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Ba(ClO3)2
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[*] posted on 15-1-2017 at 23:00
Tin dioxide preparation


I've managed to get hold of some pewter, which is an alloy containing about 95% tin with some copper, antimony and bismuth. I was wondering how one could go about preparing tin dioxide from this.

The most obvious route is to dissolve the pewter in HCl then precipitate the tin as the carbonate, and finally heat to decompose carbonate to oxide. However, I thought of a more interesting approach that I would prefer to use:

Dissolve pewter in sodium hydroxide solution to give a solution of sodium stannate. Add a slightly less then stoichiometric amount of hydrochloric acid. This should precipitate SnO2 as the hydrated oxide "stannic acid". Heat the hydrated oxide in a crucible to get tin dioxide.

My question is, would this second method I though of be likely to work?
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laserlisa
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[*] posted on 16-1-2017 at 03:12


Quote: Originally posted by laserlisa  
I want to dry K2CO3 for use in a phenolic alkylation reaction. Is it enough to dry it in an ordinary oven?
Which temperature and what duration is advisable to get it anhydrous?

Thanks

Does anybody know?
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Metacelsus
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[*] posted on 16-1-2017 at 05:27


By my experience, drying it in an oven (200 °C to constant mass) is fine. I have methylated naphthols with dry potassium carbonate and dimethyl sulfate, and it should work for phenols. Of course, be careful with strong alkylating agents.



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[*] posted on 19-1-2017 at 17:41


hi there, I have a couple of quick questions.

I´m going to extract the silver from some xray films (I know this topic has been greatly discussed in the forum) and I have already my set up planned, but I would like to ask you what is your recommendation between the two methods that I have.
as a side note my final product wont be silver, I´m more interested in silver nitrate.

xrays + HNO3 = silver nitrate and other stuff, react it with NaOH precipitate silver oxide redissolve in HNO3 and recristalice.

the second method is the same with the added step of adding NaCl obtaining the insoluble chloride and then silver oxide and HNO3.

I prefer the first method to reduce yield loses from the added step, my question is, will it precipitate unwanted oxides or other stuff adding the NaOH straigth away?, without isolating the chloride first?

second question: I have recently received my brand new heating mantle and I´m planning to distill some acetone (mainly to remove the denatonium benzoate and stuff) can I just put the round bottom in the heating mantle? I know it´s not really sensible distilling flammable liquids with open flame for obvious reasons, but all the volatile (mostly organic solvent) distillations I have seen have been made with a hotplate and a sand bath or water bath, this may have been just for personal prefferences, but is the a risk I´m not seeing in distillation of flammable liquids straigth away from the heating mantle?

Many thanks to everyone.

[Edited on 20-1-2017 by exodia]
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PHILOU Zrealone
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[*] posted on 20-1-2017 at 04:29


Quote: Originally posted by exodia  
hi there, I have a couple of quick questions.

I´m going to extract the silver from some xray films (I know this topic has been greatly discussed in the forum) and I have already my set up planned, but I would like to ask you what is your recommendation between the two methods that I have.
as a side note my final product wont be silver, I´m more interested in silver nitrate.

xrays + HNO3 = silver nitrate and other stuff, react it with NaOH precipitate silver oxide redissolve in HNO3 and recristalice.

the second method is the same with the added step of adding NaCl obtaining the insoluble chloride and then silver oxide and HNO3.

I prefer the first method to reduce yield loses from the added step, my question is, will it precipitate unwanted oxides or other stuff adding the NaOH straigth away?, without isolating the chloride first?

second question: I have recently received my brand new heating mantle and I´m planning to distill some acetone (mainly to remove the denatonium benzoate and stuff) can I just put the round bottom in the heating mantle? I know it´s not really sensible distilling flammable liquids with open flame for obvious reasons, but all the volatile (mostly organic solvent) distillations I have seen have been made with a hotplate and a sand bath or water bath, this may have been just for personal prefferences, but is the a risk I´m not seeing in distillation of flammable liquids straigth away from the heating mantle?

Many thanks to everyone.

[Edited on 20-1-2017 by exodia]

1) When using NaOH you will indeed precipitate many metals as hydroxides or oxides...thus not only Ag.
To reduce the amount of HNO3 you will use, I think you should:
a) melt-burn-calcinate the films to ashes first (this will reduce the volume and weight of starting material since most organic matter will be lost into fumes of CO2, H2O, etc.);
b) then add slight exces of HNO3 (much less required than into your proposal) and reflux.
c) filtrate and rinse filter and remaining solid with demi water; disgard the filter and solid.
d) neutralize the filtrate with Na carbonate or bicarbonate but it must remain slightly acidic.
e) concentrate the solution by evaporation to 1/4 its volume.
f) add slight excès of solid copper. Copper will displace all metals more oxydising than itself from their salts --> Gold, Platinium,...what are usually rare and of course silver. This is called cementation, the metal precipitates as crystals or dust while the copper passes into solution as blue Cu(2+).
Via a kind of electric cell reaction in shortcut:
2 Ag(+) + Cu(s) --> 2 Ag(s) + Cu(2+)
g) collect the metallic silver dust and react with slight exces of HNO3 and a little H2O2.

2) Denatorium is used into ethanol alcohol to give a bad bitter taste to it (and to get the taxes onto drinkable alcohol vs solvent or fuel), or to other chemicals sothat childrens don't drink it.
I'm not sure it will be found into aceton.

Heating mantle is no troubles with highly volatile and flamable liquids as long as you put the heat low (via dimmer switch) or that you lift a bit the boiling flask sothat there is air gap and no direct contact between the flask glass and the heating element --> only radiating heat.
Will take a little more time to boil, but will be safer.
The glass will be exposed to less heat and be submitted to less dillatation, so the risk of cracking is less.
The solvent and vapour will be less prone to self inflame if the heating element is not to dull red heat.


[Edited on 20-1-2017 by PHILOU Zrealone]




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j_sum1
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[*] posted on 20-1-2017 at 21:38


This has probably been asked and answered before, but here goes.
Why is an allihn condenser the standard for soxhlet extractors? It seems to me that any condenser would do the job. But allihns seem almost universal with grahams a distant second.
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Sulaiman
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[*] posted on 21-1-2017 at 01:39


because most soxhlet kits are sold to essential essences extractors who like the alchemy/apothecary look ?



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PHILOU Zrealone
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[*] posted on 21-1-2017 at 03:17


Quote: Originally posted by j_sum1  
This has probably been asked and answered before, but here goes.
Why is an allihn condenser the standard for soxhlet extractors? It seems to me that any condenser would do the job. But allihns seem almost universal with grahams a distant second.

I think for practical reasons...
Cooling size efficiency (volume/height) vs double tubular or simple tubular...the only limit is the sky ...but in a lab it is the ceiling ;) ... and the practical working height of the operator :P.
Also robustness vs tubo helicoidal.


[Edited on 21-1-2017 by PHILOU Zrealone]




PH Z (PHILOU Zrealone)

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j_sum1
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[*] posted on 21-1-2017 at 04:32


By that reasoning a Friedrich's would be the most common.
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Chemiston
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[*] posted on 21-1-2017 at 07:10


I will probably ask a relly dumb question
But seriously how do I get these stars that are below some people's title

e.g 5 stars is international hazard

where mine is just harmless :P




Chemistry


is what I always look for

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