Sciencemadness Discussion Board

Copper phosphate synthesis useing phosphoric acid???

Ramium - 31-1-2015 at 19:58

I plan to make copper phosphate from copper carbonate and phosphoric acid.
I heard phosphoric acid is sold as a rust remover so i looked in my local hardware store and found some.it said it was 500g phosphoric acid per litre

What percentage phosphoric acid is that??

And would it work in the experiment??

Any help would be appreciated

Ramium - 31-1-2015 at 20:01

Here is a link to the video I am using

http://youtu.be/k4k92mmo3_Q

[Edited on 1-2-2015 by Ramium]

Volanschemia - 31-1-2015 at 21:06

500g of H3PO4 equals 265mL (Density = 1.885, 500/1.885 = 265..).
So therefore 500g/L would equal 26.5% Phosphoric Acid.
I'm not sure if you'd be able to use such a low concentration in the reaction. It might work, but you'd have to recalculate the stoichiometry. You could try heating the mixture up to 110 degrees Celsius to boil off some of the water (Phosphoric Acid boils at 158 degrees Celsius). I'm not sure if it forms an azeotrope though so it might stop working at a certain point.

If you have access to Phosphorus(V) Oxide you can make Phosphoric Acid by adding it to water.

Ramium - 31-1-2015 at 21:21

Can i buy phosphorus v oxide if not can i make it?

Ramium - 31-1-2015 at 21:29

I looked at phosphorus v oxide on wikipedia it says it is made by burning phosphorus

White phosphorus or red phosphorus?

Volanschemia - 31-1-2015 at 21:58

Phosphors(V) Oxide can be bought here but is is expensive.

From Wikipedia:
In the thermal process, the phosphorus pentoxide obtained by burning white phosphorus was dissolved in dilute phosphoric acid to produce concentrated acid.

If you have access to white Phosphorus you could make conc. Phosphorus Acid by burning the Phosphorus under a stream of Oxygen then dissolving it in the dilute OTC Phosphoric Acid.

A simpler option would be to just buy the Phosphoric Acid from here.

unionised - 1-2-2015 at 07:30

Or you could just use the phosphoric acid you have already got.
The reaction might be a bit slower because of the extra water, but it will still work.

You will need to use more of it too (or less copper carbonate).

Messing about with white phosphorus and its pentoxide isn't fun.

blogfast25 - 1-2-2015 at 07:53

Quote: Originally posted by TheAustralianScientist  
500g of H3PO4 equals 265mL (Density = 1.885, 500/1.885 = 265..).
So therefore 500g/L would equal 26.5% Phosphoric Acid.
I'm not sure if you'd be able to use such a low concentration in the reaction. It might work, but you'd have to recalculate the stoichiometry. You could try heating the mixture up to 110 degrees Celsius to boil off some of the water (Phosphoric Acid boils at 158 degrees Celsius). I'm not sure if it forms an azeotrope though so it might stop working at a certain point.

If you have access to Phosphorus(V) Oxide you can make Phosphoric Acid by adding it to water.


Correct and yet baloney too.

He knows the solution contains 500 g H3PO4 per litre of solution.

The molar mass of H3PO4 is 98 g/mol, so 500 g = 500/98 = 5.1 mol. The solution is thus 5.1 mol H3PO4 per litre or 5.1 M H3PO4.

That's all you need to know and 5.1 M is strong enough for most purposes.

For chemistry molarity is far more useful than w%.

Ramium, how do you plant to prepare that copper phosphate?

Edit:

Ooops, didn't see that bit about copper carbonate, my bad.

It's a bad idea though. Dissolving an insoluble compound (copper carbonate) in an acid to obtain another insoluble compound (copper phosphate) is a recipe for occlusion: bits of copper carbonate stuck in the copper phosphate.

Better to dissolve the copper carbonate in minimal amounts of HCl or H2SO4, then add the required amount of phosphoric acid to precipitate the copper phosphate.


[Edited on 1-2-2015 by blogfast25]

Ramium - 1-2-2015 at 10:31

Thanks. I would like to get some reasonably pure phosphoric acid if possible i heard that
Brewery supply stores sell it So i will hav a look i one today.if i cant find some then maybe i will just go with that highly inpure stuff i found in the hardware store

[Edited on 1-2-2015 by Ramium]

blogfast25 - 1-2-2015 at 10:35

Quote: Originally posted by Ramium  
maybe i will just go with that highly inpure stuff i found in the hardware store



How do you know the hardware stuff is 'highly impure'?

Are you just assuming? Does the label state any other ingredients (other than water and phosphoric acid)? What's its colour for instance?

[Edited on 1-2-2015 by blogfast25]

Ramium - 1-2-2015 at 10:42

Quote: Originally posted by blogfast25  
Quote: Originally posted by TheAustralianScientist  
500g of H3PO4 equals 265mL (Density = 1.885, 500/1.885 = 265..).
So therefore 500g/L would equal 26.5% Phosphoric Acid.
I'm not sure if you'd be able to use such a low concentration in the reaction. It might work, but you'd have to recalculate the stoichiometry. You could try heating the mixture up to 110 degrees Celsius to boil off some of the water (Phosphoric Acid boils at 158 degrees Celsius). I'm not sure if it forms an azeotrope though so it might stop working at a certain point.

If you have access to Phosphorus(V) Oxide you can make Phosphoric Acid by adding it to water.


Correct and yet baloney too.

He knows the solution contains 500 g H3PO4 per litre of solution.

The molar mass of H3PO4 is 98 g/mol, so 500 g = 500/98 = 5.1 mol. The solution is thus 5.1 mol H3PO4 per litre or 5.1 M H3PO4.

That's all you need to know and 5.1 M is strong enough for most purposes.

For chemistry molarity is far more useful than w%.

Ramium, how do you plant to prepare that copper phosphate?

Edit:

Ooops, didn't see that bit about copper carbonate, my bad.

It's a bad idea though. Dissolving an insoluble compound (copper carbonate) in an acid to obtain another insoluble compound (copper phosphate) is a recipe for occlusion: bits of copper carbonate stuck in the copper phosphate.

