| Pages:
1
2
3 |
Neil
National Hazard
Posts: 556
Registered: 19-3-2008
Member Is Offline
Mood: No Mood
|
|
I used Ti/Mn oxides to produce brittle tiny metal inclusions - it was the easiest to crush slag I managed. Each 5g only took an hour in a
very heavy cast iron mortar and pestle.
Other slags were significantly harder. 
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
One route to aluminium salts and alumina that remains worth exploring is Ye Olde Waye of treating clay (kaolin, a mixture of complex
silicates/aluminates) with hot conc. sulphuric acid. In ancient times, alum (KAl(SO4)2.12H2O) was mined as a principal source of soluble aluminium
(and later name giver to the element). But extraction of aluminium from clays soon took over for the production of ‘synthetic’ alum.
Surely TheWizardisIn could rustle up some medieval recipes for our delectation?
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by not_important  | | Nope, don't need H2SO4 or HCl, CO2 will do the trick as will NaHCO3. Takes a powerful base to form aluminates, which is why using NH3(aq) doesn't
really do the job. |
Basically a displacement reaction because the carbonate is more stable than the aluminate, right?
2 NaAl(OH)4(aq) + CO2(aq) === > Na2CO3(aq) + Al(OH)3(s) + 4 H2O(l)
Hadn’t thought of that. But it requires bottled CO2 or a CO2 generator…
NaHCO3(s, aq?) + NaAl(OH)4(aq) === > Na2CO3(aq) + Al(OH)3(s) + H2O(l)
But bicar is poorly soluble in water. You just add it as a solid and keep churning?
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
Some palce it is easy to purchase 'dry ice', which is reasonable handy for immediate use.
Yeah, stir while sprinkling the bicarb in, until fizzing stops. Excess bicarb isn't going to hurt, washing the Al(OH)3 will extract any excess.
Big guys just set the concentration of NaOH right, then heat and add a little fresh Al(OH)3; this gives 9/10 of the Al in solution as Al(OH)3 and
restores the NaOH for use in another bauxite extraction.
Clays have much Si and often Fe in them that there is considerable waste of reagents, in these days there's generally easily accessible Al salts to be
found = alum itself, the sulfate, chlorohydrate, hydroxide.
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
Some research on Alumina and Ammonia as requested, and also some interesting stuff on AlN which may be present via any thermite reaction given the
temperatures involved.
First paper is "The precipitation of aluminium hydrous oxide and its solubility in ammonia" by Prideaux and Henness. The authors noted that the
"precipitation by ammonia and its residual solubility should be explicable in terms of the electrochemical properties of the hydroxide and by the
theories of the colloidal state, but the position is by no means clear." Also, the authors noted that precipitation from a sulphate solution via
alkalis "follows a course which is determined by the amphoteric ionizations of the hydroxide, but is complicated by colloidal phenomena (Britton1)."
Further reading introduces even more complicating points as "this is not the isoelectric point of the alumina itself, as the precipitate contains acid
radicle." Please note, that the authors use the term "Hydrous Oxides" as defined by H.B. Weiser in his book "Inorganic Colloid Chemistry", Volume II,
addressing the properties of Al, Fe and Cr hydroxides that are neither definite hydroxides nor crystal hydrates.
LINK to Full Paper on "The Precipitation of Aluminium Hydrous Oxide and Its Solubility in Ammonia" by Prideaux and Henness
https://docs.google.com/viewer?a=v&q=cache:ydMv90ZG1p8J:...
On the issue of the existence of ammonim aluminate, here is an interesting albeit dated discussion published in "Journal of the American Chemical
Society", Volume 38, page 1287 :
"While no such definite evidence of the existence of ammonium aluminate is available, owing to the above mentioned impossibility of securing ammonia
solutions of high alkalinity, there seems to be no reason to doubt the analogy of the solutions in ammonia and the fixed alkalies. In this connection,
it is interesting to consider the evidence presented by C. Renz (Ber., 36, III, 2751 (1903)). This author dismisses the possibility of the existence
of an ammonium aluminate, even though by an indirect method (viz., solution of Al(OH)3 in Ba(OH)2 and subsequent addition of (NH4)2SO4) he was able to
obtain a clear solution free from Ba ++ and SO4-, 50 cc. of which contained 0.1 g. Al2O3. The fact, observed by Renz, that freshly precipitated
Al(OH)3 is readily soluble in organic amines, far from being an argument against the existence in solution of ammonium aluminate, would appear to
indicate that by the solution of aluminium hydroxide in any base, aluminates are formed, the maximum concentration being dependent upon the alkalinity
of the resultant solution and its consequent ability to repress the hydrolysis of the aluminate."
http://books.google.com/books?id=FwoSAAAAIAAJ&pg=PA1287&...
