[billnotgatez]

Greetings All,

Normally I post my questions involving personal projects in the Citizen Chemist forum, but I want to be assured that list members that are interested in Analytical Chemistry will see my post and respond. We know that cross posting is frowned upon.

I have some iron oxide powder and aluminum powder mixed in Cellulose Acetate Butyrate doping paint that was painted on cotton cloth. I also have iron oxide powder and aluminum powder mixed in Cellulose Nitrate doping paint that was painted on cotton cloth. I know the concentrations of the entire constituents and coverage rate for the paint. Thus I can estimate the amount of each constituent per area. I would like to use an analytical method to confirm these estimations. I want to use a method that will not be influenced by the possibility that other iron compounds or elemental iron or aluminum compound (aluminum oxide) might be present. I would like to analyze 1-centimeter squares of the painted cloth.

What methods would you recommend? Someone has suggested to me back titration. I would like to be able to do this in a citizen chemistry laboratory. I do have a scale that does 0.01grams and I can acquire some glassware or make it myself. I also have various size graduated cylinders. Also, you can mention other methods that might be used in a regular laboratory.

Thanks in advance
Bill

[Borek]

You have any idea what other compunds can be present?

And what do you want to determine? I suppose you mean both powders, not the cellulose *.* compounds?

[billnotgatez]

The company that manufactured the iron oxide powder said any other compounds in the pigment were mostly inert silicates. I just wanted to not count any elemental iron or naturally occurring iron compounds in the unlikely case they were in the pigment.

The source of the aluminum powder said it was fairly pure, but I do not want to count any aluminum oxide should some be present due to natural oxidation.

Although the concentration of the doping paint is not as important, it might be interesting to know that parameter.

By the way thank you for responding. I am going back to sleep now and will look here again when I wake.

[Borek]

I doubt it will be easy. When you will dissolve sample all oxides will get dissloved (in case of Al) and all other sources of  iron will probably dissolve too. So you will determine sum of all forms.

[billnotgatez]

I am going to relent here so as to get some suggestions as to best method. Let us assume that the original aluminum and iron oxide is pure. What method would a citizen chemist use to get the concentrations of each on a painted square of 1 centimeter? I suppose I could build a colorimeter. A titration system would be more problematic in that calibrating the glassware. I do not think my scale is sensitive enough for 1-centimeter sample. I seem to remember a device that detects the intensity of color of a burning compound. Maybe using something that detects electric or magnetic change. What does anyone suggest?
 

[billnotgatez]

Borek or anyone –

Since I changed the parameters of the problem, does anyone have comments?

[Borek]

Since I changed the parameters of the problem, does anyone have comments?

No. I still don't see any way to differentiatie between iron/aluminum present in the coating and in possible impurities.

Where they can be present? On the surface, they can be part of the material painted?

[billnotgatez]

There is a doping paint, which is composed of Cellulose Acetate Butyrate and several organic solvents. When painted on 100% cotton cloth the solvents evaporate leaving the cotton impregnated and coated with the Cellulose Acetate Butyrate. The first coat of doping paint seeps trough the cloth. When the cloth and paint dry there is some shrinkage. It is also stiffer and resistant to water. Also air will not pass through very readily. When stretched over a frame it becomes a good method to create a fuselage and wings. The color when dry is translucent milky yellow white. To enhance the qualities for resisting the effects of weathering and the sun, pigments were added. The first coat contained iron oxide powder, which was followed by several coats containing aluminum powder. Let us say that there were 3 coats of aluminum pigmented paint applied after the first coat of iron oxide pigmented paint. 

What I want to do is confirm the concentration of the iron oxide and aluminum for a square area of the cloth. Let us assume that the pigment powders added to the doping paint are pure iron oxide and pure aluminum.

[Borek]

Basically you have repeated what you have wrote much erlier, just omitting

a method that will not be influenced by the possibility that other iron compounds or elemental iron or aluminum compound (aluminum oxide) might be present

So I will repeat my question: what other compounds do you expect? Could it be that the cotton cloth was already impregnated with some Fe/Al containing substances? If so, you may start with analysis of the not-yet-painted cotton, then do the analysis of painted cotton and simply substract results.

[billnotgatez]

Borek et al,

Seems that I have muddied the waters by mentioning impurities in the first post. Let us assume that there are NO impurities in the sample. You have a piece of cotton cloth painted with 1 coat of iron oxide pigmented doping paint and three 3 coats of aluminum pigmented doping paint. Can you suggest what method you might use to get the concentration of the pigment metals for a square area of painted cloth? How much aluminum and how much iron oxide?  I hope I am clearer this time.

[Borek]

Makes sense now. Dissolve in acid, then two titrations - iron by manganometry, sum with EDTA (although it will be backtitration with zinc to be precise, as Al³⁺ gets complexed too slowly).

But it can be hard as amount of metals on the small surface may be too low for volumetric methods. If so, some spectroscopic method will probably work, at least for Fe - but as I understand these are beyond your reach.

[billnotgatez]

but as I understand these are beyond your reach

LOL - much is beyond my reach

You have given me some ideas - let me ponder.

[billnotgatez]

Could someone move this to  Citizen Chemist

[Borek]

It fits AnalChem forum perfectly

[billnotgatez]

Borek  --   as always your are correct, but here is my reasoning.

First -
After reading your titration regimen for this problem I figured it might be too time consuming.  Many spectroscopic methods may not be suitable for a citizen chemist as far as equipment availability. But, maybe a colorimeter might be just within reach. In fact building one may well be a possibility for the hobbyist. I thought that that building would be more of a citizen chemist discussion.
Second –
I posted here because I thought that we would get responses from several people. I am not sure this forum is the place for brain storming. So as soon as you answered the question precisely and accurately, any others just moved on. I was hoping for a little debate. It happens on occasion (too many sometimes) that I assume too much.

Therefor I thought moving to the citizen forum might get a little more action. I thought with changing the proposed process that it would be a good time to shift. It is ironic, but I think I might not get any debate there. Probably the best location is in the philosophy forum <grin>. In any case, I yield to your desires. Heavens knows I am not the best decider.