The precise stoichiometry of "argentic oxynitrate" has been elucidated by analytical and thermal analytical techniques. A decomposition path of the oxynitrate has been proposed and values of the enthalpy changes obtained. TG has been used as the criterion of purity of silver(II) oxide and new values for the heat of formation of silver(I) and silver(II) oxide are reported.Considerable attention has been focused on the preparation and properties of compounds containing silver in the +2 oxidation state. Perhaps the most important of these compounds is silver(II) oxide, AgO [1-6]. As part of an investigation into the use of silver(II) oxide as an oxidant in the determination of transition and transuranic elements it was necessary to obtain the oxide in a high state of purity by prolonged boiling of an aqueous suspension of the socalled argentic oxynitrate, "AgTNOn". There is considerable variation in the literature as to the precise stoichiometry of the oxynitrate, Ag28.550~4.s6N4.08 [7], Ag28044N 4 [8] and Ag28.57041,92N3.93 [9] having been variously reported. No direct calorimetric studies of the oxynitrate or indeed of silver oxides appear to have been published. This paper records the results of our thermal analysis investigations of these systems and the resulting stoichiometric implications. The precise route of the thermal decomposition of "argentic oxynitrate" and the associated enthalpy changes are also reported.
This paper summarizes the findings of a study to evaluate the strength, fatigue, and elastic characteristics of recycled asphalt pavement materials and to develop a preliminary mixture design procedure. Mixtures with different types and amounts of additives for three recycling projects in Texas were evaluated. The primary method of evaluation was the static and repeated-load indirect tension test. Estimates of tensile strength, resilient elastic characteristics, and fatigue characteristics were obtained. A preliminary mixture design procedure was formulated which was based on the results of this study and standard tests on the mixture and extracted asphalt and a review of pertinent literature and past experience. The objective of this preliminary design procedure is to allow engineers to begin routinely to design mixtures involving recycled, deteriorated asphalt cements. Preliminary findings indicate that recycled asphalt mixtures can be treated through the addition of asphalt or reclaiming agents to produce a material which exhibits satisfactory engineering properties as measured by laboratory tests on both laboratory-prepared specimens and field cores. A preliminary mixture procedure which can be used to design recycled mixtures is presented. Future work will lead to modifications of this procedure. However, at present it is felt that the procedure is practical and capable of being used routinely.
Questions concerning when a road ceases to serve the public well or has failed are closely related to the ride quality of the road. The quantification of the rideability or serviceability of road deals with the human rating of ride quality. For the most thorough rating, a select panel of raters has been used to rate a road section after having either driven or ridden over the section. The average of the ratings may be called the present serviceability rating (PSR). Given a set of PSR covering a wide spectrum of roads of different surface characteristics, the essential question is how to explain the PSR in terms of the explanatory variables describing human sensitivity in some relevant functional form. It is apparent that a rater responds to the vibration environment in a moving vehicle induced by the longitudinal roughness of a road. This paper presents an analytical model connecting the characteristics of a road profile, and the dynamic response of a vehicle to the profile, to the human ratings of the ride quality. Analytical expressions for various dynamic indices in a moving vehicle are derived. Very good agreement between the model prediction and the ratings is demonstrated using actual field data. Obtaining a good model prediction would give the means of obtaining a rating of road quality comparable to that provided by experts, without the associated expense of employing such experts.
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