Interesting but not necessay definite source as it is a MSDS on Al2O3 (also confirmatory Aluminum MSDS)
Al2O3 is "Slowly soluble in aqueous alkalie solution-forming hydroxides. Very slightly soluble in acid, alkali."
Also, "Very slightly soluble in cold water. Insoluble in hot water."
Assuming complete accuracy of the 1st sentence (we have observed aqueous ammonia slowly dissolve Al2O3/Al and the apparent formation of Al(OH)3 ), my
chemical translation of this statement is:
Al2O3 + 3 H2O + 2 OH- --> 2 Al(OH)3 + 2 OH-
Note, I am not stating the formation of a soluble aluminate and further, as written the aqueous alkali (like NH4OH, for example) may act solely as a
catalyst. Interestingly, this is precisely the comment on a previously alluded to thread on another forum that was not documented as to source. There
is also a parallel to AlN wherein its hydrolysis induction stage is eliminated in the presence of a base with a pH of over 10.
Al2O3 MSDS Source:
https://docs.google.com/viewer?a=v&q=cache:k5ni0DPtE7UJ:...
I also found a similar comment on a chart on page 9 of a report entitled "Aluminum Compounds Review of Toxicological Literature Abridged Final
Report", prepared by Integrated Laboratory Systems, namely Al2O3 is "slowly soluble in aqueous alkaline solutions" given possible concerns on the
quality of some MSDS statements.
Link:
http://www.scribd.com/doc/2895150/Aluminum
On the burning/thermite reactions with aluminum:
Reference: "Study of aluminum nitride formation by superfine aluminum powder combustion in air" by Alexander Gromov and Vladimir Vereshchagina at
Chemical Department, Tomsk Polytechnic University, 30, Lenin Ave., Tomsk, 634050, Russia (available online 18 November 2003).
"ABSTRACT
An experimental study on the combustion of superfine aluminum powders (average particle diameter as0.1 μm) in air is reported. Formation of
aluminum nitride during combustion of aluminum in air is focused in this study. Superfine aluminum powders were produced by wire electrical explosion
(WEE) method. Such superfine aluminum powder is stable in air but, if ignited, it can burn in self-sustaining way. During the combustion, temperature
was measured and actual burning process was recorded by a video camera. SEM, XRD, TG-DTA and chemical analysis were executed on initial powders and
final products. It was found that powders, ignited by local heating, burned in two-stage self-propagating regime. The products of the first stage
consisted of unreacted aluminum (70 mass%) and amorphous oxides with trace of AlN. After the second stage AlN content exceeded 50 mass% and residual
Al content decreased to 10 mass%. A qualitative discussion is given on the probable mechanism of AlN formation in air."
Note, the reaction of any Aluminium Nitride formed in water is reportedly slow with the release of NH3 gas:
AlN + 3H2O --> Al(OH)3 + NH3
Also found a reference on the hydrolysis of AlN which inerestingly parallels that of Aluminum, Title: "The course of the hydrolysis and the reaction
kinetics of AlN powder in diluted aqueous suspensions" by Andraž Kocjan, Aleš Dakskoblera, Kristoffer Krnela and Tomaž Kosmača at Engineering
Ceramics Department, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
Available online 3 January 2011.
