Evaporating sulfuric acid

[gregory-d]

Heat about 100 c only, but I forgot it till all water evaporated

Ok thanks heaps.
That answers my question about what temperature is required to evaporate the water.
It also makes it very clear this is a very silly idea.
As Jon suggested at 100C the reaction speed is 512 times is is at 10C which is pretty aggressive.

 

[Shark]

Add a few drops of room temperature sulfuric to a piece of dry wood and watch the reaction. Warm the sulfuric up to 100F and try it again. The results can be quite the surprise.

 

[gregory-d]

Add a few drops of room temperature sulfuric to a piece of dry wood and watch the reaction. Warm the sulfuric up to 100F and try it again. The results can be quite the surprise.

I'm not game to even think about heating sulphuric acid to 100C
So I'll take your word for it.
There is a youtube video where a guy burn a piece of chicken though.

 

[ssmontecarlo]

To answer your question as to what's wrong with the idea:

I don't know how well kitted out you are from a safety perspective however concentrated Sulphuric is nasty stuff even at room temperature because it is so hungry for water. I'm also unsure as to what you understand about the relationship between temperature and reaction speeds so please bear with me:

For every ten degrees C you increase the temperature of that acid, it doubles the speed that it reacts. That doesn't sound like a lot however the chart below puts what that means into context when heating this to 250 degrees C

Temperature	Reaction speed
10	1
20	2
30	4
40	8
50	16
60	32
70	64
80	128
90	256
100	512
110	1024
120	2048
130	4096
140	8192
150	16384
160	32768
170	65536
180	131072
190	262144
200	524288
210	1048576
220	2097152
230	4194304
240	8388608
250	16777216

In essence at 250 degrees C that acid will "work" 16 million times faster than when it's at 10 degrees C. It's a concept that is used in wet ashing of organics but no way heaven made would (edit) I want to be anywhere remotely in the vicinity of that. I'm no shrinking violet and I do take managed risks however I think this one goes beyond risk management.

I hope that's of some help Gregory.

Jon

Holy moly. I spoke with Shark about cleaning chips in sulfuric acid. He described the reaction time as heat increases...plus living in the south. Were relative humidity in the summer months is always high, I went with incineration. Sulfuric acid has the potential being very very bad stuff. Be safe.

 

[Shark]

I'm not game to even think about heating sulphuric acid to 100C
So I'll take your word for it.
There is a youtube video where a guy burn a piece of chicken though.

100C never again for me. Heck I don't even try 100F anymore.

 

[PeterM]

After a little experimentation I am curious.
In an attempt to remove some of the water I slowly warmed my sulphuric acid on a heat controlled hot plate at 250c.
The hotplate being set to 250c I very much doubt that the acid got up to that temperature in that time.
I have a IR thermometer on it way.
It was only there for an hour but as it cooled I covered it with a piece of plastic.
Coming back later there was indeed water condensed on the plastic.

My question is simple really
Has anyone tried heating sulphuric slowly to 300c.
By slowly I mean so that it never actually boils.
My thinking is that as the boiling point increases with the concentration and as the liquid gets close to it's boiling point the water will evaporate and the concentration will increase.

As the boiling point is 300c at 95% I am thinking that this could be a safe way to concentrate sulphuric acid.
Instead of trying to go all the way to 98% as many horror stories I have read here suggest it's not much of a clever idea

Or is this idea just another one of my "Don't be an idiot Gregory" ideas?

I don't advise it. If you got burned with Hot Fuming Sulfuric Acid, you'd had wished you had died as a child.

 

[4metals]

If you got burned with Hot Fuming Sulfuric Acid, you'd had wished you had died as a child.

As harsh as this sounds, it is unfortunately true, don't mess with hot sulfuric.

I know of a good number of refiners that frost CZ's to separate them from real diamonds and they use boiling hot sulfuric. That is an effective old method, I much prefer cold Hydrofluoric Acid but the old timers say they are afraid of HF. To set the record straight, cold HF is tame compared to boiling sulfuric. However both require careful handling, you can buy a HF burn kit which is calcium gluconate if you get HF on your skin and it is effective if applied in a reasonable time (like minutes). But if you spill boiling sulfuric acid on you, remember what PeterM said!

 

[gregory-d]

Ok just to sum up.
Here is my understanding of this after doing some more research.

Sulphuric acid has a high affinity with water but water will still evaporate out of it as it is heated.
It will even evaporate below the boiling point of water until the humidity of the air on the surface is high enough for this to be no longer possible.
Edit: however if you just leave it in the open air the reverse will happen and it will absorb water.
The really dangerous part of all of this is that when it is heated and the water evaporates to around 98.3% it goes into the azeotropic state where the bonds between the sulphuric acid and the water are too strong for more water to evaporate.
At this point things become very different very quickly as suggested in this thread that is exponentially higher per degree than at 10C.
So no matter how slowly you come to that point in a micro second you have a very dangerous situation where sulphuric acid is evaporating then you have 300C sulphuric acid vapour in the air.
Even the guy who was monitoring his sulphuric at 100c would not have been able to turn off the heat quickly enough to stop this happening.
To add heat to something you need to apply extra heat and as the water is evaporating that will keep the temperature lower and you will need to apply extra heat to keep it at 100c. But once the water was gone that extra heat goes directly into the 98.3% sulphuric acid and it heats really quickly to above it's evaporation point.
Adding more heat (no heating system can stop instantly) makes it worse.
Also in the lab stuff is put at the bottom of the liquid for the gases to form around, closest to the heat source rather than at the surface.
These bubbles also seems to happen very quickly as the bubbles don't slowly form they just appear, so it lets off large bubbles suddenly.
Without this stuff in the bottom the process happens at the surface which will always be cooler than the liquid below it.
So then this another place where things will go very very wrong very very quickly.
I am going to learn from the experience of others and follow the very good advice given here.

