Is sonic velocity measurement a good alternative for pH measurement ?

[WG Chem]

I have a scrubbing system for Dimethylamine that employs HCl 33% for pH adjustement. The problem is, as you know, field pHmeters demand high maintenance and are very prone to failures. Besides, "being cheap" is definivelly not one of the things you could point in their favor.

I found the sonic velocity principle very interesting for measuring concentrations, and i intend to determine the amount of dissolved Dimethylamine or dimethylammonium chloride as a function of sonic velocity instead of pH (there is no need for a very acurate measurement). The instrument itself also seems very robust for any kind of operational conditions or fluids (

http://www.sensotech.com/cms/produkte0.html?&L=1).

The operating conditions are:
DMA: Target <1%
Manual pH verification and HCl adjustment.
pH: 5-8 (target: 6,0)
Temperature: 30-40°C
"Batch operation" (25% of water exchanged each 24 hours)


I would like to have some opinions of more experienced professionals regarding this technology that is completely new to me. Do you have some similar aplication?For what i have seem, there is a broad range of aplications.

Best regards.

 

[Latexman]

As far as I can tell, the technology has nothing to do with measuring sonic velocity of solutions.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[WG Chem]

Latexman,

For what i understood, it is not the sonic velocity of solutions. Its the velocity of sonic waves propagating through the solution.
In theory, this propagation should be affected by slight changes in density and/or the compressibility of the fluid, wich are altered by concentration (as well as by temperature).

 

[jari001]

These "tuning fork" (as I like to call them) density meters are good to use, but you have to make sure that the instrument will be able to detect the amount the density will change during its sampling time and be able to send the output to the controller to adjust the acid flow rate, if applicable. I have seen them in use to monitor density of biologic products during cold storage and as the sensor for continuous recycle stream concentration correction.

My initial thoughts are that you should be able to use this to monitor the density of the holding tank without much trouble; it is common to see the density correlated to concentration so maybe you can correlate to pH directly.

 

[EdStainless]

I have seen it done with a coriolis flow meter since they directly measure mass flow, density is easy to get.

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P.E. Metallurgy, Plymouth Tube

 

[IRstuff]

Based on their graphs:

http://www.sensotech.com/cms/619.html?&L=1

you have two issues:

> it looks like you're going to be at least 4 orders of magnitude LOWER concentration than they are capable of measuring
> you need to do a precise and accurate correlation of concentration vs. pH for your specific solute. maybe this exists already, but there's nothing obvious on the website about that

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[Latexman]

Sorry, the day I clicked on the url in Post #1, it did not pull up a webpage for some reason. When I tried just

http://www.sensotech.com,

I did not see any mention of "sonic velocity", thus my comment. Now that I have studied the web site somewhat thoroughly, you are correct! I think I will contact the company and study this instrument further. Thank you.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[WG Chem]

Uptating the post:
After some research and contact with vendors, i think it is possible to use it for the intended application. But...is not exactly "cheap". It costs roughly four times more than a pHmeter. It would only be justifiable in more specific applications, (high maintenance cost of keeping a reliable pHmeter or the need to know concentrations). IMHO, it would be a great instrument to optimize difficult crystallizations, but not so cost effective for simpler aplications, like scrubbing system control (at least in small-mid sized systems).

If someone has a deepest knowledge or the opportunity to see its performance in real applications, please share with the rest of us.

Thank you all for your responses.

Best regards