{
  "name": "Two routes to the diffusion coefficient of a 1 µm bead, and the Avogadro number from Perrin's data",
  "desc": "Perrin's measured Brownian displacements from 1909 and 1913, the diffusion coefficients and Avogadro numbers they give, route A (Boltzmann constant and the viscosity of water) against route B (Perrin's data scaled to a 1 µm bead in water at 20 °C), and the modern Avogadro constant; one claim per row, with assumptions stated",
  "lic": "CC BY 4.0",
  "lic_url": "https://creativecommons.org/licenses/by/4.0/",
  "by": "Ants, Cells & Atoms",
  "url": "https://antscellsandatoms.com/scale/brownian-motion/",
  "from": [
    "Perrin 1909, Annales de chimie et de physique 8e série 18, §29",
    "Perrin 1913, Les Atomes, ch. IV §73 and §75",
    "CODATA 2022 Boltzmann constant, molar gas constant and Avogadro constant",
    "media/water-properties.csv (shared file; viscosity of water at 20 °C, IAPWS R12-08)"
  ],
  "how": "Compiled by Ants, Cells & Atoms from the data listed",
  "data_by": [
    "Perrin J 1909, Mouvement brownien et réalité moléculaire, Annales de chimie et de physique 8e série 18:5–114, public domain (author died 1942), https://fr.wikisource.org/wiki/Mouvement_brownien_et_r%C3%A9alit%C3%A9_mol%C3%A9culaire: gamboge grains 0.212 µm in radius, water at 17 °C, viscosity 0.011 poise, mean square 50.2 µm² in 30 s, N = 66e22; read 2026-10-25",
    "Perrin J 1913, Les Atomes (Paris: Félix Alcan), chapter IV, public domain (author died 1942), https://fr.wikisource.org/wiki/Les_Atomes/IV: mean square spread 2Dt; 500 displacements of grains 0.367 µm in radius, e = 7.84 µm in 30 s; viscosity 0.01 poise and N = 68.8e22 for series VII; read 2026-10-25",
    "CODATA 2022 recommended values, NIST Standard Reference Database 121: Boltzmann constant 1.380649e-23 J/K (exact), https://physics.nist.gov/cgi-bin/cuu/Value?k, retrieved 2026-10-25",
    "CODATA 2022 recommended values, NIST Standard Reference Database 121: molar gas constant 8.314462618 J/(mol K) and Avogadro constant 6.02214076e23 per mole (both exact), https://physics.nist.gov/cgi-bin/cuu/Value?r and Value?na, retrieved 2026-10-25",
    "Viscosity of liquid water at 20 °C, 1.0016 mPa·s: International Association for the Properties of Water and Steam, IAPWS R12-08 (2008), https://iapws.org/technical-guidance/release/viscosity; value computed 2026-10-24 (shared file water-properties.csv)"
  ]
}