Determinations of trace amounts (with one exception) of chloride are reported for 41 international geochemical reference standards, 12 of which have no previously reported literature values. All determinations were made by the chloride‐specific ion‐selective electrode method of Aruscavage and Campbell with certain refinements. Chlorine is separated from most other elements in geologic materials by acid‐dissolution in a gas diffusion cell, and is subsequently determined as the chloride ion in basic solution. A statistical F‐test was applied to 19 of the standards for which three bottles of each were analyzed in triplicate with no failures. All these standards, plus the other 22 for which six analyses were performed on a single bottle, exhibited a relative standard deviation of 1‐6% for concentrations of chloride >50 ppm. For most samples chloride values agree well both with available, reported experimental values and with recommended or consensus values.

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Nonproportionality of X-ray fluorescence intensity vs. concentration of sulfur occurs in geologic materials prepared as ground samples. Samples containing sulfur as sulfate yield higher intensities than an equivalent amount of sulfur as the Sulfide. Although the intensity of free sulfur decreases markedly during a short exposure to X-rays in a vacuum, and sulfide intensities decrease over a much longer time period, sulfate intensities show no deterioration with time.A fusion procedure utilizing a LiBO2-Ce(NH4)2(NO3)5 flux has been developed for geologic materials to oxidize all sulfur in a multiplicity of oxidation states to a single oxidation state, namely, the sulfate. The procedure is applicable over a wide range of concentrations (0.5 - 28 wt. % total sulfur) with a detection limit of 0.01%. A suite of chemically analyzed rocks containing both sulfides and Sulfates is used for standardization.