I am a computer tech at a technical college. Our Mechanical Design department just got a really cool 3D modeller which can take a CAD file and produce a actual part made of plastic. It was my task to hook this beast up to the computer control system. Never having seen one of these things before I was following the manual step by step. At that point I learned that the process has two parts, the one that makes the model and a part that chemically cleans it via a computer controlled agitation tank. Two seperate systems. I also learned that the wash tank uses sodium hydroxide powder mixed with water to a PH of 12.6. I flunked high school chemistry twice but 12.6 seemed high for an uncontrolled environment (A classroom, not even a chem lab, no safety precautions) I expressed my concerns to the instructor who pooh-poohed my concerns. I then attempted to contact the Facilities Manager who is also the safety officer, but he is out of town until Monday. So I went to the Vice President of Instruction and informed her I believed a dangerous situation was developing in one of her classrooms. She shut down the installation until the safety officer has time to review it. The instructor is more than a little torqued at me.
My question is " Is sodium hydroxide at a PH of 12.6 something that requires proper instruction to handle safely, and has no business in an unsupervised classroom, or did I over react?"
Untreated skin exposure is going to burn it; untreated mucus membrane exposure is going to slough it, and untreated (possibly even treated) corneal exposure is going to rot those corneas like they were flour paste.
Gloves; no drinking it and eye splash protection. In my personal experience in the ED it’s the corneal exposure that’s devastating. Happens rapidly and the stuff just kind of melts 'em. On average worse than acid in the eye.
According to Wikipedia ordinary household bleach is 12.5, so I’d say while some caution should be used its PH is not particularly dangerous, no. It would be more for its chemical properties in general.
Thanks all for the validation. I did do the wiki thing before I reported it, but did not understand all of it so all I got was this stuff is not to be messed with, hence my report to a supervisor. I hate it I pissed off the instructor who I have a good working relationship with for ten years, but I could not let this slide. I believe he really did not understand the dangers of what he was dealing with, although the fact it was shipped with labels of "Corrosives"and came with elbow length rubber gloves and special goggles should have been a giveaway. I will sleep better tonight knowing that I didn’t just rat out somebody, I helped prevent serious injury to students or even the instructor himself. Thanks all.
twice to understand that the danger of the sodium hydroxide is not buried in the PH, but in it’s other chemical properties. On my first read I took it as “Nothing to worry about,” but on a second read I realized you said it is dangerous, but not due to the PH. Perhaps **Chief Pedant ** made the same error.
sodium hydroxide pH 12.6 is about 0.1% solution,
mildly irritating to skin (it would start to sting after 10 sec),
a bit dangerous to eyes (in lab I would definitely wear glasses, probably not gloves in practice)
so on the low end of dangerous chemicals.
dilute Sodium hypochlorite is probably more dangerous than the equivalent sodium hydroxide as not only is it basic, but it is also oxidizing
Offhand, I would say that the chemical properties of NaOH is among the most benign possible. It consists only of Na ions and hydroxyl ions. It is not oxydizing, as ClO is and the only thing to worry about is the pH itself.
Then there is the question of how exposed the students would be to it. I would think that a warning would suffice.
I would be concerned but not alarmed about having such a unit in a classroom where personal protective equipment isn’t being used. I think you made the right call - better to be too careful than to have students splashed with caustic.
You can buy more dangerous materials in the household cleaning aisle (Liquid Plumber comes to mind). However most people know not to get Liquid Plumber in their eyes.
Anyone operating the system should be warned and trained on proper handling procedures, and it should not be used by untrained persons.
Sodium hydroxide also has a severe inhalation hazard, in addition to the causticity. It should not be handled w/o proper instruction and safety equipmemt. You were correct in reporting potential the hazard and your instructor is negligent in his cavalier attitude.
While liquid bleach, for household use, can be dangerous the sodium hydroxide is faster reacting and therefore more dangerous.
The liquid you’re talking about is 0.04 normal sodium hydroxide, around 1.6 grams/liter. When I was a wet hands chemist, we would have treated this stuff as about as harmful as water. If I wanted to hurt someone with it, I’d have dropped a bottle of it on them from the roof.
The dry powder is very harmful, the diluted stuff not so much. You’ve got some risk if someone took a part out of the bath and shook off excess fluid. It would be an eye or skin irritant, and if some where to land on a surface and the water evaporated it could concentrate to the point where it was dangerous. You’d have people seeing white residue around and sticking their fingers in it and tasting it.
There are plenty of people who can hurt themselves, or think they hurt themselves, with the most innocuous substances. It’s good procedure to treat every chemical as harmful just to keep in practice. I would not expect mechanical design students to be qualified to know when breaking the rules was acceptable. You made the right call.
Congratulations on taking workplace safety seriously! So many people don’t, and as a result, so many people get hurt in preventable accidents every year!
Even the comments of “in practice, we would treat it like water in a lab” are, while quite true (and I speak from experience, having been a chemist) an unfortunate sign that we get kind of jaded to the dangers around us when confronted with them, and once in a while it takes someone to say out loud “but it isn’t water!” just to get us to pay a bit more attention.
Anyone handling the equipment you mentioned should probably at least have some sort of protective clothing (lab coat, sleeves covering the arms), gloves (latex would probably do), and splash-proof goggles (especially if, as it sounds like, there are moving parts and therefore the risk of splashing). While you’re at it, have the safety officer check the machine to see if it is properly guarded; cover up or put up warnings about pinch points or other parts that could cause someone to be cut/trapped or otherwise hurt. Heck, if you can, make sure there is an emergency stop to the machine within reach of an operator, or develop a procedure for what to do if there isn’t (e.g. always have someone else in the room during operation who can shut the machine down in case of injury).
Ok, you probably don’t really have a budget for all that, but those really are the kind of issues that can prevent injuries in the future.
This is the second chemical-safety related post I’ve made today. Weird.
The MSDS (Material Safety Data Sheet) for this chemical details all required workplace precautions for the use of this.
It may not be any more dangerous than stuff you use at home every day, but this is a work/school environment, and so therefore fall under OSHA for use. Any organization that knowingly ignores the stated legal requirements for use is just asking to be sued and fined.
You were wise with your inexperience to seek help with this problem. A pH of 12 is not all that harmful. If you get a drop on you, wash if off. Familiarize yourself with the eyewash station in case you get a drop in your eyes.
Follow these same precautions when you are cleaning your drain with drain cleaner or cleaning your oven.