Microspheres of Organic Substances

Abstract

SPHERICAL particles of glass ranging in diameter from about one micron upwards, which can be prepared by the method of Bloomquist and Clark¹, have found a wide range of usefulness, for example, as adsorbents of known surface area², as material for the study of ‘fluidization’ of beds of particles³, and in electrokinetic measurements on cataphoresis and sedimentation velocity^4,5. For many such experiments, particularly the electrokinetic ones, it would be desirable to be able to use microspheres of substances other than glass. I have found that it is possible to obtain many organic compounds in micro-spherical form, provided that they melt below 100° C, and are more or less insoluble in water. The substance to be used is mechanically stirred at a very high rate with thirty to forty times its weight of water, at a temperature 10–15° above the melting point of the substance, thus producing an unstable emulsion of liquid drops in water. This is then run rapidly into a large excess of cold water, produoing solid spherical particles of the substance. Some degree of control over the size of particle obtained oan be exercised by modifying the rate and time of stirring. In this way, microspheres of naphthalene, octadecane, m-dinitrobenzene, cetyl alcohol, stearin, stearic acid, and several other organic compounds have been prepared. These particles are used in the study of the electrokinetic properties of organic compounds by the method of electroviscous sedimentation⁶.