Determination of PTA acid value
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According to the national standard for determining acid value, a 0.5 mol/L NaOH solution is used as the standard solution, and the error is quite large. Later, it was diluted to a 0.1 mol/L NaOH solution; dimethyl sulfoxide is used as the solvent, and a burette is employed for measurement. The error remains significant, with values around 675 occasionally being obtained. It’s really difficult. Is there anyone who can help me?
I spend every day working on this using a burette; would calibrating the burette help?
Please help, I really can’t solve this anymore. Reaching such a tight range of 675±2 is simply too difficult
This post was last edited by qugd on 2018-2-11 at 10:13. In terms of the principles of volumetric analysis and the instruments used, its accuracy and repeatability are unmatched by other analytical methods. However, volumetric analysis requires a high level of skill and experience from the operator, and it is also important to pay attention to certain key points. In volumetric analysis, it is indeed difficult to maintain a precision of around 0.3%. Could the sample volume be increased slightly, so that more standard solution is used as well? This would help ensure better precision (with a lower relative deviation). What is the accuracy of the burette? What is the accuracy of sample weighing? What is the degree of dryness of the sample? What is the accuracy and validity of the standard solution? Is the solvent blank still meeting the requirements? These are all factors that affect accurate analysis.
Are there any reverse titration methods that can be used as a reference?