I have recently ordered chemicals to make MBDCG from Aldrich, but cant get any potassium chromate as they are toxic and require HSNO Exempt Laboratory. Have anyone tried to replace it with something else? or perhaps is it a way to make it from other less toxic chemicals? which can be produced in a normal kitchen?
I can not find any supplier for it in where I live - New Zealand.
Any suggestion is highly appreciated!
Making MBDCG- is there substitute for Potassium chromate?
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a_k
Making MBDCG- is there substitute for Potassium chromate?
Hello Kolliaco
Potassium chromate can be substituted by potassium dichromate but it is difficult to obtain too. Ammonium dichromate would be usable too but it seems to be more difficult to keep the pH of the coatings constant.
I would not attempt a synthesis in the kitchen. Anyway here is a possible synthesis for potassium dichromate. Credits for the text go to Nitro.
Ahmet
=================================================================================
WARNING
This file was written for informational purposes only. You should not attempt to make it and to use this controlled (in Europe it is) stuff to ... poison someone.
Potassium dichromate is toxic. A dose of 4-10 g of it can and will cause the death of a man if ingested.
Starting material can be:
Chromium metal
Chrome-nickel wire
Any Chromium(III) salt
Synthesis:
Weigh out 104 g Chromium metal and dissolve it in 500 ml of fuming (37%) HCl (or equimolar amount of dilute H2SO4) in a preferably large beaker. Add the metal to the acid in small portions and warm if the rxn goes too slowly. When it's all dissolved, filter the solution to remove insoluble material the chrome was contained with. In another beaker, dissolve 245 g pure NaOH in enough water and let the solution cool to 20-40°C. Add this alkali solution slowly to the filtered chromium(III)-chloride solution. A greenish or grayish precipitate of Cr(OH)3 will form. Filter this, squeeze it out and wash it 3 times with distilled water. You don't need to dry it, just put it into a clean beaker and add: 1) a solution of 160 g NaOH in just sufficient water and 2) approx. 350 ml of 30% hydrogen peroxide. Add the reagents carefully for that they don't splash. The green Cr(OH)3 will dissolve and the soln will turn a very beautiful yellow of sodium chromate. If you boil the solution for some time and then crystallizate it, you can get Na2CrO4, but we want to proceed to potassium dichromate now.
Add 164 ml of concentrated HCl. The color will immediately change to orange. This is the color of the Cr2O72- anion. Now boil the solution down to approx. 50% its original volume. After cooling white crystals of NaCl can be removed and discarded.
Now weigh out 149 g of Potassium chloride (or equimolar amount of either K2CO3, KOH, or KNO3). Dissolve it in 80°C hot water to prepare a hot saturated solution. Pour this solution into the orange solution of sodium bichromate. Orange crystals of the crude product will form. Filter them after cooling to 10°C.
Recrystalizate the product twice from distilled water. Store in well-stoppered bottle.
If you started from chrome-nickle, then some insoluble nickle(II)-hydroxide will remain undissolved after adding NaOH/H2O2. This can be filtered. If you had Cr(III)-salts, then just dissolve them in water and add NaOH soln.
The solubility of K2Cr2O7 is only 7 g/100 g water, but that of Na2Cr2O7 is more than 100 g/100 g. Therefore, if you add a potassium salt solution to Na2Cr2O7 soln, K2Cr2O7 will crystallizate readily.
The yield of this synth is almost quantitative, around 280-290 g if you did it right (>95%). There is only loss of material which remains on the filter etc.
Potassium chromate can be substituted by potassium dichromate but it is difficult to obtain too. Ammonium dichromate would be usable too but it seems to be more difficult to keep the pH of the coatings constant.
I would not attempt a synthesis in the kitchen. Anyway here is a possible synthesis for potassium dichromate. Credits for the text go to Nitro.
Ahmet
=================================================================================
WARNING
This file was written for informational purposes only. You should not attempt to make it and to use this controlled (in Europe it is) stuff to ... poison someone.
