Author Topic: 100% Sulfuric Acid  (Read 1135 times)

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Rhodium

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100% Sulfuric Acid
« on: October 31, 2002, 05:16:00 PM »
Are there any distributors of 100% sulfuric acid out there? I haven't found any other grades than 98% or 100% plus X percent of dissolved SO3.

I want exactly 100% - I guess I need to do some mixing of 98% and free SO3 - but how do I aim correctly so that I neither under- nor over-shoot?

Jetson

  • Guest
ooohhh.......
« Reply #1 on: October 31, 2002, 05:45:00 PM »
now now rhodium..  you know it's against the hive rules to post sources....   :-[  :P  ;)

the devil is so lonely >:(

Rhodium

  • Guest
I didn't ask for a supplier, I merely wondered if ...
« Reply #2 on: October 31, 2002, 05:55:00 PM »
I didn't ask for a supplier, I merely wondered if it was an item of commerce, as I haven't seen it.
I further concluded that was probably not the case, and instead asked how to prepare it myself.

Chromic

  • Guest
Hmm?
« Reply #3 on: October 31, 2002, 05:55:00 PM »
Bubbling SO3 into sulfuric acid doesn't sound like fun. Wouldn't it be easier to buy an ACS grade oleum and, knowing the amount of distilled water to add, carefully and with lots of cooling and stirring, dilute it to 100%?

Rhodium

  • Guest
SO3 is a low-melting solid - no need to bubble.
« Reply #4 on: October 31, 2002, 06:00:00 PM »
SO3 is a low-melting solid - no need to bubble.

My problem is just that "knowing how much to add". Neither ACS grade oleum or sulfuric acid guarantees concentration to more than +-1%, only the level of impurities...

Barium

  • Guest
If you want to prepare AlH 3 you can use ...
« Reply #5 on: October 31, 2002, 06:21:00 PM »
If you want to prepare AlH3 you can use anhydrous AlCl3 and LAH instead

Catalytic hydrogenation freak

Rhodium

  • Guest
Yes, there are several additives that can be used ...
« Reply #6 on: October 31, 2002, 08:19:00 PM »
Yes, there are several additives that can be used to achieve the end product - but AlH3 solutions prepared from AlCl3/LAH are more unstable than those prepared using H2SO4 (Alane polymers precipitating), but the main reason I asked was not because I wanted to achieve a certain end result, it was rather that I noticed something I didn't know, and thus I felt an urgent need to fill the mental void arising from knowing that you don't know everything you want to know.

micro

  • Guest
sulfuric
« Reply #7 on: November 01, 2002, 06:00:00 AM »
Swim gets the 2 1/2 litre from the chem supply.Its reagent grade yet it reads 95-98% concentrated sulfuric acid on the label.The person working at the chemical supply business stated that the 95-98% was the highest he had ever seen it.One thing about it,it sure beats anything the home center has for sale...................

El_Zorro

  • Guest
I always thought of it like this: Commercial H 2 ...
« Reply #8 on: November 02, 2002, 12:07:00 AM »
I always thought of it like this:

Commercial H2SO4 is produced by burning elemental sulfur, which is then run through scrubbers and catalysts, and added to water to get 100% H2SO4.  But given that H2SO4 is just about one of the most hygroscopic compounds around, it would take an absolutely anhydrous environment throughout production and packaging, as well as shipping and the actual use of it for it to stay 100%.  This is, for all intents and purposes, impossible.  So the chem companies cover their asses, and put 98% min. on the bottle.  It might very well be 100%, but there's no guarentee.  And I highly doubt it.  So, in order to get 100%, they add SO3 to it, and they have it, but they also have some dissolved SO3.  So I would guess that you could have some chem company do a custom synth, for an astronomical amount of money, and get you some 100% H2SO4, or you could just add some SO3 to some 98% H2SO4, and just use the best analytical scale you can get, and use an absolutely anhydrous environment.

Who is that masked man?

Ritter

  • Guest
100% Acid
« Reply #9 on: November 02, 2002, 08:06:00 AM »
Rhody,

Don't know about a commercial supplier, but I can tell you this much-  Shulgin describes mixing a certain amount of oleum and conc. H2SO4 and that mixture works exactly as described in Pihkal.  I have also seen refs for Alane where plain 96% conc. H2SO4 was added dropwise to THF soln. of LiAlH4 and yields were same as if 100% H2SO4 was used.

Rhodium

  • Guest
Considering the huge difference in molecular ...
« Reply #10 on: November 02, 2002, 08:31:00 PM »
Considering the huge difference in molecular weight between H2O and H2SO4, those 4% water will destroy a proportionally very large number of LAH molecules, but if you say it makes no difference in practice I believe you, it just seemed to be such a waste theoretically.

acid_egg

  • Guest
since we're discussing oleum......
« Reply #11 on: November 08, 2002, 12:32:00 AM »
A while back I noticed that the nitroethane synth using oleum and ethanol(

https://www.thevespiary.org/rhodium/Rhodium/chemistry/nitroalkane.html

) mentions using one mole of 20%oleum to 2 moles ethanol.
Can someone just remind me how I'd work out the weight of one mole of oleum(the fact thats its a mixture is causing the confusion/I think I know but want to be sure).

ps never heard of 100% H2SO4 as a commodity either.

Rhodium

  • Guest
Molar weight of oleum
« Reply #12 on: November 08, 2002, 12:57:00 AM »
It is not proper to say "one mole of oleum" as it is a mixture of two substances, H2SO4 and SO3 (yes I know that the document on my page says so, but the error was in the original ref).

20% Oleum is like having 104.5% H2SO4 (as the addition of enough water to 100g of 20% oleum as to turn all the free SO3 to H2SO4 will have you ending up with 104.5g H2SO4), and its density is 1.92. The molecular weight of H2SO4 is 98 g/mole.

98 / 104.5 = 93.8 g
93.8 / 1.92 = 48.8 mL

So - to measure the equivalent of 1 mole of 20% Oleum, you need to use 93.8g, or 48.8 mL.

acid_egg

  • Guest
ty
« Reply #13 on: November 09, 2002, 12:07:00 AM »
thanks. 8)

GC_MS

  • Guest
interesting
« Reply #14 on: November 19, 2002, 09:21:00 PM »
An interesting book on this topic is:

Manufacture of sulfuric acid (ACS Monograph Series # 144)
Dueker, West
Reinhold Publishing Corporation, NY. 1959

Your local chemistry library might have it as well. There is a chapter (19 I think) describing the manufacture of different sulfuric acid and oleum grades.

Ave Hive, synthetisandi te salutant!