storing /reusing etchant

M

Matlock

Joined
Jun 26, 2002
Messages
125
Howdy all!
I went down and got some PCB etchant that I plan on cutting 4:1 with water to etch my blade (should I ever get it finshed :( ) to see the temper line, and was wondering what you guys use to store your etchant in, and when you are done etching a blade, do you dump that bunch out or put it back in with the rest?

PS. I know that when mixing with the water I need to add the acid to the water but other than that any safety tips would also be helpfull.

Matt
 
I store mine in a mason jar and you can reuse it many,many,many times. I would also start with a little more dilution, you can always add more ferric.
 
Glass is the best for most acids. Store the jar somewhere where it won't get knocked around and is out of direct sunlight and away from extremes of heat and cold. I would advise against putting used solution back in the original bottle. This way you will keep a reserve of a known molarity.

WS
 
They're good for stiring it up and keeping the precipitate from froming a coating on the blade. Pluse they're kind of funny looking.

WS
 
WS,
Any idea what the molarity of the Tandy stock actually is? I've seen claims that most FeCl3 solutions for etching are about 42% but they don't say if that's w/v or w/w. Since Tandy is discontinuing this stuff (what they told me), I figured we'd have to buy it solid and dissolve. Not a really big thing, obviously, I can experiment, but wondered if anyone knew the actual concentration.
Thanks.
 
If I remember to get the moles isnt something like adding the atomic weights and avagodros(I know thats not how you spell it) number and blah,blah,blah. Just mix it up and if it smokes you know your there.
 
piece of 4" pvc pipe, make the length a little longer than your longest blade. glue the bootom cap use the other cap for a cover.

mount it on a non tipping base, just cover the container when not in use, you get alot of use out of one batch.

If you dump it on the driveway it makes crappy brown stain. Don't ask.

Neutralize the old gunk with baking soda.

Oh yeah, just for safety sake use the thing below eye level in case of spills it is farther from the face.

My .02

PS, had mine in this rig for 6 yrs. I like it. Not the same etchant though.
 
blackboogers,
i realize it doesn't really matter, and agree "just mix it til it works".:) For me, having spent 30 years in the pharma/chem industry, it's just a matter of curiosity, a desire to know the numbers, probably just another one of my bad habits...:D
 
I have to admit that the batch I have right now I just used tap water. If I remember correctly can't you make ferric cloride by starting with HCl and adding iron? I have no idea what the starting strength of the Tandy etchant is. I steal what ferric I've used from my girlfriend. As for figuring out molarity, isn't it supposed to be a weight to volume relationship. Take the weight and divide by (atomic mass x 6.022 x 10^24) this should give you the number of moles. Put in 1 liter of water and you have a solution with molarity of (number from previous equation). I also could be off on some of this as it's been a long time since I thought of myself as a chemist.

WS
 
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