Talk:Salt bridge/Archive 1

Archive 1

Explosion Danger with KNO₃ Electrolyte and Cotton?

The purpose of this section is to try to determine whether there might be a safety problem with the potassium nitrate electrolyte solution specified by the galvanic cell diagram this article incorporates and, if so, whether that diagram (and any corresponding text in the body of article) should be changed to specify the use of a different electrolyte. Solid potassium nitrate is also known as saltpeter, and it's a critical oxidising component of black powder/gunpowder.

In my initial edit to the article I added a few words to clarify the purpose of using agar to gelify the electrolyte within a glass tube bridge. I also really wanted to add that if one chooses not to convert the electrolyte in the bridge to a gel then the ends of the bridge tube are often plugged with cotton for the same reason, i.e. to hinder the mixing of the fluids via (pick any that apply; I'm no chemist or physicist) hydrodynamics, diffusion, convection, advection, or other methods of mass transfer.

As much as I wanted to, I didn't say anything about this ubiquitous use of cotton because of my (possibly naive?) concern that bringing cotton into contact with nitrates from the KNO₃ electrolyte solution might eventually lead to the accidental production of gun cotton, a variety of nitrocellulose. I understand one can make gun cotton by soaking ordinary cotton in a nitric acid solution, and then drying the cotton. Is there any danger that the same outcome might result if one discarded the cotton in a wastebasket where it subsequently dried out?

I'd hate to think this article might cause any budding chemists to injure themselves or cause a fire/explosion in their waste baskets. Can any qualified chemist provide a definitive answer about this, i.e. about whether it would be safer to specify a different electrolyte in the galvanic cell diagram? If so, feel free to edit this my question to make it more concise. Ohiostandard (talk) 18:28, 6 March 2009 (UTC)

References

Low Importance Rating?

I realize this is only a "stub" article so far, but based on the discussion page for Galvanic Cell the composition and function of a salt bridge seems a persistent source of confusion. Can one understand how a Galvanic Cell works if one doesn't really understand how a salt bridge works? I'd say this article merits the same "mid" importance rating that the Galvanic Cell article carries. Opinions? 74.61.38.220 (talk) 12:28, 8 March 2009 (UTC)

It depends on the context. Salt bridges are limited to ECS in the laboratory scale as polymer films etc have superceded the use of salt bridges in commercial products. However I guess this page does deserve a mid-rating, so let's change it! --Deryck C. 11:25, 11 March 2009 (UTC)

wire salt bridges?

Yes I think there are those too,,... —The preceding unsigned comment was added by 211.28.37.241 (talk • contribs) .

I don't understand. Wire $\neq$ salt. —Keenan Pepper 05:00, 30 September 2006 (UTC)

A salt bridge must allow ions to flow in order to re-balance charge. Normal wires only allow electrons to flow, not ions. Therefore, a wire cannot be used as a salt bridge. --Jesse Greener (talk) 16:24, 22 November 2009 (UTC)

How does it work?

I just don't understand how the salt bridge connects the solutions of the two recipients while keeping them separate... Wouldn't osmosis just end up mixing all ions together? Ricardo Dirani 09:09, 2 February 2006 (UTC)

In osmosis, the solute can't pass through the membrane. Were you thinking of diffusion? I think the ions eventually diffuse through the salt bridge, but that takes a long time and the point is to temporarily keep them from mixing. —Keenan Pepper 05:00, 30 September 2006 (UTC)

The text mentions that a gelling agent is used (glass tube variety). The Gel allows the flow of ions but prevents the flow of liquid from one container to the next. To make an analogy to optical materials, you could say the bridge is transparent to ions, but opaque to liquids. --Jesse Greener (talk) 16:23, 22 November 2009 (UTC)

That is not a correct analogy. I can see that some people still don't quite get exactly how a salt bridge works. The gel form is used to avoid the mixing of the fluids from either side of the vessels. What moves through the bridge are the inert ions from the electrolyte which its made of, NOT the electrolytes from the vessels. In the picture, that would be potassium nitrate. The K+ would move towards the negative side (in this case the anode) and the NO3- towards the positive (cathode). Maybe another picture showing this process would be nice. There are several on the web.--Spmoura (talk) 19:34, 6 February 2014 (UTC)