I have started to pretreat some sweaty gym clothes with a mixture of 25% laundry detergent and 75% water. I have noticed that the clothes then smell heavily of ammonia. What reaction is happening here? Is the detergent reacting with the urea in sweat? Break it down for me.
Well if I had to guess, you hit the nail on the head about laundry detergent and urea. Laundry detergent is basic. Technically it is going to be the salt of various organic acids. They aren’t so basic however that protons won’t be available. Urea could lose ammonia under these conditions, but I am just talking out my ass right now, let me learn more about the contents of sweat and detergent.
I was hoping to find some indication that sweat contained amine salts but no such luck. Detergent doesn’t seem to contain amines or their derivatives (excepting EDTA but that won’t break down under these conditions.) This leads me to beleive that urea is the culprit.
Do these clothes sit out long after being soiled and prior to being washed? Does washing them immediately make a difference?
On second look, that is a pretty concentrated detergent you are using. Some version of my first guess could be happening. If you know anything about mechanisms, I could draw one out but I don’t know how to post such a thing. That amount of detergent is major overkill.
Here’s how it happens:
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After working out, my sweaty clothes get stuffed into my gym bag.
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Drive home is usually 30-45 minutes.
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When I say I pre-treat my stuff, I don’t mean I soak it totally with large amounts. My 75/25 mixture of water/detergent is in a squirt bottle. I squirt some of it on my underwear to treat, ahem, skid marks.
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Immediately, the smell of ammonia erupts. I have noticed that the same happens when squirting the mixture on non-skid mark related areas, i.e., my t-shirt. So, I figure, the detergent is not reacting with somthing in the skid marks.
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The stuff is hung up and is usually dry before being washed.
Too weird - I was just going to get on the SDMB to ask about this.
I have been doing Bikram (i.e., “Hot”) yoga for about a year. Doing 90-minutes of yoga in a room heated to over 100 degrees leads to a little sweat. 
Anyway, by halfway through the session, when I have to get down on my towel-covered yoga mat, I get a strong hit of ammonia. I have never been much of an exercise nut - some running outdoors - so don’t have a lot of experience with this situation. I had assumed that when confronted with a bunch of sweat, I would get a noseful of ManSmell™ - ick, sure, but expected. But in reality, there is very little icky sweat smell (afterwards when I get home, my wife - who has a very sensitive nose and hates a sweaty smell) rarely complains as I cool off a bit before cleaning up. Instead though, the towel I use has that strong ammonia smell.
I would love to hear what our more scientific Dopers can come up with…
bump
I had forgotten about this thread - really, no ideas?
That’s it! Exactly what I wanted to know - thank you!!