would you find it unreasonable if I told you that a jar of peanut butter costs $761 a jar and doesn't have a hard sell? But in fact, there is such peanut butter, it looks like this:

this thing is called "standard reference material". Although it is peanut butter, it is not used for food, and it is used for analytical experiments. The standard reference material in the picture is from the National Institute of Standards and Technology of the United States, and its various components have been carefully analyzed. When experimenters need to analyze their own similar samples, these reference materials can be used to calibrate their analytical instruments such as chromatograph.

in fact, in order to meet the needs of various aspects of research and analytical tests, there are many kinds of reference materials like this. For example, in terms of food samples, there are many kinds of chocolate, canned meat, coconut oil, and so on:

the following is a "standard" green tea, $542:

this is a "standard" sample of vitamin supplements:

other samples are more special. For example, human urine samples containing specific substances (freeze-dried), such standards will be very practical in urine testing. In the experiment, quantification, standardization and repeatability are all very important. And these various standards provide a guarantee for the accuracy of measurement.

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Corrigendum: the structural formula of polypropylene is shown in the comparison picture of plastic dissolution the day before yesterday, which is written in the paper. Forgot to change... _ (: arms "∠) _

I really don't have much time these days. I'm sorry to write in a hurry. _ (: sorry" ∠) _

PS: the title of this week's most popular article belongs to the article "Why armpits smell cumin". If you haven't read it, you can reply to the keyword [armpit] to enjoy this sour smell knowledge.

Corrigendum: the structural formula of polypropylene is shown in the comparison picture of plastic dissolution the day before yesterday, which is written in the paper. Forgot to change... _ (: arms "∠) _

I really don't have much time these days. I'm sorry to write in a hurry. _ (: sorry" ∠) _

PS: the title of this week's most popular article belongs to the article "Why armpits smell cumin". If you haven't read it, you can reply to the keyword [armpit] to enjoy this sour smell knowledge.