30:32 · A sign (corresponding to the Hebraic letter koph) used in Cabbalistic mysticism. was also used in eighteenth-century chemistry as a sign for phlogiston.
    The phlogiston theory flowered between 1650 and 1850. Phlogiston was considered to be a substance that existed in different proportions in other substances, a kind of fixed fire showing up and disappearing when a substance burned. Phlogiston was thought to be the element of fire in its pure dormant form (note that is the alchemical sign for fire). Coal was believed to contain a large quantity of phlogiston because of the great amount of heat it produced while burning. All metals were thought to contain phlogiston as well as something that is now called metal oxides. A whole theory was developed that corresponds closely to the modern understanding of the combustion process. It succeeded in explaining the principles of this process almost as well as the modern theory. It was, however, more complicated because it presupposed the existence of phlogiston.
    In eighteenth century chemistry phlogiston could also be drawn .
    In the same time and system was also used for resina, or resin. Compare with .
    See also the similar signs and in Group 24.