4 replies to this topic

[maud]

ppm?
am testing (or have to test) which chemical performs better with water (for a water purification plant, utilising coagulation-flocculation).
I have raw water which carries a negative charge, therfore have to destabilise that charge with (for starters) chemical 5031. Was instructed to make a 0.5% solution of chemical 5031. Which I made by diluting 25ml of 5031 into 500ml water.

Then my problem comes when I have to dose a certain amount of ppm! am working with ml so I don't understant nor know the relation between ml and ppm.

But the expected results of this test is that when am dosing that 0.5% solution, after some time flocs should form. And I should also be careful not to overdose nor underdose.

I tried dosing in 1-5ml of my 0.5% solution into 500ml raw water but could not get any flocs, but a bit milky water.

[Art Montemayor]

Maud:

I understand your dilemma and empathize. There can be no logical meaning to the term "ppm" - and I presume we all understand that the acronym stands for "Parts Per Million".

But, what parts per million? Volume parts per million volumes? Mass parts per million masses? It can turn out to be anybody's guess when the base units for the term are not employed in using the term. That's when engineers make stupid mistakes. I don't like to call anyone "stupid", but if a person dedicates 4 to 5 years of his/her life at a cost of approximately $50,000, competing in one of the hardest and most taxing studies in a University (which Chemical Engineering is) and that same person graduates and then proceeds to use the "empty" and un-specific term of "ppm" without identifying the basis --- then that graduate engineer is stupid. I'm sorry to have to use the term, but there is simply no excuse for not identifying the base units of the concentration term.

And that is where your problem lies: someone is giving you a "dosage" instruction and failing to be specific in telling you what units their term "ppm" is in. I would certainly not guess that it merely means ppm(vol). It could also mean ppm(wt). The only one who knows is the one who wrote the instructions --- the "stupid" engineer.

There is no relation between ml and ppm. The person writing the instructions must tell you the base units - or else you will never know. The answer to your dilemma is to go to the source and challenge them to tell you the correct and proper concentration that they are alluding to -- and also tell them about my opinion of their engineering communications ability.

Good Luck.

[dylant]

In your case, I think it indicates the volume.
0.5% solution = 5 mL solute/1000 mL solvent = 5000 mL solute / 1,000,000 mL solvent = 5,000 ppm.
I may not be right..... but that's my guess.
Btw, solvent = solute + solvent..... (ie. the total volume)

[JoeWong]

In your case, I think it indicates the volume.
0.5% solution = 5 mL solute/1000 mL solvent = 5000 mL solute / 1,000,000 mL solvent = 5,000 ppm.
I may not be right..... but that's my guess.
Btw, solvent = solute + solvent..... (ie. the total volume)

dylant,
I believe you still have not received what Mr. Montemayor trying his best to advise you.

Read again last paragraph of Mr. Momtemayor's post.

DON'T GUESS ==> ASK for the ANSWER


JoeWong

[dylant]

Well, I did not really read Art's last paragraph.....

My bad........