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Author: Subject: The short questions thread (2)
crazyboy
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[*] posted on 27-3-2010 at 21:46


I recently got a buchner flask and funnel, when I put a piece of filter paper in the flask with some liquid and turn the vacuum on the filter paper rips several holes. I am wetting the filter paper prior to applying vacuum. I have tried using two pieces of filter paper at the same time, this works better but it still rips occasionally. What can I do? This is an electric pump not an aspirator so I can't really adjust the vacuum without a bleeder valve.

What can I do?




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[*] posted on 28-3-2010 at 05:58


Is it a good quality filter paper? You could use the acid resistant glass based ones which would be much stronger.
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DJF90
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[*] posted on 28-3-2010 at 11:05


It sounds to me like you're trying to do vacuum filtration with a "high vacuum pump". If this is the case then you will probably need that air bleed, or to use an aspirator. Good quality filter paper (look for Whatman) will also help.
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crazyboy
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[*] posted on 28-3-2010 at 15:00


Yes I am using a high vacuum pump. And yes I am using high quality filter paper (it is Double Rings 9cm ashless 202) am not using coffee filters.

How would I establish and air bleed? Can it be made with parts from a hardware store or does it require a special part?




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Panache
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[*] posted on 31-3-2010 at 20:39


---->Yes I am using a high vacuum pump. And yes I am using high quality filter paper (it ---->is Double Rings 9cm ashless 202) am not using coffee filters.
---->How would I establish and air bleed? Can it be made with parts from a hardware -------->store or does it require a special part?


its as simple as a t-piece in the vacuum line running to the filter funnel with a short piece of hose that you clamp to the bench anywhere from open (ie no vacuum to your funnel) to closed (the situation you have currently), and an infinite no. of increments between. Of course a needle valve makes life easier.

[Edited on 1-4-2010 by Panache]




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bbartlog
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[*] posted on 10-4-2010 at 13:48


I notice after filling my lab with HCl fumes that some of the borosilicate glass surfaces are covered with a white haze. I see the same thing on the inside of some test tubes that have HCl solution in them and have been sitting closed for a few months.
What is this white haze? I don't think HCl can react directly with borosilicate glass, but something seems to be happening.
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aonomus
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[*] posted on 10-4-2010 at 13:59


Quote: Originally posted by bbartlog  
I notice after filling my lab with HCl fumes that some of the borosilicate glass surfaces are covered with a white haze. I see the same thing on the inside of some test tubes that have HCl solution in them and have been sitting closed for a few months.
What is this white haze? I don't think HCl can react directly with borosilicate glass, but something seems to be happening.


I store my HCl in a glass bottle which hazes up, and I keep that bottle inside a LDPE bag, which also gets a white haze/coating on it. I don't think its connected to the glass itself, but HCl tends to form that haze that can be wiped off with a damp cloth; the haze is also corrosive over long periods of time to tools and metals (which my pile of iron/steel stock has found out unfortunately).
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Lambda-Eyde
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[*] posted on 10-4-2010 at 16:06


Quote: Originally posted by crazyboy  
I recently got a buchner flask and funnel, when I put a piece of filter paper in the flask with some liquid and turn the vacuum on the filter paper rips several holes. I am wetting the filter paper prior to applying vacuum. I have tried using two pieces of filter paper at the same time, this works better but it still rips occasionally. What can I do? This is an electric pump not an aspirator so I can't really adjust the vacuum without a bleeder valve.

What can I do?


How large are the holes in your buchner funnel? Crappy chinese funnels tend to have fewer, larger holes (3-4 mm) compared to Coors porcelain funnels which have many smaller holes. The paper is easily ripped apart in a funnel with larger holes.
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Ephoton
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[*] posted on 17-4-2010 at 23:27


why is every one so down with chinese goods. seriously the glass I buy is chinese and ive used a lot of
glass.

I never had a problem with my supplier they are fast understanding and very very high quality and
I often do crazy stuff with my glass at high temps never a problem.

I will never go back to western glass now I have found my supplier its quicker and easier and a lot cheaper
to use them.




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densest
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[*] posted on 18-4-2010 at 11:08


@ephoton - if you're having good luck with Chinese glass, good for you. You may be dealing with someone other than the ubiquitous Bomex. I've found Bomex to be irregular in shape, uneven in thickness, and with obvious flaws where the glass is either impure or was not melted sufficiently. It seems to break more easily than my Pyrex or Kimax which would be easy to blame on the flaws. If you have a better vendor for inexpensive good glass, I'm all ears!

I do flameworking of borosilicate glass. The Chinese glass is much less expensive than US or European glass, but in general is "lumpy": parts of the glass melt at higher or lower temperatures and when they do it's more or less viscous than other parts. I blame that on insufficient mixing and melting time and perhaps variations in composition.

Unfortunately, at this end of the supply chain it's very hard to figure out exactly which factory something comes from and whether or not the manager demanded better quality that day.
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The WiZard is In
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[*] posted on 19-4-2010 at 10:52
H2SO4 - KClO3 limerick


There is a limerick 'bout a student who
mixes sulphuric acid and potassium chlorate
to his demise! Can anyone bring it to mind.
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Ephoton
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[*] posted on 29-4-2010 at 06:34


can nitrogen triiodide ammonium adduct be oxidised back to iodine with out detonation.

