woelen
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Ebay dispute, stannous oxide vs. stannic oxide.
Last week, I saw that a UK seller offers tin oxide, 88.1% Sn by weight. I did some computation and found that this corresponds to the formula SnO.
That looks very interesting. SnO is a dark (almost black) compound, which dissolves in acids, giving tin(II) salts and also in bases, giving
stannites. So, woelen was happy, finally finding a cheap and plentyful source of tin(II) salts. Price tag was only GBP 6 for 500 grams (plus GBP 6 for
shipping to NL). I ordered 500 grams and immediately paid the GBP 12 (which is almost EUR 20).
Only 5 days later, the parcel arrived, with 500 grams of tin oxide. Now comes the bad thing. The powder is white, and it does not dissolve in any acid
(not even conc. H2SO4). It also does not dissolve in conc. NaOH. I tried boiling, waiting for a few hours, nothing  . This stuff is useless.
I already have SnO2 and that powder also is white and VERY inert. Now I think that I just received another 500 grams of SnO2 which is totally useless
for me  .
I wrote a message to the seller, and explained to him that I think his description is wrong. Based on the remark of 88.1% Sn I decided to buy the
stuff, because that corresponds to SnO. SnO2 has 78.8% Sn-content. The seller responded to me, that his analysis says it has 88.1% Sn, and hence the
description on eBay is right. He did his duty by promptly sending me the material after I paid and does not want to refund.
I am 100% sure, that if the material really is 88.1% Sn, then its formula must be SnO. But is SnO really a white and very inert powder? I did some
research on Internet and found descriptions, telling it is very dark blue, almost black. Another description tells it is very dark brown, almost
black. The material is used as a source for other tin(II) salts and for electroplating tin. The only exception is wikipedia, which tells that the
material is white.
So, who is right, me or the seller? If there indeed is a white and very inert compound with formula SnO, then I will stop complaining and give
positive feedback to the seller (and then I accept the disappointment), but if he is wrong, I will ask him to refund, or otherwise I will give
negative feedback. Can anyone give some advice on this. I almost paid EUR 20 for something, which is totally useless to me, so it is worth the effort
of spending a little time on this for me.
In the past, I already ordered a few other chemicals from this eBay seller. He always is very prompt (sending material in just a few days) and has
good prices, so I really do not feel like giving him negative feedback now, but of course, I also like to get what I order.
[Edited on 20-6-07 by woelen]
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Eclectic
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Cotton and Wilkenson's "Advanced Inorganic Chemistry" says a white hydrous oxide dehydrated to black SnO at 60-70C which disproportionates to Sn and
Sn3O4 above ~250C and Sn and SnO2 above 500C.
SnO2 should dissolve in molten NaOH, just like SiO2.
It's very difficult to convince people they are wrong even when it does not involve them loosing money. But here is a way to dissolve your insoluble
tin oxide, if you can produce some sulfur dioxide:
(from "Industrial and Engineering Chemistry" Vol. 16, No. 4)
The following procedure is recommended for the treatment
of an alloy containing tin or antimony or both:
Treat 1 gram of the borings with 20 cc. of concentrated
nitric acid and 10 cc. of water. Evaporate to dryness over a
flame or a steam bath. Add 10 cc. of dilute nitric acid and
warm. Filter and wash with dilute nitric acid. The filtrate
will contain all the metals except the tin and antimony, which
are retained as oxides on the filter paper. Up to this point
this is a regular procedure for alloys.
--->Wash the oxides into a
beaker with 50 cc. of a strong solution of sulfur dioxide and
digest from 3 to 5 minutes at 60" to 70" C. Heat to boiling,
add about 10 cc. of concentrated hydrochloric acid, and boil
until all sulfur dioxide is removed. <--
If necessary to remove
traces of the oxides from the filter paper, this can be treated in
a similar manner. Tin and antimony will now be in solution
as chlorides of the higher valence in the presence of traces of
sulfate, which is a convenient form for further treatment.
[Edited on 6-20-2007 by Eclectic]
[Edited on 6-20-2007 by Eclectic]
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bio2
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According to CRC 74th edition (1993)
SnO is black, cubic, tetragonal and the hydrate (xH2O) is white powder or yellow/brown crystalline.
Solubility for both given as acid, alkali, and slightly
soluble in NH4Cl.
The dioxide SnO2 is said to be white tetragonal (also
hexagonal or rhombic crystalline form. Solubility is KOH
and NaOH with decomposition. Insoluble aqua-regia
The dioxide hydrates are amorphous or gel.
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Ozone
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Yup. 88.1 corresponds to SnO and 78.77 to SnO2. I thought at first that if impure, this could be part of it, but even at 95% purity (minimum available
from aldrich, quite expensive, too) that would give a Sn mole fraction of something like 0.87 (assuming that the 5% was SnO2).
Oh well, the specs for the product are attached.
[Edit] the SnO dihydrate would have a Sn mole fraction of 0.777... Anyway, Merck indicates that SnO2 will slowly dissolve in hot, concentrated
caustic.
Hope that helps,
O3
[Edited on 20-6-2007 by Ozone]
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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S.C. Wack
bibliomaster
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Have him try to produce this certificate of analysis. No doubt you could produce much documentation on the properties of the oxides, but perhaps the
seller was being deceptive and will continue to be so.
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Pyridinium
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Just out of common decency, the seller should give you a refund or at least a partial refund. You were misled.
Boiling the SnO2 in conc. NaOH can take a long time. You will probably ruin the glass container. Boil with an ice flask on top to reflux the water
vapor so it doesn't go dry; keep it that way for a few hours. Or just fuse the SnO2 with NaOH in a nickel crucible.
Another idea might be to fuse it with a reducing material such as sulfur. I have a bit of SnO2 kicking around here, I might try it myself later
(first in milligram quantity to see whether it's energetic).
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Fleaker
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Tell him you work with chemicals all the time, that you've been a reliable buyer and have been thusfar happy with his items, but explain that you have
not received the proper compound.
Send him a link to your website if he doesn't believe that you KNOW what you're talking about.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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