Probably the earliest record of research leading to the development of the alkyds was that of van Bemmelen, who reported in a German technical journal in 1856 the sirupy products obtained by heating together succinic acid and glycerin or citric acid and glycerin. The first investigation of the phthalic anhydride-glycerin resins was recorded in 1901.[3] Watson Smith, while engaged in research on phthalein dyes, obtained a transparent, highly refractive resinlike substance when glycerin and phthalic anhydride were heated together. Smith recommended the product as a cement for ceramic wares. During the period 1910-16 the research laboratories of the General Electric Co., engaged in research on a synthetic resin from glycerin and phthalic anhydride. As a result of these studies numerous patents were granted for this type of resin to which the trade name Glyptal was applied. Intensive research was carried on by several firms, many variations were developed, and literally hundreds of patents were granted. The paint and varnish industry has been undergoing radical readjustment. Methods and natural products, which for decades or centuries had changed very little, are giving way to synthetic creations of our laboratories. The first important departure from the traditional practices was the development of nitrocellulose lacquers. The commercial application of the alkyd resins followed, and their use is increasing rapidly. Because this development is still comparatively young, the large number of modifications offered has confused the coating manufacturer. It is probable that many of the synthetic products now being marketed have no special technical or economic justification and that they will in time lose out in competition with better products known at present, or still to be developed. United States Patent No. 1,893,873, dated January 10, 1933, granted to R. H. Kienle and assigned to the General Electric Co., was considered one of the basic patents in this field. Early in 1936 it was declared invalid in a suit claiming infringement brought against the Paramet Chemical Co. of Brooklyn, N. Y. The decision in this case seems to have opened the glycerin-phthalic anhydride resins to a large number of manufacturers. Among the principal brands of alkyd resins now on the domestic market are Beckosol, Dulux, Esterol, Glyptal, Rezyl, and Teglac. Each of these trade names identifies a series of products. Classification of alkyd resins. A number of classifications of the alkyd resins are possible and practical. Since by far the most important applications are in surface coatings, and their use in molding compositions is relatively unimportant, it seems advisable at this time to emphasize the more important use. For the purpose of this survey the following classification is used: