摘要:

An on-line thermogravimetry/gas chromatography/mass spectrometry (TG/GC/MS) system has been constructed through additions to and appropriate modifications of commercially available instruments. The system employed a Du Pont 951 thermogravimetric analyzer coupled to a Hewlett-Packard 5890 gas chromatograph/5970 mass selective detector system. A nickel tube, inserted directly into the area immediately above the TG sample pan, acted as a transfer line. An adsorbent trap with a heater and a heated six-way valve was installed between the TG and the GC. The volatile compounds generated from selected materials in the TG were adsorbed by the trap. After the heating and purging process, the trap was rapidly heated and the volatile compounds in the trap were swept into the GC injector and were then analyzed by GC/MS. The on-line TG/GC/MS system was examined by using selected natural products. A number of volatile compounds were generated from the samples by TG, separated by GC and identified by MS. The stability, the weight loss, and the evolution of compounds from the materials could be analyzed and studied.

ISSN:1073-9149    

DOI:10.1080/10739149208543747

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this paper, computer programs to evaluate kinetic analysis from non-isothermal thermogravimetric data are discussed. The flowcharts for all the programs are shown. These include those based on single-heating-rate and multi-heating-rate procedures. The single-heating-rate methods include the differential and integral calculations while the multi-heating-rate methods include those of Friedman and Ozawa.

ISSN:1073-9149    

DOI:10.1080/10739149208543748

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We have found it difficult to implement coulometry on small volumes and yet react the sample quantitatively in a reasonable time. We describe here a simple and satisfactory solution, making use of a commercial ring-disk electrode system.1A small cup-like cell is constructed with dimensions such that the ring-disk assembly can rotate freely inside it at a small distance from the bottom, as shown in the figure. The ring is used as the counter-electrode, and appears to be acceptable in spite of a much smaller area than the working electrode (the disk). The reference electrode is provided by a capillary connection at the bottom. The capillary is filled with a solution of supporting electrolyte and agar, which in turn is connected through a salt-bridge (containing electrolyte only) to a calomel electrode. The level of the electrolyte in the reference arm is higher than that in the cell, so that a very small positive flow is ensured to prevent contamination of the agar with the sample. The very smooth rotation of the ring-disk system permits speeds up to about 2000 RPM. It was found that for electrolysis of metals such as Cd and Pb on a mercury-coated glassy carbon electrode, the half-time for electrolysis is about 2.5 min at the optimum rotation speed of 800 RPM, with a sample volume of 10 μL.

ISSN:1073-9149    

DOI:10.1080/10739149208543749

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A fully programmable, current quantized, electronic coulometer totalizing 6-decades of charge (99,999.9 coulombs) and 6-decades of duration, (99 hours 59 minutes 59 seconds) for electrolysis. On the front panel: two 6-digit 7-segment-LED displays with relevant 12 BCD thumbwheels for monitoring and program setting of charge and duration respectively; charge and time resets and loading-command buttons; current polarity indication; “program-fulfilled”-cutout relay with buzzer. Zero-current detector excludes wrong totalizing due to process interruptions, e.g. electrode cleaning. This coulometer outputs charge and time BCD signals for slave indicators and data processing. It is specially meant for organic electrochemical synthesis. Electrolysis current range: 0.005A to 1.00A of either polarity.

ISSN:1073-9149    

DOI:10.1080/10739149208543750

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A spectrometer capable of measurements in either the absorption or emission mode is described. This spectrometer, built in-house from inexpensive components, uses an interference filter as monochromator, a phototransistor as detector, and glass optics. Although less versatile than a commercial instrument, it is rugged, reliable, and open in construction, serving as an excellent device to introduce students to the topic of elemental analysis by atomic spectrometry.

ISSN:1073-9149    

DOI:10.1080/10739149208543751

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The key elements in the study of chemical reaction transients are generation of forcing functions, rapid measurement of process variables and reliable computer control system. A multicomponent reaction involving propene metathesis was studied under computer control. The real-time control of the inlet gas concentrations to a Berty reactor, reactor temperature measurement and control, and acquisition of reactor effluent composition via rapid analysis in a gas chromatograph are described. The time intervals for servicing the interfaced devices were generated by hardware interrupts. The multitasking computer control program with interrupt servicing was written in FORTH.

ISSN:1073-9149    

DOI:10.1080/10739149208543752

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739149208543753

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739149208543754

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739149208543746

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor