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aga
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Tin and Zinc Chloride Synthesis
Today i had a couple of 250ml beakers containing 20% HCl, with Tin metal shavings in one and powdered Zinc in the other.
Stoichiometric ammounts were calculated then more HCl was added as the beer volume increased.
The metals are 99%+ pure, and the HCl is pretty clean too (no Fe at least).
Something that blogfast25 taught me sprang to mind when watching both reactions : Thermodyamics Makes no Pronouncent Regarding Kinetics.
So, as the Zn reaction was fizzing nicely and the Sn was not, Heat was added to increase the energy of the atoms/molecules and also their Kinetic
activity.
Both reactions become Much more interesting (faster).
Most Intersting that i went at it from that angle, wheras our fore-runners would have wondered what Heat would do, and arrive at the same result.
The Tin chloride is to make a testing reagent for another go at the deltaH Gold Dissolution Hypothesis when some gold arrives off ebay.
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Little_Ghost_again
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what was the volume of gas V the temperature?
or how much gas evolved per 0C
[Edited on 2-10-2015 by Little_Ghost_again]
Dont ask me, I only know enough to be dangerous
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aga
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Stoichiometrically speaking it would have been around, let me guess, er, 4.72 Litres of Hydrogen gas evolved, starting with 25g of Sn.
As for Total Gas, no idea, seeing as there's the HCl boiling off and some Steam, so i really dunno.
Care to Enlighten ?
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Sulaiman
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;)
Little_Ghost_again, from the posterior of the second line of the original post
evolved gas volume would initially be minimal but must rise,
depending upon environmental availability of catalysts
(such as fermentable oligo-, di-, and monosaccharides and polyolsfermentable oligo-, di-, and monosaccharides and polyols)
the volume (and associated pressure) increase may be uncontrollable.
[Edited on 3-10-2015 by Sulaiman]
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blogfast25
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Tin is definitely slower than zinc but your comparison is a bit flawed as powder implies more surface area per mol than for metal shavings.
SnCl<sub>2</sub> dihydrate is not easy to crystallise (if that's what you want to do). When there not much solvent left, prepare to go
quite slow with the rest of the evaporation.
[Edited on 2-10-2015 by blogfast25]
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aga
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Many thanks for that advice bloggers.
The procedures i found simply said 'careful evaporation of the water', which is meaningless.
Both these syntheses are for practice with crystallisations, as i find many compounds stubborn when it comes to getting them to crystallise with the
reagent concentrations i currently have on hand.
[Edited on 2-10-2015 by aga]
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aga
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Eeek !
Sulaiman's High again.
Bunkers everyone Now !
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blogfast25
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Quote: Originally posted by aga  | Many thanks for that advice bloggers.
The procedures i found simply said 'careful evaporation of the water', which is meaningless.
Both these syntheses are for practice with crystallisations, as i find many compounds stubborn when it comes to getting them to crystallise with the
reagent concentrations i currently have on hand.
[Edited on 2-10-2015 by aga] |
Carefully reduce solvent volume till liquid appears to start thickening a bit, reduce heat and simmer a bit more, you may observe bumping at this
point. Allow to cool and observe: sometimes the whole mass crystallises at once. If not, chill and leave overnight. If you find no crystals in the
morning, reheat simmer slowly for some more.
Hardly precise but doing it by means of weight loss is a pain.
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Sulaiman
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aga, from http://www.uptodate.com/contents/gas-and-bloating-beyond-the... :
Foods that cause gas — Several foods contain short-chain carbohydrates called FODMAPs (fermentable oligo-, di-, and monosaccharides and polyols).
FODMAPs are poorly absorbed and can result in bloating and gas production (table 2). A diet that is low in FODMAPs may reduce the amount of gas you
produce.
probably makes more (non)sense ?
When I was experimenting with Sn HCl and electrolysis,
dissolving part of a tin ingot in 36% HCl was slow when warm, even slower when cold.
After the electrolysis ( https://www.youtube.com/watch?v=G1sq4hnrBgM )
the tin crystals dissolved with a quick shake or stir.
I still have the SnCl2 solution from the experiment, (with some excess HCl)
so I may be copying you sometime soon.
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blogfast25
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@Sulaiman:
What does this have to do with hydrogen generation from dissolution of metals in acids?
