Procedure
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Protein-free solutions: The following procedure is used for the determination of chloride in FoIin- Wufiltrates of serum or blood. This technique may be used on other fluids with low protein content. To 2 ml of-filtrate (x = (0.1 ml of serum) in a 15 ml Erlenmeyer flask is added 0.06 ml (x = (= 4 drops) of indicator solution.Mercuric nitrate is added from a microburette calibrated in 0.01 ml intervals.The size of the drops should be such that 1 ml equals about 100 drops. The clear and colourless solution turns an intensive violet blue on the addition of the 1 st drop of mercuric nitrate so lution in excess. Protein-containingsolutions: The removal of the proteins intensifies the colour change at the end point, but deproteinization is not absolutely necessary. To 18 ml of water in a 15 ml Erlenmeyer flask are added 0.1 ml of serum and 0.06 ml of indicator. The colour of the slightly turbid mixture is first flesh-red red and change after titration has been started, to deep violet. As more mercuric nitrate is added, the solution becomes clear and pale yellow to colourless. At the end point there is a sharp change to pale violet which can be seen without difficulty. The results are 1 to 2 milli-equivalents per litre higher than those obtained with serum filtrates. A probable explanation is that a small amount of chloride is lost by absorption on the protein precipitate in thepreparation of a Folin-Wu filtrate. Standardization of Mercuric nitrate: Two ml of NaCl standard solution are titrated as described for protein free solutions. For routine work a factor F is calculated from the result of this titration, by which the amount of mercuric nitrate solution (expressed in ml) used for the titration of 2 ml of Folin- Wufiltrate has to be multiplied to give directly the result in milli equivalents of chloride per litre of serum or blood, F = 100/z, where z is the amount of mercuric nitrate solution used for the titration of 2 ml of NaCl standard. |