I have always used Rooto brand drain opener for synthesis processes requiring concentrated sulfuric acid. I am always left with the same
foul-smelling invisible residue in the glassware. I have noticed it before with nitric acid synthesis, but dismissed it. It was more apparent on a
diethyl ether synthesis by the catalytic dehydration of ethanol which I carried out recently. The impurity even carried over into the primary
distillate, which was coming over at less than 30°C at my altitude. A second distillation over sodium hydroxide solution removed most of the
off-smell from the finished solvent, but traces can still be detected in the residue if evaporated from a plate. The same is true of the fuming
nitric acid I have produced with the drain cleaner, but not nearly to the extent as in the ether synthesis probably due to the oxidizing nature of the
acid. This leads me to believe this is the source of the impurity.
The impurity does not leave a visible residue, and so must be present at only very low concentration. It does however leave a very pungent lingering
odor with metallic and sulfur-like notes. This is the most foul-smelling compound I have experienced, in my opinion beating out butyric acid and
hydrogen sulfide. It cannot be easily removed with hot water, soaps, bleach, organic solvents such as alcohols, ketones, diethyl ether, or with
hydrochloric acid. I have not tried nitric acid or methylene chloride. If a flask with boiling stones contaminated with this impurity is washed in a
sink, the odor will linger for several days after the application of hot water and concentrated soaps. It is volatile enough to have a strong odor
and, as mentioned earlier, be carried over in very volatile distillates. Only time and repeated washing with abrasives seems to remove this impurity,
which I cannot identify by smell or any chemical means.
Is this a byproduct from normal sulfuric acid, or something left from impurities in the acid or reaction byproducts thereof? It is somewhat
reminiscent of the odor of the raw drain opener, which I have noticed occasionally during pouring, but far more pungent. Maybe some of the more
experienced chemists here will be familiar with this compound based on the description.
[Edited on 6-2-2011 by kilowatt]Formatik - 6-2-2011 at 13:43
I've had a similar experience with another drain cleaner acid. The acid had something of a faint scent of used motor oil. Even though it looked
similar to light brown technical grade sulfuric acid. I recently made some dimethyl sulfide starting from methanol, drain cleaner, NaHCO3 to form a
sodium methylsulfate mush which had the odor of the acid but even stronger, this mush when it was warmed with Na2S, formed a extremely poisonous
impurity, of which only minute inhalations causes respiratory effects.
This had poisoned my entire experiment and nearly could have killed me from severe respiratory distress I experienced. Decontamination of this was
very difficult, on HDPE tubing, and cork, etc. it remained, but with a bleach wash on glass could be removed. It was extremely volatile and traveled
great distances rapidly. This impurity had an extremely foul odor and the toxic respiratory effects are that of other sulfur toxins like hydrogen
sulfide. This suggests that the original impurity in that drain cleaner acid was likely some sulfur compound (or one that causes similar effects).
I'm not sure if any of the regular impurities of sulfuric acid from the older days as mentioned here is a culprit. I'm not ruling out selenium or arsenic type impurities.
[Edited on 6-2-2011 by Formatik]DougTheMapper - 6-2-2011 at 17:04
This reminds me... one time when I was heating an older sample of hydrogen peroxide to concentrate it, it began to smell strongly of vomit. Not sure
what happened but I think it had something to do with the type of stabilizer.
As for the acid, mine says it contains "Virgin H2SO4 and inhibitors" and is a light pink color. I haven't had mojor problems so far but I have had
some odd smells in products.
It's the first one on the page and I can't find the MSDS anywhere. I usually find that unless something is "food" or "reagent" grade, it always has
something nasty and unexpected in it. I once got a bunch of rust in with KCl.
[Edited on 7-2-2011 by DougTheMapper]Formatik - 8-2-2011 at 18:57
I've found an older reference here, which mentions only briefly something about volatile impurities in conc. H2SO4, it states: "Concentrated sulfuric acid frequently
contains volatile impurities. These volatile impurities in the concentrated sulfuric acid were removed by bleeding nitrogen gas through the acid for
several hours." Though, the impurities we are talking about here might be more stubborn and might not be removable by leading nitrogen (or maybe dry
air) through the acid for several hours.roamingnome - 9-2-2011 at 04:47
Sulfur Trioxide may be among these volatile impurities.
