Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: billnotgatez on May 19, 2006, 04:54:21 AM
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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
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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?
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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.
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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.
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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?
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Borek or anyone –
Since I changed the parameters of the problem, does anyone have comments?
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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?
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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.
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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.
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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.
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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.
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but as I understand these are beyond your reach
LOL - much is beyond my reach
You have given me some ideas - let me ponder.
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Could someone move this to Citizen Chemist
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It fits AnalChem forum perfectly :)
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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.
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Borek -- as always your are correct
I am known to be occasionally wrong ;)
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Dear billnotgatez, Dear Borek,
You all may think: What a stupid, jumping between such fronts!
But I’m only a “newbie” to this particular Forum, not else !!
Sorry billnotgatez, that I’m toooo new in this Forum to have
already read Your posting about the Pigments. But You may have realised therefore,
that I usually answer a little “different” to most.
As a compensation I have figured out, that You are of the more seldom kind of
members of the Forums whit quite more then some experience!
As a maybe also experienced human (Sorry, I didn’t found out Your age.) —
You learned, as I, that every brain starts to solve problems with the tools he
knows best.
Sorry to Borek, is it not Why the old proverb tells in extremis:
“If all you have is only a hammer, every thing looks like a nail”.
Of course, it may sound hard, but - Do WE not all the same?
I’m assured, Borek was trying to do it quite well, for You too.
Now to Your Pigment-Problem:
As I have read Your Postings, and tried to filter out other answers, I have identified it
as a Pigment problem, but maybe not singular.
(Could it be, that you are working for “Dyer” or/and “varnisher”? I think.)
I think too, from Your last post, that you were already knowing the half of your “own”
answer before.
I’m happy to tell You, that Your answer (A! kind! Of! spectrometer) is absolutely right, and
ok , — BUT ….. .
As I’m “married” since ~30 years with Dyestuffs, Pigments, Cloths, Lacquers,
but also of same strength with Pharmaceuticals and Production of, - allow me
to direct two questions to You:
A.) May I be right, that You in real are more interested in the “Shade/Strength”
of the “Printing on Cloth” as on the exact concentration of the pigment(s)?
B.) Do You like, From A.), to destroy Cloths to estimate Your “liked”, if required,
concentration?
If I know Your answers, You enable me to tell you what kind of spectrometer should
be prefered AND Why IT IS the most profitable for Your problem.
YES, but IF You don’t loose the eye for the follow-up costs, a hobbyist can fullfill a lot
of others, but not that (I'm a hobbyist, too).
So, I’m waiting for Your appreciated answer in THIS Forum, because
I think it is not made for only theoretical Analytics!
Good Luck!
ARGOS++
P.S.: billnotgatez, You are absolutely right, about “cross posting”!
BUT, — Why should not “The Forum” do it for You AND Me, but mark it
as a “cross posting”!
Live could be much easier and more fun for both, with!
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thank u argoss u are the best
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I do have difficulty following your post but here is my response.
I have a paint that is without pigment to which I am adding metal powders.
The powders are aluminum and iron oxide.
A coat will have aluminum and another coat would have iron oxide.
I want to know the concentration of the metals in one square centimeter that is panted on cloth. There would be up to 4 coats with 3 coats could be aluminum pigmented and one coat of iron oxide pigmented. Let us assume that there are no impurities.
Later I would time the burn of the cloth that the sample was taken from and correlate the time versus concentration of pigment metals.
To do this I am going to build a device that can detect the concentration of a color.
This device is called a colorimeter.
http://en.wikipedia.org/wiki/Colorimeter
Although it might be less accurate than titration I think it will suffice for my project.
The question now remains what colors are involved.
Also I have to come up with the physical design and build it.
The former is harder for me than the latter.
Regards,
Bill
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Dear Bill,
Forgive me, that I implied from your earlier posts, You could be more
related to “dyeing” as it is in real, — my fault.
Even if you really do a manually painting, the process is called “dyeing”, only
not so “egal”/homogenius/uniform as mechanicly done.
Be assured, I know both Devices called “Colorimeter”, and that
a little bite better then “Wiki”.
YES, it's a “micro” little more complicate as “Wiki” can tell you, and more
correct, too! There are a Lot of faults inside, sorry!!
THE ONE — I can GUARANTY YOU —: The “Wiki”-colorimeter (WC) will not
work for you, before You HAVE NOT DISSOLVED your WHOLE square
centimeter piece of cloth into an absolutely clear solution !!!!
I think: For you a “mission impossible”!
That was exactly the reason why I was talking about spectrometer and
NOT about “colorimeters” like, OR unlike, WC.
WC’s can only measure in “Transmittance” AND NOT in “Reflectance” !!!!
Do you see the difference? “Reflectance” is absolutely required to
measure Cloth, Lacquers, and other “Such a thing”.
Pigment is the “terminus technicus” for Dyes insoluble in water, like
your “Iron Oxide” or your “Aluminium powder”.
On the other side with one wavelength of a WC, but four unknowns,
you have to be really magic for any interpretation, isn’t it.
But Your Idea is still and for ever: — Right and very close to the Best !!!
Also the spectrometer, several times called “Three-stimulus-Colorimeter” will
make you not happier, because its three values for each measurement are
mathematically not “enough” adequate to solve your problem, but to build such
needs already more knowledge as most hobbyist will give you.
What you need in this case is at least an, as cheep as possible, so
called “Color-Eye” and some Math. (I have done a Lot of such “recipes”)
Sorry that I’m not able to make it much simpler for you!
