A useful one of these substances can be produced in the wet or contact processes, and another of these substances is the namesake of a biological cycle sometimes named for Krebs.
One of these substances is separated from water and oxygen after being heated in a "roaster" as part of a regeneration process used in steel pickling. Another type of these can be produced commercially from Aspergillus niger and sucrose. High temperatures and pressures create one of these in the Monsanto Process, although more recently the Cativa Process is used. A tosic one of these substances can be reacted with an alcohol to create an ester in a variation of the Fischer esterification. A useful one of these substances can be produced in the wet or contact processes, and another of these substances is the namesake of a biological cycle sometimes named for Krebs. For 10 points, name this class of chemical compounds whose solutions have pH of less than 7.
One of these substances is separated from water and oxygen after being heated in a "roaster" as part of a regeneration process used in steel pickling.
{acid} [{go ahead} and accept a buzz on any {specific acid} mentioned before end of first sentence]