# Laboratory setup for the distillation of sulfuric acid

Purification of Laboratory Chemicals, 5th Edition, by Armarego, reads (p. 53):

Reagents such as water, ammonia, hydrochloric acid, nitric acid, perchloric acid, and sulfuric acid can be purified via distillation (preferably under reduced pressure and particularly with perchloric acid) using an all-glass still.

as well as (p. 479):

Sulfuric acid, and also 30% fuming $$\ce{H2SO4}$$, can be distilled in an all-Pyrex system, optionally from potassium persulfate. Also purified by fractional crystn of the monohydrate from the liquid. Dehydrates and attacks skin—wash immediately with $$\ce{H2O}$$.

I've never seen sulfuric acid fume (only spread with steam when heated), and Wikipedia states a boiling point of $$\pu{337 ^\circ C}$$, along the fact that it slowly decomposes to $$\ce{SO3 + H2O}$$ above $$\pu{330 ^\circ C}$$, so I'm wondering, mostly from a theoretical standpoint:

1. How far lower can the boiling temperature effectively get under reasonably strong vacuum?

2. Does the vacuum not also bring down the temperature level at which sulfuric acid degrades?

3. What would be an ideal laboratory (not industrial!) setup and process for the safe distillation of sulfuric acid in fair enough amounts for laboratory use (say producing in a batch the equivalent of $$\pu{5L}$$ at 30% concentration)?

Nota Bene: I know it's a better idea to buy sulfuric acid at the desired level of purity, but that is not the question.