Jack W. Frazer

On the Infrared Spectrum of Hydrazine Matrix‐Isolation Studies of the System NH2NH2:N2 (I)

Matrix isolation spectra of the system NH2NH2:N2 were obtained in the region 4000–270 cm—1 at 4.2°K. Spectra taken in this manner are free of complications due to association, over‐all rotation, etc. The unusual features of these spectra are that the bands usually assigned to the bending modes which are present in gas‐phase spectra at ∼1500–1600 cm—1 are not found; and, that the torsional mode is apparently split. Anomalous behavior for the 6.3‐μ gas‐phase band was observed.

A sensitivity analysis of the smith predictor controller

Abstract The sensitivity of the Smith predictor controller to variations in system parameters is analyzed. The parameters considered are system gain, time constant, and delay or dead time. Both simulated and experimental results are discussed. First- and second-order models are studied. For the first-order model, a proportional plus integral control is used with the Smith predictor. A proportional plus integral plus derivative control is used with the Smith predictor for the second-order system. The controller is implemented digitally. An application of the Smith predictor with a model of the system obtained by a nonlinear least-squares parameter identification method is demonstrated on an experimental system.

Automated potentiometric analysis with selective electrodes

Abstract An automated potentiometric analyzer based on a residual-chlorine electrode has been developed that can determine chlorine concentrations of a 4–75 ppb (±2 ppb, standard deviation 0.6–1.9 ppb). A microcomputer-controlled digital buret delivers a predetermined number of aliquots of standard, and the electrode measures the potential of the test solution after each addition. An arithmetic processing unit transforms the acquired potentiometric data to the Gran (antilog) domain; the microcomputer then calculates a set of equivalence-point estimates and, using an error function criterion, selects the best estimate. The instrument includes a digital buret, 8080 microcomputer, arithmetic processing unit, real-time clock, video display, and 16-character key pad; it uses a modified version of the computer language BASIC compiled and programmed into Programmable Read-Only Memory (PROM). Although this system was designed to assay residual chlorine in water, the analyzer can also function as a digital pH (or millivolt) meter or, with minor software modifications, serve as a general-purpose instrument using any appropriate electrode system.

Characterization of the flow dynamics of an enzyme reaction system

Abstract The characterization of the flow dynamics of an automated enzyme reaction system is discussed. Parametric and non-parametric characterizations are constructed and then tested against actual experiments. The analytical model provides a more compact representation than the numerical model. A second-order lag-plus-dead-time model gives a good fit to the experimental data.

Microdetermination of ammonia using an ammonia gas-sensing electrode and a minicomputer

SummaryThe multiple addition method has been used in combination with Gran plots for the determination of 2×10−4M to 1×10−6M (2.8 ppm to 14 ppb) of ammonia nitrogen. The ammonia was determined with an ammonia gas-sensing electrode. A computer-controlled titration system was used for the titration and for dataprocessing. Results within ±2% of the added amount are obtained down to ∼1.5×10−6M (20 ppb) of ammonia nitrogen.ZusammenfassungDas Verfahren mit bekannten Zusätzen wurde in Kombination mit der von Gran angegebenen Methode der Äquivalenzpunktbestimmung für die Bestimmung von 2 · 10 bis 10−6 Mol (2,8 ppm-14 ppb) Ammoniakstickstoff angewendet. Der Ammoniak wurde mit einer gasempfindlichen Elektrode gemessen. Ein computer-gesteuertes Titrationssystem wurde für Titration und Datenverarbeitung verwendet. Ergebnisse innerhalb ± 2% der zugesetzten Menge wurden bis herunter auf etwa 1,5 · 16−6 Mol (20 ppb) Ammoniakstickstoff erhalten.

Microestimation of phosphate in the presence of large amounts of fluoride

SummaryA method for the microestimation of orthophosphate in the presence of large amounts of fluoride is described. A lead ion-selective electrode and a double-junction reference electrode are used to monitor the potentiometric titration with 0.01M lead perchlorate. Solutions are buffered at pH 8.25 to 8.75. A computer-controlled titration system is used for titration and data processing. Up to 400 mg of fluoride, a 13000-fold excess, can be tolerated in the estimation of 10−6 M phosphate.ZusammenfassungEin Verfahren zur Mikrobestimmung von Orthophosphat in Gegenwart großer Mengen Fluorid wurde beschrieben. Eine bleiionen-spezifische Elektrode und eine doppelpolige Bezugselektrode wurden zur Durchführung der potentiometrischen Titration mit 0,01-m Bleiperchlorat benützt. Die Lösungen werden auf ein pH zwischen 8,25 und 8,75 gepuffert. Ein Computer-gesteuertes Titrationssystem wird für Maßanalyse und Datenverarbeitung verwendet. Bis zu 400 mg Fluorid, also ein 1300-facher Überschuß, ist bei der Bestimmung von 10−6 Mol Phosphat tolerierbar.

Computer control for simultaneous carbon, hydrogen, and nitrogen determinations in organic compounds

SummaryThe automation, via a digital computer, of CHN determinations in organic compounds by a manometric procedure is described. The accuracy of the method is expected to be ± 0.03%.ZusammenfassungDie Automation der manometrischen Bestimmung von C, H und N in organischen Verbindungen mit Hilfe eines Digitalzählers wurde beschrieben. Sie läßt als Genauigkeit der Methode ±0,03% erwarten.

Extension of the smith predictor

Abstract An effective means of controlling non-linear systems with time delays by use of a digital computer is presented. A model of the system is required, and an extension of Smiths method is used. The method is demonstrated on an experimental enzyme reactor containing a saturating element and a large delay relative to the time constants of the system. The time optimum control of the experimental system as well as PID control is used to demonstrate the effectiveness of the method.

Applications of modern control theory to process control

This paper contains a brief description of research on the control of an enzyme reactor at the Lawrence Livermore Laboratory. One of the objectives of the research is to develop improved design methods for use in the chemical industry in order to increase productivity and efficiency in laboratory, pilot plant, and production facilities. A laboratory bench scale apparatus with a problem environment similar to that found in a commercial pilot plant has been built, and an interdisciplinary team of engineers, chemists, and mathematicians has been organized. This paper describes the project and some of its goals.

Development of adaptive instrumentation for process control

This abstract describes the operation of an automated electrochemical cell that utilizes an ion selective electrode (ISE) as the detector. The instrument can rapidly and automatically generate on-line estimates of the concentration of an ion, thus providing chemical information useful for controlling a chemical process. A typical application might be the monitoring of a sewage treatment plant to facilitate control of the concentration of a contaminant in discharged water.