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Sulaiman
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[*] posted on 5-3-2015 at 21:02


as a bearded white muslim convert that lived in a muslim country for 20 years
I'm already paranoid enough, :o
I'll give that one a miss for now, thanks. :P
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[*] posted on 5-3-2015 at 21:47


You poor man! Where's all the fun in being normal?



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[*] posted on 5-3-2015 at 21:55


Quote: Originally posted by The Volatile Chemist  
Quote: Originally posted by quantumcorespacealchemyst  
What is the white frost on glass from being near HCl(aq)? It is wipable, smells odd and forms even near sealed acid containers. It seems to certainly be from HCl gas. What it is, I don't know.

[Edited on 22-2-2015 by quantumcorespacealchemyst]

I get it all the time on things in my lab when evaporating HCl solutions. I think it's condensed HCl, or a salt of Cl-, that is, if you have ammonia vapors nearby or something.


isn't that funny though, I thought I resupplied the NH3 after I got some HCL (and it was a while since having NH3 in the lab). Possibility is urine, I collect in sealed bottles. The smell of the white salts doesn't smell like anything I know, having made urea and Ammonium chloride (presumably) and smelling the piney scent. I don't know.

[Edited on 6-3-2015 by quantumcorespacealchemyst]
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[*] posted on 5-3-2015 at 22:10


PHILOU Zrealone thanks, you are right about the chemical formulas, i got it wrong, meaning CH3COCH3 and NaOOCCH3.

[Edited on 6-3-2015 by quantumcorespacealchemyst]
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[*] posted on 5-3-2015 at 22:36


Quote: Originally posted by Zombie  
It's used as a knife. Like pulling out a car windshield.

https://www.youtube.com/watch?v=qowrEiDsdTo

They use Molybdenum because of its high tensile strength.

No idea on the purity tho. I guess you would have to find the manufacturer, and verify that yourself.

I wouldn't trust asking a seller. unless the label or packaging clearly states this.


"The easy way??? That video looked awkward to say the least.

If Mo is udes for tensile strength then it is likely that it contains a reasonably high proportion. It will probably suit my purposes.
I don't have a fine wire in my element collection so it will add something there. And It will be more than adequate for my current project. O am making gas discharge tubes of various elements. I want something with a high MP and that will resist erosion by sparking. I decided I wanted something a bit thinner and more economical than the tungsten wire I have experimented with. An Mo phone slicer will do just fine.
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[*] posted on 9-3-2015 at 21:58
peroxide formation?


Does washing/dislodging crystals of Arsenic acids, with Diethyl ether, carry risks of peroxide formation?
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[*] posted on 9-3-2015 at 22:54


Quote: Originally posted by quantumcorespacealchemyst  
Does washing/dislodging crystals of Arsenic acids, with Diethyl ether, carry risks of peroxide formation?
You have asked that question before.
You might well be one of very few people on this board who are prepared to play with arsenic.
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[*] posted on 11-3-2015 at 03:35



Just how nasty is CS2?

I wanted to demonstrate to my students the dissolving of sulfur. It was in the context of a series of experiments on sulfur and sulfur compounds. The aim was to build up an understanding of the relationship between intermolecular forces and physical properties. Solubility in various solvents of course being a physical property.

While completing my risk assessment documents I found that CS2 was a prohibited substance -- that is according to the software being used (which admittedly belongs to a different jurisdiction but we use it anyway.) Restating this, it is not allowed for state schools to use the stuff at all. I am at a private school so I have a loophole.
Risks obviously are toxicity -- ingested, fumes and skin. Also volatility and explosive combustion.

I decided to proceed with the dissolving as a demonstration on a micro scale. About 0.5mL of CS2 dissolving some sulfur in a test tube. Full protective kit and completed in a fume cupboard. Interesting contrast between the carbon disulfide and xylene and some good learning happened.

But it leaves open for me the question of how dangerous this stuff is. Any thoughts and comments?
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[*] posted on 11-3-2015 at 04:02


Quote: Originally posted by Sulaiman  
it appears that CS2 is a risk in industrial environments but low risk in small ammounts.
http://www.epa.gov/airtoxics/hlthef/carbondi.html

unless you dissolve yellow phosphorous in it then pour the liquid over a small pile of sodium chlorate and wait ..... :D
I only did this experiment once, a teaspoon full cracked the concrete slab that it was on!

Ok. On reading that, the RfC is 0.7 mg/m^3. That is, regular exposure to anything greater than that is estimated to have chronic effects.
The smell threshold is only 0.05 mg/m^3. This suggests that as far as inhalation goes, if you can't smell it then you are below the level where damage is going to be caused. I am happy with that. I like it where the smell threshold is lower than the toxicity threshold. Little chance for nasty surprises.

The procedure I used meant that no smell was detected and there was no chance of it contacting skin. I conclude that our risk assessment process is a little over-cautious in this particular case.
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[*] posted on 11-3-2015 at 04:18


Quote: Originally posted by j_sum1  

I wanted to demonstrate to my students the dissolving of sulfur. It was in the context of a series of experiments on sulfur and sulfur compounds. The aim was to build up an understanding of the relationship between intermolecular forces and physical properties. Solubility in various solvents of course being a physical property.


