Myelin Birefringent

These phenomena are most rapid and easiest to observe in fairly concentrated aqueous detergent solutions, that is, minimally 2—5% detergent solutions. In a practical quaHtative way, this is a familiar effect, and there are many examples of the extraordinary solvency and cleaning power of concentrated detergent solutions, for example, in the case of fabric pretreatment with neat heavy-duty Hquid detergents. Penetration can also be demonstrated at low detergent concentrations. As observed microscopically, the penetration occurs in a characteristic manner with the formation of a sheathlike stmcture, termed myelin they are filled with isotropic Hquid but have a Hquid crystalline birefringent skin. 

Stirring 0.7 wt% surfactant in water for several hours produced a turbid bluish-white system. A specimen under the microscope and between crossed polarizers revealed numerous birefringent spherulites 5 to lOOy in diameter, with characteristic Maltese crosses. Similar textures were also observed with 0.3 or 1.0 wt% NaCl present. Figure 1 is a photomicrograph of typical spherulites together with so-called myelinic figures (17b), which are caused by interference phenomena. 

Birefringent tubes which grow from lipoid-containing material after the addition of water (for example, from myelin sheaths of nerves, from the protoplasma surface of many cells — by addition of alkali — and from isolated lecithin). The parallel orientation of the hydrocarbon chains causes the birefringence. See A. Frey-Wyssling, Submikroskopische Morphologic des Protoplasmas und seiner Derivate, 1938, p. 62. 

Myelin Cylinders. Long-chain polar compounds, above their solubility limit, may interact with surfactants to form mixed micelles that separate (as a coacervate) in the form of cylinders. These are termed myelin cylinders or myelinic figures. They are usually quite viscous and may be birefringent. 

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