Bulletin Board Ideas by Theme. Our Bulletin Board Ideas by Theme pages provide you with resources to help display your students' learning while keeping your classroom walls looking great all year long. Within each theme you will find fun and educational resources that are specific to the various topics covered within that theme. Several of the bulletin boards even include photos.
Background for the Kjeldahl determination of Organic Nitrogen. The Kjeldahl method is an analytical method for the determination of nitrogen in the trinegative state in certain organic compounds. The method was developed in 1883 by Johan Kjeldahl, a Danish chemist, and is used extensively in the determination of protein in foods, since protein is a macromolecule made up of nitrogen containing amino acids linked together.
Hygrometer, instrument used in meteorological science to measure the humidity, or amount of water vapour in the air. Several major types of hygrometers are used to measure humidity. 1  Mechanical hygrometers make use of the principle that organic substances (particularly finer substances such as goldbeaterâs skin [ox gut] and human hair) contract and expand in response to the humidity. Contraction and expansion of the hair element in a mechanical hygrometer causes the spring to move the needle on the dial.