Perhaps substitute hot toluene? You can recrystalize without needing to evaporate the solvent then-

http://www.sciencemadness.org/talk/viewthread.php?tid=3902




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[*] posted on 11-3-2015 at 04:45


Thanks for that Bert.
Unfortunately no toluene available and only a few mL of xylene. (I have ordered a bottle of each because I think a lab without these is deficient. Even if it is just a school lab and does very little organic and (at the moment) few separations involving solvents.)

I found that xylene dissolved a little sulfur but that amount increased dramatically with a little heating -- just the same as GarageChemist reported for the toluene. It would be good to do a comparison of the two solvents (although on reading down the thread you linked I can see that it has been done at least in part.) CS2 however was a much better solvent. A lot of sulfur dissolved.

As an aside, I love the idea of growing some larg(ish) sulfur crystals. They would be great in the element collection.




I love the way that around here you ask one question and you open a box full of interesting possibilities. Thanks Bert.
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[*] posted on 11-3-2015 at 05:07


I like the look of the large Sulfur crystals from toluene too-

In USA, I can just go to the paint store and buy quarts of xylene or toluene- No questions asked. They can be re-distilled if purity is an issue-

Australia controls these?

The idea of adding Phosphorus dissolved in a flammable and fast evaporating solvent to potassium chlorate had not occurred to me... Probably because I spend my time with chlorate mixtures trying to keep them from going off prematurely, rather than encouraging it!

Was it spontaneously explosive on drying, or did it require heating/shock/friction to explode?




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[*] posted on 11-3-2015 at 05:17
Phenolphthalein indicator preparation


I have some Phenolphthalein powder from an old chemistry set.
Normally it is dissolved in alcohol for use as an indicator, but at the moment I have
methylated/de-natured alcohol with a purple dye in it, or pure acetone.
Is there any problem using acetone?
or should I distil the methylated spirit to get colourless alcohol?

The tube that it is in reads : diluted with salt, 1:14
I don't know why that is done but I assume that very little sodium chloride will dissolve in pure acetone,
and some may dissolve in the alcohol due to the water content?

EDIT: just answered my own question,
added 3.5g of the powder to 50 mL acetone, mixed thoroughly, decanted the liquid off of the undissolved salt, tested ..OK.
...............................................................................................................

Bert, it explodes after the CS2 has evaporated, leaving the phosphorus and oxidiser in intimate contact,
it took about 10 to 20 minutes to spontaneously detonate (decades ago, in my youth, memory fading)

[Edited on 11-3-2015 by Sulaiman]
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[*] posted on 11-3-2015 at 05:18


Quote: Originally posted by Bert  
I like the look of the large Sulfur crystals from toluene too-

In USA, I can just go to the paint store and buy quarts of xylene or toluene- No questions asked. They can be re-distilled if purity is an issue-

Australia controls these?


I was referring to the stocks in my school lab.
Xylene is available at hardware stores although it is not especially cheap. Not sure of the purity. Toluene I haven't seen but that doesn't mean that it is unavailable. There are a huge number of paint thinner products that aren't fully labelled. I have no idea what is in them. (Ditto for oils and paraffins. They all say "petroleum distillate", which is not that useful.)

I have a litre of xylene at home and so that might do just fine for a sulfur crystallisation. I might work out a way of lowering the temperature slowly first.
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[*] posted on 14-3-2015 at 15:14


What is the best glue to attach nylon to steel (or other metals)?
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[*] posted on 14-3-2015 at 15:34


Due to the significantly different coefficients of thermal expansion for steel and nylon
and the stretchiness of nylon I think it will be difficult,
physical methods such as screws, bolts, clamps or straps would be the most reliable,
'stretchy' adhesives such as silicone or rubber may work for light loading.

I'm not an expert, just based on experience.
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[*] posted on 14-3-2015 at 16:53


Quote: Originally posted by DrMario  
What is the best glue to attach nylon to steel (or other metals)?



Depending on the application... There are many adhesives that will work.

The key is to rough up the mating surfaces with a grinding wheel or 60 - 80 gritt sand paper. The rougher the better.

The best overall adhesive I can think of for MOST applications would be 3M's 5200 Marine adhesive.

It's the one "glue" I despise in the marine trades. You can not cut / pry, this stuff off of anything.



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[*] posted on 19-3-2015 at 15:22


Something I've seen but can't find anywhere

When mixing H2O2 with pool water treatement pills it gave a red chemiluminiscence, am I right?

If I am, what is the reagent in the pills? (I think trichloroisocianuric acid, but can't remember)
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[*] posted on 20-3-2015 at 11:53
How to choose a stir bar?


