The Wagner Turbidimeter as an Instrument for the Determination of Specific Surface and Particle-Size Distribution of Portland Cement. An Instrument for the Measurement of the Thermal Conductivity of Water, and for the Investigation of Phenomena in He

The Wagner Turbidimeter has given promise of being a suitable instrument for use in the determination of the surface exposed by the particles in samples of Portland cement. Since the extent of this surface is an important factor in controlling or predicting the behavior of cements in the production of concrete, a simple but accurate method for its determination is highly desirable in connection with investigations and acceptance tests. The purpose of the present investigation was to make a critical study of the advantages and short-comings of this instrument and to recommend modifications of apparatus or procedure which might improve its performance. The various steps in the procedure and the possible sources of uncertainty and error in the results have been examined in detail. Several modifications of the apparatus have been found beneficial and numerous changes in the procedure to be used have been found essential for obtaining satisfactory results. With the suggested improvements, the instrument appears to offer a reasonably satisfactory method for routine tests of specific surface (usually expressed as square centimeters of surface per gram of cement), and also for approximation of the distribution of the sizes of the particles of the cement. Although the results are not entirely accurate and reproducible, they are within useful limits and the instrument is recommended for use in acceptance test work on specific surface measurement, until a more accurate method, utilizing instruments of reasonable cost and with simple operating procedure has been developed. For research or investigational purposes, where cements of varying chemical and physical characteristics (including optical properties) are -being studied, it is believed that the turbidimeter method may not be sufficiently accurate and should not be depended upon, unless special precautions are observed and great care taken in the work.