I am finding it hard to find information on this any help would be great.

of course it is under water and not dry :).


[Edited on 29-4-2010 by Ephoton]




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not_important
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[*] posted on 29-4-2010 at 07:26


Not directly, SFAIK. Alkali plus H2S will convert it to the alkali iodide. But the stuff is so darn sensitive, alpha particles can set it off, that I'd not convert a bunch at one shot. Perhaps just plain alkali, Na/KOH, would do the same.

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manimal
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[*] posted on 2-5-2010 at 19:50


Which is more correct in the verb usage, "sublime" or "sublimate"?
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DJF90
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[*] posted on 3-5-2010 at 05:06


A material sublimes, the collected solid is the sublimate.
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Paddywhacker
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[*] posted on 3-5-2010 at 14:15


Or you can sublimate your passion for chemistry by indulging in the preparation of sublime meals.
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Panache
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[*] posted on 3-5-2010 at 17:34


Is there a trick to fitting thread parts together so that the orientation you require can be assured at the correct level of tightness. Inevitably my t-pieces always end up pointing at the wall or something, very frustrating.



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jokull
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[*] posted on 4-5-2010 at 06:07


Dear Panache,

if your are talking about Swagelok-like connections, a good result can be achieved if you insert the T against the tubing, then you can screw the nut while keeping the T in a desired position.
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manimal
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[*] posted on 7-5-2010 at 16:22


What is the approximate solubility of hydrogen chloride in ethanol?
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entropy51
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[*] posted on 7-5-2010 at 17:06


41 gm per 100 mL. Get a Merck Index; pure gold.
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JohnWW
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[*] posted on 7-5-2010 at 18:45


Quote: Originally posted by entropy51  
(cut) Get a Merck Index; pure gold.
I have uploaded the editions 12.3 and 11 of the Merck Index to my Rapidshare premium account, and have posted the links for downloading them as DJVU, PDF, and EXE files in appropriate threads in the References section. In fact, I have today had to reupload the 11th edition, the previous link as a DJVU file of about 4 years' standing for which had been broken this morning, thanks to the Copyright Gestapo (still operating on the 65th anniversary of VE Day, to remind us that they are still around!). At some stage soon, I will be uploading the 13th and 14th editions, as EXE files which require installing a setup program.

[Edited on 8-5-10 by JohnWW]
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[*] posted on 11-5-2010 at 15:15


hello! a not so small question for you all

i was experimenting copper chemistry again the other day when i find myself "carbonating" CuCl2 with NaHCO3. I was thinking that the Cu will precipitate with the CO3 anion to form insoluble CuCO3. I didn't ask myself where the H would go in this reaction.

I was using a left over CuCl2 "I think" solution made by dissolving Cu2O in HCl in excess, until all the white CuCl get in solution. The solution also contain copper acetate and acetic acid for some reason. it is important to note that no nitrogen compound were present in the solution. The blue solution had the property of turning to a dark green one on heating and revert as the temperature drop.

A small sample (100 ml) was moved to another beaker and heat in the microwave. To the heated solution, a hot NaHCO3 solution was add slowly. Lots of bubbles come off. At a certain point the solution turn dark blue with a bright blue precipitate. I separate the blue solution from the precipitate to make some investigation later as i never saw this before. I neutralizes everything else with NaHCO3 until all was in a bright blue precipitate. Then got bored and stop...

The next day, I found that the dark blue precipitate had crystallized in small needle turquoise crystals with the mother solution still around them.

The interesting property "for me at least" of those crystals is that they don't look soluble at all but was made from a water soluble 'state'.

I tried adding more (a lot) water to dissolve but they stay out of solution. On adding NaOH, the turquoise crystals turn sky blue (the same blue as the originating solution) but they don't dissolve.

They dissolve in acid to give the respective copper salt, without giving any gas off. ( i tried with vinegar in excess they return to the turquoise color before getting dissolved)

I am clueless here about their composition. Some articles talk about a Na and copper hydroxide like compound but they don't describe it enough.

what do you think about those crystals?




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[*] posted on 11-5-2010 at 15:39


Copper forms a carbonate complex.

I once tried electrolyzing copper metal in a sodium carbonate solution. Didn't work. Make the most amazing cobalt-but-not-actually-cobalt blue solution.

I don't know if this complex is stable, or if it's metastable in that it will precipitate a basic carbonate over time (you seem to have grown crystals of azurite or malachite, which is neat).

Neutralizing a green (concentrated) CuCl2 solution tends to produce a lot of pastel green oxyhydroxide, Cu(OH,Cl)2. When diluted, the chloride complex is decomposed, the solution becomes bluish, and the majority product is light blue Cu(OH)2.

With an excess of carbonate, there may be a lot of Cu(OH,CO3) as well.

The extra H on NaHCO3 goes off as H2O, while the extra CO2 goes off as CO2 gas (hence the foaming).

Tim




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Hamilton
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[*] posted on 11-5-2010 at 16:47


can i test them further? if it is malachite, dissolving in vinegar should release CO2 gas but it don't. For azurite, does it get dark blue in NaOH solution?

I will tried to make more crystals later!

thx for your fast answer
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[*] posted on 11-5-2010 at 18:23


If you dissolve only a small amount, the CO2 may remain in solution. Can you get a pile of the stuff and drop acid on it (>10% HCl would be best)?

Tim




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