I am going to make ionic silver solution for medicinal use
and I want to stir the solution whilst the silver wires are electrolytically ionised
my questions are a bit vague so any explanations of general principles appreciated

1) which is best, a small stir bar rotating quickly or a large bar rotating slower?


2) which is the best shape?

2.1) ovoid, e.g http://www.ebay.co.uk/itm/2pcs-Model-A-Teflon-PTFE-Magnetic-...

2.2) rod, e.g. http://www.ebay.co.uk/itm/2pcs-Model-C-PTFE-Teflon-Magnetic-...

2.3) rod with ring, e.g http://www.ebay.co.uk/itm/2pcs-Model-B-PTFE-Teflon-Magnetic-...

I can make the motor virtually any speed/power
Later I will also mix various aqueous fluids for other general purpose chemistry, e.g. titration, nitration ......
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[*] posted on 22-3-2015 at 08:56


antibacterial properties of spices
hi, checking the old post I see a link to a page with the antibacterial properties of spices. mozilla crash and bye bye. I found 1 but exist another with the page background of color red or orange. I put a lot of search terms and see all messages with spices, oils... and does not appear.
someone remenber the link?
TIA


[Edited on 22-3-2015 by pneumatician]
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[*] posted on 24-3-2015 at 15:58


Tin(II)chloride solubility.
References I have looked at indicate that SnCL2, both the anhydrous and dihydrate are very soluble in water. However, I have had a dog of a time getting them to dissolve. Wikipedia reports 83.9g/100mL @100°C. I have been unable to get a tenth of that. I have been working at RT however.
I have also tried reacting tin granules with HCl which has proved an extremely slow process but after a couple of days appears to be working.

I know that SnCl2 solutions are used in a lot of different applications. So what is the procedure? And why the discrepancy that I have noted between my results and the literature?
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[*] posted on 24-3-2015 at 21:44


Quote: Originally posted by Sulaiman  
I am going to make ionic silver solution for medicinal use
and I want to stir the solution whilst the silver wires are electrolytically ionised
my questions are a bit vague so any explanations of general principles appreciated

1) which is best, a small stir bar rotating quickly or a large bar rotating slower?


2) which is the best shape?

2.1) ovoid, e.g http://www.ebay.co.uk/itm/2pcs-Model-A-Teflon-PTFE-Magnetic-...

2.2) rod, e.g. http://www.ebay.co.uk/itm/2pcs-Model-C-PTFE-Teflon-Magnetic-...

2.3) rod with ring, e.g http://www.ebay.co.uk/itm/2pcs-Model-B-PTFE-Teflon-Magnetic-...

I can make the motor virtually any speed/power
Later I will also mix various aqueous fluids for other general purpose chemistry, e.g. titration, nitration ......


I have always used the rod with ring type stirbar, and I think they give you the best stir power so to speak. As for small/fast or large/slow, I would choose large/slow because it gives you a better idea of how fast the liquid is rotating. Just my opinions.




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[*] posted on 25-3-2015 at 01:58


The Australian Scientist, Thanks for your info. I'll go for the rod with ring types.

i_sum1, when I reacted tin metal (scrapings from a solid ingot) with 36% HCl, I had to warm it to get a rapid reaction,
at r.t. it was very slow, as you found.
I think that the solubility of SnCl2 is very temperature dependant (a quick google gave no solubility curves)
but from the Wikipedia article on SnCl2;

"Tin(II) chloride can dissolve in less than its own mass of water without apparent decomposition, but as the solution is diluted hydrolysis occurs to form an insoluble basic salt:

SnCl2 (aq) + H2O (l) is in equilibrium with Sn(OH)Cl (s) + HCl (aq)
Therefore if clear solutions of tin(II) chloride are to be used, it must be dissolved in hydrochloric acid (typically of the same or greater molarity as the stannous chloride) to maintain the equilibrium towards the left-hand side (using Le Chatelier's principle). Solutions of SnCl2 are also unstable towards oxidation by the air:"

so it looks like an HCl acidic solution is required?

For my tin crystal growing https://www.youtube.com/watch?v=G1sq4hnrBgM I used excess HCl.
The tin crystals easily and quickly react with the solution they grew from,
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[*] posted on 25-3-2015 at 09:55


j_sum1, Tin(II) chloride can dissolve in less than its own mass of water without apparent decomposition, but as the solution is diluted hydrolysis occurs to form an insoluble basic salt:

SnCl2 (aq) + H2O (l) <--> Sn(OH)Cl (s) + HCl (aq)
If you add a little hydrochloride acid it should shift the equilibrium to form less chlorohydroxide.




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[*] posted on 26-3-2015 at 13:30


Quote: Originally posted by Argentum  
Something I've seen but can't find anywhere

When mixing H2O2 with pool water treatement pills it gave a red chemiluminiscence, am I right?

If I am, what is the reagent in the pills? (I think trichloroisocianuric acid, but can't remember)


Is it possibly Pyrogallic acid? ;) I'm sure it isn't. That's the only source of red chemoluminescence I know of that uses H2O2. I'd be interested in knowing what does if/when you find out.




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