VOL. 8. No. 5
DETECTION OF T I N GROUP METALS
951
(2) Nourrs. A. A,, "Qualitative Chemical Analysis," 9th ed., The Macmillan Co., New York City, 1926, p. 72. (3) CURTMAN, "Method of Analysis for the Metals of Group 2B." Copyright manuscript, 1925. ( 4 ) BASKERVILLEAN D CURTMAN. "Qualitative Analysis," 2nd ed., The Macmillan Co.. New York City, 1926, p. GG.
Something New in Varnishes. The varnish industry is in a period of radical readjustment. Methods and products which have stood the test of centuries are giving way before the synthetic creations of the laboratories. Although the art of the varnish maker is an ancient one, the basic raw materials a t his disposal have, until recently. been confined t o the gums and resins which occur in nature. The first major departure from traditional practice, and one which profoundly affected the industry as a whole, resulted from the development d low-viscosity nitrocellulose lacquers, the use of which expanded with extraordinary rapidity. Now the industry must adjust itself to the situation created by the advent of several types of new synthetic resins. One of the most interesting and important of these is a synthetic phenol resin which should not be confused with the other and older phenol resins used primarily in molding compounds and which are heat reactive, that is, which react on heating to become infusible and insoluble. The new material is called by its makers "oil reactive" resin to distinguish it from other synthetic "oil-soluble" resins and from natural gums and ester gums. Ordinary phenol resins are not soluble in the drying oils unless other materials such as rosin are added to promote solubility. The new "oil reactive" resin is easily soluble in Chinawood oil in any desired proportion. But of greater technical interest is the daim that there is a chcmical reaction between the resin and the oil which may account for the accelerated hardeninx of the resin-oil mixture. This resin is, therefore, very different from theordinary naturalvarnish gums, and, as might heexpected, the quality of the coatinxs obtained with this new resin in oil is superior to the tung-oil-gum varnishes hitherto available. Flexibility, rapidity of drying, durability, toughness, resistance to moisture, and alkalies, all of which are fundamental and desirable requisites of a varnish, are reported greatly improved by the use of the "oil reactive" resin. Because of the accelerated drying effect on the oil, only a fraction of the usual amount of metallic drier is required with the result that the usual tendency of a varnish t o continue t o oxidize destructively is greatly reduced. The "oil reactive" resin may be used alone or mixed with other varnish gums. The addition of only 10% of the oil reactive resin to a n ester gum varnish reduces the drying time from over seven hours to about three. Another synthetic coating has for its basis the synthetic resin known commercially as Glyptal, which, rather curiously, is derived from glycerin and phthalic anhydride. The physical propertics of resins of this type may vary widely from hard, brittle resins to extremely flexible resins, depending a n their composition. Coatings containing this resin are particularly useful for covering surfaces that are ordinarily difficult to coat, such as galvanized iron and aluminum. The Glyptal varnish films are extraordinarily tough and adhesive. This adhesiveness, together with ability to withstand high temperatures, makes them ideal for use on furnace stacks, electric furnace parts, engines, and boilers. These varnishes are also excellent as a seal against water, gas, and oil leaks and find extensive application as lacquer primers.-Ind. B d l . of Artlrur D. Little.Inc.
