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Author: Subject: The Short Questions Thread (4)
mackolol
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[*] posted on 13-8-2018 at 01:05


No it won't. Even in some procedures it says that you use "tetrahydrofuran freshly distilled from sodium".
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Tsjerk
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[*] posted on 13-8-2018 at 01:31


How dry do you need your THF?
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gluon47
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[*] posted on 19-8-2018 at 19:49


So the other day I made quite a large amount of bromine from NaBr/HCl/TCCA. I plan to use it to brominate vanillin to 5-bromovanillin. Problem is, the bromination requires dry/anhydrous bromine and I'm out of sulfuric acid which is the obvious choice for drying bromine.

So my question is: is it likely anhydrous MgSO4/CuSO4/CaCl2 would be effective for drying bromine?

EDIT: why the hell this pictures here I cant work out, can't get rid of it. It's not related...:mad:
[Edited on 20-8-2018 by gluon47]


[edit by moderator]
Offending picture removed (hopefully).

[Edited on 20-8-2018 by j_sum1]




reality is an illusion :D
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karlos³
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[*] posted on 20-8-2018 at 22:39


I have a short question I wonder about lately, and can't seem to find anything conclusive for.
Is it possible to prepare bromine in some solvent to use that instead of doing a distillation for purification of the bromine?

Since I would need a solution of bromine in a solvent anyway, I thought that it could be possible to directly prepare the bromine solution, in-situ one could say?
Anything similar to overcome the need to do a distillation of the bromine would be helpful.
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JJay
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[*] posted on 21-8-2018 at 00:10


Woelen has a writeup on his site where he prepares bromine without distillation. I think MrHomeScientist has a video of the process.



I'm no longer involved in this forum.
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karlos³
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[*] posted on 22-9-2018 at 07:15


Thanks JJay, for your knowledge, I overcame that problem by iodinating my substrate instead, even in much higher yield :)

Sadly I have a stupid question again...

Right now, I need a Cu(II) salt and only have the metal.
The last attempt using 30% H2O2+H2SO4 and NaCl+Oxone both weren't that fruitful, also wasteful or obnoxious...
Quite a lot of possibly useful chemicals for this are on hand, but what is in the chemical cabinet is lacking in the head...
In short, I do not know what would be a fast, effective and least annoying(i.e. possibly no evaporation of lots of water, least gasses as possible involved, things like that) way to make the piece of copper to a neatly handled Cu(II) salt?
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DraconicAcid
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[*] posted on 22-9-2018 at 09:08


Electrolysis of copper wire in a an acid solution. Hydrogen peroxide and hydrochloric acid (or NaCl and sulphuric). Precipitate the copper with sodium carbonate, and dissolve in your choice of acid.



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RogueRose
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[*] posted on 22-9-2018 at 10:21
Slow crystal formation on recrystalization of FeSO4


I am trying a recrystalization of FeSO4 and I'm wondering why it is taking so long. I had about 120g of heptahydrate and it lists the solubility at 51.35g/100ml @ 54C, so I used 210ml of water, dissolved and filtered 2x. It has cooled to below room temp and is in the fridge but no crystals.

Do some comounds take a lot longer to form crystals? When I would work with things like Ca(NO3)2 and (NH4)2SO4 I would dissolve in boiling water until saturated and then they would fall out very quickly as it cooled. Pretty much the same with CuSO4 but a little slower due to lesser solubility, but it is very close to FeSO4.
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SHADYCHASE54
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[*] posted on 7-10-2018 at 05:28
pid power supply question


I bought a used thermolyne 21100 tube furnace one of the old analog types, unfortunately the pyrometer is broken and completely useless. Anyway, at first I was going to swap the pyrometer for the same or a similar model. However, I soon found, what I thought would be a simple swap, was cost prohibitive. Thusly, it is my intent to hollow out the base and install a pid with a SSR-40AA relay.