Using crude H2SO4 in some microwave heating reactions offgased a horrible cloud. Try the nitrogen purge not_important - 9-2-2011 at 14:05
To me this suggests that the treatment of the warm-hot acid with small amounts of H2O2 might be helpful, as most organics would be oxidised away. A
little HNO3 might work similarly, although nitration could be a competing path.
If drain cleaner sulfuric acid is indeed waste from the petrochemical industry, sulfonated compounds would be expected and these could be reduced to
sulfides and such by oxidising some of the hydrocarbon groups.
jamit - 12-2-2011 at 01:10
I think it would be good if some how we can test the purity of Rooto concentrated H2SO4. It's a oily yellowish liquid with a heavy density. I've
used it for nitric acid distillation with a nitrate salt but now because of this thread, I'm wondering if my nitric acid is contaminated?
Anyone have any idea on testing for the purity of drain cleaner, Rooto, sulfuric acid?
I haven't noticed any "foul smelling odor" from any reaction unless it was really noticeable. This is really bugging me now, since I've invest a
gallon of this Rooto, draining cleaning sulfuric acid.
Magic Muzzlet - 12-2-2011 at 10:04
You could "invest" in a liter of H2SO4 from eBay, a well known biodiesel supplier sells it cheap. Not only is it pure, it isn't suspicious and it cuts
out possibilities of all the inhibitors and other stuff in the drain cleaners.
It's worth the $25, and makes life much easier.
I have to say I've never even had problems with drain cleaning acid. I have used it for all the regular nitric, ether, alkyl halide etc distillations
and I've never had a problem. I guess it's just dependent on the batches.
[Edited on 12-2-2011 by Magic Muzzlet]497 - 12-2-2011 at 13:24
Interesting. I have always used boiled down battery acid (fresh, not from batteries) for my concentrated sulfuric, but I'm intrigued by kilowatt's
description of the contaminant in home made ether. I encountered a very similar thing when I tried that synthesis. It was an impressively persistent
smell that was very challenging to clean off of anything but never was present in visible quantities. I tried many of the sames solvents and cleaning
agents that kilowatt did with little success. Also I had a hell of a time getting it out of the ether, in fact I never really could fully, when you
compared the smell to a sample of commercial ether. I think even activated carbon was ineffective. It smelled unlike anything I have smelled, so it's
hard to describe, but from what I remember it was consistent with his description.
At the time I assumed it was a small impurity produced by a side reaction during the ether synth, but it was confusing because I had not seen anyone
else mention it. But this might lead to even more ambiguity because I wasn't using drain cleaner, and I had always heard that battery acid was
relatively pure. I am glad this subject came up now, because I was just contemplating another batch of ether, and I'd really like to a least find out
what the stench is before contaminating my house with it... and preferably find how to avoid/destroy it.
PS I did make nitric acid and other things with the same acid and never encountered the smell.
PPS The only other source of a contaminant that I can think of is the ethanol. I'm pretty sure the stuff I used was denatured with bitrex, and maybe
other stuff too. Could that somehow react to form the stench in question? Kilowatt, was your ethanol denatured?
Hah, I hadn't even read entropy's post when I wrote that.. great minds think alike?
[Edited on 12-2-2011 by 497]
[Edited on 12-2-2011 by 497]
[Edited on 12-2-2011 by 497]entropy51 - 12-2-2011 at 13:30
Since the impurity occurred with H2SO4 from two different sources, might it be due to impurities in the ethanol? Was it pure ethanol, or denatured?kilowatt - 15-2-2011 at 23:01
Adding H2O2 to the acid would be a bit dangerous wouldn't it? If there are significant organic impurities in it, it could produce a lot of heat.
Besides, that would increase the water content of the acid. If the drain cleaner acid is the problem, I will simply find another source as there are
many (not excluding various forms of SO3/Oleum production).
Interesting that you had the same experience with a different source of acid, 497. It has been suggested that perhaps this is a thioether of some
sort, perhaps produced from an organic additive or contaminant in the acid in a heat-aided side reaction. Anyone who has more experience with organic
sulfates and sulfides might find the essence familiar.
