Concentration-Dilute sulfuric acid is heated at 100C normal atmospheric pressure until all moisture (water) is vaporized and condensed seperately.
Purification-The resulting sulfuric acid is boiled at 340C normal atmospheric pressure and condensed seperately.
All this is done in pyrex glassware using an oil bath to prevent steam explosions.

This is a summary of an industrial procedure for concentration and purification which I found somewhere on the internet. Is this correct? If so, what important details should I not forget while operating such a process? Thank you.

Yes it works. Just be careful not to inhale any sulfur trioxide which is driven off from H2SO4 decomposition at a high temp. I quite sure this has been many posts on this.

I'm on a massive search on this topic. Also does anyone have any material safety data sheet on sulfur trioxide.


-tom

Tom you have created mahem at sciencemaddness about this topic. You created so many useless posts. "Where can I find the MSDS for SO3"
Fucking search.
www.google.com
sulfur trioxide MSDS

God some people are ignorant, first hit on google:


Safety (MSDS) data for sulfur trioxide

--------------------------------------------------------------------------------

General
Synonyms: sulfan, sulfuric anhydride, sulphuric anhydride, sulphur trioxide
Molecular formula: SO3
CAS No: 7446-11-9
EC No: 231-197-3
Physical data
Appearance: Needles or polymer
Melting point: 16.8 C
Boiling point: 44.7 C
Vapour density: 2.8
Vapour pressure: 280 mm Hg at 20 C
Specific gravity: 1.97
Flash point:
Explosion limits:
Autoignition temperature:
Water solubility: reacts violently

Stability
Stable. Incompatible with organic materials, finely powdered metals, bases, water, cyanides and a wide variety of other chemicals. Reacts violently with water, oxygen and other chemicals - read a full data sheet before use.

Toxicology
Highly toxic - may cause cancer. May be fatal if inhaled, swallowed or absorbed through skin.
Risk phrases
(The meaning of any risk phrases which appear in this section is given here.)
R8 R14 R23 R24 25 R34 R45.


Personal protection
Safety glasses or face mask, gloves. Good ventilation.


How hard was that, clicking twice and typing 32 charaters :mad:

okay dokay

What kind of oil do you plan on heating to 340 degrees centigrade?

For fucks sake you're getting really irritating tom. It's a classical kewl strategy to crosspost the same question at several boards to make sure you don't have to get off your lazy ass.

Oil would be problematic, but there are labdesigned silicone oils that will handle those temperatures. But why bother using an oil bath? Just suspend in borosilicateglass above a bunsenburner and SLOWLY heat up.

or use molten lead/tin alloys which melts at about 230-250 C, without the risk of any oil decomposing or creating flammable gases (always a risk with open flames nearby)


there are thermal oil capable of with standing up to 350-400 C but they are not easily accessible .

for the luxurious ones, purchase a fluidized sand bed heat bath , excellent heat transfer and only silica /air used as a media (or build one yourself)

/rickard

Or try a white metal alloy like the HAYESOL 70 here (http://www.hayesmetals.co.nz/white_metals.html) with a melting point of only 68C.
I'm sure you could find something similar in your part of the world

I have a few questions about the process, if you don't mind. What kind of temperatures will it take to start producing sulphur trioxide, and how much gas will it produce? I have about 3 litres of battery acid in my possession which is basically it when it comes to acid right now (just building up my lab), and I want to conc. for use in reactions (the conc. right now can't do didly shit, nor do I have litmus paper or scales to figure out the conc.) I would like to boil some down and get the concentrated stuff, but I don't want to end up fumigating myself.

What kind of procedures do you guys use? I doubt my vent hood in the kitchen is going to cut it, it would have to be done outside. Which means campfire in the woods for me ;-). I don't have any good pyrex that I could heat like that, would regular bottle glass be able to take that kind of heat shock?

Bah, it would be so much easier to raid the Chem Lab...

YayItGoBoom!-

Read this (http://www.roguesci.org/theforum/showthread.php?s=&threadid=2660) A search will answer a question like that every time...

To YaYItGoBoom:

To boil the acid you must have a very good ventilation system, the vent hood in the kitchen is not able to do this work well. Safety is the most important thing! Boil the acid outdoor and wear a mask, googles and gloves. The pyrex is not a problem, you can buy it in a supermarket, it is sold everywere!
About the procedure: i boil my acid a lot, this means that when white fumes appear i continue for about 30/45 minutes. It's very usefull to use a graduated pyrex so you can control the right amount of concentrated acid you need.
For example: if you start boiling 500 ml of 50% H2SO4 you will have to boil it untill it reaches 250 ml to have about 98%-100% H2SO4. You have to calculate the right amount of remaining acid after the boiling procedure. It's not difficult.
Concentrating H2SO4 is simple but stay sharp during the procedure because SO3 is noxius.

For example: if you start boiling 500 ml of 50% H2SO4 you will have to boil it untill it reaches 250 ml to have about 98%-100% H2SO4 But that's only correct if the concentration is given in volume percent. Usually mass percent are used.

It's not even correct in volume percent. The density of sulfuric acid increases with the concentration, so you'll need to boil quite a bit past 250ml.

It seems a rather common mistake to forget about density changes and then people wonder why their nitrations with their "98%" acid don't work.

EDIT: Rhadon, you have been forgiven. Now go in peace and...nevermind...:p

:eek: sure. Forgive me that mistake.

Just want to point out that concentrated sulfuric acid expands on heating with more than 10% by volume (by observation..) so you have to keep this in mind also ;)

Yeah, mine goes from 900 mL to past 1100 mL.