My therapist and friend was curious about the sulfuric acid he purchased to work with SP cactus. Unlike the descriptions he had read, which said it was colorless, it is a deep maroon. The bottle says 'concentrated,' and indeed, it is! (He 'over-salted' whatever that means) He wonders if it's safe to use in these extracts. The assumption is that it's fine, as such tiny, tiny amounts are needed, but he is no chemist, and he has been consistently amazed at the high level of expertise on this forum. It's really a credit to the web.

Sulfuric acid is a colorless, odorless, and syrupy liquid.
Coloration indicates contamination, it could be from the storage container or the cap, some people report discoloration of H2SO4 when stored in polyethylene containers in elevated temperature.
It could possibly be organic/inorganic/metal contamination. Technical grade H2S04 is not pure and it's not colorless. Where did you get the acid from? Is it homemade? Some people purify drain cleaners containing H2SO4, to obtain it, because it is a watched chemical in some places. Improper cleaning of the drain cleaner can be the reason for the color.

NOTE: Don't do this if you don't have the appropriate facilities, equipment and knowledge, you can seriously injure yourself.
If you need small amounts of H2SO4 you can consider making it yourself (on small scale).
You can bubble sulfur dioxide in hydrogen peroxide or even better nitric acid and then concentrate the solution. Nitric acid is better option because it forms nitrogen dioxide, when no more NO2 is formed the reaction is completed, hydrogen peroxide dont indicate completion but its safer.
Sulfur dioxide can be generated by burning sulfur or with sodium metabisulfite and HCL.
DO THIS ONLY IN FUME HOOD!

Personally i wouldn't use it, atleast until i clean it.
Wait for more responses and opinions!
Good Luck

Thanks so much for the reply. Ok wow that is really good to know! It was purchased at [redacted], and it's brand name is [redacted] 'professional strength fast acting sulfuric acid'. Normally the fact that it's labeled as drain opener would have kept my friend from trying it, but it said 'pure' and 'concentrated' on the bag that it came in. (and it was cheap) It was made in Florida by [redacted]. Maybe it's not such a good idea to use it after all, My friend would not be able to do the proposed operation but definitely appreciates the feedback and info. Thank you.

No problem, glad i helped.

In future posts make sure to be more clear and share as much information regarding your problem as possible, without ruffling too many feathers. If you started with the fact that its from a Home Improvement store and its technical grade (drain cleaner) you would have gotten a lot more responses and assistance regarding your problem. When unclear, misinformational posts are made you leave your viewers guessing, and most of the time they dont even bother replying because they cant give clear answear to unclear question.

Check some of the big selling sites for small amounts of H2SO4, since your "friend" cant make it himself i would suggest he never try to purify technical grade/drain cleaner H2SO4, the only real way is to distill it which is quite dangerous process.
Hot corrosive liquid is a BIG no no for the kitchen chemist.

Good Luck!

Thanks for the advice! That was literally my first post ever, so I really do appreciate that.

Commercial sulfuric acid used for drain cleaning usually contains organic inhibitors to protect the plumbing. Although probably safe, I would not use this for salting alkaloids.

Here is a video on sufluric acid purification but I would strongly advice against doing any of this in amateur conditions, especially sulfuric acid distillation, which is extremely dangerous.

I believe you can obtain small amount of dilute reagent grade sulfuric acid - you need just a tiny amount anyway; maybe battery acid is good enough for the purpose, but always read MSDS.

Thanks very much. The plan is to do an acetone clean-up after, so wondering if that would negate any potential hazards. But in truth it doesn't seem worth it, since folks are giving me all these good ideas for alternatives! This is great!

By the way, this video in the link you sent is excellent. I will watch more of that channel. Really well done, professional and informative.

Cleaning H2SO4 with Acetone????????
One thing is for sure: this "plan" of yours wont clean the acid, but it sure can/will cause a reaction which will form numerous products.

oh no I'm sorry... cleaning the end product, not the acid, with acetone. that's the plan. Getting different acid is now also the plan!

So the extraction is from SP cactus, and the end result has impurities and needs a purification step. So wondering if any potential contamination from salting with this colored acid would be negated in the final purification step. Sorry for the confusion

Ah good!
Thanks for clarifying.
If you have any doubts or questions ill be glad to help if i can and if i have the time, good luck be carefull.


Edit: Im not sure exactly what the imurities in the drain cleaner are, so i cant tell you with certainty if acetone purification step will remove all of them. Like blue.magic mentioned (which i forgot to) was that they use inhibitors, they are there to protect the pipes.
Maybe you can get away with using the drain cleaner and later doing adequate purification of the end product, i personally wouldnt use it tho.

Thanks again! I'm thinking it's best to have caution. It's easy to order better stuff. It's been a long-term project anyway, and we haven't had to skimp on anything really thus far and I think that's the best way to proceed.
Right on. Hey, really appreciate your point about not ruffling feathers. That got by me last night but I see what you mean