My first question is will I burn out the heating tube if I use the SSR-40AA when the furnace is a 110v 50/60hz AC 12-15 amp system? I, as you may have concluded from the content I have provided thus far, am relatively new to electronics. Therefore I ask some indulgences on what might be your frayed patience, as I sincerely appreciate any help or advice offered, if it will aid my project and expand my understanding.

I am also confused with how amperage effects a system when V is in line with specs. Obviously it is good form to match everything as closely as possible to the (V) (I) requirements. However I also know that sometimes exact matches are not possible and at other times unnecessary. although in this case I suspect a difference +25 amp might be testing the limits of tolerance a tad. In either case, I ask for some guidance. Should I buy a SSR-15AA or will the 40AA model work as is. If neither of these will work and the pid for ac control is a shit plan altogether, pleas offer your assessment as well as an explanation. thank you in advance of any replies.

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Sulaiman
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[*] posted on 7-10-2018 at 05:45


The original controller would have been able to go to near 'full' power,
i.e. you could connect the heating element directly across the ac supply for full power.
An SSR controller cannot supply more than full power,
so should cause no harm.
________________________

Generally electronic components are rated for maximum allowable limits to variables,
so if you use a lower voltage/current/power than specified for the semiconductors,
usually there will be no problem.
In this specific case I would use an SSR with the highest rating practicable,
and a little spare,
so a 40A SSR is quite suitable for a 15A load,
I would choose it over a 15A SSR

either a 15A or 40A SSR should be 'heatsinked'.

I use a 40A SSR for my 1.6 A heating mantle.

If you go to extremes then secondary considerations such as leakage currents may become significant,
but not in this case.

[Edited on 7-10-2018 by Sulaiman]
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SHADYCHASE54
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[*] posted on 7-10-2018 at 05:53


thank you very much for your reply I will get it up and working today.
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[*] posted on 7-10-2018 at 05:56


does silica gel desiccant expires?
i found some old desiccant packets in my university lab, it clearly says "blue=active pink=activity reduced" so i suppose is the kind with cobalt chloride. i removed the powdered silica gel from the packets and put it into a beaker, i then heated it to 110-120°C with stirring, but after about 1 hour just a few crystals were blue, most of them were this orange/pink (more on the orange side) color, i kept heating but nothing happened, just a few crystals turned blue, the 95% of them kept their original color, so my question is: can i regenerate old silica gel? am i doing something wrong?





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S.C. Wack
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[*] posted on 7-10-2018 at 10:52


Quote: Originally posted by SHADYCHASE54  
Should I buy a SSR-15AA or will the 40AA model work as is.


I would not cheapskate and get an SSR without a heat sink...you may even want a small fan.

Quote: Originally posted by Ubya  
i then heated it to 110-120°C with stirring, but after about 1 hour


More heat and time.




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Mesa
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[*] posted on 8-10-2018 at 04:58


Quote: Originally posted by Ubya  
does silica gel desiccant expires?
i found some old desiccant packets in my university lab, it clearly says "blue=active pink=activity reduced" so i suppose is the kind with cobalt chloride. i removed the powdered silica gel from the packets and put it into a beaker, i then heated it to 110-120°C with stirring, but after about 1 hour just a few crystals were blue, most of them were this orange/pink (more on the orange side) color, i kept heating but nothing happened, just a few crystals turned blue, the 95% of them kept their original color, so my question is: can i regenerate old silica gel? am i doing something wrong?


remove the beads from soln. spread on a ceramic tray. bake in oven at 200*c+ for a few hours(until pink beads turn blue again.)

voila. regenerated silica gel dessicant.
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[*] posted on 9-10-2018 at 13:45


I found a reference for a Czech journal that is stated as:


Bohumil, P., Unsaturated androstanes. Czech. 127,564, 1968;
Bohumil P. Chem Abstr 1969;70:68637.

Anyone have any idea what the full name of this "Czech" journal is?




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[*] posted on 9-10-2018 at 18:06


From the list:

http://images.webofknowledge.com/images/help/WOS/C_abrvjt.ht...

the only chemical journal containing "Czech" is the Collection of Czechoslovak Chemical Communications, but that seems to be a miss. A search on Google Scholar turns up a few works by a "Bohumil, Provaznik" who may be Czechoslovakian:

https://patents.google.com/patent/US3340961A/en

but this could just be a coincidence.




