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# Mixing time of caustic with water at 25 C

## Mixing time of caustic with water at 25 C

(OP)
Hi there, does anybody know the mixing time of caustic soda (NaOH) with water at 25C, total mass is 1782.358 kg solution should be 40 %

### RE: Mixing time of caustic with water at 25 C

(OP)
EmmanuelTop's thank you for your reply,unfortunately there is nothing related to mixing time,which is needed

### RE: Mixing time of caustic with water at 25 C

Dilution time will strongly depend on the volume of solution and agitation intensity. There is no simple equation which can cover all scenarios and configurations. Depending on volume and agitation, this can be a matter of seconds (small volumes, high agitation) or hours or days (big ponds without agitation) till solution concentration is equal in all points.

One thing I can think of is to monitor dilution temperature. If you add known quantity of NaOH to a known volume of water at given temperature, you can easily calculate the resultant temperature rise of the solution, by using value of enthalpy of dilution.

Dejan IVANOVIC
Process Engineer, MSChE

### RE: Mixing time of caustic with water at 25 C

(OP)
The total mass is 1782.358kg(1570litre)which is large amount i guess.Consists of 712.943kg Naoh and 1096.415kg Water both at 20 C.Agigator power is 77-80 W,i just need aproximation/assumption will it take 1-2 hours or just seconds ? and about temperature change: i know the specific heat capacity of water at naoh at given temperature.i use equation Cp(1)m1T1+Cp(2)m12T2=Cp(3)(m1+m2)T(3) but Cp(3) and T(3) are unknown.how to calculate ? Sorry for taking your time

### RE: Mixing time of caustic with water at 25 C

Caustic will mix very quickly, within seconds.

### RE: Mixing time of caustic with water at 25 C

Define what you mean by "mixing time". 90% homogeneous? 95%? 99% And, what are you starting with? Prills? 50% solution? These details makes a difference.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

### RE: Mixing time of caustic with water at 25 C

(OP)
Mixing time-time needed to mix caustic with water to get 100%homogeneous(assumption)solution within the mixing vessel.starting with process water 1096.415 kg and solid caustic flakes 712.943kg both at 20C,at 1atm

### RE: Mixing time of caustic with water at 25 C

I thought you were referring to liquid caustic. Flakes takes a few minutes:

- Wear PPE because this material is hazardous.

- Ideally, the starting water should be cold.

- Meter the caustic soda flakes into the water while mixing, taking care to do this neither too fast nor too slow. The soda should be sprinkled in because it will sink to the bottom quickly if dumped in. Always add the soda to the water, never vice versa.

### RE: Mixing time of caustic with water at 25 C

Theoretically, 100% homogeneous needs infinite time. But 99% takes a few minutes. This is easily tested in the lab. Mimic what you plan to do in a beaker and stir until the temperature stops changing. The best place to get this answer is in the lab.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

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