Abstract
"The reactivity of AlN powder in diluted aqueous suspensions in the temperature range 22–90 °C was investigated in order to better understand and
control the process of hydrolysis. The hydrolysis exhibits three interdependent stages: during the induction period (first stage) amorphous aluminum
hydroxide gel is formed, followed by the crystallization of boehmite (second stage) and bayerite (third stage). The hydrolysis rate significantly
increased with higher starting temperatures of the suspension, but was independent of the starting pH value; however, the pH value of 10 caused the
disappearance of the induction period. The kinetics was described using un-reacted-core model, and the chemical reaction at the
product-layer/un-reacted-core interface was the rate-controlling step for the second stage of the hydrolysis in the temperature range 22–70 °C, for
which the calculated activation energy is 101 kJ/mol; whereas at 90 °C, the diffusion through the product layer became the rate-controlling step."
|
|
|
sinai
Harmless
Posts: 10
Registered: 10-8-2011
Member Is Offline
Mood: No Mood
|
|
@blogfast25 that piece sure looks nice :-) yeah, al oxide is v. Hard, hence it being used on sand papers.
@Neil yeah, I always redirect heat into the house so to not waste the energy. I also tried the NaOH method, and it isn't too economic, right now i'm
trying the electrolysis methods, experimenting with ways to accumalate a powder form. E.g. pulsing the electrolysis.
Right now im waiting on a decision for Kingstn University for Pharmaceutical sc. and funnily the faculty leader is also called Neil. Hope I get in. So
guys pray for me
"Speak good, Behave good, and See good" - Ahura Mazda
|
|
|
Neil
National Hazard
Posts: 556
Registered: 19-3-2008
Member Is Offline
Mood: No Mood
|
|
Do you mean forming powdered oxide or metal?
I used a fixed DC current and ended up with slime which would turn into a wet powder as more aluminum was fed in. I set up two ring shaped electrodes
which I set aluminum extrusion in so the whole thing was self feeding.
@AJKOER - wtfbbq? You're spamming with irrelevant gibberish...
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
It's largely a replica of the previous run: reports from 1916, MSDSs etc etc. Some things never change...
|
|
|
White Yeti
National Hazard
Posts: 816
Registered: 20-7-2011
Location: Asperger's spectrum
Member Is Offline
Mood: delocalized
|
|
Reaction of aluminium chloride with sodium hydroxide will yield an aluminium hydroxide precipitate. Filter, dry, and dehydrate to get aluminium oxide.
Guys, this not a tough question STOP ARGUING! Every day I spend on this forum, people are beating each other up, getting angry at one another, arguing
etc... Learn to get along, science is not what it used to be. To get something done, you can't work alone, you need the help of others, you need
feedback, input, fresh and original ideas and information, cooperation and constructive criticizm. I thought this forum would bring intelligent people
together, promote cooperation, but no. All you guys do is argue amongst one another, trying to prove you are smarter and better than the rest,
shrinking those who are already small. Nothing gets done when you argue, and time is wasted.
|
|
|
Bezaleel
Hazard to Others
Posts: 444
Registered: 28-2-2009
Member Is Offline
Mood: transitional
|
|
blogfast25, it was me who asked for the information, the "previous run". Edit: and I'm happy it was posted.
In addition, in a few respects, reports from the beginning of the 21st century are more valuable to a simple home chemist than that which is published
these days. Simply for reasons like a home chemist doesn't usually work with ultra pure chemicals, usually has no access to advanced measurement
methods like chromatography, X-ray diffraction, etc. And so, information such as a description of colour, appearance, and ease of dissolution are of
much practical use to a simple chemist. Your experiences may be different, but mine are that such information is more frequently found in the older
publications.
[Edited on 20-8-2011 by Bezaleel]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Bezaleel | In addition, in a few respects, reports from the beginning of the 21st century are more valuable to a simple home chemist than that which is published
these days. Simply for reasons like a home chemist doesn't usually work with ultra pure chemicals, usually has no access to advanced measurement
methods like chromatography, X-ray diffraction, etc. And so, information such as a description of colour, appearance, and ease of dissolution are of
much practical use to a simple chemist. Your experiences may be different, but mine are that such information is more frequently found in the older
publications.
[Edited on 20-8-2011 by Bezaleel] |
I’m not opposed to using older reports and do it all the time. But often the information has been superseded, by use of HiTech or not (it matters
not one jot - being able to understand modern texts does not rely on being able to replicate the experimental data contained therein).
