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Langmuir mica adsorption experiment 2026-10-18
In 1918, Irving Langmuir measured adsorption using freshly split mica strips, handled at their edges, separated by iron spacers and held with brass fasteners. A glass bulb contained the bundle; a similar blank contained matching iron and brass but no mica. Evacuated glass connections, Mercury seals, liquid air traps, and McLeod gauges provided controlled gas handling. Calibrated compartment volumes and pressure readings before and after expansion gave free-gas amounts; their deficit indicated uptake. Lowering pressure and measuring released gas tested desorption.[ref]
The Adsorption of Gases on Plane Surfaces of Glass, Mica and Platinum by Irving Langmuir. Langmuir 1918, printed pp. 1376–1377: Experiments with Mica, preparation, blank, apparatus and Methods I–II
Hydrogen blank runs calibrated cooling-related pressure differences. Irving Langmuir pre-cooled the bulbs to reduce thermal delay; he suggested slow diffusion between strips could control the remaining approach to equilibrium. Critically, blank uptake was not subtracted: he estimated the mica-bulb results were 10–30% too high. Liquid air temperature drift was unrecorded. These limits constrain inference of intrinsic binding from the uptake curve. The paper's pressure unit called “bar” was , unlike the modern bar used above.[ref]
The Adsorption of Gases on Plane Surfaces of Glass, Mica and Platinum by Irving Langmuir. Langmuir 1918, printed p. 1365: pressure-unit definition; pp. 1377–1378: cooling calibration; p. 1381: equilibration; p. 1385: blank bias and bath drift
Guiding light and retaining useful optical power are different achievements. Charles Kuen Kao and George Alfred Hockham argued that impurities need not impose the measured losses of existing glasses on every future optical fiber. Their 1966 paper treats wave absorption, scattering of light and guidance separately; reducing impurity absorption leaves intrinsic material losses and geometric losses to address. This was a route toward practical communication, building on existing optical fibers, rather than the invention of every use of guided light.[ref]
Dielectric-fibre surface waveguides for optical frequencies by Charles Kuen Kao and George Alfred Hockham. pp. 1152–1154, §§3.1–4.2; p. 1158, §7
The launch experiment used clad glass optical fibers fixed in capillary tubes with epoxy for end polishing. Laser illumination gave transverse normal mode patterns; input-spot displacement and polarization of an electromagnetic wave controlled excitation. These observations tested guidance, not kilometre-scale optical fiber attenuation.[ref]
Dielectric-fibre surface waveguides for optical frequencies by Charles Kuen Kao and George Alfred Hockham. pp. 1157–1158, §6.2, Fig. 15, Table 2
Charles Kuen Kao's lecture describes the complementary material experiment: short, polished glass samples, including plasma-deposited fused silicon dioxide, were examined with purpose-built single-beam and later double-beam spectrophotometers. A separate ellipsometry measurement assessed end-surface specular reflection, a check against confusing interface loss with bulk wave absorption. The readout was loss versus wavelength. Comparing glass samples supported impurity reduction as a route to lower loss. Surface contamination and the tiny bulk loss of short samples limited inference; the result did not itself demonstrate a long drawn optical fiber. The lecture also credits subsequent manufacturing work at Corning.[ref]
Nobel Lecture: Sand from centuries past: Send future voices fast by Charles Kuen Kao. Published 2010 version of the 2009 lecture, p. 2302, §V, short-sample measurements, ellipsometer and later fiber manufacture
An original scale comparison makes the material problem tangible. In the uniform optical fiber attenuation model, a stipulated leaves of launched optical power after ; a stipulated leaves . Both guides could satisfy the same total internal reflection condition. A successful spot pattern at the output therefore cannot by itself establish a useful communication distance.
The 1935 primary paper The Spin-Isomerization of Hydrogen at Paramagnetic and Diamagnetic Surfaces, pp. 1251–1252, describes evacuated catalyst samples cooled before admitting molecular hydrogen. Gas samples were analyzed in a glass cell in liquid air: a heated platinum wire and Wheatstone bridge converted changes in thermal conductivity into electrical resistance readings, calibrated against normal hydrogen.[ref]
The Spin-Isomerization of Hydrogen at Paramagnetic and Diamagnetic Surfaces by Hugh Stott Taylor and H. Diamond. p. 1251, Experimental Details: sample handling and heated-wire thermal-conductivity analysis
Its comparison of oxide surfaces supplied a control: specimens exhibiting strong paramagnetism converted the gas much faster than the comparison exhibiting diamagnetism despite all adsorbing molecular hydrogen. Contact time, pressure, and temperature were recorded. This supports a role for surface magnetic properties beyond adsorption alone; it does not identify every microscopic surface site or directly measure nuclear-spin orientations.[ref]
The Spin-Isomerization of Hydrogen at Paramagnetic and Diamagnetic Surfaces by Hugh Stott Taylor and H. Diamond. p. 1252, Table I description and Discussion of Results: rare-earth oxide comparison and adsorption qualification
The inference chain is preparation, contact with a specified surface, then a calibrated bulk transport readout of composition. It is distinct from a direct calorimetry measurement of heat capacity: transport and heat capacity can both depend on the spin populations, but they are different measured quantities. Changing the catalyst's own surface structure, introducing magnetic impurities, or changing the detector's gas pressure can confound an uncalibrated comparison. The free-rotor partition functions predict equilibrium populations and stored energy, not the conversion rate on a particular surface.