1. ## 15% Sodium Hypochlorite

Anyone know what the weight % is for 15% Sodium Hypochlorite trade is off the top of their head.

2. ## Re: 15% Sodium Hypochlorite

[EDIT] This post has been corrected since it initially just looked at Weight % Available Chlorine and not Weight % NaOCl [END-EDIT]

Weight % Available Chlorine = Trade % / Specific Gravity (density)
Weight % NaOCl = Weight % Available Chlorine * (74.442 g/mole) / (70.906 g/mole)
Weight % NaOCl = 1.0499 * Trade % / Specific Gravity

The specific gravity (density) of 12.5% chlorinating liquid is around 1.16 g/ml (though I've seen some that are 1.20) so I'm going to guess that it's around 1.20 g/ml.

So 15% / 1.20 = 12.5% available chlorine by weight and 1.0499 * 15% / 1.20 = 13.12%. PoolMath appears to be using weight %, not Trade %. If one uses Trade %, then adding 1 liter of product to 10000 liters would result in an FC increase equal to the Trade %. So adding 1 liter of 12.5% chlorinating liquid to 10,000 liters should increase FC by 12.5. Similarly adding 1 gallon of product to 10,000 gallons. Instead, what I find is the following for the % entry vs. FC:

% ......... FC
6.00 ..... 6.17 ....... CORRECT
8.25 ..... 8.49 ... This looks like this assumes a density of 1.0499*8.49/8.25 = 1.08 instead of 1.10 that it should be using
10.0 ... 10.29 ... This is using weight % NaOCl and a density of 1.08 instead of using Trade % and a density of 1.14
12.5 ... 12.86 ... This is using weight % NaOCl and a density of 1.08 instead of using Trade % and a density of 1.16
15.0 ... 15.43 ... This is using weight % NaOCl and a density of 1.08 instead of using Trade % and a density of 1.20

So PoolMath is behaving as if the input is a weight % with a constant product density of 1.08. In my Pool Equations spreadsheet, I assume that 6% and 8.25% bleach is specified by weight % and I assume a density of 1.08 for 6% and 1.10 for 8.25% while for 10% and 12.5% I assume this is Trade % (volume % available chlorine) and the density isn't relevant if one looks at volumes added, but if I need that for a calculation I assume a density of 1.14 for 10% and 1.16 for 12.5%.

3. ## Re: 15% Sodium Hypochlorite

Playing with your spreadsheet vs. PoolMath seems to show a few differences. To wit: CSI and what I believe to be recommended FC....

4. ## Re: 15% Sodium Hypochlorite

I've corrected my post above. Nevertheless, there are still differences. PoolMath is always using weight % NaOCl. That's OK if it said that explicitly, but it should allow one to enter Trade % (or at least display it) since that is more common for chlorinating liquid. Also, it is using a constant density of 1.08 and that is clearly wrong because the higher chlorine concentrations have higher density. Unfortunately, it's not always consistent for real product because they vary in how much excess lye they have and that also affects the density, but I use "good chlorine" density numbers that have smaller amounts of excess lye in them.

So at a minimum, we'll correct this to use an interpolated table of density so that at least the weight % entry will be more accurate. As to whether Trade % can be added or used, we'll see. I'm in communication with Jason on this since he wrote the app based on my spreadsheet numbers.

As for the CSI, the PoolMath calculation does not account for ion pairs since that is rather complex, but the error is only around 0.02 so not anything to worry about.

5. ## Re: 15% Sodium Hypochlorite

Try PoolMath now. I have improved the FC calculation for bleach/liquid chlorine.

6. ## Re: 15% Sodium Hypochlorite

Well now I am confused when the box changes from "trade" to "weight" (the T is not visible BTW) ... so I can only imagine that this could lead to questions in the future.

7. ## Re: 15% Sodium Hypochlorite

It uses weight percentage for anything <=9%, and trade percentage for anything >9%. Whichever one it picks is shown in text.

The trailing 't' in weight should be back.

8. ## Re: 15% Sodium Hypochlorite

Thanks for the replies. I didnt mean to cause an issue. Lol.

When I opened pool math, the default numbers for FC is 140 (now) and 140 (target). What does one do if you run upon 10% bleach weight? Seems like I remember seeing some for industial use. Maybe a drop down menu for weight or trade would be better if possible.

9. ## Re: 15% Sodium Hypochlorite

Nevermind, I cleared my cookies and the default is 4. Must have just been something in the cookie.

10. ## Re: 15% Sodium Hypochlorite

Usually bleach which is less than 10% (usually 8.25% is the highest) is sold as weight % of sodium hypochlorite while most chlorinating liquid is 10% or higher and sold as Trade % which is volume % of available chlorine. There are exceptions, but this is the most common. Thanks Jason for making the changes.

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