7. Flame photometry was used to determine the sodium content in wastewater from soda production. Direct determination is carried out when the sodium content in the sample is from 0.1 to 10 mg/l. More concentrated water is pre-diluted, and less concentrated water is evaporated. The volume of the initial sample is 500 ml, after evaporation - is indicated in table 2. The determination was carried out by the calibration curve method. The data for its construction are given in Table 1. Calculate the sodium content (mg/l) in the investigated waste water.
Table 1
Results of photometry of NaCl standard solutions
Sodium concentration, mg/dm3 1.0 2.0 3.0 4.0 5.0 7.0 10.0
Relative radiation intensity (Irel.) 30.0 36.0 40.0 44.0 48.0 56.0 70.0

Characteristics of the studied solutions
Parameters Variants and initial data

7
Sample volume after evaporation, ml 100
Relative radiation intensity (Irel.) 58

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