2 From table [51] (refined).
3 From table [54] (grade not specified, but chiefly refined).
4 Production plus imports minus exports.
5 Not available.
6 Preliminary.
Up to 1924 (except 1920) imports consisted principally of crude glycerin, much of which was refined in the United States and included in United States production; thereafter imports of refined glycerin became important relative to the crude. Exports are insignificant compared to either production or imports.
17. RAW MATERIALS FOR TAR-ACID RESINS
The first tar-acid resins were made from phenol and formaldehyde. As a result this group of resins is frequently spoken of as phenolic resins. This is true despite the fact that coal-tar acids other than phenol, particularly the cresols and xylenols, are used in large volume today.