Test procedure/results wetting time

Additional problems are encountered with petroleum hydrocarbons due to the wide range in volatility, solubility and matrix effects. Knowledge of holding times should also be considered. Likewise, sample handling procedures within the laboratory will have a profound effect on the test result i.e. drying and crushing samples will lose volatile species, whereas a GC characterisation of a wet (as received) soil may sometimes show an unusually high aromatic content due to relative solubility effects. 

With respect to chlorides (Cl ), the most widely used procedure is the chloride candle, a gauze wick in a flask of reagent water. The candles tire exposed for a fixed period of time, usually 30 days, then removed. After leaching the exposed gauze into the flask water, the total chlorides are determined analytically, and reported as chloride deposition per unit of exposed area per unit of time (mg/m /day). This method is described in ASTM G 140, Test Method for Determining Atmospheric Chloride Deposition Rate by Wet Candle Method. The other method more recently introduced uses a dry fabric panel, which is also exposed for a predetermined length of time, usually 30 days. Then the chlorides are washed out of the fabric and analyzed. Both procedures are currently described in ISO Standard 9225 however, the dry plate method has been found to produce inconsistent results, and probably will be dropped from the ISO document at its next revision. 

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