The nitration of phenolic-type compounds has been investigated following the report by Holler and Huch that these compounds are specific and sensitive spectrophotometric reagents for nitrate determination. An ion is considered to interfere in the nitration of the reagent if the percentage change in absorbance is greater than twice the coefficient of variation. Hence there are no serious interferences from most of the anions studied, including nitrite and chloride, to which most methods for nitrate determination are normally intolerant. The chemiluminescence analysis method then is of importance in environmental analyses, chemical oceanography, and other applications where trace nitrite and nitrate data are needed. Parts-per-billion concentrations can be analysed with milliliter sample volumes while parts-per-million and higher concentrations can also be determined by using microlitre range sample sizes or by dilution. Hydrogen sulphide is generated from sedimentary acid volatile sulphides via acidification, from greigite using sodium borohydride and potassium iodide, and from pyrite using acidic chromium (II).