I found a rust remover product in the local big box national chain store today that contains ~25% phosphoric acid. The product is labeled as 'eco friendly' and biodegradable, so does not contain organic polymers or hexavalent chromium salts like some similar products do. The MSDS states that anything else that may be present makes up less than 1% of the concentrated product. So once diluted, the 'anything else' that might be present would be negligible. It does have green dye, but this is easily removed with activated charcoal.
So if you're like me, and hate ordering stuff off the internet, this could be a solution for you. Roughly one liter of clean (not food safe) 25% phosphoric acid for 6 bucks is not too shabby in my book.

*** Deleted due to a glaring inaccuracy ***

The battery acid here is 30% H2SO4. 30% phosphoric would be nice though.

Not. Battery acid is sulphuric acid. Do not use battery acid even if you want to use sulphuric acid for substances that are to be ingested. It may contain additives, some of which are relatively innocuous, others are dangerous.


Do not use this with substances that are intended for human ingestion. Food grade phosphoric acid can easily be acquired OTC. One source is the hobby brewer's market. Another source is as a generic food additive, though it may be less easy to find for private individuals.

Even hydroponics grade phosphoric acid is preferable over cleaning grade.

In general, if you cannot find an ingredient as food grade, change your procedure to one that uses chemicals that you can acquire as food grade.

^This. Why anyone risks using technical grade anything in extraction is beyond me.
Vinegar is perfectly fine as an acid in any extraction & food grade lye, 98+% purity limonene specifically made to be safe & environmentally friendly, & food grade fumaric acid can all be easily sourced inconspicuously.
Acetone is a bit trickier but provided you have friends who are either A. Chemists or B. Work at or own a business where ACS or USP grade acetone is used normally it is far from out of reach.

Edit: i forgot you seem to be having trouble with vinegar locally Mdtraveller. As an alternative, food grade ascorbic acid is easy to find cheap in bulk & works well.

I've witnessed, with my own eyes, technical grade DCM being used to decaffeinate coffee by one of the larger coffee companies. They didn't even bother covering up the label on the drum that it was stored in, so there must not be that huge of a difference as far as they are concerned. And aside from additives that might be in a downstream product, there isn't much difference in phosphoric acid, either. A large company that produces much of the phosphoric acid used in North America via a thermal process, is located close to me. They aren't shy about putting out that sort of info.

Not saying technical grade stuff can`t be used safely. Just that the regulations on purity are not quite as strict as food grade or ACS grade products. Many use technical grade naphtha & lye here.
Lye I don`t think is of much concern provided it is only NaOH & not mixed with other things for clean in drains.

The same goes for solvents. As far as naphtha goes, different hydrocarbon mixes or more aromatics may provide different results but generally an evaporation test is recommended on every bottle even within the same brand for the very reason I mentioned above. One batch may leave some residue while the next may not, because regulation is not particularly strict for technical grade reagents.

What I am getting at though is that given you are producing something you intend to ingest & many hold sacred, should you not put in the time & effort to produce a product clean & devoid of whatever potential things may be present in some technical grade reagents?

I guess maybe it is a matter of personal opinion but minimizing use of potentially hazardous chemicals in extraction & any contamination via byproducts or impurities aside from maybe some plant fats or oils is unacceptable to me.

Citric acid is another example of an acid that is generally available as food grade.


Well, I've worked in factories and meat plants and seen some unpretty ghastly stuff too. That doesn't make me apply those standards at home in my kitchen, or advise others that it would be safe practice.

Look, if you want to use gasoline as a nonpolar for extractions, I cannot and will not stop you. But if you write on this forum that it is a sound idea to do so, I shall object and will try to point out why. You can point out the fact that a huge industry processes coca leaves this way, but to me that still does not make it a good idea.

I'm not disagreeing with any of the points made here. Everyone should by all means use the best quality reagents available to them. I was mostly just furthering the discussion. Fortunately, I'm able to get most anything I can afford from the large scientific chemical supplier that everyone knows, but I would rather not if I don't have to.

Not. Battery acid is sulphuric acid. Do not use battery acid even if you want to use sulphuric acid for substances that are to be ingested. It may contain additives, some of which are relatively innocuous, others are dangerous.

My error is noted and I tried to clean it up best I could. Thank you for quickly clarifying my mistake.

I'm not sure how much you want to dilute it by but carcinogens and mutagens have a cut off limit of 0.1% (according to GHS legislation). So do several other hazards.

Also check the oral LD50 value in section 11 of your MSDS and do the math for the dilution. If it's below 2000 mg/kg then it's harmful or toxic. Below 5000 mg/kg is not advisable.

... or just go for something guaranteed food safe

Right. That's the main distinction in most cases between food grade and tech grade. This particular phosphoric acid product has no LD50 and does not contain carcinogens, mutagens or reproductive hazards. In other words, it is considered non toxic. Otherwise I probably wouldn't have mentioned it for use in extractions.

Correct me if I'm wrong, but I believe phosphoric acid is actively used in the food industry, in mixology, and molecular gastronomy... Food grade supplies should be available from sources tending these markets.

So why would someone even consider using rust remover?