The evaporation properties of benzalkonium chloride

Almost as GQ specific as a GQ question can get:

Does anyone know whether benzalkonium chloride evaporates at room temperature (i.e., 60-90 F,) and if not, what temperature it does evaporate at?

I don’t know anything about benzalkonium chloride specifically, but I’d be willing to bet that it has a nonzero vapor pressure at 24 ºC, because everything has a nonzero vapor pressure at every temperature. Which means that the real question is how much evaporation you’re willing to tolerate.

It appears to be a solid at these temperatures and at standard atmospheric pressure … so the vapor pressure will be very very low … and the evaporation (actually sublimating) will be very very slow … as slow as rocks evaporate, and after 4.6 billion years you can see what I mean by slow …

OK but what if it’s an ingredient of foaming soap (which it often is) - can evaporate or gets left behind?

Yay. Something I worked with is topical. I feel so useful.

BZK is a USP registered detergent. Its a really good one, and well characterized and understood. A good disinfectant. Well, any soap or detergent will more or less kill germs, but BZK is well characterized, so that’s what gets used.

I’m sorry the Wikipedia article is low on details, or I’d send you there. In “pure” form, its an oily liquid, and probably won’t evaporate quickly. However, its been determined effective as a cleaning agent/disinfectant spray or wipe at 0.15% concentration, and is even ingestible, in eye preparations, at 0.01%. Ref: https://en.wikipedia.org/wiki/Benzalkonium_chloride#Medicine

Although not volitle, this is a trivial amount to try to pay attention to. These tiny amounts may cling irreversibly to surfaces, or oxidze in the air into something non-active, or just … we don’t know what. We can’t “see” it by contemporary laboratory methods after wiping and drying. So we don’t bother. Don’t tell Dr. Oz and his “Not even one atom of arsenic is safe” crowd.

Heavy use, repeatedly, on food surfaces are probably contraindicated. You’re expected to use something else, and/or rinse thoroughly with water. If we can see it, then it is a problem. Its just that the manufacturer forgot a zero (or a couplea zeros) while working.

Just an FYI to those who are unfamiliar:

**Benzalkonium chloride **has recently become much, much more common in “antibacterial” soaps and such, after the phasing out of the use of Triclosan and Triclocarban in such consumer products was mandated by the FDA.

ETA: Benzalkonium chloride was initially supposed to be phased out along with those other chemicals, but the manufacturers pushed back and got the FDA to delay any requirement to eliminate it from consumer products until they can do more testing or find a suitable replacement.

Solids can sublimate with surprising alacrity. Ice is such a thing. Make some ice cubes in your freezer, check on them in a year or so, and you’ll find that they’ve lost substantial amounts of mass.

That’s true for frost-free freezers only, where periodically dry warm air is circulated through the compartment … in older freezers the ice will increase in mass and it will need to be removed manually … when we replace the air inside with 20ºC at 100% RH, as we cool the air down to -10ºC, water vapor will deposit … if the 20ºC air is at 0% RH, then at first the ice will sublimate, and then deposit as temperatures are lowered …

Missed edit window … the work-around is after the ice cube trays have frozen, break them out and store them in an air-tight container … this greatly minimizes the ice loss …