Better to dissolve the copper carbonate in minimal amounts of HCl or H2SO4, then add the required amount of phosphoric acid to precipitate the copper phosphate.


[Edited on 1-2-2015 by blogfast25]
i hav some HCL so i will dissolve the copper carbonate in that. But wouldent that make copper chloride?????

[Edited on 1-2-2015 by Ramium]

cyanureeves - 1-2-2015 at 10:43

i have phosphoric acid and i put some copper in a little bit of phosphoric acid and not much happened until i added hydrogen peroxide.i got a blue solution over time that was oily looking.was that copper phosphate i produced?

Ramium - 1-2-2015 at 10:49

Quote: Originally posted by blogfast25  
Quote: Originally posted by Ramium  
maybe i will just go with that highly inpure stuff i found in the hardware store



How do you know the hardware stuff is 'highly impure'?

Are you just assuming? Does the label state any other ingredients (other than water and phosphoric acid)? What's its colour for instance?

[Edited on 1-2-2015 by blogfast25]
it says 500g/l isn't that highly impure??

[Edited on 1-2-2015 by Ramium]

blogfast25 - 1-2-2015 at 11:00

Quote: Originally posted by Ramium  
it says 500g/l isn't that highly impure??


OF COURSE IT DOESN'T MEAN THAT.

It simply means that your hardware stuff contains 500 g of H3PO4 per litre of solution, the rest being water.

You don't need (or want!) 100 % H3PO4 for what you are trying to do.

By 'impuriries' here in this context is meant: substances present in the H3PO4/water mixture OTHER than H3PO4 or H2O.

The water in that solution doesn't impede using that solution in your application, quite the opposite actually.

Tell me, if you ever plan make some sulphates, will you only want to use pure, 100 % H2SO4? I hope not because that would be ABSURD.

Of course there are applications for 100 % H3PO4 too, it's just not needed here. 5.1 M H3PO4 will do just fine.

Water here is not an 'impurity', it's a solvent.


[Edited on 1-2-2015 by blogfast25]

BromicAcid - 1-2-2015 at 12:51

I remember purchasing some industrial stainless steel cleaner that was ca. 25% phosphoric acid. However, when I went to actually do experiments with it it had such a combination of inhibitors and surfactants that I either ended up with a beaker of foam or had no visible reaction :P

Volanschemia - 1-2-2015 at 16:36

Quote: Originally posted by blogfast25  

Correct and yet baloney too.

He knows the solution contains 500 g H3PO4 per litre of solution.

The molar mass of H3PO4 is 98 g/mol, so 500 g = 500/98 = 5.1 mol. The solution is thus 5.1 mol H3PO4 per litre or 5.1 M H3PO4.

That's all you need to know and 5.1 M is strong enough for most purposes.

For chemistry molarity is far more useful than w%.


I know that M is more useful than % but if you recall the opening post:
Quote:

I plan to make copper phosphate from copper carbonate and phosphoric acid.
I heard phosphoric acid is sold as a rust remover so i looked in my local hardware store and found some.it said it was 500g phosphoric acid per litre

What percentage phosphoric acid is that??

And would it work in the experiment??

Any help would be appreciated



[Edited on 2-2-2015 by TheAustralianScientist]

Ramium - 1-2-2015 at 23:23

Quote: Originally posted by blogfast25  
Quote: Originally posted by Ramium  
it says 500g/l isn't that highly impure??


OF COURSE IT DOESN'T MEAN THAT.

It simply means that your hardware stuff contains 500 g of H3PO4 per litre of solution, the rest being water.

You don't need (or want!) 100 % H3PO4 for what you are trying to do.

By 'impuriries' here in this context is meant: substances present in the H3PO4/water mixture OTHER than H3PO4 or H2O.

The water in that solution doesn't impede using that solution in your application, quite the opposite actually.

Tell me, if you ever plan make some sulphates, will you only want to use pure, 100 % H2SO4? I hope not because that would be ABSURD.

Of course there are applications for 100 % H3PO4 too, it's just not needed here. 5.1 M H3PO4 will do just fine.

Water here is not an 'impurity', it's a solvent.


[Edited on 1-2-2015 by blogfast25]
sorry i am new to chemistry. I will just use the 500 /l stuff then.

[Edited on 2-2-2015 by Ramium]

Volanschemia - 1-2-2015 at 23:30

Quote:
sorry i am new to chemistry. I will just use the 500 /l stuff then.


No need to apologize. Everyone started at some point and I think SOME people need to remember that.

I think you could use the 5.1M stuff. You'll just need to recalculate the stoichiometry. Would you like me to show you how?
I gather you're planning on making Copper(II) Phosphate? Not Copper(I) Phosphate?

[Edited on 2-2-2015 by TheAustralianScientist]

[Edited on 2-2-2015 by TheAustralianScientist]

Zombie - 1-2-2015 at 23:54

At the risk of sounding "simple" couldn't you use a desiccant such as silica gell or Calcium Chloride to remove some of the water

blogfast25 - 2-2-2015 at 08:49

Quote: Originally posted by TheAustralianScientist  
Would you like me to show you how?


Do that by all means but make it educational, i.o.w. let the OP do most of the work, so that at least he learns as much as possible.

He needs to acquaint himself with stoichiometry, moles and molarity at a very minimum.

blogfast25 - 2-2-2015 at 08:55

Quote: Originally posted by Zombie  
At the risk of sounding "simple" couldn't you use a desiccant such as silica gell or Calcium Chloride to remove some of the water


There is no need whatsoever to remove some or all of the water. The water here is in fact beneficial or at least doesn't hurt a fly.

Removing water here would be done by simple evaporation of it, because H<sub>3</sub>PO<sub>4</sub> has a much higher BP than water. About 75 % acid can be obtained this way.

Silica gel and CaCl<sub>2</sub> (anh.) are limited in how much water they can absorb. They are mostly used to dry stuff that is already fairly dry, not stuff that's floating in an ocean of water.