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 2-11-2018 at 23:58
Benzocaine synthesis


Hi i am looking for help on a test I am running would it be possible to recrystallise benzocaine using diethy ether and Hydrochloric acid

[Edited on 3-11-2018 by Frankie1]
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[*] posted on 18-11-2018 at 20:43


Is it viable to prepare stearoyl chloride by chlorinating stearic acid with triphenylphosphine dichloride?

I'd rather not deal with (the difficulty of obtaining) phosphorus chlorides and (the mess that is) thionyl chloride, so I would like some expert input on if the chlorination reaction above is possible.




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ninhydric1
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[*] posted on 24-12-2018 at 11:33


Can you dry THF with calcium chloride? I know that alcohols, ketones, etc. can't, but there hasn't been anything on using it to try THF.



The philosophy of one century is the common sense of the next.
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[*] posted on 25-12-2018 at 02:14


Quote: Originally posted by ninhydric1  
Can you dry THF with calcium chloride? I know that alcohols, ketones, etc. can't, but there hasn't been anything on using it to try THF.


See http://delloyd.50megs.com/moreinfo/drying.html




Borosilicate glass:
Good temperature resistance and good thermal shock resistance but finite.
For normal, standard service typically 200-230°C, for short-term (minutes) service max 400°C
Maximum thermal shock resistance is 160°C
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[*] posted on 25-12-2018 at 02:28


The document pointed to above suggests 4A molecular sieves to dry THF,
I'd use 3A sieves ... because I have 3A sieves and they are cheap and generally re-usable.




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S.C. Wack
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[*] posted on 25-12-2018 at 07:45


Quote: Originally posted by Sydenhams chorea  
I found a reference for a Czech journal that is stated as:


Bohumil, P., Unsaturated androstanes. Czech. 127,564, 1968;
Bohumil P. Chem Abstr 1969;70:68637.

Anyone have any idea what the full name of this "Czech" journal is?


That of the Czech patent office.

Quote: Originally posted by ninhydric1  
Can you dry THF with calcium chloride?


Quote: Originally posted by Tsjerk  
How dry do you need your THF?




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[*] posted on 25-12-2018 at 10:33


I second the recommendation to use molecular sieves. 3Å or 4Å will both work fine and they can get the THF quite dry. Molecular sieves are a good investment, since they're reusable. They can be regenerated by heating in a microwave oven (I think there's a thread about this here on Sciencemadness).



As below, so above.
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[*] posted on 6-1-2019 at 12:30


Hey peeps,

So I'm planning to do a blanc chloromethylation reaction, but unfortunately my formaldehyde seems a bit outta wack. The bottle says it's a 37% solution, but it is very old and there's a lot of white residue in the bottle. I assume this is paraformaldehyde that formed over time. So I'm wondering how to redissolve the paraformaldehyde as formaldehyde so i can trust i actually have a 37% solution?

Any advice would be appreciated. This CH2O shit is causing me pains!
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TheMrbunGee
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[*] posted on 6-1-2019 at 12:33


Quote: Originally posted by Amphoteria  
Hey peeps,

So I'm planning to do a blanc chloromethylation reaction, but unfortunately my formaldehyde seems a bit outta wack. The bottle says it's a 37% solution, but it is very old and there's a lot of white residue in the bottle. I assume this is paraformaldehyde that formed over time. So I'm wondering how to redissolve the paraformaldehyde as formaldehyde so i can trust i actually have a 37% solution?

Any advice would be appreciated. This CH2O shit is causing me pains!


wiki:
Paraformaldehyde can be depolymerized to formaldehyde gas by dry heating and to formaldehyde solution by water in the presence of a base or heat. The high purity formaldehyde solutions obtained in this way are used as a fixative for microscopy and histology.

The resulting formaldehyde gas from dry heating paraformaldehyde is flammable.




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