odd reaction

[bob000555]

I recently mixed together powdered ferric ammonium sulfate, borax and sodium carbonate. I then heated the powder over a Bunsen burner and the mixture started turning red as the reaction continued it got redder. I didn’t smell the so2 or ammonia one would expect when heating FeNh4(SO4)2, does anyone know what happened in this reaction?

[woelen]

You obtained Fe2O3, which made the mix appear red, mixed with ferric borate and many other things. Actually, you made quite a mess. With further heating I do expect you to smell NH3, but no SO2. SO2 is not formed under these conditions, there is no reducing part available.

[bob000555]

Is it possible to purify the ferric borate from the mixture, also is it possible to extract boron from borax?

[YT2095]

you can dissolve the borax in HCl and use fractional crystalisation, boric acid isn`t very soluble so it would be fairly easy.

[woelen]

Extracting boron from borax can be done, but it is not easy. First make boric acid, as suggested by YT. Then isolate that acid and heat it, until it forms a glassy mass, which is mainly B2O3. Let this solidify and then crush the solid and mix this carefully with powdered Mg. Use excess B2O3. When the mix is ignited, then you'll get magnesium borate, magnesium oxide and some free boron. When this stuff is added to dilute HCl and boiled for some time, then all dissolves, except the boron. With this method you can make boron, but its purity is not very good. If you can make 90% pure boron, then you have done a very good job.

 

Don't use too much Mg. If you do that, then excess Mg will reduce boron and MgB2/Mg2B3 is formed.

[YT2095]

my bad, I didn`t read "Boron"

there`s a thread about this here: http://www.scienceforums.net/forums/showthread.php?t=15619

 

and yes 90% would be fantastic, I esstimate mine was only about 10-20%, but enough for a small a sample, also, Don`t use your favorite test tube for this, it`s quite messy!

[bob000555]

I have another one, I mixed FeSO4 with Na2CO3 and it turned blue. Does any one have clue what reaction happened. Also ,unrelated, is there a proxy acid of nitric acid?

[woelen]

FeSO4 and Na2CO3 normally gives rise to formation of white FeCO3. However, what people call FeSO4 (from gardening suppliers, or pattery/ceramics suppliers) hardly can be called so. It is insanely impure stuff, of green color, with yellow/brown crap in it. It is a mix of iron(II) and iron(III) sulfate and basic sulfate. When this stuff is mixed with carbonate, or hydroxide, then both iron (II) and iron (III) precipitate as carbonate and hydroxide. This mixed precipitate then turns to Fe3O4, which is black, but when finely divided and mixed with lighter turbid material, it looks dark blue. IIRC the black material is called hematite.

[YT2095]

it`s also possible that your sodium carbonate contains sodium hexacyanoferrate (and anti-caking aget), that will react with iron sulphate to make a very noticable blue color also, and it only needs a tiny amount to do this

[woelen]

YT, that is not possible. The blue compound only is stable in neutral and acidic environments and in basic environments it will not even be formed. Even weak bases destroy the blue color. This is in fact a nice demonstration, which you could try yourself. Make some of the blue material and then add some base. Either NaOH, or Na2CO3, and even dilute NH3 destroy the blue color again, leaving behind lightbrown Fe(OH)3 only.

[YT2095]

potassium iron (ii) hexacyanoferrate(iii) KFe[Fe(CN)6] Mrs. Stewart's liquid laundry bluing is used to whiten clothes and may be found in the detergents section of the market.

 

taken from: http://www.csun.edu/science/ref/equipment/acquisition/common.htm

 

also doesn`t Cyanotype work in a Basic reaction (Ammonia) : http://www.astro.wisc.edu/~mukluk/blprint.html

if it agricultural grade iron sulphate, you can bet there will Ammonium salts in it also.

 

just a thought

[woelen]

Ammonium salts are not basic, they are acidic. The ion NH4(+) is slightly acidic.

 

But really, the blue iron(II)iron(III) cyanoferrate complexes do not withstand alkaline liquids. Even a simple base like Na2CO3 will destroy it. Try it. Maybe that some washing products with a pH of 8 still allow this complex to exist, but only at a little higher pH it will be destroyed. So, I truly do not believe that the blue color can be due to hexacyanoferrate complexes. It must be due to formation of Fe3O4.

[bob000555]

All the chems where reagent grade what is the blue compound? Is it FeCo3? I know NaSo4 isn’t blue….

[woelen]

FeCO3 is white, so it cannot be FeCO3. Fe(2+) ions are VERY prone to aerial oxidation in alkaline environments. Then that must be the reason for the blue color. You first make FeCO3/Fe(OH)2, which then is partly oxidized by air to form a dark compound, containing both Fe(2+) and Fe(3+). Have a look at the things I did with Fe(2+) and hydroxide and at the extreme air-sensitivity of this.

 

http://woelen.scheikunde.net/science/chem/solutions/fe.html

[YT2095]

in my CRC book, Fe3O4 is listed as Black(red), FeO as just Black, and the sulphide also as Black, if the PPT is fine enough it`s possible for these to look blue in the right light.

 

try taking a test tube of this and leave it to stand still for a few days, see if any ppt settles out, you could also try using a magnet also, as Fe3O4 is magnetic (its used to make Video tape).

 

Woelen, when you say Ammonia is Acidic, do you mean as a Lewis acid?

[woelen]

Woelen, when you say Ammonia is Acidic, do you mean as a Lewis acid?

I said that ammonium is acidic. Ammonia is not. Ammonia is a base, both in the Bronstedt way (accepts protons, forming ammonium) and also in the Lewis way (shares/"donates" a lone pair of electrons).

 

Iron sulphate may contain ammonium sulfate and then it makes the solution more acidic, because of the acidity of ammonium ions.

[bob000555]

Is the reaction CH4+CO2->2C+2H2O perhaps under extreme pursuer and in the presence of a catalyst? Im thinking so because coal scrubers use

2H2S+SO2->3S+2H2O

[woelen]

Comparing sulphur with carbon is like comparing apples with oranges. You can't use such analogies.

 

And no, CH4+CO2 do not react, unless when heated to such extreme temperatures, that everything does react. It is even the other way around. Carbon reacts with water at sufficient high temperature to make CO and H2 (this mix in the past was used as fuel gas).

[bob000555]

I tried another experiment. I mixed copper sulfate, magnesium sulfate , and sodium bicarbonate . The Mixture was then heated to 280 degrees Celsius it formed to distinctive compounds ; a black one and a green one. The sulfates where reagent grade the sodium bicarbonate was medical grade. Ideas as to what happened.

 

I’m going to grind the mixture and heat it agene.

update: i ground and reheated it all the green is gone now its all black. Maybe the green was copper carbonate? Ohhh and my lab mits were on fire for about 2secs i wasnt burned.

[woelen]

The green material indeed most likely is copper carbonate, or some basic copper carbonate/sulfate. The black material probably is CuO.