There is no endpoint in the silver nitrate titration method for determining chlorine content

This method has been in use for at least fifty years; only when you start using it do you realize the error – isn’t that a bit too late to discover it? There is likely an issue with your experiment or procedure, or there is a problem with your samples or reagents. If there are factors in the sample that affect the observation of the endpoint, potentiometry can be used to indicate the endpoint; this eliminates influencing factors such as the color and turbidity of the sample.

I leave it blank; there is no end point. Using potassium chromate as a blank is acceptable. Silver nitrate: 0.02820 mol/L; starch: 10 g/L. For the blank, use 100 ml of distilled water with 10 ml of starch added. No response when dropped? Where did I go wrong? ? ? I’ve read your replies to many friends’ posts, and I know that you’re an expert in analytical chemistry. Therefore, I would like to ask for your advice.

Since I’ve never used this method before and don’t have a potentiometer on hand, and since this indicator doesn’t require high precision, I plan to try the fluorescein indicator method. Upon checking online, it turns out that “dichlorofluorescein” is a silver nitrate indicator; hence I wondered whether there was an error in some national standard that failed to clarify this point. According to you, the standard is correct.

This post was last edited by qugd on 2018-7-17 at 09:09. For how many years has the Fayang method been used for the determination of chloride ions? If there were any errors in the standards, you wouldn’t have only just noticed them today. In an experimental method, there are many factors that can lead to abnormalities, both subjective and objective. Failing to look for reasons in one’s own experimental procedure steps and instead making a subjective judgment that the standard method is wrong is not a scientific attitude at all. Also, don’t rely on the internet for everything. If your organization doesn’t even have a reference room, you can go to the local library to find the full text of standard methods as well as related professional books. Much of what is available online is copied from various sources by liberal arts students, which increases the likelihood of errors.

There must be some interfering factors if that method is used directly for estimation; try the indirect titration method with potassium thiocyanate.

This post was last edited by sdwfsgyykai on 2018-8-15 at 17:30. Could it be a problem with the materials? People have used WuXi AppTec’s products, so it’s recommended to give them a try.

It is recommended to first prepare a solution using analytically pure reagents, and use standard analytical methods to determine whether correct analysis results can be obtained; if so, then proceed with the analysis using the actual product. I once developed an analysis method for sodium chloride in mixtures containing sodium thiocyanate, sodium thiosulfate, sodium sulfate, sodium carbonate, sodium bicarbonate, and sodium chloride; I tested each ingredient individually. The analysis showed that pure sodium thiocyanate contained 0.35% chloride ions, and at first I thought the analysis method was incorrect.

It is recommended to use a potassium dichromate indicator at a concentration of 50 g/L. The endpoint is reached when the color takes on a slight bluish tint; after adding one more drop, the color turns yellow like that of a ripe egg. If one or two more drops are added, the color becomes slightly red, indicating that too much has been added. The color change at this point is quite pleasing to look at