solvent I found actually contains only 70% HCl and rest is Ammonia . would this still be usable?
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a_k
Making MBDCG- is there substitute for Potassium chromate?
Hello Kolia
The pdf was written in openoffice and the original pictures are 8M pixels. I'll prepare a version with reduced format images. That will make the pdf much smaller.
Fusing chrome oxide with potassium nitrate at 700°C during 1-3hrs gives potassium dichromate. NO and NO2 are generated, which are toxic. In addition it is not very easy to maintain the high temperatures during several hrs. Besides that some of the potassium dichromate will decompose which is not a good thing.
A better and less dangerous variant (only H2O is released) of this reaction is:
. In a metal can mix 3.9g Chrome oxide and 5.7g KOH.
- At low heat mix until the salts melt.
- Slowly add 7.8g KNO3 in small portions. Before adding the next portion wait until the last one has molten.
- Caution: Parts of the mixture might squirt around, so protect yourself and especially your eyes
- After adding the last portion of KNO3 let the mixtures simmer at low heat. Some water will be released and escape.
- If no water steam is produced anymore the mixture should be stirred
- After 7-10 minutes the reaction is complete. For larger batches it might take longer.
- Let the can cool down and dissolve the product in 100ml deionized water.
- Filter. There will be some unreacted chrome oxide and very fine particles might pass throught the filter. So if you are using a coffee filter, place a ball of cotton for a better filtering result. You'll get a clean transparent yellow liquid.
- In a shallow dish slowly evaporate most of the water.
- Recrystallise the potassium chromate for purification
You can use a spiritus burner as heat source. Don't burn yourself. Work outdoors. Stick to small batch sizes until you master the process.
Ahmet
The pdf was written in openoffice and the original pictures are 8M pixels. I'll prepare a version with reduced format images. That will make the pdf much smaller.
Fusing chrome oxide with potassium nitrate at 700°C during 1-3hrs gives potassium dichromate. NO and NO2 are generated, which are toxic. In addition it is not very easy to maintain the high temperatures during several hrs. Besides that some of the potassium dichromate will decompose which is not a good thing.
A better and less dangerous variant (only H2O is released) of this reaction is:
. In a metal can mix 3.9g Chrome oxide and 5.7g KOH.
- At low heat mix until the salts melt.
- Slowly add 7.8g KNO3 in small portions. Before adding the next portion wait until the last one has molten.
- Caution: Parts of the mixture might squirt around, so protect yourself and especially your eyes
- After adding the last portion of KNO3 let the mixtures simmer at low heat. Some water will be released and escape.
- If no water steam is produced anymore the mixture should be stirred
- After 7-10 minutes the reaction is complete. For larger batches it might take longer.
- Let the can cool down and dissolve the product in 100ml deionized water.
- Filter. There will be some unreacted chrome oxide and very fine particles might pass throught the filter. So if you are using a coffee filter, place a ball of cotton for a better filtering result. You'll get a clean transparent yellow liquid.
- In a shallow dish slowly evaporate most of the water.
- Recrystallise the potassium chromate for purification
You can use a spiritus burner as heat source. Don't burn yourself. Work outdoors. Stick to small batch sizes until you master the process.
Ahmet
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a_k
Making MBDCG- is there substitute for Potassium chromate?
Concentrated HCl is about 35-38%. Sometimes it is sold at concentrations around 20-25% too. Maybe the 70% is a mistake. HCl + NH3 will form NH4+ and Cl-
Any concentration will be ok. Using concentrated HCl will help to keep the total volume of liquid low so there will be less water to get rid off, that's all.
Any concentration will be ok. Using concentrated HCl will help to keep the total volume of liquid low so there will be less water to get rid off, that's all.