Long story short i've had a 5L jug of 96°c sulfuric for a good while now, probably 8+ months.

Went to check my chemicals this morning and the acid is "black". Not black as in "completely" but dark-grayish.

Is that normal ? First time it happens :/

I've had this happen with dyed up shitty store bought H2SO4. It still works in all the reactions I've tried it in, I would guess its some sort of sell by date, possibly the dye oxidises? Either way, its still good as far as I can tell, but obviously you still wouldn't use it on anything important, nothing that would go in your mouth, nothing that might do something unwanted if the structure was altered slightly.

Try running it through activated charcoal, might do something for the dyes.

Well, it's not supposed to contain any dye. It's "retail", straight from a chemical company :/

When i bought it it was crystal clear (slightly off-yellow).

Edit: It appears it's even more corrosive than before o_O It chew through cotton like alien blood :O

Is it a local chem supplier or a big national brand? Either way its not suppose to happen. Are you sure your bottle was properly closed?

Store it in amber bottles in a cool dark place with a good cap:)

Is it a local chem supplier or a big national brand? Either way its not suppose to happen. Are you sure your bottle was properly closed?

Store it in amber bottles in a cool dark place with a good cap:)

Local supplier but first delivered by sigma aldricht.

Yeah it's those big-ass jugs with "rolling" security caps, so blah :/

What could have triggered this change ? Air absorption ? Eating of some plastic on the inside ?

Poured a little off and while the jug certainly is attacked on the inside, it still has the consistency of regular H2SO4, only that it's "gray"

It could be carbon from some kind of contamination.

organic gets in jug...acid eats organic...carbon left over...

Local supplier but first delivered by sigma aldricht.

Yeah it's those big-ass jugs with "rolling" security caps, so blah :/

What could have triggered this change ? Air absorption ? Eating of some plastic on the inside ?

Poured a little off and while the jug certainly is attacked on the inside, it still has the consistency of regular H2SO4, only that it's "gray"

Yeah i have the same! But from Acros, anyways. Could be that some residue got in it when you opened last time. Possible attacking the cap? I always coat my caps with "teflon tape", works great for Bromine and for other acids :)

You could try and distill your acid, but damn, not something i would like to be doing in 5L amounts :s

You could run a couple of test and check out if the impurities interfere with any of them.

My last batch of Isopropyl Nitrite went just fine, so i guess it's ok.

I'm gonna try a standard AN/H2SO4 nitration of cellulose today, see if it gives the same results as before :)

Sounds good, let us know what it looks like!