Table VI. Silicon Determination in Calcium Oxide" with and without Fluoride Treatment (7 silicon per 100 ml.) With Without Fluoride & Fluoride 137 98 138 96 136 96 136 91 137 95" A 1-gram sample was dissolved in dilute hydrochloric acid, transferred 100-ml. volumetric flask, and made to volume. Solution was filtered and 2-ml. aliquots were removed for analysis.b The 2-ml. aliquots were diluted with water, treated with 0.5 ml. of zirconium-fluoride solution, and warmed for 0.5 hour.The effect oí fluoride treatment is vividly illustrated in Table VI. The results show that a filtered solution may contain unreactive silicon. Conventional recovery experiments may not indicate this type of interference and consequent lack of accuracy.The problem oí loss of silanes during solution of calcium metal was not investigated. It has been reported ( 7) that slow addition of the metal to dilute sodium hydroxide minimizes the loss of silicon, provided the solutions are kept cool.Metal. Dissolve a 1-gram sample of metal by slowly adding the fine chips to a Fluorethene beaker containing 15 ml. of about 0.35 M sodium hydroxide. The solution should not be permitted to become warm. After all the metal has been added, acidify the solution by the addition of dilute hydrochloric acid. Add 0.5 ml. of the zirconium-fluoride solution and warm for 0.5 hour at low heat on the hot plate. Complete the analysis, using the recommended procedure.
Nondestructive evaluation (NDE) of masonry has been, to date, essentially an adaptation of available methods which have been used for evaluation of concrete. There has been an increasing amount of study and application of these methods in recent years. Limitations on the efficiency and utility of these methods has been observed. Improved methods of NDE of masonry are needed. Recent NDE developments in the medical, aerospace and other fields should be studied for their application to masonry.
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