The alcohol was Sunnyside brand denatured alcohol. I did not distill it before this synthesis, however I have done so before while finding the
boiling points of alcohols (methanol, ethanol) at my altitude. I have never distilled it to complete dryness, however. There is no dye or bitterant
in the denatured alcohol. I did find an MSDS, and it doesn't contain any sulfur. However I'm not well-versed enough in organic synthesis to tell whether any of the organic denaturants
(esters, ketones) in the alcohol could lead to such a compound.
If the denatured alcohol is the source of the side reaction or impurity, it could explain why I have encountered this smell to some degree before
during other syntheses than the ether while others here have not. I have had this denatured alcohol through my glassware before and may have had
traces in the reflux packing when doing other reactions which I presumed would destroy it. not_important - 16-2-2011 at 14:51
Adding H2O2 to the acid would be a bit dangerous wouldn't it? If there are significant organic impurities in it, it could produce a lot of heat.
Besides, that would increase the water content of the acid. ...
You add only a rather small amount of H2O2 at a time, with good stirring and time for reactions to complete. Try it first on a very small scale,
repeatedly add a drop or two of H2O2 until no further colour change is note, then repeat on a larger scale using the colour end point as a guide to
when enough H2O2 has been added.
Yes, it adds a bit of water, more from the H2O2 solution than the oxidiation. But unless you have really trashy drain cleaner there's not that much
goop in it, so only a small percentage of water is added. Slowly bringing the acid to fuming eliminates both excess water and H2O2, and may oxidise
some of the remaining impurities.
SWIM - 7-10-2017 at 10:24
Some commercial grade sulfuric acids have appreciable arsenic in them.
Anyway, arsenic forms quite a few very stinky compounds. Maybe you are accidentally creating some of these.
I've heard about tellurium and selenium compounds that stink even when the quantity is incredibly tiny, but I've never heard of those as significant
impurities in H2SO4.
JJay - 7-10-2017 at 10:48
Distillation of Rooto drain cleaner causes an impurity to start to crystallize out after around 70% of the volume has been removed. I'm not sure what
the impurity is, but it is crystalline and has a pale color: https://www.sciencemadness.org/whisper/viewthread.php?tid=75...
Rooto drain cleaner is known to contain organic inhibitors as well; I think these tend to produce dark-colored polymers when the sulfuric acid is
heated.
Any sulfuric acid drain cleaner is likely to contain adulterants to prevent it from attacking pipes. These don't matter for many applications, but for
others they do.Melgar - 10-10-2017 at 05:25
I remember getting a smell exactly like what's being described, when I tried to dissolve steel wool in sulfuric acid. Other forms of steel didn't
generate that smell, and I still don't know what it was. My best guess was that there was some sort of grease on the steel wool, that reacted with
partially reduced sulfur somehow, but that's just a wild guess.AJKOER - 18-10-2017 at 12:39
Assume transition metal impurities (iron, copper, manganese, or cobalt in trace amounts), and pass air (even including some CO2) through the
contaminated H2SO4 under UV light.
In essence, attempting a photo Fenton (or Fenton-type) based advanced oxidation process (creating reactive oxygen species and/or the carbonate
radical) to remove undesirable organics.
The advantage of this method is no dilution or the introduction of significant amounts of further impurities. It may, however, require many hours of
treatment.
[Edited on 18-10-2017 by AJKOER]feacetech - 18-10-2017 at 16:32
We get spent acid @ ~98.5% im not sure which process it comes from but its isnt petrochem (Nickel smelting or iron roasting)
the main impuity we find is iron (30ppm) however the acids is crystall clear and colourless normally
we also test suspended solids (max 30 ppm), reducing test (pass/fail a test using KMnO4) and clarity (qualitative)
we also sell this acid direct to other suppliers and some of our other plants manufacture virgin H2SO4
the main issue is its from drain cleaner they will add inhibitors and the base acid they start with will unlikely be virgin acid as spent acid is
really cheap and of good quality normally
The inhibitors could be anything i worked for a company that sold inhibited acid cleaners i think the primary inhibitors amine based inhibitors but
these were indusdrial and it was for HCl or other weaker acid cleaners (lactic or citirc based)