As many people have said here this is a very bad idea.

I hope that sums up the process and explains why you shouldn't do it.

 

[slsmp40]

Yes my ideas can be pretty crazy sometimes.
I know.
But you don't know unless you either swallow your pride and ask or try and blow yourself up with your ego intact.

Gregory let me be the voice of reason here. As someone who has distilled probably 4000 lbs of sulfuric acid azeotrope over the years let me say that you are only going to produce a very expensive product with much more dangerous than necessary conditions and spend much more time to do it. Get a heating mantle, two neck round bottom flask, V. column, thermometer take off adapter, condenser, vacuum take off adapter and receiver flask. Hopefully you have a suitable vacuum source. Get some boiling chips also. Learn how to use this equipment by distilling wine into brandy. Once you can do that you’ll be ready to run H2SO4. Your present endeavors will not only be a waste of time but will sooner or later make itself a real threat to you or someone you hold dear.

 

[gregory-d]

Gregory let me be the voice of reason here. As someone who has distilled probably 4000 lbs of sulfuric acid azeotrope over the years let me say that you are only going to produce a very expensive product with much more dangerous than necessary conditions and spend much more time to do it. Get a heating mantle, two neck round bottom flask, V. column, thermometer take off adapter, condenser, vacuum take off adapter and receiver flask. Hopefully you have a suitable vacuum source. Get some boiling chips also. Learn how to use this equipment by distilling wine into brandy. Once you can do that you’ll be ready to run H2SO4. Your present endeavors will not only be a waste of time but will sooner or later make itself a real threat to you or someone you hold dear.

I guess you didn't read my last post then.
Useful addition to the information though thanks.
My initial idea was just to remove some of the moisture not all of it but now I understand the process a lot more completely and hopefully anyone coming to this forum can see also why it is a bad idea.
I think this thread has covered everything now.

 

[Shark]

Learn how to use this equipment by distilling wine into brandy. Once you can do that you’ll be ready to run H2SO4.

Not me, I will stick to the brandy. I feel better leaving hot sulfuric to the professionals.

 

[gregory-d]

Just one more thing.
I saw a video where the guy heated the sulphuric to bring the fine gold powder to a clump.
If you are working with fresh 98% sulphuric acid that is a very bad idea especially if you do as it appears he is saying it to 250c.
Youtube like AI needs to be treated with much caution.

 

[Yggdrasil]

Ok just to sum up.
Here is my understanding of this after doing some more research.

Sulphuric acid has a high affinity with water but water will still evaporate out of it as it is heated.
It will even evaporate below the boiling point of water until the humidity of the air on the surface is high enough for this to be no longer possible.
Edit: however if you just leave it in the open air the reverse will happen and it will absorb water.
The really dangerous part of all of this is that when it is heated and the water evaporates to around 98.3% it goes into the azeotropic state where the bonds between the sulphuric acid and the water are too strong for more water to evaporate.
At this point things become very different very quickly as suggested in this thread that is exponentially higher per degree than at 10C.
So no matter how slowly you come to that point in a micro second you have a very dangerous situation where sulphuric acid is evaporating then you have 300C sulphuric acid vapour in the air.
Even the guy who was monitoring his sulphuric at 100c would not have been able to turn off the heat quickly enough to stop this happening.
To add heat to something you need to apply extra heat and as the water is evaporating that will keep the temperature lower and you will need to apply extra heat to keep it at 100c. But once the water was gone that extra heat goes directly into the 98.3% sulphuric acid and it heats really quickly to above it's evaporation point.
Adding more heat (no heating system can stop instantly) makes it worse.
Also in the lab stuff is put at the bottom of the liquid for the gases to form around, closest to the heat source rather than at the surface.
These bubbles also seems to happen very quickly as the bubbles don't slowly form they just appear, so it lets off large bubbles suddenly.
Without this stuff in the bottom the process happens at the surface which will always be cooler than the liquid below it.
So then this another place where things will go very very wrong very very quickly.
I am going to learn from the experience of others and follow the very good advice given here.

As many people have said here this is a very bad idea.

I hope that sums up the process and explains why you shouldn't do it.

No mate.
This as you said in another post, not a digital process.
It is what will happen if something go bad at these conditions that is of concern.
Sulfuric will be cooking around at 300C all day until it no longer boils.
But at these harsh conditions the risk of something breaking increases and the outcome of that will be catastrophic, so to speak.
It is not like the Sulfuric itself becomes a monster with unexpected attributes at a certain temperature.
But as the temperature rises the bad attributes become an increasing concern.

 

[Wolosiewicz Art]

I just finished concentrating Sulfuric acid this weekend. Started with 1800ml battery acid and kept it between 90-100 Celsius until I was no longer getting steam off of it. As soon as the steam started turning to white smoke (roughly 700ml remaining) I knew it was ready for what I needed it for. I have no idea of the strength of the concentration, but after watching numerous videos from our members and from the loss of the evaporated water amount, I know it was in the range of high 70’s to low 80’s, which was plenty strong for my needs. The evaporative process was done outside, and full safety gear was used…..Sulfuric acid is nasty stuff.

 

[4metals]

The evaporative process was done outside, and full safety gear was used…..Sulfuric acid is nasty stuff.

Good that our neighbors to the north realize this fact too. It cannot be said too often!

 

[Wolosiewicz Art]

Good that our neighbors to the north realize this fact too. It cannot be said too often!

Of course…..chemical dangers don’t care much about geography or climate!