[xchcui]

Hello.

After some searching in google,i found out that as much as the cerium oxide is purer,it will be better and more effective to remove light scratches from the car's windshield.
In wikipedia i read that the pure cerium oxide has a pale white-yellow color.
So,i started searching for the pure white optical grade cerium oxide.While i was pretty sure,that the red-brown cerium oxide,which offered at the net stores,are not pure(i assumed that it is low cerium oxide percentage/a mix with other materials).The problem is that the red-brown cerium oxide on many stores is described as 99.6% optical grade powder as the white one.So,it made me confused.
Can the brown-red powder be 99.6% pure cerium oxide,while a pure cerium oxide is actually pale yellow-white?
 

[xchcui]

Hello.

What is the difference between 99.6% white cerium oxide powder and 99.6%
red-brown cerium oxide powder?

Thanks.

[xchcui]

Hi.

What is the different between 99.6% white cerium oxide powder vs 99.6% red-brown cerium oxide powder?
And please,billnotgatez,don't remove this thread.You may remove my previous,thread(as i requested through the report section),which i didn't phrase well.

Thanks.

[AWK]

Different impurities - pure ceric oxide is a pale chamois color (see wikipedia).
Defects of structure (since thermal synthesis) may add some grey color.


PREPARATION OF PURE CERIUM SALTS AND THE COLOR OF CERIUM OXIDE.1
Arthur C. Neish
J. Am. Chem. Soc., 1909, 31 (5), pp 517–523
DOI: 10.1021/ja01935a001

[xchcui]

Different impurities - pure ceric oxide is a pale chamois color (see wikipedia).
Defects of structure (since thermal synthesis) may add some grey color.

Yes,i had already read it in wikipedia and this is what
i thought.Until i saw that:

http://www.ebay.com/itm/99-9-Pure-CERIUM-OXIDE-FAST-GLASS-WINDOW-SCRATCH-Rare-Earths-POLISH-1-5oz-Z-/191616588697?var=&hash=item2c9d3d1b99:m:mPu09VZIkjqatlL8mQIdcVA

This is 99.9% pure cerium oxide and the color is red-brown
I gave only one address for example,but there are dozen more examples.
How is it 99.9% pure while has red-brown color?
Maybe it is a kind of new cerium oxide powder?
Since i see that the cerium oxide is offered to sell as 99.9% white powder and as 99.9% red-brown powder

[AWK]

Just read this more than one hundred years old publication from JACS.
removing thaces of iron or rare earth oxides from CeO₂ is very difficult. Its color depends on method of purification.

[xchcui]

... Its color depends on method of purification.

I don't understand.What is the connection between the method of the purification,to the end result color,while it is purified to 99.9%?
It is 99.9% cerium oxide!
How can the 0.01% impurities make it,one time white
and one time brown?

[Arkcon]

You should read, more carefully, the reference provided to you by AWK:.  It says that the color is influenced by the crystal structure, as well as impurities.  Also, there's no reason optical grade cerium oxide can't be brown -- cerium oxide optics are used for infrared windows and lenses -- they could be pitch black to visible light and still function.

I've merged your older threads back into this one.  I think they were good questions.  If you look again at what you've asked you'll see where you started to get confused.

You're making a very common mistake, equating the % purity with what the impurity is, and how it effects a particular application.  Usually someone shows up, upset that food grade or USP grade chemicals are less pure percentage-wise than analytical reagents, so why can't we eat analytical reagents.  And they get just as randomly angry as you have.

[xchcui]

In wikipedia they mentioned that the pure cerium oxide is pale yellow-white in color.They didn't mentioned other color.I,also,read several articles about that and they all mentioned that the cerium oxide is yellow-white and if it isn't pure by mixed with other rare earth material,its color changes.
You says that the color depended on the method purification,but it doesn't sound logical to me and i didn't find any place that support this,on the contrary.
BTW,i am not angry,at all.i just emphasize and focus the issue that i don't understand.

[AWK]

JACS reference discusses all your doubts at the end of publication.

[xchcui]

JACS reference discusses all your doubts at the end of publication.

This article is before about 107 years and i was able to read only first page.
Its says that the purify cerium oxide process is hard and  the color of pure cerium oxide has been much disputed.
But again,that was before 107 years and it,anyway,hasn't any explanation that could clear my doubts.

[xchcui]

I am not sure about that and it is just my feeling,
But when i asked my question,i feel like you began to look for the answer in the net,since you don't know the answer.And the only thing that you find is the JACS reference from 1909(which didn'y help me at all).I am not an expert in chemistry,but one elementary rule that i learned is that every element has a specific color,every molecula has a specific color and it doesn't matter what is the method of purification,if you get the same pure element or molecula it has to be the same color.

[mjc123]

Your cerium oxide is not "pure" i.e. 100% pure. It is 99.9% pure. It has 0.1% of impurities. Depending on what the impurities are, they could give it a different colour. For a colourless or white material, it only takes a very small amount of coloured impurity to impart a distinct colour to the whole sample. For example, a 0.01M solution of copper sulfate will be distinctly blue, although it is 99.84% water. Pure diamond is colourless, but actual diamonds can have a range of different colours due to small amounts of impurities of different kinds. So it is not strange that "99.9% pure" cerium oxide from different sources could have different colours.

[xchcui]

Ok.so we agree that the impurities are the reason  to the cerium oxide color difference.
But it is not logical that 0.01% of impurity will change a white-yellow cerium oxide to red-brown in color(as the photo in the address that i provided before).
Yes,of coarse a tiny impurity in water will change the color of the water(we see it every day:tea,syrup with water etc.),but they are liquids and they are transparents.
The diamond is also transparent,so of coarse even tiny amount of impurity will be seen.
Oppose to that,the cerium oxide is not liquid and is not transparent.It is solid with a white-yellow color.If you take one kilogram flour,add to it 1 gram(0.01%)powder of instant coffee and mix it,will the mix will become brown?You may look at the brown cerium oxide photo at the address that i provided before.It is way too much brown.

[AWK]

Not only impurity! - size of particles
https://www.alibaba.com/product-detail/Automobile-rearview-mirrors-CeO2-Rare-Earth_60201386585.html
and oxygen vacansies (up to black)