AJKOER’s claims of being able to dissolve aluminium with ammonia flies in the face of the simple fact that ammonia is used frequently in analytical
chemistry to precipitate hydrated alumina from aluminium salt solutions because the weakly alkaline ammonia solution doesn’t have the power to
dissolve ANY alumina. By contrast, using stronger alkalis like alkali metal hydroxides or alkali metal carbonates, risks ‘overshooting’: add a bit
too much and alumina starts to redissolve again because it is amphoteric. These observations are perfectly in agreement with theory. Rarely does one
see such an open and shut case.
AJKOER’s observations, by contrast, remain largely shrouded in mystery. We’re not explained what exactly he’s done, which reagents and at what
strength were used, in what conditions. No calculations or quantitative data were ever presented.
Well, if you’re going to make strong and unusual claims, present strong evidence. If not, others will have the tar and feathers at the ready.
T’was thus in olden time, t’is thus still today.
|
|
|
Neil
National Hazard
Posts: 556
Registered: 19-3-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by White Yeti | | ...Guys, this not a tough question STOP ARGUING! Every day I spend on this forum, people are beating each other up, getting angry at one another,
arguing etc... Learn to get along, science is not what it used to be... |
No argument there.
AJKOER is posting irrelevant pieces of data out of context. For example he says that the nitride data is in relation to thermites, it has
nothing to do with thermite.
Further, by selectively quoting the article he omits the data that the aluminum was not burned in open air but rather in a sealed reactor - the
difference is night and day. Aluminum nitride has nothing to do with this thread.
That is not bad science, that is fraud. Up until that the thread was largely in self agreement. Pissing contests are one thing and yes, they bring the
quality of the forum down. Posting BS and then re-posting it over and over and over again should be met with rigid objection because this is science,
not BS.
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
I apologize for not being even more clear and adding the person's name as to why I was supplying the references.
OK, to get the record straight, I believe the reaction of ammonia and Al2O3 is best described as the ammonia acting solely as a catalyst. The
mechanics, I suspect, are that the ammonia raises the pH and reduces the inception period as has been observed in the hydrolysis of AlN. Thus, the
product of NH3 and Al2O3 is most likely a NH3 peptised/supersaturated hydrated alumina (with no chemical reaction). Other possibilities are less
likely, in my opinion. On a point of full disclosure, my catalyst depiction is not an original opinion, as it was presented on another thread, but
left undocumented as to source (in spite of my direct attempts to secure documentation).
However, interesting from a patent law perspective, since one might claim that there is an ostensible reaction that seemingly produces Ammonium
aluminate (as I described in my dated reference from Journal of the American Chemical Society, a legally authentic source), one cannot, from a patent
law perspective, categorically declare that is does not exist. Hence, interestingly I have seem references to it in Patents, possibly to cover bases,
and in my opinion, not due to its likely existence. This legal point is also why I find it important to quote the reference, however foreign to my
personal opinion. My source is taken from the US Government Patent Office ( per 2173.05(t) Chemical Formula - 2100 Patentability), "A compound may
also be claimed in terms of the process by which it is made without raising an issue of indefiniteness", where indefiniteness is a cause to dismiss a
patent claim. Interestingly, Ammonium aluminate has been cited in at least one patent, possibly since one cannot claim its "indefiniteness".
Now, my presentation of the AlN material was mostly due to its interesting hydrolysis properties as described earlier and to confirm the observed
difficulties in burning Al to form Al2O3. I also noted that it MAY (or may not especially in completely sealed environments) be of any significance in
thermite reactions. However, to be honest, when people are producing some very hard materials at home, given the hardness properties of AlN, I wonder
if any AlN could be present in spite of claims of purity from home chemists (which, may indeed, be the case here).
GOOD LINK TO PRIDEAUX PAPER
https://docs.google.com/viewer?a=v&q=cache:ydMv90ZG1p8J:...
[Edited on 21-8-2011 by AJKOER]
[Edited on 21-8-2011 by AJKOER]
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
On references, I should also cite an influential one on my thinking supplied by Neil. To quote Neil's specific reference taken from : "Pitting
Corrosion Mechanisms and Characterization of Aluminum in solar Heating Systems" by Liang and Zhang (2006):
"The complex characteristics and mechanisms of aluminum pitting corrosion in a solar heating system were studied by the chemical immersion method and
electrochemical techniques as well as fractal theory. The results showed that pitting corrosion of Al occurred in a tap water environment due to the
local enrichment of Cl- ions."