[Edited on 2-2-2015 by blogfast25]

Amos - 2-2-2015 at 09:05

If anyone's making copper phosphate just skip all of this and precipitate it using a water-soluble copper salt and sodium phosphate. Not only is sodium phosphate cheap OTC, it can very easily be made simply by neutralizing sodium bicarbonate or carbonate with phosphoric acid, and it's strikingly easy to crystallize, too.

blogfast25 - 2-2-2015 at 09:07

Quote: Originally posted by No Tears Only Dreams Now  
If anyone's making copper phosphate just skip all of this and precipitate it using a water-soluble copper salt and sodium phosphate. Not only is sodium phosphate cheap OTC, it can very easily be made simply by neutralizing sodium bicarbonate or carbonate with phosphoric acid, and it's strikingly easy to crystallize, too.


Sure but since he as access to cheap 5.1 M H<sub>3</sub>PO<sub>4</sub> he might as well use that.

Amos - 2-2-2015 at 09:16

Quote: Originally posted by blogfast25  
Quote: Originally posted by No Tears Only Dreams Now  
If anyone's making copper phosphate just skip all of this and precipitate it using a water-soluble copper salt and sodium phosphate. Not only is sodium phosphate cheap OTC, it can very easily be made simply by neutralizing sodium bicarbonate or carbonate with phosphoric acid, and it's strikingly easy to crystallize, too.


Sure but since he as access to cheap 5.1 M H<sub>3</sub>PO<sub>4</sub> he might as well use that.


Well doing it this way, either the end product will contain leftover copper carbonate or it will have to be washed of syrupy leftover phosphoric acid and any possible contaminants in the product. Sure, a solution of simply phosphoric acid and water sounds nice but there might be more to it.

Oh, one more thing. The effervescence produced as a result of carbon dioxide formed is going to be a real pain given the viscosity of phosphoric acid and the fact that there's a bunch of insoluble material in the way.

[Edited on 2-2-2015 by No Tears Only Dreams Now]

blogfast25 - 2-2-2015 at 09:35

Quote: Originally posted by No Tears Only Dreams Now  

Well doing it this way, either the end product will contain leftover copper carbonate or it will have to be washed of syrupy leftover phosphoric acid and any possible contaminants in the product. Sure, a solution of simply phosphoric acid and water sounds nice but there might be more to it.

Oh, one more thing. The effervescence produced as a result of carbon dioxide formed is going to be a real pain given the viscosity of phosphoric acid and the fact that there's a bunch of insoluble material in the way.



You don't seem to have read this thread fully.

I've already recommended converting the copper basic carbonate to CuCl2 or CuSO4 first, to avoid problems of carbonate occlusion later on.

After that, basically dilute the Cu<sup>2+</sup> solution to about 1 M. Add the stoichiometric amount of 5.1 M H3PO4 to precipitate the Cu<sub>3</sub>(PO<sub>4</sub>;)<sub>2</sub>. Filter, wash and dry.

In a nutshell...

[Edited on 2-2-2015 by blogfast25]

Ramium - 2-2-2015 at 10:54

Quote: Originally posted by TheAustralianScientist  
Quote:
sorry i am new to chemistry. I will just use the 500 /l stuff then.


No need to apologize. Everyone started at some point and I think SOME people need to remember that.

I think you could use the 5.1M stuff. You'll just need to recalculate the stoichiometry. Would you like me to show you how?
I gather you're planning on making Copper(II) Phosphate? Not Copper(I) Phosphate?

[Edited on 2-2-2015 by TheAustralianScientist]



[Edited on 2-2-2015 by TheAustralianScientist]


Yes copper 2 phosphate. Could you tell me how many ml of phosphoric acid (5.1M) and how many grams of copper carbonate???
Thanks


[Edited on 2-2-2015 by Ramium]

[Edited on 2-2-2015 by Ramium]

gdflp - 2-2-2015 at 11:41

That depends, how much copper phosphate do you want to synthesize? Remember, you will need to dissolve the copper carbonate in an acid such as hydrochloric, nitric, sulfuric, acetic, etc., then add the phosphoric acid to precipitate out insoluble copper phosphate. Theoretically, to calculate how much copper carbonate to use, first take the desired amount of copper phosphate and divide that number by the molar mass, in this case, 434.63g/mol. Then multiply the product with the molar mass of copper carbonate to determine how much is needed. In this case, that won't work because copper carbonate has varying compositions with differing molar masses. In this case, take roughly half of the desired weight of the product of copper carbonate and add a dilute acid until it is completely dissolved. Then add phosphoric acid slowly until no more precipitation is observed. Filter the precipitate and wash it with water to yield copper phosphate.

Ramium - 2-2-2015 at 19:16

Sorry i'm very bad at maths and have trouble understanding this.
I need a simple equation with specific quantities which i can either use directly or change as needed if i don't have enough chemicals.
To make lets say 20 grams of copper phosphate
I have some 33% hydrochloric acid which i could use to dissolve the copper carbonate. How dilute should i make the HCl?

Zombie - 2-2-2015 at 19:39

He stated it very clearly Ramium.

Just read it thru slowly one more time.

Quote:
" In this case, take roughly half of the desired weight of the product of copper carbonate and add a dilute acid until it is completely dissolved. Then add phosphoric acid slowly until no more precipitation is observed. Filter the precipitate and wash it with water to yield copper phosphate.";)

blogfast25 - 2-2-2015 at 19:58

Quote: Originally posted by Ramium  
Sorry i'm very bad at maths and have trouble understanding this.


"Maths" doesn't come into it: at worst; arithmetic.

"If 5 apples cost 39 cents, how much do 9 apples cost?"

That's the level we're talking about here. Can't do that? Go back to school.

Look up 'moles' (chemistry), 'Molar mass', get back.



[Edited on 3-2-2015 by blogfast25]

Ramium - 2-2-2015 at 20:48

Sorry just skimed threw the post.i tried the experiment i added the dilut(10%ish)HCL to the copper carbonate and got a green solution.then when i added the phosphoric acid the solution turned blue and there was no pricipitate.you seem to imply that the copper phosphate is not soluble but the video i posted in my second post seems to imply it is soluble i looked at copper phosphate on wikipedia and it said it is not soluble but wikipedia can be edited by eneyone.so is it soluble??

