Potassium bicarbonate dry chemical fire extinguishers, as the principal component of the Purple-K dry chemical, and in some applications of condensed aerosol fire suppression. It is the only dry chemical fire suppression agent recognized by the U.S. National Fire Protection Association for firefighting at airport crash rescue sites. It is about twice as effective in fire suppression as sodium bicarbonate. Potassium bicarbonate is an effective fungicide against powdery mildew and apple scab, allowed for use in organic farming. Potassium bicarbonate has widespread use in crops, especially for neutralizing acidic soil. The word "saleratus", from Latin "sal æratus" meaning "aerated salt", was widely
Period 4 element Period 4 element A period 4 element is one of the chemical elements in the fourth row (or "period") of the periodic table of the elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The fourth period contains 18 elements, beginning with potassium and ending with krypton. As a rule, period 4 elements fill their 4s shells first, then their