Maybe if you explain your, I hope not private, project to “X-Rite”, or other,
they will “rent” it to you for the short project time, for FREE.
But, please keep all time in mind, that “Reflectance” have not the same
high precision as “Transmittance” have !!!
I think for your needs the precision should be satisfying.
Now the problem of calibration and the Math. is still remaining to US.
So, let’s “settle it down” , before WE do the next steps!
Good Luck! — till soon, I still hope!
ARGOS++
P.S.: Thank you Bill for being still here!!
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Sorry I did not make the protocol apparent.
I do not have the steps precisely but I will give an example to kick this off.
Cut a 1-cm square piece out of the cloth that has been painted with coats of paint that has been pigmented with metal powders and dried.
Put that square in a test tube with 5 ml of sodium hydroxide solution.
Leave it set overnight so that the cloth and paint are dissolved.
The metal powders will settle to the bottom.
Remove 4.5 ml of liquid with pipette
Refill with water and repeat removal 3 times
Put in chemical solution that will dissolve the aluminum and form a colored liquid
Colorimeter measure
Repeat the removal process of above
Put in chemical solution that will dissolve the iron oxide and form a colored liquid
Colorimeter measure
PS – titration is looking better hmmmm
you might be right about mission impossible
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Not sure how you'd go about making it, but iron makes a nice coloured complex with phenanthroline that I've used for colorimetric measurements before.
I really don't know how you'd go about colorimetry with aluminum, though. The only aluminum complex I remember as being brightly coloured was a red lake that I came across in gen chem lab many, many years ago. Unfortunately...you might have a solubility issue there.
(Trying to be helpful, but I'm not really so friendly with metals.)
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Dear Bill,
( Sorry, to have not been present the few last days, because I have
sometimes something to do for my private customers, too)
I’m not sure you have seen it by yourself, that with your last
posting you have re-shuffled a little bit the card-game.
The procedure you describe looks not very reliable on one side and on
the other I have certain troubles to believe, that you will have cloth of
such a special kind.
But let me answer from the stirrup, as I have not very much time for, but
I'm pretty sure I know the answers you need:
A.) The Very, very start looks ok, but what goes in solution with the
sodium hydroxide is the Aluminium and not the Iron Oxide.
Metallic Aluminium gives with sodium hydroxide a very exothermic
Reaction, but not a solution by itself.
To build the real solution you must:
a.) Use Strong sodium hydroxide (high concentrated) and
b.) Heat it for a certain while to build Al[O3]3- as quantitative as possible,
which is soluble inside an excess of OH-.
B.) The “Likelihood” that you will have a cloth that is such easy to dissolve in
sodium hydroxide can not be believed, but dose not interfere the
“quantitative” Determination of Aluminium.
If you have the possibility to get a small glass-funnel with sintered disc
(Nr. 5 should already do it, otherwise Nr. 6; Ø = ~2cm) it will be the
much better choice as Decantation, and faster all the time too.
Filter it directly into a Volumetric-Flask and wash with fresh sodium
hydroxide solution; NOT with water !!!! (Why?).
C.) In the Volumetric-Flask you can prepare a Complex with Alizarin to be
measured with a “”Colorimeter"”, maybe around ~500nm - 530nm in
relation to a Standards. Lambdamax for Alizarin as I remember is 435nm.
The required recipe you will find at least in Complex Chemistry Books.
Keep care that you may have to measure NOT on Lambdamax to protect
your result as good as possible from other present Me-Complexes.
D.) Set your glass-funnel on the top of fresh Volumetric-Flask.
Cover the on the sintered disc remaining cloth and Iron Oxide several times
with always a small amount of “Aqua regia” for some time, and wash the
build Solution through the disc with small amount of dest.water.
As more fresh the “Aqua regia” is build as less repetition you have to do.
You can easily control it by Eye!
For your surprise, now most of your used cloth may also disappier.
E.) Thank you ?*? very much, Your posting covers one of the good,
adequate Method for quantitative determination of Iron.
I don’t know the Lambdamax but maybe ?*? can inform you about.
The only other often used Complex for this task I know, without consulting
any book, is the Acety-Salicillic-Acid-Complex with a Lambdamax
close to ~540nm.
To build the Complexes, there are Standard-method written elsewhere,
BUT keep in mind, that you have FIRST to destroy the still
remaining but unused oxidative power of “Aqua regia”
This whole procedure is adapted for conventional “Colorimeters” where
you are quite easier able to change the wavelength.
But with home-made “Colorimeters” you will mostly miss this feature, and that
means as a consequence you will miss a Lot of selectivity.
So, Please take care for!
Home-made “Colorimeters” mostly use a colour LED as a selective source
of Light, but then you are very limited.
I remember, that once a KIT was/”maybe still is” available with a Foil, to have
much better options for wavelength selection.
As for Titration you have to do anyway most of the procedure, AND additional
preparations to be able for the reliable Titration, it could be easily possible that
your Colorimetric is simpler to handle.
Please, as I had to do it in a hurry from the stirrup, validate all information,
before you start.
I hope it maybe anyway of help to you.
Good Luck!
ARGOS++
P.S.: Please keep in mind, that in the moment I have not so much
time to answer Questions as till jet! Sorry.
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The sodium hydroxide step at the beginning was to dissolve the organic material at the beginning. This would include the 100% cotton cloth as well as the doping paint. Thus we would leave behind the aluminum and iron oxide particles. everything would be liquid at that point except the metal solids of iron oxide and aluminum.
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Thank you
?*?
ARGOS++
Borek
For responding