Sciencemadness Discussion Board - Dilute sulfuric acid in fruit dehydtrator

Dilute sulfuric acid in fruit dehydtrator

DrEvil - 1-10-2015 at 00:52

I had a crazy ide of putting dilute sulfuric acid around 40% in my fruit dehydrator with a heat range of 35-70C.
Was thinking of putting it in a 1-2liter beaker and leave it there until its thicken acid. Is it possible to do this and can i reach a concentration of up to 98% if I leave it long enough.
Is it better to have a moderate temperature less then 70C or can i leave it at 70C for a couple of days, and see.

I don’t have distillation equipment, maybe i`ll get one when the moneys there. In the meantime is this a way to go?

DrEvil - 1-10-2015 at 01:53

Here is the fruit dehydrator.

I`ll make it a littel different from what you see here so that there will fit a beaker in it but else its the same as in the picture.
Got 4 open holes at the top for wapors to come out.

woelen - 1-10-2015 at 02:18

This will not work. Sulphuric acid attracts water very eagerly and even at the boiling temperature of water you will not get near 90% or so. Maybe you will get to 50% or 60% but then it is over.

If you want to concentrate to beyond 90% then you will have to heat the acid to well over 250 C. At that temperature quite some acid vapor will escape as well, as a white dense and very corrosive smoke. Concentrating to 98% is impossible, the best you get is 92% or so at temperatures near 300 C.

DrEvil - 1-10-2015 at 02:50

Tyvm for awnser.

Then i have to buy distillation equipment and a heating mantel

ave369 - 1-10-2015 at 03:56

Sulfuric acid requires high-temperature distillation equipment, not the standard one. Most water-cooled condensers, for example, will be mercilessly thermally cracked by the vapors of sulfuric acid.

You can use a standard round-bottom flask made of good crack-resistant glass, and make sure your heating mantle is powerful enough (I use a propane burner, and its power is barely sufficient to make conc. sulfuric boil). But for the condenser, you need a wide air-cooled glass tube with ground glass joints. You will also need to thermally insulate the boiling flask with something like rockwool.

Or you can just use a retort, similarly thermally insulated.

Also, Zintl and Karyakin recommend to add chromic anhydride or a dichromate salt into the acid before distillation. If I understand correctly, it's an azeotrope breaker, and you will get 99+% acid.

However, if you do not need 98-99% concentrations, you can just boil it down. It's best to do it in two steps. First, you boil dilute sulfuric acid down in a big beaker until it fumes. This will give you Glover acid with strength about 70-80%.

Second, you pour this Glover acid in a RBF or retort and distill water from it. Here, normal distillation equipment will suffice. Add crystal violet into the receiving flask and thermally insulate your boiling flask. When you see crystal violet discolored to pale blue, turn off water in your condenser and bleed it dry: really hot vapors will soon appear. Stop the distillation when you see it discolored to yellow. This will mean that concentrated sulfuric acid started to evaporate, and your still bottoms are now 94-95%. And now these still bottoms can be used for step III: Zintl-Karyakin distillation to yield pure 98+% sulfuric acid, or used as is.

You see, concentrated sulfuric is a listed chemical in my country, there's no way to buy it legally. So I have to know much about making it from the Bat (battery acid, 36%).

[Edited on 1-10-2015 by ave369]

[Edited on 2-10-2015 by ave369]

Deathunter88 - 1-10-2015 at 06:08

Quote: Originally posted by ave369

You see, concentrated sulfuric is a listed chemical in my country, there's no way to buy it legally. So I have to know much about making it from the Bat (battery acid, 36%).

YESSSSS, someone who finally understands my pain.
Something I would like to add is that you can also use one of those bare element radiators for heating the sulphuric acid, gets hot enough to use an 1cm air bath and still boil 98% acid in about 10 minutes. You can also use a vigreux column for the air condenser.

Never heard of using chromic anhydride, might try that sometime since that is so plentiful here.

DrEvil - 14-10-2015 at 11:15

Is it possible to leave a beaker of nitric acid 10-30% and Get upto 50-68%?
Will only the water evaporate or the acid to? What is the temp to use? If i leave it for a long time with 30-40c. Is it possible.

If not please explane to me why.

Or is distillation the only way to go here to?

DrEvil - 14-10-2015 at 11:28

Or concentration of Low hydrogen peroxide solutions?
That Will Work?

ParadoxChem126 - 14-10-2015 at 12:21

Nitric acid is considerably volatile, it will evaporate straight off with the water and will not concentrate in solution.

Hydrogen peroxide will likely decompose with the extended heating necessary to drive off a significant amount of water. There are many threads discussing the concentration of hydrogen peroxide using other means, it should not be too difficult to find useful information.

Consider the vapor pressure and hygroscopy of the liquid you are trying to isolate. There are much better ways to concentrate solutions, a food dehydrator is ineffective for this purpose.

Oscilllator - 14-10-2015 at 19:38

Actually, it is very possible that you will be able to concentrate H2O2 by this method. It has been posted here a couple of times that one way to concentrate H2O2 is to use an aquarium bubbler to bubble air through a hot solution of H2O2, so I don't see any reason why it wouldn't work with a food dehydrator.

DrEvil - 14-10-2015 at 22:42

Quote: Originally posted by Oscilllator

Actually, it is very possible that you will be able to concentrate H2O2 by this method. It has been posted here a couple of times that one way to concentrate H2O2 is to use an aquarium bubbler to bubble air through a hot solution of H2O2, so I don't see any reason why it wouldn't work with a food dehydrator.

I`ll try and see. I think it will work, but do i need to bubble air to the solution when it is in this hot enveroment?. Or can i leave it ther to the solution is where i want it to be with the wanted consentration?

What will be the correct temp to use.
Can I use 70c all over without it decompose?
It decomposes at 150C? or is it just boiling point and it starts decomposing before?

DrEvil - 14-10-2015 at 22:47

Quote: Originally posted by ParadoxChem126

Nitric acid is considerably volatile, it will evaporate straight off with the water and will not concentrate in solution.

Hydrogen peroxide will likely decompose with the extended heating necessary to drive off a significant amount of water. There are many threads discussing the concentration of hydrogen peroxide using other means, it should not be too difficult to find useful information.

Consider the vapor pressure and hygroscopy of the liquid you are trying to isolate. There are much better ways to concentrate solutions, a food dehydrator is ineffective for this purpose.

The nitric acid is ok, I need to buy my self a distillation equipment.
But your sure I cant concentrate hydrogen peroxide this way?
I seen many heating in a beaker on the stove or any other heating sourse to evaporate of water to the wanted concentration.
Please explain why it is not possible.

ave369 - 15-10-2015 at 01:10

Quote: Originally posted by DrEvil

But your sure I cant concentrate hydrogen peroxide this way?
I seen many heating in a beaker on the stove or any other heating sourse to evaporate of water to the wanted concentration.
Please explain why it is not possible.

It is possible, but losses are too great. Concentrating hydrogen peroxide at normal pressure requires too high temperature, and most of it decomposes.