My favorite quote from this paper is:
"However, the passivation film over Aluminum and Al alloys is easily destroyed in the solution containing active anions, such as Cl-, which leads to
localized corrosion".
I believe this is directly referring to the removal of the protective Al2O3 layer by Chloride anions. My take on this is that there may be many
compounds that are possible catalysts to induce the Al hydrolysis reaction by disrupting the pH of the solution for which the authors noted that
"Aluminum and Al alloys are passivated in neutral solutions".
LINK:
http://proj3.sinica.edu.tw/~chem/servxx6/files/paper_7425_12...
I would also mention that Neil performed experiments seemingly confirming the action of chloride anions on Al as the paper noted.
[Edited on 21-8-2011 by AJKOER]
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
A point on a common thermite starting mixture:
2 KNO3 + 4 Al + S --> K2S + N2 + 2 Al2O3
So, it is possible to have nitrogen gas present even in a sealed environment, although this may not be the case here.
More of concern to me does any of the very hot Al2O3/Al mix cool in air, and could this produce any AlN? Note the surprising large percent of the arc
heated Al converted to AlN in my cited reference when burned in open air.
However, if any of you more experienced thermite guys are convinced that AlN is not a factor, I will accept it.
[Edited on 21-8-2011 by AJKOER]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by AJKOER | A point on a common thermite starting mixture:
2 KNO3 + 4 Al + S --> K2S + N2 + 2 Al2O3
So, it is possible to have nitrogen gas present even in a sealed environment, although this may not be the case here.
More of concern to me does any of the very hot Al2O3/Al mix cool in air, and could this produce any AlN? Note the surprising large percent of the arc
heated Al converted to AlN in my cited reference when burned in open air.
However, if any of you more experienced thermite guys are convinced that AlN is not a factor, I will accept it.
[Edited on 21-8-2011 by AJKOER] |
Sulphur is sometimes added to these ignition mixes but it's not strictly speaking necessary. The sulphur would combine with the Al though, because
Al2S3 has a high value for HoF. That's why the system 2 Al + 3 S === > Al2S3 is used to heat boost silicon thermirtes. Smelly but effective and
cheap...
The overwhelming majority of thermites aren't carried out in 'sealed environment', as that would be a general call for explosions to occur.
AlN in thermite conditions? Forget it. Firstly AlN has a much lower HoF than Al2O3 which means that the oxide is much, much more preferentially formed
than the nitride.
Also: here the oxidising power is provided by the oxydiser (the oxyde, mixture of oxydes or oxyde + booster oxidiser). Nitrogen simply doesn't get a
look in.
[Edited on 21-8-2011 by blogfast25]
|
|
|
Bezaleel
Hazard to Others
Posts: 444
Registered: 28-2-2009
Member Is Offline
Mood: transitional
|
|
8 days ago, I put some strong ammonia (18/20° Baume) in an erlenmeyer flask and put a piece of aluminium foil in it. Teeny tiny amounts of gas
evolved, the bubbles being on the verge of visibility for the human eye. This was left to react for 8 days, at a temperature of around 20°C.
Today, I took out what has remained of the foil, and poured off the solution. On the flask, a white substance had formed. It did not dissolve in 10%
acetic acid, and neither in 5% hydrochloric acid, not even when heated to boiling.
Below are some pictures of the results. The substance formed was pure white, but in the pictures it is a bit coloured due to the lighting conditions.
 
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Try dissolving it in stronger acid and stronger alkali (NaOH or KOH). If it dissolves in the latter you can be fairly sure it's (hydrated) alumina.
If it really is hydrated alumina, what this would clearly suggest is that there's enough OH- (but not much: even at that strength an ammonia solution
is a weak base) to attack Al and produce hydrated alumina but not enough to create aluminate
(Al(OH)<sub>4</sub><sup>-</sup> because:
NH3(aq) + H2O(l) < === > NH4+(aq) + OH-(aq)
... leans strongly to the right.
