CHLORIDE DETERMINATION

•Chloride ions exist in a mud system as Salts of Sodium, Magnesium, Calcium, or Potassium.
The determination of the Chloride ion present in the mud filtrate may give an indication of a Salt water flow, or the presence of a Salt formation or stringer.
•In mud systems to which Salt has been added, the Chloride measurements show the amount of salinity present in the mud.

Test Procedure:
•Measure 1.0 ml of filtrate into a white titration dish and dilute to a convenient volume with distilled water.
•Add a few drops of Phenolphthalein indication solution. If a pink color develops, add N/50 Sulfuric Acid until the pink color completely disappears.
It is not necessary to record the volume of N/50 Sulfuric Acid added.
•Add 4-5 drops of Potassium Chromate indicator to obtain a yellow color.
•Add Silver Nitrate while swirling or stirring until the color changes from yellow to orange-red (brick red), and persists for 30 seconds. Calculations:
•If 0.0282 N Silver Nitrate is used: –mg/L Chlorides = 1000 X ml of Silver Nitrate added
•If 0.282 N Silver Nitrate is used: –mg/L Chlorides = 10000 X ml of Silver Nitrate added Remarks:
•mg/L Salt (NaCl) = 1.65 X mg/L Chlorides
•The Chloride test may be run on the same sample used in the Pf determination, if the Mf test was not performed.
•Avoid contact with the Silver Nitrate solution. Wash immediately with water if Silver Nitrate gets on the skin or clothing.
•The end point of the reaction is when the Silver Chromate is when the first detectable permanent color change from yellow to a light brick red occurs.
•When using the weak Silver Nitrate solution, the end point is approached very gradually. Therefore, the formation of the Silver Chromate can be seen by a color change for yellow to brick red.
•If the strong Silver Nitrate is used, the end point is approached much more rapidly. Hence the early formation of the Silver Chromate, and is brick red color may be missed due to the larger amounts of Silver Nitrate being added. The color change will go from yellow to red. As soon as the red color is seen, the titration is complete.
•White lumps of Silver Chloride form when titrating high concentrations of Salt. This should not be mistaken for the end point.
•A high pH will precipitate Silver Oxide.