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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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[*] 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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[*] 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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[*] 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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[*] posted on 21-1-2017 at 01:39


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



CAUTION : Hobby Chemist, not Professional or even Amateur
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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]




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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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ficolas
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[*] posted on 21-1-2017 at 08:32


Quote: Originally posted by Chemiston  
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

Shitposting, spamming the forum, etc.
No justo kidding, but not really. They correspond to the number of posts (and make them as constructiva as posible!!! No shitposting and spam :D)
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PHILOU Zrealone
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[*] posted on 21-1-2017 at 09:06


Quote: Originally posted by j_sum1  
By that reasoning a Friedrich's would be the most common.

Yes for efficiency,
but
No because more fragile and expensiver (a lot of precision glassery work).




PH Z (PHILOU Zrealone)

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[*] posted on 25-1-2017 at 17:33


Does anyone use this method for cleaning glassware?
https://www.youtube.com/watch?v=rJik_EnmgM0

ferrous chloride and hydrogen peroxide

I have not come across it before. Looks to be a similar idea to pirahna but perhaps more foamy and messy. And perhaps safer too.
But I am not really sure that I understand the chemistry behind it. I presume there is a bit of catalysis going on to react carbon with H2O2 and maybe some oxidation of the Fe(II).
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[*] posted on 25-1-2017 at 18:49


I haven't used it before personally, but the chemistry behind it is fairly well known.(At least, it's famous enough to have its own name;)) [url=https://en.wikipedia.org/wiki/Fenton's_reagent]link[/url]

EDIT:Hmm, the hyperlink function of the forum doesn't seem to be working.

[Edited on 1-26-2017 by gdflp]




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[*] posted on 27-1-2017 at 06:28
Question


I was using an oil bath for a synthesis. I was using coconut oil for my oil bath. Well long story short, some of it got on my hotplate (which is ceramic top) and left a large carbon deposit on it. My basic solvents won't get it off and I don't want to scrape it and risk scratching and scraping the chemical resistant layer off the hotplate top. Is there a way to get rid of the carbon without destroying the surface of my hotplate?
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[*] posted on 27-1-2017 at 14:19
Cleaning hotplate


Hot piranha seems to do the trick! ;)

I personally wouldn't bother, my hotplate is covered with stains which do not interfere with its function. Thick deposits of carbon can be easily scraped off, maybe try a kitchen scrubbing pad for the residues left? Most ceramic hotplates can take a bit of abuse, but then again not all are equal.

Edit: Sharp metal tools can and will scratch the surface of the ceramic, so avoid these if the hotplate still looks nice. My Corning's ceramic is 4mm thick so it would be difficult to break through and ruin the chemical resistance.

[Edited on 1/27/2017 by Geocachmaster]
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[*] posted on 27-1-2017 at 14:48


Mine is a Corning PC-420D. How thick do they make the chemical res surface and would steel wool work okay? I'm too scared to work with hot piranha out on my lab bench lol.

[Edited on 27-1-2017 by TheNerdyFarmer]
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[*] posted on 27-1-2017 at 15:11


I have a Corning PC-351 which has 4mm thick ceramic. I believe that the ceramic is the chemical resistant part (pretty non-reactive stuff by nature). Other Cornings probably have similar thicknesses. I tested #00 steel wool and ~10 seconds of vigorous scrubbing had no damaging effect and made no visible scratches. So #00 and finer steel wool will be good. For reference #00 has a texture of rough woolen clothing.
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[*] posted on 27-1-2017 at 17:22


How about burning off the C with a Bunsen burner or Bernz-0-Matic?
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[*] posted on 28-1-2017 at 07:39


I will first try the steel wool and if that doesn't work I may try taking the torch to it to burn it off. Thanks for the replies and all the help. :)

[Edited on 28-1-2017 by TheNerdyFarmer]
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[*] posted on 28-1-2017 at 15:08


Also what kind of material do they use in industry
as a reaction vessel make hydrofloric acid???


[Edited on 28-1-2017 by TheNerdyFarmer]
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[*] posted on 28-1-2017 at 15:31


Nickel alloys (for example, monel) are passivated by HF and thus resist its corrosive properties.



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[*] posted on 28-1-2017 at 19:12


A quick question which I've not seen answered elsewhere:

During the process of recrystallising something, my aqueous solutions of the substance after filtration quite often go mouldy. This has happened to cool, saturated solutions of Magnesium sulfate, potassium chlorate and potassium chloride. I am particularly surprised that an organism can live and grow in a saturated solution of potassium chlorate.

Does this happen to anyone else? If so, what methods do you employ to prevent micro-organism growth in your chemical solutions?




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[*] posted on 28-1-2017 at 19:59


I recently noticed some mold growth in a container of MnO2 waste, very odd. This was only after sitting undisturbed for a couple weeks though. Do you have a history of/ongoing mold problems in your lab space?

IMG_0434.JPG - 1.3MB

Edit: this is the only time I have ever seen mold in my lab

[Edited on 1/29/2017 by Geocachmaster]
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[*] posted on 28-1-2017 at 20:15


Geocachmaster, I've never had any kind of mould issues in or on the building itself, but persistently solutions of various chemicals will go mouldy.

Evaporating a solution by leaving it sit on a windowsill is almost nonviable as mould or bacteria will develop before the solution is fully evaporated, requiring filtration, pasteurisation and recrystallisation to purify again.




Li
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