If it is could my blue solution be a solution of copper phosphate??

[Edited on 3-2-2015 by Ramium]

Zombie - 2-2-2015 at 21:29

Here are 2 reference pages you may want to print out or convert to PDF for long term use.
The first link answers your question, and the second link explains how it is answered.

I hope they help.

http://www.solubilityofthings.com/water/ions_solubility/ksp_...

http://chemwiki.ucdavis.edu/Physical_Chemistry/Equilibria/So...

Ramium - 2-2-2015 at 23:44

To mathematical i am only 13 and dont understand a word.i just want to know if i am looking for a precipitate or a solution

[Edited on 3-2-2015 by Ramium]

Amos - 3-2-2015 at 03:49

You're looking for a precipitate. And I'm confused how a lot of you seem to think that phosphoric acid itself is going to form a precipitate of copper phosphate.
@blogfast Are you claiming that the copper phosphate is just going to fall out of solution into newly formed sulfuric acid? If not, what's the equation you're going by?

I just took some of my copper phosphate(I have it on hand, having made it several times) and found that it dissolved completely and easily in dilute sulfuric acid(about 10% concentration) to form a light blue solution. So no, I don't think that adding phosphoric acid to copper sulfate solution will form a precipitate, and it's probably better to go with the high-yield and straightforward synthesis from sodium phosphate.

blogfast25 - 3-2-2015 at 07:42

Quote: Originally posted by No Tears Only Dreams Now  

I just took some of my copper phosphate(I have it on hand, having made it several times) and found that it dissolved completely and easily in dilute sulfuric acid(about 10% concentration) to form a light blue solution. So no, I don't think that adding phosphoric acid to copper sulfate solution will form a precipitate, and it's probably better to go with the high-yield and straightforward synthesis from sodium phosphate.


Ok, your experiment shows that copper phosphate is soluble, in which case adding sodium phosphate to a Cu<sup>2+</sup> solution will of course not precipitate copper phosphate either.

So by NTODN's information, copper phosphate is soluble.

And in that case I would dissolve the copper basic carbonate in phosphoric acid:

3 Cu<sub>2</sub>CO<sub>3</sub>(OH)<sub>2</sub> + 4 H<sub>3</sub>PO<sub>4</sub> === > 2 Cu<sub>3</sub>(PO<sub>4</sub>;)<sub>2</sub> + 2 CO<sub>2</sub> + 8 H<sub>2</sub>O

I'll put some calcs in my next post.

[Edited on 3-2-2015 by blogfast25]

blogfast25 - 3-2-2015 at 07:58

Ramium:

Take 22.1 g (0.1 mol) of copper basic carbonate and mix it with about 200 ml of water into a slurry.

Add slowly about 30 ml of the 5.1 M H3PO4 solution. Beware of fizzing, so add in small aliquots.

Simmer for a bit on a hot plate , filter if still turbid.

Slowly boil in the clear solution until the first crystals appear and allow to cool, the copper phosphate should crystallise out.

Amos - 3-2-2015 at 08:16

Quote: Originally posted by blogfast25  
Quote: Originally posted by No Tears Only Dreams Now  

I just took some of my copper phosphate(I have it on hand, having made it several times) and found that it dissolved completely and easily in dilute sulfuric acid(about 10% concentration) to form a light blue solution. So no, I don't think that adding phosphoric acid to copper sulfate solution will form a precipitate, and it's probably better to go with the high-yield and straightforward synthesis from sodium phosphate.


Ok, your experiment shows that copper phosphate is soluble, in which case adding sodium phosphate to a Cu<sup>2+</sup> solution will of course not precipitate copper phosphate either.

So by NTODN's information, copper phosphate is soluble.

[Edited on 3-2-2015 by blogfast25]

That isn't even close to what I was saying, and I'm frankly quite surprised that you interpreted what I said the way you did. If you'd listened when I said I've already synthesized the compound, and I've told you that it's insoluble, and if you knew how acid and base reactions work, I don't see how you could've arrived at the conclusion you just made. I dissolved the copper phosphate in sulfuric acid in order to prove that your earlier advice was misplaced and incorrect.
Quote: Originally posted by blogfast25  

I've already recommended converting the copper basic carbonate to CuCl2 or CuSO4 first, to avoid problems of carbonate occlusion later on.

After that, basically dilute the Cu<sup>2+</sup> solution to about 1 M. Add the stoichiometric amount of 5.1 M H3PO4 to precipitate the Cu<sub>3</sub>(PO<sub>4</sub>;)<sub>2</sub>. Filter, wash and dry.

In a nutshell...

[Edited on 2-2-2015 by blogfast25]


Copper phosphate is INSOLUBLE in water, and forms as a gelatinous deep blue precipitate or a pale blue powder when dry.

Earlier in the thread, you claimed that rather than use my recommended synthesis, that Ramium should add phosphoric acid to copper(II) sulfate in order to precipitate copper(II) phosphate. This would never happen in a million years because sulfuric acid is a stronger acid than phosphoric acid, hence why adding sulfuric acid to copper(II) phosphate dissolves it and ordinary water does not. I have no idea how you gleaned that copper phosphate was water-soluble based on the fact that sulfuric acid reacts with it.

Here's a bit more info on the compound, it's an article that zts16 and I wrote: http://sciencemadness.wikia.com/wiki/Copper(II)_phosphate

Yes, the reaction between copper(II) carbonate and excess phosphoric acid will produce insoluble copper(II) phosphate if the two are very well mixed and every single square nanometer of copper(II) carbonate's area comes into contact with the acid. This will be very messy due to carbon dioxide evolved and the viscosity of the acid. IT IS MUCH SIMPLER TO COMBINE SOLUTIONS OF COPPER SULFATE AND SODIUM PHOSPHATE, which WILL generate an INSOLUBLE PRECIPITATE. So hopefully saying everything again in a clear way will remove any further confusion.

