You will have to download the pdf of the section you are looking at because you will need to identify the section and page number that you are referring too. What you see on the webpage does not provide that information. Because it is in pdf, you are now technically looking at the print edition. You would site it like this:
Example:
CRC Handbook of Chemistry and Physics, 84th Ed.; Lide, D.R., Ed.; CRC Press: Boca
Raton, FL, 2003; Section 3, p 476.
Do not click the "how to cite" button. This is showing you how to cite the entire section, not the page containing the element you are looking for.