March 24, 2006 -- A torn ACL in the knee can be replaced -- but it can't be healed.A new technique now shows promise to change this. Doctors long ago gave up trying to repair a torn ACL (anterior cruciate ligament).arch 24, 2006 -- A torn ACL in the knee can be replaced -- but it can't be healed.
In chemistry, pH (/piËËeÉªtÊ/) is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the logarithm to base 10 of the molar concentration, measured in units of moles per liter, of hydrogen ions.
The pH scale was developed to measure how acidic or basic a substance is. This scale measures pH from 0-14. Acids have pH values between 0 and 7 and bases have pH values between 7 and 14. Pure water is neutral and has a pH of exactly 7. Indicators are used to measure the pH of a substance. Often times, plant extracts will change color if exposed to acidic or basic conditions and can therefore be used to indicate if a substance is an acid or a base. Todayâs experiment focuses on the use of litmus paper, a most basic pH paper dating back many years.