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Sulaiman
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my first post was an attempt at humour in response to the response of Little_Ghost_again to OP.
clearly I have a 'unique' sense of humour 
my second post was to explain my first,
and add that even with 36% HCl the synthesis of Zinc Chloride using 'lumps' of Sn proceeds slowly
and in a form with much greater surface area the reaction proceeds rapidly.
since aga has Sn, HCl and SnCl solution, I posted a link to what I think is a quick/easy yet fascinating adjunct experiment.
sorry if I detracted from the thread.
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ave369
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I don't like to dissolve metals in hydrochloric acid directly. Not fast enough. My favourite method of chloride synthesis is through nitrate (70%
nitric acid is a really fast metal devourer!), then hydroxide or carbonate (precipitated with NaOH or Na2CO3), then hydrochloric acid, the base
dissolves really fast.
Smells like ammonia....
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Little_Ghost_again
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All I was asking was you said they got more interesting (faster), I wondered if you measured the increase of the reaction as you applied heat,
interesting and faster. You bang on about measuring and experimentation so i assumed you had measured how much faster the evolution of gas was for the
temperature applied.
Apparently not you just did what we all do 
Dont ask me, I only know enough to be dangerous
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blogfast25
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| Quote: Originally posted by Little_Ghost_again | All I was asking was you said they got more interesting (faster), I wondered if you measured the increase of the reaction as you applied heat,
interesting and faster. You bang on about measuring and experimentation so i assumed you had measured how much faster the evolution of gas was for the
temperature applied.
Apparently not you just did what we all do |
This outburst appears to be a sequel to another recent rant of yours, here and borne out of spite more than science.
'Banging on' about the need to measure where possible is entirely appropriate on a forum about science. We should ALL do more measuring.
And no, he didn't 'do what we all do': some of us do present actual measurements. You should be supportive of that, rather than show your
petty side, as you're doing here.
As regards aga's experiment on dissolving tin and zinc in HCl, its purpose from what I understand was to prepare the hydrated chlorides of these
elements, not to measure the rate of reaction. He noticed greater activity with the zinc than with then tin and concluded rightly zinc reacts faster.
No measurement was needed here, simple observation sufficed. But to actually measure reaction rate would of course require, well.. some measurement or
other.
So think about that for 5 seconds next time, before you shift into 'nene nenener' mode.
[Edited on 3-10-2015 by blogfast25]
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blogfast25
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This is such a broad statement that it's almost meaningless. The rate of dissolution of metals in HCl varies vastly, from very fast to almost zero.
[Edited on 3-10-2015 by blogfast25]
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aga
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| Quote: | | sorry if I detracted from the thread. |
It's one of my threads Sulaiman - no danger of detracting from it !
I didn't get the joke so yours must be a very oblique sense of humour 
| Quote: | | I don't like to dissolve metals in hydrochloric acid directly. Not fast enough. |
The Nitrate route sounds interesting and this dissolution of Sn in HCl solution is painfully slow even with heating.
Strangely the ZnCl2 has gone Ferric Chloride colour. I tested it for Fe2/3 ions, and the result was negative. Same for SO4 ions.
Will try boiling it dry.
| Quote: | | You bang on about measuring and experimentation |
These experiments started with a spreadsheet to calculate the stoichimetry of the HCl gas needed using sodium chloride/sulphuric acid based on 25g of
metal, and also to set a target yield figure.
A quick test of the Zn powder convinced me to just use the 20% HCl i have instead of HCl gas. The metal samples were weighed to 0.01g at the
beginning.
Seeing how the steam and HCl boils off at an unknown rate, i decided to add more, then some more, then add an RBF for a bit of reflux, then some more
HCl.
All noob errors as i have not done either of these before.
If either (or both) succeed, then i'll refine the details down to a simple process with exact quantities of reagents required.
Edit :
Post an experiment here yourelf one day LG2.36, maybe even with some calculations.
[Edited on 3-10-2015 by aga]
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blogfast25
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| Quote: Originally posted by aga |
The Nitrate route sounds interesting and this dissolution of Sn in HCl solution is painfully slow even with heating.
Strangely the ZnCl2 has gone Ferric Chloride colour. I tested it for Fe2/3 ions, and the result was negative. Same for SO4 ions.
Will try boiling it dry.
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Tin dissolves in nitric acid but only to yield highly insoluble SnO<sub>2</sub>. In the presence of lots of chloride ions I expect the
complex ion hexachlorostannate, SnCl<sub>6</sub><sup>2-</sup> to form. Note that that's an Sn(+4) species and
not Sn(2+)!
