The vial may look empty, but it isn't. ULTRA sells its neat
standards in very small quantities, usually 100 milligrams or less. Thus, the
volume of the standard may be very small compared to the volume of the vial.
For example, 5 milligrams of a liquid PCB occupies about 4.2 microliters of
volume, making it very difficult to see in a 4 milliliter vial. Look for a tiny
drop lodged in the corner of the vial.
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