THE NAVAL STOEES INDUSTRY. 9 



ROSIN. 



Rosin is employed extensively in the manufacture of soap, paper, 

 oilcloth, linoleum, sealing wax, fly paper, printing inks, roofing mate- 

 rials, brewer's pitch, electric wiring, lubricating compounds, medicinal 

 preparations, etc. 



Rosin soap. — Rosin has the property of combining with alkalies, 

 such as caustic soda and potash, to form " soaps" which are readily 

 soluble in water. Their color is yellowish or yellowish-brown, depend- 

 ing on the color of the rosin used. At ordinary temperatures rosin 

 soaps have the consistency of butter, and on account of their relative 

 cheapness, are usually added to the hard soaps made from tallow. 

 In themselves, however, rosin soaps possess valuable properties, and 

 their addition to tallow or other hard soaps can not always be consid- 

 ered an adulteration. 



Resin driers. — The metallic salts of the resin acids are known as 

 driers. They are made by adding a solution of the salt of a metal 

 such as manganese to a solution of "rosin soap" when the insoluble 

 manganese resinate precipitates; or the rosin is fused with the 

 metallic oxide. These metallic resinates, known as "Japan driers," 

 cause the oxidation or "drying" of oil paints and varnishes and are 

 extensively used for this purpose. The lead and manganese resin- 

 ates are used most frequently. 



The various enamels used in ceramics consist of resinates of the 

 various heavy metals. The resinates are dissolved in turpentine and 

 the resulting solution painted on the earthenware, after which the 

 vessels are "fired." 



Rosin size. — One of the most important uses of rosin is as a "size" 

 or coating for writing or printing papers, which must take ink. A 

 rosin soap, containing about 3 pounds of rosin to 1 of soda, is added 

 to the pulp in the hollander, and after that a solution of alum. The 

 latter decomposes the rosin soap, and the result is a precipitate of 

 free rosin and some alumina which becomes entangled in the fibers 

 of the paper. When the paper is passed over hot calendar rolls in 

 finishing, the rosin fuses to a smooth, varnish-like layer on the 

 surface. 



Brewers' pitch. — Barrels intended to hold beer or other fermented 

 beverages are coated with brewers' pitch, which renders the barrels 

 easy to clean and improves the taste of the beer. The pitch is made 

 of pure rosin, with the addition of a certain amount of turpentine or 

 refined rosin oil to prevent brittleness. Some manufacturers make 

 the pitch supple by adding rosin soap. 

 88767°— Bull. 229—15 2 



