# The Naked Scientists Forum

### Author Topic: How do I calculate solution concentration  (Read 22622 times)

#### Jolly- Joliver

• Hero Member
• Posts: 584
##### How do I calculate solution concentration
« Reply #50 on: 29/03/2011 11:22:30 »
Bored Chemist would this be fair

I know he has 3.6368mg in the gallon giving him 0.8

I know for a gallon to get 16ppm you add 72.7376mg.

So minusing off 3.6368mg from 72.7376 = 69.1008mg

Using your 4.54Litres for a gallon an increase of 75ml is 4,615ml

to get 16ppm in 4,615ml we need 73.84mg or 0.07384grams

he already has 0.8 in a 4,615ml mix

We are adding another 75ml taking it to 4,690ml needing 75.04mg to achieve 16ppm

----------------

So to get 0.8 in 4,615ml he must have 3.692mg of stuff

We are going to add 75ml increasing the volume to 4,690ml

to get a 16ppm we need 75.04mg in 4,690ml

So minuing off the 3.692mg from 75.04mg we get 71.348mg needed

so making a 75ml solution of 71.348mg

at 71.348mg / 100 = 0.71348 x 62 = 44.23576mg of sodium bicarbonate

71.348mg - 44.23576mg = 27.11224mg sodium sulfate

You know what, actually chemistry is quite beautiful

Ok so mixing 27.11224mg of sulfide and 44.23576mg of bicarbonate to 75ml Ro

Then adding that in total to the mixture

A 71.348mg in 75ml solution, added to 4,615ml with a 0.8ppm

Gives total liquid 4,690ml and total solids of 75.04mg

That gives on the calculator a ppm of 16ppm.

-----------------------------------------------

He has 4,615ml RO water with a 0.8ppm

adding to that, 71.348mg of sodium sulfate(38%) and sodium bicarbonate(62%) in 75ml solution.

Should give

4,690ml with a ppm of 16.0ppm

Bored chemist hows that?

it's 75.04mg in 4,690ml  or  0.07504Grams in 4.69 litres

« Last Edit: 29/03/2011 11:33:53 by Wiybit »

#### Jolly- Joliver

• Hero Member
• Posts: 584
##### How do I calculate solution concentration
« Reply #51 on: 29/03/2011 13:06:33 »
I work at a water bottling plant and I'm just trying to figure out how to test our mineral solutions.  I'd appreciate it if anyone can help me with this one.

One blend of water uses a sodium sulfate/sodium bicarbonate solution which is injected in RO water at a rate of .75ml per 1 gallon.  The mineral solution is made of 96 gallons RO water, 30.72 lbs sodium sulfate and 50 lbs sodium bicarbonate.  TDS on RO averages approx 0.8 ppm and the desired TDS on finished product is 12 - 18 ppm.  What should the TDS on the mineral solution be to give me the desired result on finished product.

Hi Mr H

O.k you have 96 gallon mix ro water with 80.72 lbs solids or 36.6139761064kg

Your ppm for that mixture are 83863.3ppm(a correction they are 83895.3)

You are then adding 75ml of that to another RO Gallon and seeking a 12-18ppm

96 gallons into litres is 4.54 x 96 = 435.84 litres with a 83863.3ppm

435,840ml / 75ml = 5811.2 doses. say 5811

83863.3ppm / 5811 = 14.43ppm and lots of other 1s and 3s and such.

So I think what your asking is "why am I only getting 0.8ppm? Because the 75ml solution I add should have about 14.43ppm in it"

Except that's going into a Gallon.

So if I put that in a gallon(uk) I get a ppm of 0.237567ppm

You claim you're getting 0.8ppm, which to me suggest that the concentration is slightly higher than .00108grams probably around .0037grams per 75ml you add, giving you around 0.8ppm.

If I'm right.

You need to increase the 96 RO gallon mixture you use for the 75ml soultion.

By well lets think about it,

To get a ppm in gallon(uk) of 16ppm you need your 75ml solution to have 0.073grams or 73mg in it.

73mg times by 5811.2 = 424217.6 which is 424.2176KG

I believe your ratios are 62% Sodium bicarbonate and 38% sodium sulfate

so 424.2176 / 100 = 4.242176 x 62 = 263.014912kg or 263kg of sodium Bicarbonate

424.2176 / 100 = 4.242176 x 38 =  161.202668 or 161.2kg of Sodium Sulfate.

So if that is what you are doing.

Your current 36.6kg of sodiums, in the 96 Gallons RO mixture for the 75ml solution is way too small.

What you need to do is put in 161.2kg of sodium sulfate to the 96 gallons and 263kg of sodium bicarbonate. Then your 75ml solution from that should have a concentration high enought for 75ml to increase the ppm in a gallon of RO water to 16ppm.

It's 424.KG of solids in 436.litres roughly.

That mixture should give you a solution where 75ml of it will cause a Gallon(uk)of  RO water to get a ppm of arround 16ppm.

If that's what you are doing.

Rosy or Bored Chemist if that is what he wants, to make up a 96 gallon Ro solution of two different sodiums, then to use 75ml of that solution to make another Gallon have a ppm of between 12-18ppm is that right?

From what you have shown me I think it is.

What should the TDS on the mineral solution be to give me the desired result on finished product.

TDS on the 75ml solution 73mg. ppm on 75ml solution 973.333ppm

TDS On RO 96 gallons for the 75ml solution 424.203Kg and you should get around 5811- 75ml solutions from it.

TDS on a Gallon RO for a 16ppm  0.073grams

73mg / 100 = 730 micrograms x 62 = 45.26mg sodium bicarbonate 62%
73mg / 100 = 730 micrograms x 38 = 27.73mg sodium sulfate     38%
« Last Edit: 29/03/2011 19:40:30 by Wiybit »

#### Jolly- Joliver

• Hero Member
• Posts: 584
##### How do I calculate solution concentration
« Reply #52 on: 29/03/2011 16:47:55 »
Todays episode of sesame street

Was brought to you but the letter C

The search for Dalton(who ever he is), micrograms, the number 142.

And this handy KEY. Someone suggested I put up.

--------------------------------------

RO- Reverse Osmosis

PPM- Parts per million

ml- mililitre

mg-miligram

Kg- kilogram

Lbs- Pounds weight

TDS- Total disolved Solids. or it can also mean. Total Dry solids

Dalton- or DA, a number for the atom weight of a chemical or substance. SAME AS: AU- Atomic Unit.

MATHS:-

/ Divide

= equals

X multiply

+ plus

- minus

Calculators:-

For solution concentrations:-
http://www.calctool.org/CALC/chem/molecular/solution

http://www.currentprotocols.com/tools/solution-concentration-calculator

For mililters

http://www.metric-conversions.org/weight/milligrams-to-grams.htm

http://www.unitconversion.org/weight/centigrams-to-grams-conversion.html

Calculator normal

http://www.calculator.com/pantaserv/makecalc

converters

Gallons to litres

http://www.metric-conversions.org/volume/uk-gallons-to-liters.htm

Lbs to KG

http://www.convertunits.com/from/lbs/to/kg
« Last Edit: 29/03/2011 20:07:14 by Wiybit »

#### The Naked Scientists Forum

##### How do I calculate solution concentration
« Reply #52 on: 29/03/2011 16:47:55 »