[Edited on 2-3-2015 by No Tears Only Dreams Now]

blogfast25 - 3-2-2015 at 08:26

Quote: Originally posted by No Tears Only Dreams Now  
This would never happen in a million years because sulfuric acid is a stronger acid than phosphoric acid, hence why adding sulfuric acid to copper(II) phosphate dissolves it and ordinary water does not. I have no idea how you gleaned that copper phosphate was water-soluble based on the fact that sulfuric acid reacts with it.


The fact that sulphuric acid is a stronger acid than H3PO4 isn't relevant here, copper sulphate doesn't contain any sulphuric acid.

If, e.g. you were to add H3PO4 to a solution of CaCl2, insoluble calcium phosphate would precipitate because the solubility product of calcium phosphate would have been exceeded. The strength of HCl has nothing to do with it.

If copper phosphate is insoluble then 10 % H2SO4 would be far too weak to dissolve it.

If copper sulphate is truly insoluble then combining copper sulphate solution with trisodium phosphate solution would of course work, no contest there.

That wikia link contains a glaring error BTW: CuCO<sub>3</sub> simply doesn't exist.


[Edited on 3-2-2015 by blogfast25]

Amos - 3-2-2015 at 08:33

Quote: Originally posted by blogfast25  
Quote: Originally posted by No Tears Only Dreams Now  
This would never happen in a million years because sulfuric acid is a stronger acid than phosphoric acid, hence why adding sulfuric acid to copper(II) phosphate dissolves it and ordinary water does not. I have no idea how you gleaned that copper phosphate was water-soluble based on the fact that sulfuric acid reacts with it.


The fact that sulphuric acid is a stronger acid than H3PO4 isn't relevant here, copper sulphate doesn't contain any sulphuric acid.

If, e.g, you were to add H3PO4 to a solution of CaCl2, insoluble calcium phosphate would precipitate because the solubility product of calcium phosphate would have been exceeded. The strength of HCl has nothing to do with it.

If copper phosphate is insoluble then 10 % H2SO4 would be far too weak to dissolve it.

[Edited on 3-2-2015 by blogfast25]


Okay, post your equation for the conversion of copper sulfate to copper phosphate by the addition of phosphoric acid so I can see what you think is going on. What you appear to be describing is this:
3 CuSO4 + 2 H3PO4 = Cu3(PO4)2 + 3 H2SO4

And for the record, none of what I'm posting here is theory. I have personally conducted every reaction I've stated; I've intentionally synthesized copper phosphate at least 3 times the same way I've repeatedly described. Its solubility in water is akin to that of copper hydroxide at best.

[Edited on 2-3-2015 by No Tears Only Dreams Now]

blogfast25 - 3-2-2015 at 08:42

The first search result here (a *.pdf):

https://www.google.co.uk/?gws_rd=ssl#q=copper+phosphate+solu...

... gives the solubility products of calcium phosphate and copper phosphate resp. as: 2.07 x 10<sup>-33</sup> and 1.4 x 10<sup>-37</sup>. This confirms the insolubility of both with the copper phosphate being even more insoluble than the calcium phosphate.

Based on these I will now calculate whether H3PO4 is supposed to precipitate them or not.


[Edited on 4-2-2015 by blogfast25]

Amos - 3-2-2015 at 08:45

Quote: Originally posted by blogfast25  
The first search here (a *.pdf):

https://www.google.co.uk/?gws_rd=ssl#q=copper+phosphate+solu...

... gives the solubility products of calcium phosphate and copper phosphate resp. as: 2.07 x 10<sup>-33</sup> and 14 x 10<sup>-37</sup>. This confirms the insolubility of both with the copper phosphate being even more insoluble than the calcium phosphate.

Based on these I will now calculate whether H3PO4 is supposed to precipitate them or not.


Besides what you think will happen, the author of the thread already described adding their phosphoric acid to a solution of copper(II) chloride and receiving no precipitate. When I get home today I will gladly combine solutions of copper(II) sulfate and phosphoric acid, and then do the same with calcium chloride and phosphoric acid, and I'll take a video of both.

Oh, and if what you're saying about the strength of an acid not mattering is true, I should be able to produce sulfuric acid by adding aspirin to a copper sulfate solution, because the copper acetylsalicylate will precipitate out.

[Edited on 2-3-2015 by No Tears Only Dreams Now]

blogfast25 - 3-2-2015 at 09:16

Quote: Originally posted by No Tears Only Dreams Now  

Oh, and if what you're saying about the strength of an acid not mattering is true, I should be able to produce sulfuric acid by adding aspirin to a copper sulfate solution, because the copper acetylsalicylate will precipitate out. PO<sub>4/sub><sup>3-</sup>



You are completely neglecting the solubility products in your truncated 'theory'. One of the weakest acids known, H<sub>2</sub>S, precipitates CuS (also HgS) from any copper salt, sulphate included. Copper acetylsalicylate will precipitate out, IF it is insoluble enough.

Simple calculation shows that for a 1 M H3PO4 solution the expected pH is about 1. Using the equilibrium equations for the deprotonation of H3PO4 it can the be calculated that the PO<sub>4</sub><sup>3-</sup> concentration would be in the order of 10<sup>-24</sup> M and that is too low to exceed the solubility product for either copper or calcium phosphate and neither would indeed precipitate.

A sodium phosphate solution would achieve that because the PO<sub>4</sub><sup>3-</sup> is much higher.

That has however nothing to do with the strength of the acid of the conjugated base of the copper or calcium salt and everything with the solubility products of the phosphates and the extremely weak third deprotonation of H3PO4.

Let me now also calculate whether Cu3(PO4)2 is supposed to be soluble in 10 % H2SO4 or not.


[Edited on 3-2-2015 by blogfast25]

Amos - 3-2-2015 at 09:32

If I'm neglecting solubility products, then I'm only doing what you did you for the first 90% of this thread while repeatedly claiming that a precipitate would form(it won't, as you now know). I'm only discussing a general trend on how NOT to produce insoluble transition metal salts; it's generally going to be a better idea to produce a soluble salt of the acid and a soluble salt of the transition metal and combine the two. This whole argument lifted off because you threw my tried and true method out of the conversation entirely and claimed the smarter way was to dump phosphoric acid into a copper salt solution. A better time to have brought out the mathematics you're doing now would have been BEFORE you misinformed the author of this thread who then proceeded to waste their reagents carrying out your unresearched methods.