Potassium dichromate is toxic. A dose of 4-10 g of it can and will cause the death of a man if ingested.Starting material can be:
Chromium metal
Chrome-nickel wire
Any Chromium(III) salt
Synthesis:
Weigh out 104 g Chromium metal and dissolve it in 500 ml of fuming (37%) HCl (or equimolar amount of dilute H2SO4) in a preferably large beaker. Add the metal to the acid in small portions and warm if the rxn goes too slowly. When it's all dissolved, filter the solution to remove insoluble material the chrome was contained with. In another beaker, dissolve 245 g pure NaOH in enough water and let the solution cool to 20-40°C. Add this alkali solution slowly to the filtered chromium(III)-chloride solution. A greenish or grayish precipitate of Cr(OH)3 will form. Filter this, squeeze it out and wash it 3 times with distilled water. You don't need to dry it, just put it into a clean beaker and add: 1) a solution of 160 g NaOH in just sufficient water and 2) approx. 350 ml of 30% hydrogen peroxide. Add the reagents carefully for that they don't splash. The green Cr(OH)3 will dissolve and the soln will turn a very beautiful yellow of sodium chromate. If you boil the solution for some time and then crystallizate it, you can get Na2CrO4, but we want to proceed to potassium dichromate now.
Add 164 ml of concentrated HCl. The color will immediately change to orange. This is the color of the Cr2O72- anion. Now boil the solution down to approx. 50% its original volume. After cooling white crystals of NaCl can be removed and discarded.
Now weigh out 149 g of Potassium chloride (or equimolar amount of either K2CO3, KOH, or KNO3). Dissolve it in 80°C hot water to prepare a hot saturated solution. Pour this solution into the orange solution of sodium bichromate. Orange crystals of the crude product will form. Filter them after cooling to 10°C.
Recrystalizate the product twice from distilled water. Store in well-stoppered bottle.
If you started from chrome-nickle, then some insoluble nickle(II)-hydroxide will remain undissolved after adding NaOH/H2O2. This can be filtered. If you had Cr(III)-salts, then just dissolve them in water and add NaOH soln.
The solubility of K2Cr2O7 is only 7 g/100 g water, but that of Na2Cr2O7 is more than 100 g/100 g. Therefore, if you add a potassium salt solution to Na2Cr2O7 soln, K2Cr2O7 will crystallizate readily.
The yield of this synth is almost quantitative, around 280-290 g if you did it right (>95%). There is only loss of material which remains on the filter etc.
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a_k
Making MBDCG- is there substitute for Potassium chromate?
There is another simple synthesis for potassium dichromate. Electrolysing the solution of caustic potash with a ferro-chromium anode (e.g. chrome steel) and a copper oxide cathode will yield potassium dichromate.
You can find a more detailed description of the process on page 39f. of this document:
http://a2.no-ip.org/holo/doc/chemistry/ ... olysis.pdf
Ahmet
You can find a more detailed description of the process on page 39f. of this document:
http://a2.no-ip.org/holo/doc/chemistry/ ... olysis.pdf
Ahmet
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koliaco
Making MBDCG- is there substitute for Potassium chromate?
Thank you so much Ahmet for posting this infomation and Nitro for instructions!a_k wrote:Hello Kolliaco
Potassium chromate can be substituted by potassium dichromate but it is difficult to obtain too. Ammonium dichromate would be usable too but it seems to be ....... which remains on the filter etc.
This is really helpful, if I cant get potassium chromate anywhere will give this a go, might still be hard to get HCl though.
a_k wrote:There is another simple synthesis for potassium dichromate. Electrolysing the solution of caustic potash with a ferro-chromium anode (e.g. chrome steel) and a copper oxide cathode will yield potassium dichromate.
For this method i guess i can just use chrome steel bearing ball and copper wire in KOH solution?
Cheers
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a_k
Making MBDCG- is there substitute for Potassium chromate?
Hello Kolia
Sorry for misspelling your name. HCl (muriatic acid) is used to clean concrete etc., so it might be available at a building supplies store. It can be replaced with diluted sulfuric acid as long as you you use an equimolar amount, that is about 2.7x the amount of HCl.
As anode you can use any alloy containing chromium. The iron will be converted to ferric hydroxide sludge which will be filtered off and discarded. The higher the chromium content is, the more potassium dichromate you'll get.
