[Siro]

I have been reading over this synthesis trying to gain a full comprehension: http://www.amasci.net/syntheses/hydrobromic-acid-synthesis.php?lang=eng

At the end, I would assume the remaining mixture contains, Water, HBr, some remainder Sulfuric Acid, and some Elemental Bromine.

From what I understand the solution would be heated at low heat and magnetically stirred until the solution becomes clear(all bromine has left). And then supposedly "If one wants to prepare highly concentrated acid, it is important to collect only the fraction which distills over at approximately 122 °C (the boiling point of the azeotropic mixture of water and hydrobromic acid, in which the mass fraction of HBr equals approximately 48%)."

Would this mean the solution is slowly heated below 122°C until it no longer boils, and then heated up to boiling at 122°C at which the distillate is strictly going to be a 48% solution of Hydrobromic acid? Would I have to use a fractionating column in the distillation rig to do this?

I'm still trying to understand the nature of azeotropic mixtures... Is my understanding of the above method correct, or incorrect?

[Babcock_Hall]

You would probably want to have a fractionating column, but I have not done this distillation myself, so I am not certain.  You would heat and collect liquid boiling at temperatures less than 122 °C in one flask, then switch flasks and collect the a separate fraction that boils at approximately 122 °C.  Why do you want to make your own hydrobromic acid, when you can buy it?

[Siro]

Because it's extremely expensive? With about $50 bucks of Sulfuric Acid, and that's a generous estimation, a person can make about $400 worth of Hydrobromic acid. Not that I would ever need that much, but I figure if I can get a better price per ml, then why not do it? When equipping a full lab a lot of money can be saved by synthesizing some of the more expensive chemicals yourself.

So what I would do is boil until it no longer boils at 122 C with a fractionating column, then switch receiving flasks and *Ignore me, I am impatient* the temperature up to 122 C and continue boiling the initial flask until no more distillate comes over?

Or could I also do the above, but instead of distilling just boil it from a lower temperature and creep upwards toward 122 C until it stops boiling. Indicating that if it only boils at 122 C then the maximum concentration has been attained?

[Babcock_Hall]

If the acid is less concentrated that 48% to start with, the initial portion of the distillation will be mostly water (that would be the first fraction), then the composition will change as the distillation head temperature rises, and the second fraction will be the 48% HBr.  I still think that when one factors in time and cost of equipment, one is better off buying it.

[AlphaScent]

Its not that expensive.  It is 90 bucks for a liter from aldrich.  That seems like a real pain to save 50 bucks.

[Siro]

Yes but at that price the larger quantities are back ordered. That 40 extra backs might not seem like much but if you think of going through 10-20 liters per month, hypothetically, you're talking 400-800 you would be saving.

I realize I could do the above reaction and with the equation calculate how many moles of HBr would be produced, and gas it into some water that is being stirred. Just have it calculated so that enough HBr gas that goes over to put the concentration in the water at >55%. Some would be lost clearly, but the concentration would be near it's maximum. I could do this and easily save a bunch of money with not much time lost in the process.