Salicylaldehyde be prepared from the corresponding phenol by the Duff reaction, or by treatment with paraformaldehyde in the presence of magnesium chloride and a base. Salicylaldehyde was identified as a characteristic aroma component of buckwheat. It is also one of the components of castoreum, the exudate from the castor sacs of the mature North American beaver ("Castor canadensis") and the European beaver ("Castor fiber"), used in perfumery. Furthermore, salicylaldehyde occurs in the larval defensive secretions of several leaf beetle species that belong the subtribe Chrysomelina. An example for a leaf beetle species that produces salicylaldehyde is the red poplar leaf beetle
Pith and substance Pith and substance Pith and substance is a legal doctrine in Canadian constitutional interpretation used to determine under which head of power a given piece of legislation falls. The doctrine is primarily used when a law is challenged on the basis that one level of government (be it provincial or federal) has encroached upon the exclusive jurisdiction of another level of government. The Constitution Act, 1867, which established a federal constitution for Canada, enumerated in Sections 91 and 92 the topics on which the Dominion and the Provinces could respectively legislate. Notwithstanding that the lists were framed so as to