[Edited on 28-8-2011 by blogfast25]
|
|
|
condennnsa
Hazard to Others
Posts: 217
Registered: 20-4-2010
Location: Romania
Member Is Offline
Mood: No Mood
|
|
shouldn't aluminum hydroxide dissolve readily in dilute HCl?
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Depends a bit on strength and age of the oxide, really... Of course the precipitate could have been something in the ammonia but I can't think what it
could be.
[Edited on 28-8-2011 by blogfast25]
|
|
|
Neil
National Hazard
Posts: 556
Registered: 19-3-2008
Member Is Offline
Mood: No Mood
|
|
Crystallized oxide dropped when the material under it was dissolved?
Possibly protective coatings?
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Neil | Crystallized oxide dropped when the material under it was dissolved?
Possibly protective coatings? |
Too much stuff for that, IMHO...
|
|
|
Bezaleel
Hazard to Others
Posts: 444
Registered: 28-2-2009
Member Is Offline
Mood: transitional
|
|
| Quote: Originally posted by blogfast25 | Try dissolving it in stronger acid and stronger alkali (NaOH or KOH). If it dissolves in the latter you can be fairly sure it's (hydrated) alumina.
If it really is hydrated alumina, what this would clearly suggest is that there's enough OH- (but not much: even at that strength an ammonia solution
is a weak base) to attack Al and produce hydrated alumina but not enough to create aluminate
(Al(OH)<sub>4</sub><sup>-</sup> because:
NH3(aq) + H2O(l) < === > NH4+(aq) + OH-(aq)
... leans strongly to the right.
[Edited on 28-8-2011 by blogfast25] |
To the left, that is... And indeed, no aluminate is formed.
Since not all of the foil dissolved, the white material is not the oxide skin of the foil.
IIRC, aluminium hydroxide is a voluminous, jelly substance, so I'm inclined to say the white substance be the oxide. In addition, the hydroxide would
have easily dissolved in 5% HCl.
I discarded the reaction products, so I can't do any furhter testing. I'm amazed though, that with a weak base like ammonia, the foil has reacted at
all.
|
|
|
Neil
National Hazard
Posts: 556
Registered: 19-3-2008
Member Is Offline
Mood: No Mood
|
|
In the first pictures it looks like there is more white material, a slime or gel?
Is it possible that some of the material was lost when you poured of the original liquid or during subsequent filtration/decantations?
I agree, the amount of material is to great. Ammonia is used in a number of anodizing mixtures for Al, is it possible it catylised the crystallization
of the aluminum hydroxide?
The oxide layer on the foil may have been thick enough to provide seed crystals.
Did you happen to handle the foil with your bare hands before it was added to the ammonia?
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
Caution, while the voluminous jelly substance is most definitely Al(OH)3, the white substance you saw could be an impurity from the Aluminum foil as
it is commercial grade Al, which is anywhere from 92% to 99% pure, or some alpha Al2O3, formed in a hardening process, which is not soluble in acids
or bases.
On impurities, we have mentioned Silicon, some foils have Fe for added strength, at times Mn, but would anyone believe a small amount of Lead (Pb
maybe country specific due to manufacturing process) as a possible impurity? See article reference below (I hope I am misreading).
"The effect of lead impurity on the DC-etching behaviour of aluminum foil for electrolytic capacitor usage" by W. Lina, , G. C. Tua, C. F. Linb and Y.
M. Pengb
a Institute of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan R.O.C., at Materials Research Laboratories,
Industrial Technology Research Institute, Hsinchu, Taiwan R.O.C.
Received 26 June 1995; revised 17 October 1995. Available online 16 February 1999.
"Abstract
The effects of lead impurity on the etched morphology of high purity aluminum foils for electrolytic capacitor applications were investigated in this
work. The lead impurity was either present in as-received aluminum foils or deposited purposely on the foil surface through an immersion-reduction
reaction. The amount and distribution of deposited lead varies with the lead content in as-received foil. The as-received foil with higher lead
content gave a higher concentration and a more uniform distribution of deposited lead."
Note, Aluminium is reported to be chemically resistant in contact with substances in the pH range 4 to 9.
|
|
|
| Pages:
1
2
3 |
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