[Edited on 2-3-2015 by No Tears Only Dreams Now]

blogfast25 - 3-2-2015 at 09:36

10 % H2SO4 is very approx. 1 M H2SO4. The pH would be close to 0.

At that pH the PO<sub>4</sub><sup>3-</sup> concentration would be in the order of 10<sup>-22</sup> M, again this value is not high enough to exceed the solubility product of Cu3(PO4)2 and the prediction is that 10 % H2SO4 would dissolve it.

The distribution of the phosphate as PO<sub>4</sub><sup>3-</sup>, HPO<sub>4</sub><sup>2-</sup>, H<sub>2</sub>PO<sub>4</sub><sup>-</sup> and H<sub>3</sub>PO<sub>4</sub> species is another matter.


[Edited on 3-2-2015 by blogfast25]

blogfast25 - 3-2-2015 at 09:39

Quote: Originally posted by No Tears Only Dreams Now  
If I'm neglecting solubility products, then I'm only doing what you did you for the first 90% of this thread claiming that a precipitate would form.


No, what I did was assume, wrongly, that the solubility product was low enough for copper phosphate to form with phosphoric acid.

That last burst was deeply childish, No Tears. 'Nerner nernnerner' type thing.

Your accusations are rather rich considering you based your arguments on a truncated theory of acid displacements.

You should perhaps also consider why oxalic acid precipitates calcium oxalate from any calcium salt, including calcium nitrate.

[Edited on 3-2-2015 by blogfast25]

Amos - 3-2-2015 at 09:44

Quote: Originally posted by blogfast25  
Quote: Originally posted by No Tears Only Dreams Now  
If I'm neglecting solubility products, then I'm only doing what you did you for the first 90% of this thread claiming that a precipitate would form.


No, what I did was assume, wrongly, that the solubility product was low enough for copper phosphate to form with phosphoric acid.

That last burst was deeply childish, No Tears. 'Nerner nernnerner' type thing.


I agree it was, but what I said wasn't wrong. As you were responding I was furiously editing the post to include more substance, but you probably won't enjoy the rest of that much.

blogfast25 - 3-2-2015 at 09:51

You're being puerile.

I gladly owe up to my mistake of judging the solubility of copper phosphate wrongly. I believed it was insoluble enough. Move on.

Do you owe up to yours?

[Edited on 3-2-2015 by blogfast25]

Amos - 3-2-2015 at 10:11

Yeah, I knew what happened in the case of this synthesis but I wasn't exactly sure of the reason, so the science of what I was discussing was just as flawed as what I've accused you of. Hopefully both of us will walk away with something as a result of this.

blogfast25 - 3-2-2015 at 10:18

Lets just try and get old Ramium back on track.

If he hasn't ditched the copper and phosphoric acid bearing solution and remembers the amounts used, then a simple neutralisation of the H3PO4 with NaOH or ammonia would still yield the desired copper phosphate.

Alternatively he can neutralise the required amount of H3PO4 5.1 M and add it to a neutral solution of copper basic carbonate in H2SO4 or HCl.

Considering the low value of the K<sub>a3</sub> of H3PO4, pH control is important here.

[Edited on 3-2-2015 by blogfast25]

Ramium - 3-2-2015 at 10:48

Quote: Originally posted by No Tears Only Dreams Now  
Quote: Originally posted by blogfast25  
Quote: Originally posted by No Tears Only Dreams Now  

I just took some of my copper phosphate(I have it on hand, having made it several times) and found that it dissolved completely and easily in dilute sulfuric acid(about 10% concentration) to form a light blue solution. So no, I don't think that adding phosphoric acid to copper sulfate solution will form a precipitate, and it's probably better to go with the high-yield and straightforward synthesis from sodium phosphate.


Ok, your experiment shows that copper phosphate is soluble, in which case adding sodium phosphate to a Cu<sup>2+</sup> solution will of course not precipitate copper phosphate either.

So by NTODN's information, copper phosphate is soluble.

[Edited on 3-2-2015 by blogfast25]

That isn't even close to what I was saying, and I'm frankly quite surprised that you interpreted what I said the way you did. If you'd listened when I said I've already synthesized the compound, and I've told you that it's insoluble, and if you knew how acid and base reactions work, I don't see how you could've arrived at the conclusion you just made. I dissolved the copper phosphate in sulfuric acid in order to prove that your earlier advice was misplaced and incorrect.
Quote: Originally posted by blogfast25  

I've already recommended converting the copper basic carbonate to CuCl2 or CuSO4 first, to avoid problems of carbonate occlusion later on.

After that, basically dilute the Cu<sup>2+</sup> solution to about 1 M. Add the stoichiometric amount of 5.1 M H3PO4 to precipitate the Cu<sub>3</sub>(PO<sub>4</sub>;)<sub>2</sub>. Filter, wash and dry.

In a nutshell...

[Edited on 2-2-2015 by blogfast25]


Copper phosphate is INSOLUBLE in water, and forms as a gelatinous deep blue precipitate or a pale blue powder when dry.

Earlier in the thread, you claimed that rather than use my recommended synthesis, that Ramium should add phosphoric acid to copper(II) sulfate in order to precipitate copper(II) phosphate. This would never happen in a million years because sulfuric acid is a stronger acid than phosphoric acid, hence why adding sulfuric acid to copper(II) phosphate dissolves it and ordinary water does not. I have no idea how you gleaned that copper phosphate was water-soluble based on the fact that sulfuric acid reacts with it.

