BASF - 11-1-2003 at 15:45
does anyone know a good method for synthesizing this amazing stuff(needed for HNB-synth for instance)?
When i think of H2O2 synth i remember an electrolytic way(electrolysis of ammoniumpersulfate solutions), treatment of BaO2 with H2SO4, the industrial
anthrachinon-process and the air-oxidation of 2-propanol(good old "isopropyl alcohol").
Does anyone have some idea how these rather dilute solutions(10-30%) could be concentrated without extensive lab setup for vacuum distillation?
I´m glad about any input(other than just saying hello
)
vulture - 11-1-2003 at 16:57
The methods of synthesis you mention will yield a maximum concentration of 45%.
I'm afraid the only way of concentrating is vacuum destillation I fear. Which is rather dangerous. Perfectly clean glassware,
sufficiënt vacuum and joints coated with PTFE.
A dust particle or any other contamination = heavy explosion and a sudden burst of hot oxygen gas which will ignite anything flammable.
So If you're going to distill it, you'll have to clean your glass with K2Cr2O7/conc. H2SO4.
I remember some guy from mexico selling distilling setups specially designed to produce rocket grade H2O2. Can't remember the URL though.
yikes
Polverone - 11-1-2003 at 18:18
I think I would use analytical grade HNO3 to clean the glassware, not a dichromate solution! I believe that the concentration can be raised to 90%
merely by drying over a large quantity of conc. H2SO4. I know that there is a book of preparative inorganic chemistry in the school library that
details how to prepare 100% H2O2. I will try to find and transcribe those instructions next time I am on campus.
rikkitikkitavi - 12-1-2003 at 00:04
wouldnt it be better to use a distillation setup made out of Al or stainless steel, or perhaps PTFE, thourugly cleaned of course?
These do not shatter in the same way as glass either , especially not if you have some sort of pressure relief, like a stop cooker popping out if
pressure goes high.
Glass releases OH- , which catalyses decomposition. That is probably why you use HNO3 to leach out OH- and to increase SiO2 content on the surface of
the glass.
over about 60 % , heat of decomposition is enough to completely vaporize the products.
/rickard
BASF - 12-1-2003 at 12:34
hmm.......drying over conc. sulfuric acid would be the "holy grail-method"
......although i doubt that a simple method like this really exists.
Polverone:
But on the other hand, i would be amazed if u find such a procedure.
A file for the library, no?
Looking up another book about inorganic chemistry for H2O2-synth i found another method for concentrating H2O2:
fractionated crystallization at low(very) temperatures....
-Nah, not a promising method for the backyard-chemist, i know. 
a_bab - 13-1-2003 at 10:42
Well, I might have the solution to your issue. From an old book, of course ...
"In three days one can concentrate the solution of H2O2 from 25% up to 88 %, loosing in the process 19 % from the total quantity of H2O2. The final
solution of 88% can be concentrated further by cooling it, and at -10 degrees C the pure H2O2 start to crystalise"
The 65 % H2O2 is able to start fires, an also to explode due to impurities, as stated before. Even storing such concentrated H2O2 is dangerous.
The exicant is concentrated sulfuric acid, under vacuum. Though, it shouldn't be too difficult to set up a vacuum system. We are in the 21 century,
with lots of scrapyards around (refrigerator vacuum pumps, got the idea ?
BASF - 13-1-2003 at 14:09
Is there anything more specific about the process?-Like temperature, the used glassware or the vacuum?
Sounds cool so far, although additional information would be necessary.
a_bab - 16-1-2003 at 04:41
No. But it's obviously that the glassware should be VERY clean (actually they state this).
The vacuum ? Well, just not that strong to crush the glassware, I'd say. And the temperature is room temperature.
BASF - 16-1-2003 at 07:22
Coool.
So it is made at room temperature.
-Fine.
My proposal for the procedure:
In a desiccator(cleaned with warm technical grade HNO3 and distilled water with some EDTA(ethylenediamine tetraacetate; many of the more valuable
hand-soaps contain it, but i would´nt recommend it) are placed two 250ml-Beakers(not to mention that they are also cleaned using the same method).
One is filled with 200ml* conc. H2SO4,
*(170ml are needed for the dehydration of 100g~120ml 30% H2O2 to 88%H2O2 assuming only the strong first stage of hydration of the H2SO4 molecule can
make it)
the other is filled with 120ml 30% H2O2(possibly it would be necessary to begin with analytical grade H2O2, although i assume also technical grade
H2O2 would contain some EDTA and phosphoric acid as stabilizers..).
A common 20mbar water-hose vacuum pump(right translation?) is connected and the whole setup is left running for 3-5 days.
Considering the data from a_bab´s book we could then expect to get a yield of about 34g 88% H2O2.
Finally, this 34g could then be purified by freezing the 100% H2O2 out using the same beaker and a CaCl2*6H2O/ice cooling mix.
The maximum yield with this method would be 30g - 30*0.19 = 24.3g 100% H2O2.