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Author: Subject: The Short Questions Thread (4)
bfesser
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[*] posted on 11-7-2013 at 21:15
The Short Questions Thread (4)


In Nicodem's words:
Quote:
The old thread has become too long so please continue here. Those who never received a proper reply in the old thread, please feel free to repost the question.

Quote:
This is a thread where you can post all those short questions you always wanted to ask but did not consider them worthy of a new thread. You can ask amateur science related questions of all kind as long as you think they are simple enough to be answered by other forum members in a preferably single post.
Consequently, self discipline in avoiding off topic replies is expected.

I would like to add that it would be helpful if you enter "Question"/"Answer" or something similar into the Subject field when posting.

[Edited on 7/12/13 by bfesser]




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[*] posted on 11-7-2013 at 21:47
Question


I bought some Clean Shot H2SO4 drain cleaner the other day, it says it contains inhibitors in it. It has a clear purple color to it. I was wondering if anyone knew what these inhibitors were? Ive done some research on this, but havent found much, some say they are flourinated. I would also like to know the purity of this stuff, ive read about suspected Se impurities (eek)! What could the applications and constraints be of this H2SO4 vs say technical grade?

[bfesser: added to subject field]

[Edited on 7/12/13 by bfesser]




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[*] posted on 11-7-2013 at 21:55
Question


How fast does urea hydrolize in Ca(OH)2? I don't care if ammonia is still in solution I just don't want any urea present there.

[bfesser: added to subject field]

[Edited on 7/12/13 by bfesser]
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[*] posted on 12-7-2013 at 10:31


Quote: Originally posted by Variscite  
I bought some Clean Shot H2SO4 drain cleaner ..(cut).. What could the applications and constraints be of this H2SO4 vs say technical grade?


I don't know much about the 'inhibitors' but I have heard it has something to do with its reactivity.
The purple color is just dye to make it seem more dangerous to anyone who uses it. As you know H2SO4 is clear.
What is most likely is that your acid is recycled from some industrial plant, meaning it will be riddled with metal impurities and other unknowns, possibly suspended carbon. The limitations are endless with recycled H2SO4 you don't want to get metal into your energetic materials or it will sensitize them. Whatever you use the acid for will be much harder to get 'pure'.
You should be able to clear it up a little bit by heating on a hot plate (may get rid of water also) but that is very dangerous so wear eye protection and use fume hood. Also, small additions of H2O2 should work as well look into 'Piranha solution' before attempting though.
You should also perform a titration on the acid to get its actual %, it would be nice if you could measure ppm somehow.




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[*] posted on 14-7-2013 at 14:07
Question


If anyone has some certified pure, finely ground anhydrous sodium bromide, could you tell me if it tends to clump or stick together, but then breaks down easily when knocking the bottle?

I'm curious to know if the cohesion I'm seeing is due to moisture or just ionic attraction (I've ground and heated the material to 200 C, so I should think all water has been driven off).

Thank you.
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[*] posted on 15-7-2013 at 11:53


I know that dry KBr clumps readily due to moisture. But for very dry powders, often static will cause them to hold together in clumps or staticy strings, for lack of a better word, even after they are ground into a fine powder.
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[*] posted on 15-7-2013 at 12:14
Answer (kind of, and to my own question)


Thanks for the input.

The KBr NaBr was finely ground after being baked for two hours at 200 C, and then loaded into a glass bottle, which was again heated at 200 C for an hour before removing it from the oven and capping it tightly.

The KBr NaBr clumps and reclumps readily, but breaks apart relatively easily when the bottle is knocked. As two hours at 200 C should be long enough to destroy the dihydrate (which melts at 36 C) and completely dry the powder, I'm leaning towards the explanation being ionic attraction or static as you suggest. Also the fact that sodium chloride is sold with anti-clumping and other agents to keep it free flowing leads me to think that this is typical behavior.

Edit: I meant sodium bromide, but wrote potassium bromide. Must've had KBr on the brain after Dr. Bob referred to it.

