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Application Note Caustic Soda

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Application Note Caustic Soda Powered By Docstoc
					Application Note
Caustic Soda




Measurement of sodium hydroxide concentration with an ultrasonic analyser


Industries
Chemicals production, cellulosic industries, petroleum, pulp and paper, textiles, soaps and detergents,
sodium hydroxide manufacturing, scrubbing processes
Introduction
Sodium hydroxide (NaOH), popularly known as caustic soda, is manufactured as an electrolytic co-
product of chlorine.
Test Conditions
Aqueous solutions of sodium hydroxide with concentrations from 0% to 50% by weight NaOH have
been tested at temperatures from 20° C to 100° C at ambient pressures.
Results
Figure 1 shows the expected error of analysis at various concentrations of sodium hydroxide. The
accuracy of measurement is approx. ±0.03% NaOH for concentrations of 0% to 35% by weight NaOH,
and it is between ±0.03 and ±0.13% for concentrations of 25% to 50%. The variation of the sound
velocity with concentration and temperature is shown in Figure 2. Figure 3 shows the relationship
between the sound velocity and the temperature coefficient at various concentrations.
Discussion
In the concentration range from 0% to 25% NaOH, the change in sound velocity with concentration is
very good. Good mixing is advised to minimize concentration gradients in solutions. The measuring
accuracy is better in the lower temperature range and better at lower concentration range.
Conclusion
The ultrasonic analyser can monitor sodium hydroxide concentration continuously, dependably and
accurately. The lack of moving parts and the ability to operate in corrosive media make of the sound
speed analyser the natural choice for NaOH.




AD-200401NaOH-EN                                                                          09/03/2004
No responsibility is accepted for the accuracy of this information
Figure 1:

                                                            average error versus concentration
                                                                 at different temperatures

                                          0,14
                 average error, weight%

                                          0,12                                                              40 °C
                                                                                                            50 °C
                                           0,1
                                                                                                            60 °C
                                          0,08
                                                                                                            70 °C
                                          0,06
                                                                                                            80 °C
                                          0,04
                                                                                                            90 °C
                                          0,02
                                                                                                            100 °C
                                             0
                                                 0          10         20        30         40        50
                                                         caustic soda concentration, weight%


Figure 2:

                                                            sound speed versus concentration
                                                                at different temperatures

                                          2520
                                          2420                                                              40 °C
             sound speed, m/s




                                          2320                                                              50 °C
                                          2220                                                              60 °C
                                          2120                                                              70 °C
                                          2020                                                              80 °C
                                          1920                                                              90 °C
                                          1820                                                              100 °C
                                          1720
                                                 0      10        20        30         40    50       60
                                                         caustic soda concentration, weight %


Figure 3:

                                                     temperature coefficient versus concentration
                                                              at different temperatures

                                            0
             temperature coefficient




                                          -0,5                                                               45 °C
                                           -1                                                                55 °C
                                                                                                             65 °C
                                          -1,5
                                                                                                             75 °C
                                           -2                                                                85 °C
                                          -2,5                                                               95 °C
                                           -3
                                                 0     10         20        30         40        50    60
                                                                       concentration




AD-200401NaOH-EN                                                                                                    09/03/2004
No responsibility is accepted for the accuracy of this information

				
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