# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DaEXn4vPUQv
- **Gondola URL:** https://gondola.cc/posts/67155477-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/6d0b47a8a4.jpg
- **Posted:** 2026-06-26T23:55:37.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Pass a current through tin(II) chloride and a silver forest erupts from the cathode.

Stannous chloride dissolved in acidified water carries Sn2+ ions. The instant you apply a few volts of DC, reduction begins at the negative electrode:

Sn2+ + 2e- -> Sn

But the metal doesn’t spread as a smooth film. It climbs outward as branching, fractal trees. The reason is instability. As tin plates out, it depletes Sn2+ inside a thin Nernst diffusion layer hugging the electrode. Any tiny protrusion pokes further into fresh, ion-rich solution and grows faster, while its sharpening tip concentrates the local electric field and pulls in still more ions. This runaway is the Mullins-Sekerka instability (1964): a flat deposition front is mathematically unstable, so noise amplifies into ramified structure.

What emerges is a textbook case of diffusion-limited aggregation, the model Witten and Sander introduced in 1981. Ions random-walk toward the cluster and stick where they first make contact, statistically favouring exposed tips over shielded inner crevices. The branches are self-similar across scales, with a fractal dimension near 1.71 in two dimensions: denser than a line, sparser than a filled plane.

Voltage tunes the morphology:

- Low current density gives compact, faceted growth
- High current density starves the diffusion field and drives wild, feathery dendrites

Faraday still sets the budget. Every 96485 coulombs reduces half a mole of tin. But geometry alone decides where that metal lands.

Alchemists called crystalline tin growths the Arbor Jovis, Jupiter’s tree, centuries before anyone wrote the equations. Same metal, same eerie beauty, finally explained.

Electrochemistry doesn’t just plate surfaces. It grows landscapes.

#stemantics #electrochemistry #fractals #materialsscience #chemistry

## Stats

- **Views:** 0
- **Likes:** 392
- **Shares:** 0
- **Comments:** 7

## Tags

fractals, electrochemistry, materialsscience, chemistry, stemantics

---
Copyright (c) Gondola