Before you can determine the reliability of any test you must also confirm the accuracy of the analytical device being used and it's optimal application.
In this instance your using a DIGITAL THERMOMETER specifically designed for biologic temps. And the difference is significant since those thermometers ARE NOT designed to measure chemical temps.
Note the clear difference in HOW a sample temp is processed and measured when a device designed for that purpose is utilized.
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A more simplified MP device
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A more complicated, accurate and expensive MP device
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Your pic readily depicts the first problem, which is the glass receptacle being used must be heated first and BEFORE the test compound even begins to melt. This will falsely elevate the MP of any sample, bc both the glass receptacle and sample must be heated!
For these reasons IF you are going to use a MP BUY THE CORRECT device to obtain reproducible information.
Also notice the NORMAL variance of roughly THREE DEGREES for T-e according to USP standards (Under the physical and chemical properties caption)
Orginaly posted in the wrong forum and I think went from there. Live and learn. And some patience on the senior members.