Here's a bit more info on the compound, it's an article that zts16 and I wrote: http://sciencemadness.wikia.com/wiki/Copper(II)_phosphate

Yes, the reaction between copper(II) carbonate and excess phosphoric acid will produce insoluble copper(II) phosphate if the two are very well mixed and every single square nanometer of copper(II) carbonate's area comes into contact with the acid. This will be very messy due to carbon dioxide evolved and the viscosity of the acid. IT IS MUCH SIMPLER TO COMBINE SOLUTIONS OF COPPER SULFATE AND SODIUM PHOSPHATE, which WILL generate an INSOLUBLE PRECIPITATE. So hopefully saying everything again in a clear way will remove any further confusion.

[Edited on 2-3-2015 by No Tears Only Dreams Now]
is it possible that i added to much HCL so when the copper phosphate formed it was dissolved by the HCL forming a solution

[Edited on 3-2-2015 by Ramium]

blogfast25 - 3-2-2015 at 10:59

Quote: Originally posted by Ramium  
is it possible that i added to much HCL so when the copper phosphate formed it was dissolved by the HCL forming a solution



Yes but it doesn't matter: as Tear's experiment and my calcs show H3PO4 will not precipitate copper phosphate from CuCl2 solutions.

For future efforts you will need to keep tight control of the amount of HCl used to dissolve the copper basic carbonate. If you 'overshoot' and the resulting solution is acidic then you need to neutralise the excess HCl with NaOH.

You will need to neutralise some of your 5.1 M H3PO4 with NaOH solution to get a Na3PO4 solution.

H3PO4 + 3 NaOH === > Na3PO4 + 3 H2O

[Edited on 3-2-2015 by blogfast25]

Amos - 3-2-2015 at 16:32

Rather than use NaOH, you can also add simple baking soda(sodium bicarbonate) to a solution of your phosphoric acid until the fizzing stops and then add a small amount of additional phosphoric acid to destroy excess base. Be sure not to add the sodium bicarbonate too fast, as the reaction bubbles a lot and can easily cause the solution to overflow.

Zombie - 3-2-2015 at 16:58

Yes Ramium. Your Copper Phosphate is still in solution, and needs a base to precipitate it.

I have to give you a LOT of credit for your age. You managed to hang w/ the big dogs. All the while keeping track on your project.
Good work.

blogfast25 - 3-2-2015 at 19:10

Quote: Originally posted by No Tears Only Dreams Now  
Rather than use NaOH, you can also add simple baking soda(sodium bicarbonate) to a solution of your phosphoric acid until the fizzing stops and then add a small amount of additional phosphoric acid to destroy excess base. Be sure not to add the sodium bicarbonate too fast, as the reaction bubbles a lot and can easily cause the solution to overflow.


Yes, that would work.

Did you remove that link to 'wikia' on copper phosphate? If so can you post it again? I'd like to comment there that CuCO<sub>3</sub> simply doesn't exist.

Shivachemist - 3-2-2015 at 19:22

Yeah Zombie is right. It precipitates only under alkaline conditions or at least the salt you using for precipitation must be neutral and we can use any basic phosphate (trisodium phosphate) to precipitate it from the metallic salt. Does anyone have basic salt like Magnesium or Calcium acetate? or even we can use trisodium phosphate for precipitation as it is alkaline in nature. Just wanted to show how it works. But I have only monosodium phosphate which is almost neutral to slightly acidic.

Ramium - 3-2-2015 at 21:58

So if i add a small amount of sodium bicarbonate to my solution copper phosphate will pricipitate???

Ramium - 3-2-2015 at 22:02

Also my solution has turned greener is that bad???


[Edited on 4-2-2015 by Ramium]

Zombie - 3-2-2015 at 23:12

It's simply continuing the reaction. It's actually a good thing.

Shivachemist - 3-2-2015 at 23:35

Yep, but I would recommend you to use trisodium phosphate to precipitate phosphates as it is strongly alkaline in nature and cheap as well (cheaper than phosphoric acid).

Amos - 4-2-2015 at 06:32

Quote: Originally posted by blogfast25  


Did you remove that link to 'wikia' on copper phosphate? If so can you post it again? I'd like to comment there that CuCO<sub>3</sub> simply doesn't exist.


I don't think I did, but here it is again: http://sciencemadness.wikia.com/wiki/Copper%28II%29_phosphat...

You've got me curious now, when did copper(II) carbonate stop existing? The wikipedia article appears to have changed quite recently, and there's also now a wikipedia article on copper(II) phosphate that seems to disagree with most of the work I've done with the compound.

blogfast25 - 4-2-2015 at 06:36

Quote: Originally posted by Ramium  
So if i add a small amount of sodium bicarbonate to my solution copper phosphate will pricipitate???


No. The amount of sodium bicarbonate needs to be at least equivalent to the amount of phosphoric acid you originally added:

H3PO4 + 3 NaHCO3 === > Na3PO4 + 3 CO2 + 3 H2O

Just keep adding NaHCO3 slowly until fizzing stops and precipitation starts.

Metacelsus - 4-2-2015 at 07:14

Will that reaction go all the way to trisodium phosphate, or will it stop at the disodium salt? Sodium bicarbonate isn't very basic, and the pKa of disodium phosphate is 12.38, according to Wikipedia. You might need to use sodium hydroxide for the last deprotonation.

(Sorry, didn't read the full post. You might not need to deprotonate it all the way, as the copper phosphate will nonetheless precipitate.)

[Edited on 4-2-2015 by Cheddite Cheese]

blogfast25 - 4-2-2015 at 07:40

Quote: Originally posted by Cheddite Cheese  
Will that reaction go all the way to trisodium phosphate, or will it stop at the disodium salt? Sodium bicarbonate isn't very basic, and the pKa of disodium phosphate is 12.38, according to Wikipedia. You might need to use sodium hydroxide for the last deprotonation.



A small excess of NaHCO3 will create the pH in which phosphate ions can exist and you don't need much of it to exceed the solubility limit of copper carbonate!

