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Ammonium hydroxide NH4OH is usually manufactured by a known batch process wherein a large tank (e.g., 3000 gallons). It is first filled with pure water which is then pumped to an injector/sparger wherein it is mixed and combined with ammonia gas (NH3). The resulting ammonium hydroxide solution is then recirculated back to the reactor tank in a closed loop until the target level of ammonium hydroxide, usually 29 wt. %, is attained. Once the target level is achieved, the process is terminated and the tank is drained. Like sodium hydroxide, the concentration of the is very easy to measure accurately in the pipes or in the tank with the 8500 controller.
As the speed of sound is depending on the temperature, the concentration is compensated for temperature changes by means of the integrated thermistor. The TAM (Total Accuracy of the Measurement) is depending on the selected range. For 0-30 w/w% NH4OH the TAM is 0.01%, which is at least 4 times better then any other online analyser. Lower levels have even a higher accuracy, because the speed of sound is lower. Therefor, the Rhosonics 8500 is the best choice for the online (insitu and extractive) measurement of ammonium hydroxide in the full range of dilution. For this application a choice of different cells can be made: The MP-130 measuring cell, is the best choice for an inline continuous explosion proof analyser with an extreme high accuracy and repeateability. Alternatively, the MP-54 probe or the recently introduced MP-48 may be chosen, as it is more cost-effective for applications that do not call for explosion-proof equipment. This probe is mounted inside a special pre-fabricated pipe section, ensuring minimal obstruction of the flow of the liquid. For applications, demanding for the extraction of the sample out of the product line, the MP-42 sensor with cell is the most suitable solution. The cell is equipped with Swagelok connectors for convenient integration is the process line.
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