The organic carbon fraction in aquifer materials exerts a major influence on the subsurface mobilities of organic and organic-associated contaminants. The spatial distribution of total organic carbon (TOC) in aquifer materials must be determined before the transport of hydrophobic organic pollutants in aquifers can be modeled accurately. Previous interlaboratory studies showed that it is difficult to measure TOC concentrations <0.1% in aquifer materials, when total inorganic carbon (TIC) concentrations are > 1%. We have tested a new analytical method designed to improve the accuracy and precision of nonvolatile TOC quantitation in geologic materials that also contain carbonate minerals. Four authentic aquifer materials and one NIST standard reference material were selected as test materials for a blind collaborative study. Nonvolatile TOC in these materials ranged from 0.05 to 1.4%, while TIC ranged from 0.46 to 12.6%. Sample replicates were digested with sulfurous acid, dried at 40~ and then combusted at 950~ using LECO or UIC instruments. For the three test materials that contained >2% TIC, incomplete acidification resulted in a systematic M. E. Caughey ([~) Illinois State Water Survey,

A thermal evolution method is a method of destructive analysis in which the sample is subjected to heating, combustion, or fusion1 to quantify the chemical composition of iron and steel. Thermal evolution methods have been used for many years to determine carbon, sulfur, oxygen, nitrogen, and hydrogen contents of iron and steel. Carbon and sulfur are determined using combustion techniques. Oxygen and nitrogen are determined using inert gas fusion techniques. Hydrogen is determined using either inert gas fusion or hot extraction techniques. Analytical instrumentation for all of these techniques is commercially available.

Sulfur in very low concentrations can have adverse effects on several alloys, especially high‐temperature nickel base alloys. The high‐purity metals used to produce these alloys must contain very low levels of sulfur. The determination of sulfur in these materials is routinely performed by the high‐temperature‐combustion infrared detection method. The LECO® CS444LS is a state‐of‐the‐art analytical instrument that utilizes the high‐temperature‐combustion infrared‐detection method. This paper reviews the key features of the LECO® CS444LS and the important analytical techniques required to produce accurate sulfur data. Peformance data on a variety of high‐purity base metals and nickel base alloys is presented.

Thermogravimetric analysis (TGA) is an analytical technique in which changes in physical and chemical properties of materials are measured as a function of temperature and/or time. TGA is commonly used to determine selected characteristics of materials that exhibit either mass loss, or gain, because of decomposition, oxidation, or loss of volatile material, such as moisture. Common applications of TGA are materials characterization through analysis of characteristic decomposition patterns and determination of combustible materials and combustion residues from a sample. Macro TGA systems that use gram-size samples have been used for a couple of decades for monitoring industrial processes. The larger sample sizes allow more accurate mass measurements for characterization of materials. Flue-gas desulfurization (FGD) solids are industrial byproducts that have been monitored using macro TGA systems. Compounds reported to have been successfully measured include free moisture, moisture in hydrates, CaSO4•2H2O, CaSO3•½H2O, and CaCO3. A LECO TGA701 macro TGA system was used in a study to characterize the components in various FGD solids. Pure materials, including those listed above, were first analyzed with the TGA701 followed by the measurement of various mixtures of the pure materials. Although Ca(OH)2 is a material present in limestone slurries used in flue-gas desulfurization, previous studies have not indicated the presence of this compound in FGD solids. The TGA reaction profiles for Ca(OH)2 and CaSO3•½H2O show they decompose in the same temperature range. Pure CaSO3•½H2O is not available and was not used in the study. The study of pure materials and mixtures demonstrated the accuracy of the TGA701 in characterizing the compounds. A macro TGA analysis program developed during this study can be used to accurately quantify the various materials in flue-gas desulfurization FGD solids. Carbon and sulfur analysis data support the macro TGA results for the FGD solids.

For over 2 decades, fuel scientists have tried to reconcile the differences between the coal and coke volatile matter yields obtained using either a pre-heated (950°C) minimum volume vertical furnace (ASTM Method D3175) or a macro thermogravimetric analyzer (TGA) system heated to a final temperature of 950°C (macro TGA systems are those using 1 g or larger samples). This paper will describe experiments designed to help explain the differences in volatile matter yields. Parameters studied include sample heating rates, final temperatures, and pre-drying samples. Factors contributing to the differences between the two methods, such as observed differences between plastic and non-plastic coals and fixation of sulfur as sulfate in the pyrolysis residues, will be explained. Results from two interlaboratory studies, each involving over 10 laboratories, and other research projects were used to derive predictive equations to reconcile results from the two methods for determining volatile matter yields in coals.