[Edited on 7/15/2013 by Sublimatus]
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[*] posted on 27-7-2013 at 11:36
[question(s)]


Q. Why do hotplate manuals say not to cover the surface with Al foil?
Q. I plan to heat asphalt in a soup can on my metal-top hotplate. Will it be okay to put some Al foil on the top just this once?
Q. Should I go buy a fire extinguisher and burn cream, or just pre-dial 911?

[Edited on 27.7.13 by bfesser]




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[*] posted on 27-7-2013 at 12:34


Aluminum is amphoteric, dissolving in either acids or bases; so beware the pH of what you're cooking.

[Edited on 2013-7-27 by ElectroWin]
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[*] posted on 27-7-2013 at 12:35


Why it is prohibited to extinguish a man on fire with the help of fire extinguisher ?
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[*] posted on 29-7-2013 at 07:17


Quote: Originally posted by papaya  
Why it is prohibited to extinguish a man on fire with the help of fire extinguisher ?


It depends on the type of extinguisher that you use. CO2 extinguishers are highly compressed, so when they come out they're very cold, which can cause frostbite. Also, if the person is on the ground, the CO2 can suffocate them. Some ABC dry chemical extinguishers are safe because their contents are of negligible toxicity, but you should check their MSDS to make sure. Of course, the person will want to cover their face with their hands if you use a dry chemical extinguisher on them, but other than that it's fairly safe.

http://www.homeofpoi.com/lessons_all/teach/Fire-Extinguisher...
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[*] posted on 29-7-2013 at 07:25


Quote: Originally posted by bfesser  
Q. Why do hotplate manuals say not to cover the surface with Al foil?

[Edited on 27.7.13 by bfesser]


I think it may be due to the aluminum reflecting the heat back to the heating surface which may cause problems with the thermostat... My ceramic top plate also says to not heat metal vessels on it, I went against this and heated a stainless steel bowl for a hot water bath. The entire unit became very hot after about an hour- this never happened before when using glass water baths. I could have seen it leading to a failure of some sort if I kept it up. My theory about the aluminum reflecting the heat back may be wrong though- maybe somebody knows more on this.
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[*] posted on 29-7-2013 at 13:22


Al foil can trap air pockets which insulate the heating surface, causing the aluminium plate to melt. Peach experienced this first hand IIRC... came back to look at his reaction and found his hotplate had turned to a puddle of molten Al (exaggeration on my part, but it was pretty serious!).
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[*] posted on 1-8-2013 at 04:38


I would like to ask, that if I would react an alkene with OsO4 in methanol, some potassium methoxide and NMO as an oxidant, than what would be my product be?

Or asking in another way: if I use an alcohol instead of water for opening the osmium-alkene intermedier, than would an ether form or not?


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[*] posted on 1-8-2013 at 07:56


I'm attempting a hydrogenation reaction and it calls for rhodium catalyst on alumina... I only have a small quantity of rhodium powder, can this be used instead or is it imperative that the rhodium/alumina be used? It is for the synthesis of zingerone btw.

Thanks
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[*] posted on 1-8-2013 at 08:29


Quote: Originally posted by Mailinmypocket  
I only have a small quantity of rhodium powder, can this be used instead or is it imperative that the rhodium/alumina be used?


The surface of the Rh powder, compared to the Al2O3/Rh is several fold smaller and for heterogenous catalysis this one of the most important thing.

Make some Rh/Al2O3 or Rh/C from the powder, it's not that hard to make and if you regenerate the catalyst properly, it could be used several times.




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[*] posted on 1-8-2013 at 10:40


Ah, makes sense. Do you happen to have any facile ways of preparing a rhodium catalyst on alumina or carbon? I'm having a bit of difficulty locating such a procedure...
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[*] posted on 1-8-2013 at 16:35


From US5597772

Rhodium was next added to the fumace-aged alumina. A
14 g sample of furnace-aged alumina was mixed with an
aqueous solution of rhodium nitrate con-
taining a total of 0.085 grams of rhodium. The mixture was
first dried at room temperature, then at 100° C., and subse-
quently calcined at 550° C. for 4 hours. The process outlined
above constitutes the rhodium impregnation/drying/calcin-
ing step according to Scheme l of FIG. 2 (comparative
example). The catalyst at this point was in the so-called
“fresh” state, designated D-l , with a Rh loading of 0.6 wt %,




