wilke_1950 ========== C\. R\. Wilke, "A Viscosity Equation for Gas Mixtures", J\. Chem\. Phys\. 18, 517 \(1950\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1063/1\.1747673 `__ **Source kind:** theory **Recorded technique:** Theory\: a kinetic\-theory approximation for the viscosity of a gas mixture from the pure components' viscosities and molecular weights alone\. Sutherland's form as written by Buddenberg and Wilke \(Eqs\. 1\-3\), with the binary diffusion coefficient eliminated through the self\-diffusion coefficients \(Eqs\. 4\-9\), for binary mixtures \(Eqs\. 10\-11, ideal gas\) and any number of components \(Eqs\. 12\-14\); compared with measured viscosities of binary and multicomponent mixtures at atmospheric pressure \(Tables I\-III, Fig\. 1\)\. **Materials in structured entries:** None recorded. **Dataset quantities:** None recorded. **Contents:** 0 datasets; 0 formulas. Curation notes -------------- Identity VALIDATED\_WITH\_WARNINGS by the library\. The library pdf's first page is the publisher's cover; journal pages 517\-519 are pdf pages 2\-4\. Single author \(University of California, Berkeley\)\. THE RULE \(p\. 519, Eqs\. 13\-14, checked against the page image at 600 dpi\)\: mu\_m = sum\_i mu\_i / \[1 \+ \(1/x\_i\) sum\_{j \!= i} x\_j phi\_ij\], with phi\_ij = \[1 \+ \(mu\_i/mu\_j\)^\(1/2\) \(M\_j/M\_i\)^\(1/4\)\]^2 / {\(4/sqrt 2\) \[1 \+ \(M\_i/M\_j\)\]^\(1/2\)}\. mu\_i are the pure components' viscosities at the mixture's temperature and pressure \(Nomenclature, p\. 519\)\. Written with phi\_ii = 1 \(which Eq\. 14 gives\), this is mu\_m = sum\_i x\_i mu\_i / sum\_j x\_j phi\_ij, the form of OEP 1 \(its section 4\.3\), and \(4/sqrt 2\) \[1 \+ M\_i/M\_j\]^\(1/2\) = \[8 \(1 \+ M\_i/M\_j\)\]^\(1/2\)\. The binary form, Eq\. \(11\) \(p\. 518\), is the same rule for two components; Eq\. \(10\), with the densities rho\_1, rho\_2, precedes the ideal\-gas reduction\. The paper states the equation 'contains no empirical numerical constants, the constant 4/sqrt 2 coming from the kinetic theory' \(p\. 518\)\. Extraction error in the library's text\: Eq\. \(14\) and Eqs\. \(10\)\-\(11\) are rendered with \(M\_j/M\_i\)^\(1/2\) where the page prints the exponent 1/4\. The image is authoritative; Table I's phi values confirm 1/4 \(below\)\. REPRODUCED \(Table I, p\. 518, phi\_12 and phi\_21 of 17 pairs at atmospheric pressure\)\: Eq\. \(14\) with the printed viscosities and modern molar masses gives He\-A \(20 C\) 2\.4192 and 0\.2716 against the printed 2\.417 and 0\.2716; He\-A \(200 C\) 2\.3176 and 0\.2788 \(2\.318, 0\.2789\); Ne\-A \(200 C\) 1\.6057 and 0\.6166 \(1\.606, 0\.6166\); Ne\-He \(200 C\) 0\.4863 and 1\.5523 \(0\.4862, 1\.552\); H2\-A 1\.8684 and 0\.2383 \(1\.870, 0\.2384\); N2\-CO2 1\.3676 and 0\.7277 \(1\.368, 0\.7281\); Ne\-N2 1\.6113 and 0\.6550 \(1\.612, 0\.6552\); H2\-N2 1\.9103 and 0\.2750 \(1\.905, 0\.2750\)\: within 0\.3 %\. One inconsistency\: N2\-O2 \(27 C\) prints phi\_21 = 1\.014, while its own phi\_12 = 0\.994 and the identity phi\_21 = phi\_12 \(mu\_2/mu\_1\) \(M\_1/M\_2\) give 1\.005 \(Eq\. 14 gives 0\.9938 and 1\.0048\); a slip in the table, not in the formula\. Nothing is transcribed\. ACCURACY STATED\: for the binary data of Fig\. 1 \(He\-A, N2\-O2, H2\-A, C2H6\-C3H8, H2\-CCl2F2, C3H8\-H2\) the average deviation, excluding terminal points, is 0\.97 %, and 0\.49 % without hydrogen\-argon, the least satisfactory \(p\. 518\); for the thirteen multicomponent mixtures of Tables II and III, 1\.9 % \(p\. 519\)\. The mixture viscosities compared are Trautz and coworkers' \(1929\-1931\), Buddenberg's \(1948\) and Herning and Zipperer's \(1936\), cited in the table notes\. **Recorded bibliographic identity status:** VALIDATED\_WITH\_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- No datasets are recorded. Formulas -------- No formulas are recorded. Corrections ----------- No dataset errata are recorded in this source record. Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the :doc:`review register ` for the checks and decisions.