Perchlorination issue in sodium hypochlorite solutions
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Currently, company customers have reported that the sodium hypochlorite solution delivered is white in color, and they brought it back to the company on the same day for return. We took samples for inspection and found that the color indeed had turned white, the temperature was above 50°C; the test results showed that the effective chlorine content was less than 1%, no free alkali was detected, and the pH of the solution was neutral. Subsequent analysis suggested that there are two possible explanations: 1. The tank truck transported acidic substances before carrying the sodium hypochlorite solution, resulting in a neutralization reaction. 2. Excessive chlorine was introduced into the sodium hypochlorite solution during the production process. But considering the actual circumstances, it seems impossible. Experts, please share your opinions – how can we strengthen the supervision of liquid products at the time of production?
A typical sodium hypochlorite solution is a light yellow, transparent liquid; it is a strong oxidizing agent that remains stable in alkaline conditions. It must be kept sealed during transportation, and the shipping container must be corrosion-resistant. As you said, the temperature during testing is above 50°C, no free alkali is detected, and the pH of the solution is neutral; it seems that a reaction has taken place with an acidic substance.
There’s no one with the knowledge to answer this technical question; fortunately, a moderator is here to deal with it. However, the answer seems not specific enough. I’m waiting for an expert to provide a solution!
This is also the first time we have encountered such a problem: there were 22 tons of sodium in this batch, and the test results for that day showed a free chlorine content of 12.5% and a free alkali content of 0.5%； The customer responded positively to the shipment of 8.8 tons sent in the morning, and the same reaction was observed from the two shipments sent in the afternoon. When we first received feedback, we checked the shipping process and inspected the sample kept for reference, and everything seemed fine. Therefore, upon seeing that the sodium hypochlorite solution was returned by the customer, we suspected there might be an issue with their delivery vehicle. However, soon after we received feedback from the second customer as well; we went to their factory to inspect things and take samples, and the test results were identical. We also tested the sodium chloride content, which was 251.8 g/L. Since problems occurred simultaneously when shipping to both customers, it should be possible to rule out issues with the customers themselves. So I’m really stuck now; we have to prepare a quality incident report! I would like to ask everyone whether it is possible that, when the product is shipped and it is near saturation – that is, when there is very little free alkali left – chlorine gas might escape during transportation (in sealed tank trucks) and react with the alkaline solution to form perchlorine. This could alter the alkalinity of the solution, thereby leading to such quality issues.
Reply to 4# solidy66: Well, it’s very likely! Let’s analyze and investigate each aspect carefully; no one dies from nothing.
The factory inspection showed no issues, yet the customer is complaining about product quality problems; there must be some problem in the process. As mentioned on floor 5, nothing serious will happen without a cause, so there is definitely an issue with the process. It is recommended to start by examining the samples and then check the conditions in the shipping workshop. . .
So what’s the conclusion? I encountered it too