What is the loss of strength of stored liquid chlorine over time based on the storage temperature?
[1]I finally got around to making a spreadsheet using the rate constants from this link plus some fitting and fudge factors to be consistent with half-life and this paper[2] so I'm showing decomposition rates for 12.5% (trade %) chlorinating liquid below over time vs. temperature.[3]
| TIME | 100ºF | 95ºF | 90ºF | 85ºF | 80ºF | 75ºF | 70ºF |
|---|---|---|---|---|---|---|---|
| Initial | 12.50% | 12.50% | 12.50% | 12.50% | 12.50% | 12.50% | 12.50% |
| 1 day | 11.92% | 12.10% | 12.22% | 12.31% | 12.37% | 12.41% | 12.44% |
| 2 days | 11.42% | 11.74% | 11.97% | 12.13% | 12.25% | 12.33% | 12.39% |
| 3 days | 10.99% | 11.41% | 11.73% | 11.96% | 12.13% | 12.25% | 12.33% |
| 4 days | 10.61% | 11.12% | 11.51% | 11.80% | 12.02% | 12.17% | 12.28% |
| 5 days | 10.28% | 10.85% | 11.30% | 11.65% | 11.91% | 12.09% | 12.22% |
| 6 days | 9.98% | 10.60% | 11.10% | 11.50% | 11.80% | 12.02% | 12.17% |
| 1 week | 9.71% | 10.37% | 10.92% | 11.36% | 11.69% | 11.94% | 12.12% |
| 2 weeks | 8.33% | 9.13% | 9.87% | 10.51% | 11.04% | 11.46% | 11.78% |
| 3 weeks | 7.45% | 8.29% | 9.10% | 9.85% | 10.50% | 11.04% | 11.47% |
| 1 month | 6.68% | 7.51% | 8.36% | 9.18% | 9.93% | 10.57% | 11.11% |
| 2 months | 5.14% | 5.90% | 6.73% | 7.60% | 8.49% | 9.33% | 10.10% |
| 3 months | 4.27% | 4.95% | 5.72% | 6.57% | 7.48% | 8.40% | 9.28% |
| 4 months | 3.79% | 4.42% | 5.13% | 5.93% | 6.81% | 7.74% | 8.67% |
| 5 months | 3.47% | 4.05% | 4.72% | 5.48% | 6.33% | 7.24% | 8.18% |
| 6 months | 3.23% | 3.78% | 4.41% | 5.13% | 5.95% | 6.84% | 7.78% |
The following shows the decomposition rates for 8.25% (weight % sodium hypochlorite) bleach below over time vs. temperature.
| TIME | 100ºF | 95ºF | 90ºF | 85ºF | 80ºF | 75ºF | 70ºF |
|---|---|---|---|---|---|---|---|
| Initial | 8.25% | 8.25% | 8.25% | 8.25% | 8.25% | 8.25% | 8.25% |
| 1 day | 8.10% | 8.15% | 8.18% | 8.20% | 8.22% | 8.23% | 8.24% |
| 2 days | 7.96% | 8.05% | 8.11% | 8.15% | 8.19% | 8.21% | 8.22% |
| 3 days | 7.83% | 7.95% | 8.04% | 8.11% | 8.15% | 8.18% | 8.21% |
| 4 days | 7.70% | 7.86% | 7.98% | 8.06% | 8.12% | 8.16% | 8.19% |
| 5 days | 7.58% | 7.77% | 7.91% | 8.02% | 8.09% | 8.14% | 8.18% |
| 6 days | 7.47% | 7.69% | 7.85% | 7.97% | 8.06% | 8.12% | 8.16% |
| 1 week | 7.36% | 7.61% | 7.79% | 7.93% | 8.03% | 8.10% | 8.15% |
| 2 weeks | 6.75 | 7.11% | 7.42% | 7.65% | 7.83% | 7.96% | 8.05% |
| 3 weeks | 6.28% | 6.72% | 7.10% | 7.41% | 7.65% | 7.83% | 7.96% |
| 1 month | 5.82% | 6.31% | 6.75% | 7.13% | 7.43% | 7.67% | 7.85% |
| 2 months | 4.77% | 5.32% | 5.86% | 6.37% | 6.82% | 7.20% | 7.50% |
| 3 months | 4.10% | 4.64% | 5.22% | 5.78% | 6.32% | 6.79% | 7.19% |
| 4 months | 3.70% | 4.22% | 4.79% | 5.37% | 5.94% | 6.46% | 6.92% |
| 5 months | 3.41% | 3.92% | 4.46% | 5.04% | 5.63% | 6.19% | 6.69% |
| 6 months | 3.20% | 3.68% | 4.21% | 4.78% | 5.37% | 5.95% | 6.48% |
Since day and night temperatures are not the same, one must use a special average that accounts for the non-linearity of degradation as a function of temperature. As derived in this post, the following table shows how you can take a known temperature difference between day and night and add an effective temperature adder to the nighttime temperature to get the effective temperature to look up in the above tables.
| TempDiff | EffAvgTempAdder |
|---|---|
| 5 | 2.7 |
| 10 | 5.8 |
| 15 | 9.4 |
| 20 | 13.2 |
| 25 | 17.3 |
| 30 | 21.7 |
| 35 | 26.2 |
| 40 | 30.9 |
In the Handbook of Chlorination by Geo. C. White, 1999 it states that sodium hypochlorite degradation is as follows:[4]
| Days | 12% | 10% |
|---|---|---|
| 10 | 11.5 | 9.7 |
| 20 | 11.0 | 9.0 |
| 30 | 9.7 | 8.7 |
| 40 | 8.8 | 8.5 |
| 60 | 6.2 | 8.0 |
| 90 | 4.7 | 7.2 |
It looks like the 10% is more stable for a longer time at 77 degrees.
What is the freezing point of Bleach?
Household bleach is commonly sold with 6% chlorine and will freeze at roughly 19° Fahrenheit. For 12% Liquid Chlorine commonly sold at Pool Stores, the freezing temperature will be approximately 27° Fahrenheit.[5]
How To Test the Actual Chlorine %?
Taylor sells the K-1579 test kit for measuring bleach concentrations in % value. It's marketed to the industrial cleaning industry to test the effectiveness of bleach stored in large-volume tanks. A pool owner could use it just as easily, but since one would use it very infrequently, it may not be worth the cost.
- ↑ https://www.troublefreepool.com/threads/breakdown-of-bleach-over-time-by-storage-temperature.60837/#post-511942
- ↑ https://www.odysseymanufacturing.com/ultrachlor-bleach Odyssey Manufacturing
- ↑ https://www.troublefreepool.com/threads/breakdown-of-bleach-over-time-by-storage-temperature.60837/page-2#post-725315
- ↑ https://www.troublefreepool.com/threads/breakdown-of-bleach-over-time-by-storage-temperature.60837/#post-538058
- ↑ https://www.troublefreepool.com/threads/bleach-freezing-point-consequences.3429/#post-28177