Ks = [Cu]<sup>3</sup>[PO4]<sup>2</sup> = 1.4 x 10<sup>-37 </sup>

For [Cu] = 1 M, [PO4] = (1.4 x 10<sup>-37</sup>;)<sup>0.5</sup> = 3.7 x 10<sup>-19</sup> or pPO4 = - log[PO4] = 18.4

Also:

[H3O]<sup>3</sup> [PO4]/[H3PO4] = K1 K2 K3

Assume [H3PO4] = 1 M and take - log of both sides:

3 pH + pPO4 = pK1 + pK2 + pK3

3 pH + 18.4 = 21.7 = > pH = 1.65

So even a quite partial neutralisation of the phosphoric acid will cause copper phosphate to <i>start</i> precipitating.

[Edited on 4-2-2015 by blogfast25]

Shivachemist - 4-2-2015 at 08:07

Well, carbonates and bicarbonates are usually used to prepare Disodium hydrogen phosphate.


H3PO4 + 2 NaHCO3 ------> Na2HPO4 + 2 CO2 + 2 H2O

Then the solution should be warmed gently to expel excess of CO2 present in the solution. Disodium hydrogen phosphate is feebly basic in nature. So, it may not precipitate phosphate if the salt solution is moderately or very acidic. But, It will work for neutral salts or feebly acidic salts I believe.

However, trisodium phosphate can be obtained just by treating the aqueous solution of Disodium hydrogen phosphate with calculated quantity of Sodium hydroxide solution.

Na2HPO4 + NaOH -----> Na3PO4 + H2O

The anhydrous form can be prepared by fusing it up with Sodium carbonate:

2 Na2HPO4 + Na2CO3 -----> 2 Na3PO4 + H2O + CO2

[Edited on 4-2-2015 by Shivachemist]

blogfast25 - 4-2-2015 at 08:16

Quote: Originally posted by Shivachemist  
Well, carbonates and bicarbonates are usually used to prepare Disodium hydrogen phosphate.


H3PO4 + 2 NaHCO3 ------> Na2HPO4 + 2 CO2 + 2 H2O

Then the solution should be warmed gently to expel excess of CO2 present in the solution.


Nah, just use NaOH:

H3PO4 + 2 NaOH === > Na2HPO4 + 2 H2O

Shivachemist - 4-2-2015 at 08:32

That is possible too. There is always more than one route to prepare a compound.

[Edited on 4-2-2015 by Shivachemist]

Amos - 4-2-2015 at 10:05

The sodium phosphate(not precisely sure which salt) I produced to make my copper phosphate only used baking soda and phosphoric acid, and an excess of this salt was sufficient to completely convert the copper sulfate I used.

blogfast25 - 4-2-2015 at 10:31

Thanks for the wikia link, NTODN.

It does indeed not matter much which type of soluble orthophosphate is used, as long as the solubility product of copper phosphate is exceeded when mixing the solutions.

Ramium - 4-2-2015 at 11:08

So my understanding is if i add sodium bicarbonate very slowly to the solution untill the fizzing stops
The copper phosphate should pricipitate is that correct???

[Edited on 4-2-2015 by Ramium]

gdflp - 4-2-2015 at 11:22

Yes, dissolving the bicarbonate in water first might help make it easier to control the amount you are adding. By adding the basic bicarbonate, you're increasing the pH and consequently increasing the number of free phosphate ions in solution. I apologize, I completely forgot in my first post that phosphoric acid doesn't dissociate much.

blogfast25 - 4-2-2015 at 11:33

Quote: Originally posted by gdflp  
I apologize, I completely forgot in my first post that phosphoric acid doesn't dissociate much.


Actually, with a pK<sub>a1</sub> of 2.15 (Wiki) phosphoric acid is a fairly strong acid but subsequent deprotonations are quasi non-existent in pure H3PO4 solutions.

[Edited on 4-2-2015 by blogfast25]

gdflp - 4-2-2015 at 12:12

I meant that it doesn't dissociate much into PO43- ions, there are quite a bit of H+ and H2PO4- ions as you said based on the pKa1.

Ramium - 5-2-2015 at 13:52

I just added the sodium bicarbonate it bubbled up very high(3 times the volume of the origanil solution)the foam has bits of blue in it i think thats the copper phosphate so i will let the sun debubble it then filter to get the copper phosphate

blogfast25 - 5-2-2015 at 15:10

Try and filter it off, wash and dry properly and determine yield.

Ramium - 5-2-2015 at 17:56

Yes yes yes yes yes!!! It worked i got heaps thank you all so much i love you all

Zombie - 5-2-2015 at 20:13

I assume most of the fellas wear X large, and everyone loves hot chocolate. X-mass list Ramium!:)

Good for you sir!

Lion850 - 16-11-2020 at 17:20

Copper orthophosphate was made by reacting copper carbonate with orthophosphoric acid. The copper carbonate was from a pottery supply shop and the orthophosphoric acid 85% lab reagent quality.

3CuCO3 + 2H3PO4 = Cu3(PO4)2 + 3H2O + 3CO2

- 10.8g phosphoric acid added to small beaker
- Measure out 15g copper carbonate and start adding in small amounts with hand stirring (acid should be in small excess).
- Bubbles (of CO2) and blue suspension forming. Lumps appear to form that had to broken up with the glass rod.
- Add 30g water to thin the solution and the remaining copper carbonate – the extra water seemed to speed up the reaction. Photo below.
1.jpg - 525kB

- Heat to near boiling for 10 minutes or so, then switch off heat but leave on hot plate to cool slowly. Left for the night.
- Next day – no more signs of any reaction. Blue ppt.
- Transfer to big beaker and wash with 3 portions of 300ml water by stirring, waiting for the ppt to settle, and decanting the wash water. pH between 3-4 after last wash. Photo after final wash below.
2.jpg - 631kB

- Gravity filter and wash a few times in the funnel with water. Clear filtrate, Photo of wet ppt below.
3.jpg - 369kB

- Dry on steam bath. First dry (3 hours) weight went from 29.3g to 15.7g.
- 2nd dry, 2 hours: Weight still the same, 15.7g.
- 2g used for test, 13.7g bottled. Photos of final product below, drying did lighten the color slightly.
4.jpg - 392kB 5.jpg - 439kB

Test product with hydrochloric acid – no bubbling, thus there do not seem to be a significant amount of carbonate left, and dissolves slowly to form a light green solution.