Thread: Chromium Oxide 1.0?

Originally Posted by hi_bud_gl

Cr2O3 will not change it is size ,weight etc etc. it is permanent.

I'll the him answer on his own, but my $0.02 in case he doesn't come back around for a while.

You're looking at this the wrong way..

You are correct that a single molecule of Cr2O3 will not change it's size, weight, etc, etc.

However, a single molecule of CrO2 is not 0.5 microns. A 0.5 micron grain of Cr2O3 contains a HUGE number of molecules. What we see as powder, is in fact a pile of Cr2O3 crystals. Those crystals could have been milled down to any size.

Originally Posted by VeeDubb65

I'll the him answer on his own, but my $0.02 in case he doesn't come back around for a while.

You're looking at this the wrong way..

You are correct that a single molecule of Cr2O3 will not change it's size, weight, etc, etc.

about it is structure weight etc check this link right side table
Chromium(III) oxide - Wikipedia, the free encyclopedia

Originally Posted by hi_bud_gl

about it is structure weight etc check this link right side table
Chromium(III) oxide - Wikipedia, the free encyclopedia

That's base spec for the chemical compound Cr2O3.... but that single molecule is tiny, way, way smaller than you could ever measure. When millions of this molecule align themselves in a repeating pattern you get a .5 micron crystal. When billions of them align you get a brick. The individual molecule does not change, but the crystals of Cr2O3 can be milled to any grit size.

Try this: Chemically, it is always the same. Physically it can be manipulated.

I'm really sorry Hi_bud_Gl, but you're not right in this.

Do You know what diamond is from?
Coal. Have You see a diamond in a ring?
And in a diamond paste?
It' the same molecule structure, but very different in size.

Or let's see another example:
Do You know how computer chips were made?
You take a piece of SiO2, put in a "jar" of liquid Si, and grow a SiO2 crystal.
ONE crystal!!! And it can be a size of a dime!
And it's SiO2 NOT one molecule, one CRYSTAL!
They call it Si ONECRYSTAL!

I hope this help.

Originally Posted by mry314

I'm really sorry Hi_bud_Gl, but you're not right in this.

Do You know what diamond is from?
Coal. Have You see a diamond in a ring?
And in a diamond paste?
It' the same molecule structure, but very different in size.



I hope this help.

This is different. Now you are talking about configuration(how and in which type joining they have) of the molecules. the best example i remember is
diamond and grafit (Pencil) is exactly same but molecular configuration is different that is why they are totally different one from another.
pencils price a lot cheaper the diamonds .
if you want to go a little deeper it will confuse more people . There is Different covelent etc junction and position of the molecules will affect of the characteristics of the material. in that case name is changes to something else.
Doesn't stay same.
You don't have to be sorry while saying your opinion. thank you for that.

You're right with Diamond& graphite.
They are different molecule structures. And this is the key!
A crystal is a bunch of molecules! This is why they can be different in size.
I said (or at least i wanted to say) in the nature You can find diamond in a size of let's say a bean, and You can find the same molecule structure (diamond) in a size of an ant. They are differnt sizes with the same molecule structure, and the same "ingredient" (coal atoms).

hi_bud_gl-
Think of these compounds...
Salt. Salt is always always NaCl, whether you burn Na in the presence of Cl2 or dry salt water or anything. But, you can take the salt crystals from your salt shaker and crush them smaller.
Sandpaper. Sandpaper is either SiO2 or Al2O3. But you get different grits depending on crystal size.
Arkansas stone. Also all the same type of rock, different grits.

Cr2O3 has molar mass of 152 g/mol. This means one mole is 152 g. So 152g of Cr2O3 contains 6.0221415x10^23, or written out 602,214,150,000,000,000,000,000, molecules of Cr2O3.

It's density is 5.22 g/cm^3, thus 5.22g/ml. One teaspoon is 5 ml. So in one teaspoon you have 26.1g of Cr2O3. This is equal to (from above number of molecules per 152 g) roughly 1.6 x10^23 molecules in one teaspoon. Thats roughly 3 x10^22 molecules per cm^3. One cm^3 is 1,000,000,000 micron^3. If every Cr2O3 particle was 1 micron wide/long/tall, in one cm^3 you could only fit 1 x 10^9. If they were .5 micron, this number would be 8 x 10^9. 8 x 10^9 is a lot less than 3 x 10^22, so I'm gonna go ahead and say that actual Cr2O3 molecules are around 10,000,000,000,000 (10^13) times smaller than 1 micron. Therefore, our pastes use Cr2O3 CRYSTALS.

(Your Co2 example works, except it is a gas. Gases are individual molecules, solids are clumps of molecules bonded together)

Think of it this way guys. If you take as (an example) a xtl of quartz SiO2 6 inches long and you have enough magnification the single molecule of that xtl (the smallest amount you can have) will look exactly like that xtl. The xtl is made up of a gadzillion tiny molecules. The mineral substance always wants to look like its basic component however most of the time there was insufficient time, temperature or space for the xtl to grow. So when you go out to your back yard and pick up a piece of milky quartz it has the same exact chemical composition as the pretty xtl but the molecules are haphazzardly arranged because one or more of those factors wasn't ideal. The molecules which look like a tiny xtl will look like a basic 6 sided polygon to match the xtl system its in just that the habit of the xtls will change depending on the physical factors present when the stuff formed.

The fact you can grind up either the rock from your yard or the pretty xtl no matter how fine you make it you will never (practically speaking) get to a fineness of one molecule whether the grit size it .5 or .00000005. because once you get down to the size of one single molecule the next step down is to be looking at the individual atoms making up the anion and cation making up the quartz.

Even if the material like the CrO is not naturally forming it still obeys the same laws. You can make some very pretty artificial xtls.

clear as mud?

Originally Posted by hi_bud_gl

about it is structure weight etc check this link right side table
Chromium(III) oxide - Wikipedia, the free encyclopedia

I actually already looked all that information up in my CRC handbook.

The point, is that it's irrelevant to the discussion. The molecular weight and basic crystalline structure of a compound, be it CrO, Cr2O3, NaCl or whatever you want, has NOTHING to do with the sized the crystals can be milled to for practical application.

The basic unit of two Chromium atoms and 2 Oxygen atoms is infinitely smaller than 0.5 microns, and the only limit to the maximum size of a Cr2O3 crystal is the total volume of chromium and oxygen in the planet, and our ability to creat the right conditions for them to bond and crystalize.

If it was useful to mill and sell Cr2O3 crystals the size of golf balls, then people would do it.

"Most" of it is sold milled to 0.5 micron because that's the size that people buy. There is absolutely no reason why it "can't" be produced at a 1.0 micron size, except that practicality dictates you probably want something harder when using abrassives that hard, making diamond more popular.

The crystal explanation makes sense to me. Here's a place that sells CR203 in average grit size of 50 MICRONS. I ordered a small packet just to see how different that would be from the reported .5 micron we all know and love.

50 micron Chrome Ox

Under "About our Pigments" area it states: "All of our pigments are ground to 50 microns for ease of mixing." I confirmed this in a prompt email reply from the company when I asked for the MSDS sheet since it was not one of the ones listed on the site. They also reiterated that the Viridian (Chromium Oxide CR203) averages 50 microns in particle size.

Chris L