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Author: Subject: The Short Questions Thread (4)
alexleyenda
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[*] posted on 8-1-2014 at 12:42


Then I guess it would be friction, cork is good at creating heat with friction so it makes sense, thought i'm not sure it can create enough heat to ignite H2. Anyways to me it's more plausible than static electricity as it takes quite a lot of static e to create a spark at my knowledge. Unless you rub your cork in your hair for luck before you experiment I doubt it explains the ignition :p
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Pyro
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[*] posted on 8-1-2014 at 15:12


is rectapur (chemically pure, http://www.surechem.co.uk/pdf/chemicalCompweb14509.pdf) anhydrous AlCl3 supposed to look like this? I can tell 3 different colors...

WP_20140103_003.jpg - 69kB

and is it really necessary to grind it to a powder? My lab is kind of damp and the fumes...




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Zyklon-A
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[*] posted on 8-1-2014 at 15:56
Storing magnesium.


I got some Mg ribbon a few months ago, and put it in a ziplock bag, and then forgot about it. When I took it out, it was coated with a white powder (MgO or Mg(OH)2), anyway I put it in very dilute HCl for about 5 mins. It's mostly shiny now, but I don't want that to happen again, so I want to find a way to store it without it oxidizing anymore.
I put it in a glass jar and filled it with CO2, I know Mg reacts with CO2, but slower than air and only at high temps right?
Would this be affective for long time storage of magnesium?
(The jar of course was sealed.)

[Edited on 8-1-2014 by Zyklonb]




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Pyro
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[*] posted on 8-1-2014 at 16:02


Just protect it from damp air, in a jar or air tight bag. the oxidation is minimal, I have 2 rolls of Mg ribbon, one was lying around for a year, the other was in an airtight bag. there isn't much difference between the two.



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Zyklon-A
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[*] posted on 8-1-2014 at 16:45


Well I live in Texas, where it is very humid, and even though the bag was airtight ( I think), it still oxidized quite a bit.
But I guess the jar will work then?




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thebean
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[*] posted on 8-1-2014 at 17:49


I put my magnesium under mineral oil, it works fairly well.
My question would be about oxalic acid ester syntheses. Does the Fischer Esterification work? If I want to produce dimethyl oxalate or diethyl oxalate will a simple reflux of the oxalic acid the alcohol and a sulfuric acid catalyst work?




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[*] posted on 8-1-2014 at 18:35


Answer @thebean:

Yep, pretty much. There is a synthesis on orgsyn.org that does just that if I remember correctly. I don't have the link off hand, but a structure search for dimethyl oxalate brings it up.
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thebean
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[*] posted on 8-1-2014 at 19:20


Oh and one other question/conundrum.
I wanted to produce benzoic acid, so I took stoichiometric amounts of sodium benzoate and hydrochloric acid but I didn't see any sort of reaction. The odor is the same and the crystals look untouched. What happened, what can I do to fix it, and if it isn't fixable without a lot of work is the sodium benzoate salvageable?




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[*] posted on 8-1-2014 at 20:14


Benzoic acid is scarcely soluble in water, so the result isn't much of a surprise. The crystals are likely benzoic acid. I think you can extract with a non polar solvent, dry with desiccant of your choice and evaporate to recover.
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[*] posted on 8-1-2014 at 21:07


You should have dissolved it in water, then added the acid to get a precipitate.

If what you have is benzoic acid (as it should be), dissolve it in hot water (not boiling, or you'll hate the smell), and let it cool slowly to crystallize. They should be white and feathery.




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thebean
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[*] posted on 9-1-2014 at 10:14


I added approximately 400mls of water to a beaker if the acid is included so I should think it would work. If I remove some precipitate and put it in hot water that should determine whether it is benzoic acid or not, yes?



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[*] posted on 9-1-2014 at 10:35


400 mL of water should dissolve about 1.2 g of benzoic acid at RT, and 18 g at 90oC. How much did you add? Heat your solution, and if everything dissolves, cool it slowly.



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thebean
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[*] posted on 9-1-2014 at 13:35


I added .1 moles of sodium benzoate and .1 moles of HCl (actually a tiny bit more because excess HCl would be easier to deal with than benzoate).



