Chlorides cooling fluids

The presence of chlorides, even in small amounts such as 10 ppm, promotes corrosion [12], which is why cooling fluids used in circuits comprising heat exchangers (or radiators in the case of cooling systems for car engines) are specially conditioned for this use. 

The extract is collected by depressurizing the fluid into a sorbent trap or a collection solvent. A trap may retain the analytes selectively, which may then be selectively washed off by a solvent. This can offer high selectivity, but requires an additional step. The trap can be cryogenically cooled to avoid the loss of analytes. Using a collection solvent is more straightforward. The choice of solvents often depends on the analytical instrumentation. For example, tetrachloroethene is suitable for infrared determination, while methylene chloride and isooctane are appropriate for gas chromatographic separations. 

Procedure Place 194 grams (6.8 oz.) of 98% sulfuric acid into a beaker, and then place the beaker in an ice bath and cool to 0 Celsius. When the sulfuric acid reaches a temperature of 0 Celsius, slowly add in portions, 100 grams (3.5 oz.) of potassium nitrate or 84 grams (3 oz.) of sodium nitrate over a period of 1 hour while stirring the sulfuric acid and maintaining its temperature at 0 Celsius. After the addition of the potassium or sodium nitrate, slowly add over a period of one hour, 260 milliliters (8.8 fluid oz.) of cold tap water while continuously stirring the sulfuric acid mixture and maintaining its temperature at 0 Celsius (note a precipitate may form before or after the addition of the water. If this is happens, never mind it). Then remove the ice bath and then extract the acid mixture with seven 150-milliliter portions (seven 5.07 fluid oz. portions) of methylene chloride. Afterwards, combine all seven portions of methylene chloride (if not already done so), and then add 7 milliliters (0.23 fluid oz. or 1.4 tsp) of water to the methylene chloride. Then place the entire methylene chloride (two phase) mixture into a distillation apparatus (see the illustration in method 3 below), and carefully distill at 40 Celsius until no more methylene chloride is collected in the receiver flask. 

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