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[*] posted on 2-8-2013 at 06:00


Quote: Originally posted by kristofvagyok  
From US5597772

Rhodium was next added to the fumace-aged alumina. A
14 g sample of furnace-aged alumina was mixed with an
aqueous solution of rhodium nitrate con-
taining a total of 0.085 grams of rhodium. The mixture was
first dried at room temperature, then at 100° C., and subse-
quently calcined at 550° C. for 4 hours. The process outlined
above constitutes the rhodium impregnation/drying/calcin-
ing step according to Scheme l of FIG. 2 (comparative
example). The catalyst at this point was in the so-called
“fresh” state, designated D-l , with a Rh loading of 0.6 wt %,


Thank you! It sounds like a bit of a challenge but ill give it a shot.
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[*] posted on 2-8-2013 at 10:14
Absorption of Water and HCl by Strong Bases


My gas generator releases small amounts of HCl gas when it's producing CO2. Additionally, some water vapor is also released. I need a source of clean CO2 for experiments, and I was wondering what the best way tould be to remove these gases. Could I run the output through a tube of sodium hydroxide?

Any help is appreciated.




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[*] posted on 2-8-2013 at 10:15


You just answered your own question. You'll lose a little CO2 in the formation of Na2CO3 and NaHCO3, however.
Quote:
13. GAS GENERATORS

(a) Carbon Dioxide, Hydrogen, an Hydrogen Sulphide. The simplest form of generator for these gases is shown in Fig. 7. The solid material, cracked marble for carbon dioxide, feathered zinc for hydrogen, and ferrous sulphide for hydrogen sulphide is placed in the 300-cc. thick-walled generator bottle. The tubes are fitted as shown, and in the drying tube is placed a plug of cotton wool to strain the acid spray out of the gas, or if the gas is to be dried, granulated calcium chloride held in place with a plug of cotton wool on either side. Enough water is poured in through the thistle tube to cover its lower end and then about 5 cc. of 6 N HCl. The gas begins to generate rather slowly, but if one is impatient and adds more acid at once the reaction will soon become so violent as to drive foam out through the delivery tube. After a few minutes add more acid, 1 cc. at a time, in order to keep up the evolution of gas at the desired rate.

Synthetic Inorganic Chemistry: a Course of Laboratory and Classroom Study for First Year College Students. Blanchard, Phelan, & Davis. 5th ed., Wiley & Sons, 1936.
figure_7.jpg - 45kB
Oh, for fuck's sake! I just realized that we have this book in the library —pages 18–19 in the book (28–29 in the PDF). PDFs of this and other editions are also freely available elsewhere. I need to get used to finding things online rather than immediately jumping to my bookshelves. I'd rather not think about how many times I may have done this in the past. This damned newfangled internets thing! After all that effort of selecting the book from my shelf, finding the section from memory, transcribing the text, taking the photo, carefully cleaning it up in Photoshop... :(

[Edited on 2.8.13 by bfesser]




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[*] posted on 2-8-2013 at 18:08


Thank you.



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[*] posted on 5-8-2013 at 12:05


Can 1,4-dimethoxybenzene be alkylated with ethylene epoxide using Iron(III) chloride?



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[*] posted on 9-8-2013 at 17:49
Grignard Addition to Nitriles


When a Grignard reagent reacts with a nitrile, an imine salt is formed, which is usually hydrolyzed to a ketone.
http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch20/ch20-3...
Is there any way to form an amine from this intermediate imine salt, without going through the ketone?

(For example, sec-butylamine from ethylmagnesium bromide and acetonitrile.)




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[*] posted on 10-8-2013 at 02:06


Yes, and in good yields. One may add diborane/THF or methanol/NaBH4 etc. For an example of the former: http://www.sciencedirect.com/science/article/pii/S0040403902...
Search on google scholar; there are plenty of examples and links to freely-accessible papers.
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