Copper gets oxidized slowly in contact with oxygen from the air. You can accelerate this process by heating the copper surface. Or you can get a copper oxide layer on the metal surface if you put it in diluted ammonia mixed with H2O2. You'll notice that the colour will get darker.
The speed of the electrolytic reaction depends on the current density used. In the paper i posted (P27f. original numbering / P39f. of the pdf) 0.1A/cm2 is used for the anode and 0.8A for the cathode. This means the surface of the anode is 8x larger than the cathode.
If you can't find a purer source for copper, you could try a 1c coin, it contains about 90% Cu and has a surface of ~5cm2 and would require a current of 4A. The 1c coin would need a 4cm diameter bearing ball. Alternatively you can calculate the surface of your bearings with A=4pi*r^2 and use a copper oxide cathode which is 8x smaller.
Using a spherical anode and a flat cathode could be problematic because the anode gets used up and it's surface area will decrease and therefore the ratio of the surfaces of both electrodes will constantly change.
Ahmet
Sorry for misspelling your name. HCl (muriatic acid) is used to clean concrete etc., so it might be available at a building supplies store. It can be replaced with diluted sulfuric acid as long as you you use an equimolar amount, that is about 2.7x the amount of HCl.
As anode you can use any alloy containing chromium. The iron will be converted to ferric hydroxide sludge which will be filtered off and discarded. The higher the chromium content is, the more potassium dichromate you'll get.
Copper gets oxidized slowly in contact with oxygen from the air. You can accelerate this process by heating the copper surface. Or you can get a copper oxide layer on the metal surface if you put it in diluted ammonia mixed with H2O2. You'll notice that the colour will get darker.
The speed of the electrolytic reaction depends on the current density used. In the paper i posted (P27f. original numbering / P39f. of the pdf) 0.1A/cm2 is used for the anode and 0.8A for the cathode. This means the surface of the anode is 8x larger than the cathode.
If you can't find a purer source for copper, you could try a 1c coin, it contains about 90% Cu and has a surface of ~5cm2 and would require a current of 4A. The 1c coin would need a 4cm diameter bearing ball. Alternatively you can calculate the surface of your bearings with A=4pi*r^2 and use a copper oxide cathode which is 8x smaller.
Using a spherical anode and a flat cathode could be problematic because the anode gets used up and it's surface area will decrease and therefore the ratio of the surfaces of both electrodes will constantly change.
Ahmet
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Colin Kaminski
Making MBDCG- is there substitute for Potassium chromate?
If you choose a 1C coin in the US (penny) becareful. In the 90's they switched to copper jacketed zinc. I don't rmemeber the exact year. If you find an old penny it is all copper.
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a_k
Making MBDCG- is there substitute for Potassium chromate?
The NZ cents i was referring to should be bronze and contain the said percentage of Cu, the rest being tin and traces of other metals. But using an old all copper coin would have the added benefit of being sufficiently oxidised
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a_k
Making MBDCG- is there substitute for Potassium chromate?
An alternative source for chromium, "stainless steel 18/10" means that its Cr content is 18%.
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Danny Bee
Making MBDCG- is there substitute for Potassium chromate?
wow this is way cool... I think you both should write a paper. this is very creative way to out smart the goverment rules. so potash I think in the usa found in drano the suff we use to un clogs drains.a_k wrote:An alternative source for chromium, "stainless steel 18/10" means that its Cr content is 18%.
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a_k
Making MBDCG- is there substitute for Potassium chromate?
Unfortunately i was not able to run the second reaction with a 18/10 chrome/nickel steel because it turned out to be very corrosion resistant. A 40% caustic solution and temperatures up to 70°C did not do anything to the spoon during 12hrs, only O2 was generated. Maybe either higher temperatures or an alloy with less chrome or chrome nickel instead of chrome steel would be better. I did not want to try higher temperatures though.
There some simple ways for making ammonium/potassium/sodium chromate/dichromate which start with Cr2O3, which should be easy to get as it is used for pottery.
There some simple ways for making ammonium/potassium/sodium chromate/dichromate which start with Cr2O3, which should be easy to get as it is used for pottery.