That's a drawback of using nitric acid or HCl + nitrate: it oxidises the metal to its highest oxidation number.
Concentrated solutions of ZnCl2 in strong HCl do appear yellowish.
[Edited on 3-10-2015 by blogfast25]
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deltaH
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Tin-chloride pourbaix diagram courtesy of https://theses.ncl.ac.uk/dspace/bitstream/10443/891/1/Buckle...
if anybody's interested.
Notice that the dominant species of tin will be SnCl4(2-) at low pH and E. Perhaps by using a 1:2 amount of salt and HCl on a mole basis as the
etchant, the tin can be isolated as the salt Na2SnCl4. That might crystallise considerably easier than SnCl2 and should still be good for a gold test.
[Edited on 3-10-2015 by deltaH]
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S.C. Wack
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Blanchard uses nitric acid...with the HCl, and "nearly the calculated yield of stannous chloride should be obtained"...I'd go with Blanchard.
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deltaH
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Yes, the trick is not to use an excess of nitric acid. Then the tin(0) can reduce tin(IV) to tin (II), dissolving more metal in the process. You can
also try bubbling oxygen through instead of using nitric acid. You would need to stop bubbling the oxygen before you dissolve all the tin, else you
will end up with tin(IV), as SnCl6(2-) solution.
[Edited on 3-10-2015 by deltaH]
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blogfast25
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| Quote: Originally posted by S.C. Wack | | Blanchard uses nitric acid...with the HCl, and "nearly the calculated yield of stannous chloride should be obtained"...I'd go with Blanchard.
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Mixtures of HCl and HNO3 oxidise Sn(0) to Sn(IV). I've done this countless times and reported it on this forum a few times. It's an easy way to
prepare (NH<sub>4</sub><sub>2</sub>SnCl<sub>6</sub> or K<sub>2</sub>SnCl<sub>6</sub>.
Nitric acid alone oxidises Sn to SnO2. Personal experience and references bear that out. So do the SRPs.
Perhaps if you use a high ratio of HCl to HNO<sub>3</sub> that might speed up dissolution and yield mainly Sn(+2). Until your
HNO<sub>3</sub> runs out, of course.
Very finely divided tin dissolves in hot strong, non-oxidising acids quite quickly. For one analysis I reduced a hexachlorostannate solution with Al
strips at low pH. Fine, elemental Sn formed first, this the dissolved in the acid reserve very quickly, a matter of maybe 30 seconds, to Sn(+2).
[Edited on 3-10-2015 by blogfast25]
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S.C. Wack
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You realize there is always undissolved tin in Blanchard's preparation? More likely than not it works perfectly.
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blogfast25
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| Quote: Originally posted by S.C. Wack | | You realize there is always undissolved tin in Blanchard's preparation? More likely than not it works perfectly. |
Yes.
This one (similar) recommends adding a piece of Pt foil:
http://www.prepchem.com/synthesis-of-stannous-chloride/
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aga
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Sn -----------
Well, the Tin refuses to dissolve, and just keeps on clinking about in the beaker.
I feel sure i lost a few hours watching WATER boil off from the solution after the majority of the HCl had boiled away.
Adding fresh 20% HCl gives much finer bubbles, so too much heat was certainly a mistake.
Zn ------------
The Zinc has all dissolved and has been boiled down to a brown sludge that is very hygroscopic.
(The "99% pure" claim at the top of this thread is clearly a lie. I paid for 99% and got something else.)
Trying the 'slap the solution directly onto the hotplate' trick did not work.
After some water boiled off there were some dirty brown crystals with patches of grey, and a brown Oil separated - it did not evaporate or even smoke
!?!?!
Wiping the Oil with a paper towel created a big black smear of SOS on the hotplate, a bit like if it were conc sulphuric acid, yet it can't be seeing
as the Barium Chloride test on the solution gave no precipitate.
----
ave's Nitric suggestion was tried with 2g of Zn powder and ~7ml of 35% HNO3 added in 1ml portions.
NO gas immediatey forms on addition of the acid, making this a 'not-for-a-noob' route.
This Zn powder (plus whatever else is in there) formed a dense mass on one side of the beaker.
Heating caused the mass to explode in a new plume of NO gas as it cracked and the acid got to the middle of it. Amazingly it did not dissolve
completely even with heating.
-------
There are so many pitfalls to what seem such simple syntheses.
I forsee an Al Suph trip coming on ...
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aga
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How come i could not find that reference ?
Ah yes, lack of searching and the brains to search for the right thing !
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