Chemistry Question: Ferric chloride ? ⚗️Heisenberg Needed ;-)

Hopefully a basic question.

Can Ferric Chloride be made stronger or weaker and how do you do it ?

I guess adding water will make it stronger. And sodium bicarbonate to weaken. Am I guessing right or will it be a scene from Breaking Bad.

The reason I ask, it is for a Etching Copper plates for printing.

PS: I have a bottle of Ferric Chloride at 45 Baumes… if I can get it to 38 Baumes is this stronger or weaker?

Thoughts. Any help or pointers appreciated.

What do you actually have, what does the bottle say? Is it just iron III chloride or is it acidified?

Baume is an archaic specific gravity scale, so the higher number the denser the solution = more dissolved iron chloride. So you can make 38 from 45 but it’ll be less concentrated and therefore weaker (I assume), but you can’t make 45 from 38, unless you boil off some of the water (whether that’s possible or sensible, I don’t remember my transition metal chemistry)

https://en.wikipedia.org/wiki/Baum%C3%A9_scale

IANAE but looks like you could ‘strengthen’ it further (make more potent) by adding citric acid and turning it into Edinburgh etch. (I assume that etches something only for you to go back later and pretend you didn’t really mean to….or am I thinking of something else)

https://media.jacksonsart.com/pdf/Etching_COPPER_with_ferric_chloride.pdf

Wtf is a baume?

Theoretically you can get anhydrous, although will probably need a REACH cert.

Regular stuff is hexahydrate isn’t it?

Which fag packet maths says ~40 to 45%.

Water will dilute it.

Well, I am a (sort of) inorganic chemist and I had never heard of this scale. From a bit of digging a 45 Baume solution of ferric chloride is pretty concentrated- close to saturated if I am reading things right.

theotherjonv is right about diluting with water to make 38 from 45 but if you add bicarb it will get very messy- it’ll fizz like mad because ferric chloride is acidic and precipitate a horrible goo.

I use ferric chloride to etch Steels, and diluting with water simply makes it less potent – so yes, it simply dilutes it.

Might be different with copper, but I suspect not.

Dilute with water if to strong.
If you want it to work faster, heat it.

Hopefully a basic question.

Wrong end of the scale.

Thanks guys. I’ll pass that onto the printer. I dont want her blowing my studio (shed) roof off 😉

Water to weaken.

Heat up to make stronger/faster, probably avoid that.

I expect she will have more questions now, I’ll post later.

Thanks.

Wtf is a baume?

Thought it was what you put your chips in around Lancashire?

@theotherjonv

So what does the Citric Acid do in an Edinburgh Etch process from a chemistry point of view ?

Stronger ? More controlled etch in some way?

RT

@kayak23
https://www.britannica.com/technology/Baume-hydrometer

I never heard of it until yesterday as well.

Well, I am a (sort of) inorganic chemist and I had never heard of this scale

It crops up in the oil industry as API gravity.

It’s only benefit is it spreads out the range you sensibly use. So a “light” oil is about 10, and a “heavy” oil is about 35. Rather than specific gravity which makes everything about 0.65-0.7.

https://silhouetteuk.blogspot.com/2017/01/etch-copper-with-edinburgh-etch.html

Hopefully a basic question.

Wrong end of the scale.

Well played @GHill

The citric acid makes sense. You are supposed to avoid cooking citrus etc. in raw metal (apart from stainless) because it dissolves them a bit. Though I am not sure about ali, as my mum made marmalade in an ali pan and we didn’t die.