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[*] posted on 9-1-2014 at 13:41


That should give you about 12 g of benzoic acid, so getting it hot should dissolve it all nicely. Once it's dissolved, let it cool slowly to room temp, then chill it in an ice bath for twenty minutes or so, then filter your acid out.



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thebean
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[*] posted on 9-1-2014 at 15:03


Yeah my theoretical yield was just barely over 12 grams. I did the hot water test and it is definitely benzoic acid.



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plante1999
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[*] posted on 9-1-2014 at 17:29


Anyone got a good chemical engineering book? I already have perry.

I mean, a book that would be about design of plants. For example pipes and pumps and all the other chemical plant goodies.

Thanks




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[*] posted on 9-1-2014 at 17:47


Also, how can you tell if an oxide is nonstochiometric? I know MnO2 is and Tb4O7 may be, and they're both brownish-black. I've also seen the color of Ho2O3 explained as being caused by stoichometric defects. Can such defects create colors that subtle?



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[*] posted on 9-1-2014 at 17:52


Quote: Originally posted by Brain&Force  
Also, how can you tell if an oxide is nonstochiometric? I know MnO2 is and Tb4O7 may be, and they're both brownish-black. I've also seen the color of Ho2O3 explained as being caused by stoichometric defects. Can such defects create colors that subtle?


Yes, they can. One class of defect is called an f-centre; the f stands for "farbe" or "colour", because it can turn an otherwise colourless compound blue.

How to tell if it's nonstoichiometric? No idea....




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[*] posted on 11-1-2014 at 04:32


Hi,
I'm wondering if you can use gold electrodes to electrochemically make sulfuric acid form copper sulfate.
I don't have access (at all) to H2SO4, HCl, HNO3,... where I live so that would be very useful if I could make my own sulfuric acid.
I'd like to etch circuit boards with it (+ H2O2) so if it works I could restore my etchant for almost nothing.

I asked for platinum at my local bank but they only have gold... though I ordered a 1g gold bar anyway because I need some for my element collection.
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[*] posted on 11-1-2014 at 10:06


I think so. HCl is sold at Home Depot FYI.



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[*] posted on 11-1-2014 at 11:13


Ok thanks!

Also I live in Switzerland and very few chemicals are available here.

HCl, H2SO4, NaOH, acetone, 35% H2O2,... are readily available in France (and I live only 60km away from the border) though I need to bring them back to Switzerland and I don't think it's legal...
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[*] posted on 11-1-2014 at 11:15


You can order 1g gold bars? How much do they cost?



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alexleyenda
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[*] posted on 11-1-2014 at 11:20


He lives in switzerland, I don't know if they have any home depot. Anyways, usually you can find HCl in pool stores to lower the PH, you can also find it in hardware stores near the paint thinners. Conc. Sulfuric acid is sold in hardware stores as drain cleaner and 35% sulfuric acid is sold in car pieces shop as battery acid, you have to ask for it. You can concentrate it yourself ( very dangerous however).

HNO3 can be more tricky. At least here in Canada it's impossible to find , you have to make it yourself with nitrate salt like KNO3 (also banned but obtainable from farms) and conc. H2SO4.

edit after I saw your post: Even where I told you they don't have it? That would be real chimicalphobia. And I know what you live, I often think about going in the states to buy chemicals and bring them back but if they catch me at the border I'll be in deep trouble :p

[Edited on 11-1-2014 by alexleyenda]
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Zyklon-A
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[*] posted on 11-1-2014 at 16:02


Not that dangerous to concentrate H2SO4, as long as you do it outside and don't breath in the fumes, it takes a lot of energy though, boil it >300C.
I never realized how lucky I am, in Texas I can get almost any chemical I want, (mostly online).
Does the border patrol search you when you cross?

[Edited on 12-1-2014 by Zyklonb]




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alexleyenda
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[*] posted on 11-1-2014 at 16:29


Really? I thought it heard you could not even have chemistry glassare in Texas. Anyways the danger with H2SO4 is that it boils at 320+ °C and that it tends to splash as it bubbles, even with boiling chips. If 98% H2SO4 splashes on you, it's very bad. If 320°C 98% H2SO4 splashes on you, you're in deep _____.
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