10 BULLETIN 229, U. S. DEPARTMENT OF AGRICULTURE. 



Products of the distillation of rosin. — When rosin is heated at tem- 

 peratures above its melting point it decomposes 1 into gases and oils. 



The lightest of these oils, rosin spirit or pinoline, is used as an 

 illuminant, and also as a solvent, especially as a substitute for turpen- 

 tine. The heavier rosin oils are used in the manufacture of printing 

 inks and lubricants. Wagon grease is often made by boding rosin 

 oil with lime. 



The distillation of rosin is earned out on a large scale in Germany 

 and France, the darker grades of rosin imported from America being 

 used for this purpose. Comparatively little is distilled in the United 

 States. 



Lampblack. — Rosin oil can be used for the manufacture of lamp- 

 black which, from the standpoint of color and minuteness of division, 

 is of the highest quality. The finest grades are used in the manu- 

 facture of india ink, in lithography, and in artistic printing with 

 copper plates. 



FORMATION AND FLOW OF RESIN IN THE LIVING TREE. 



Resin suitable for the production of naval stores is found only in 

 in coniferous trees. Moreover, only pines yield resin abundantly, 

 and of these only two species, longleaf pine (Pinus palustris) and, to 

 a small extent, slash pine 2 (Pinus heterophylla) are tapped in the 

 United States. 



No universally accepted theory dealing with the formation of resin 

 has as yet been, advanced. It is generally conceded, however, that 

 resin is formed as a by-product during the transformation of food 

 materials, such as starch, into woody tissue. The resin is stored in 

 two systems of elongated passages or resin ducts. In one system the 

 ducts are parallel to the pith of the tree; in the other they lie hori- 

 zontally in radial planes. The ducts form in the growing tissue or 

 cambium layer just beneath the bark, the two systems intersecting to 

 form a continuous network of resin passages. 



When the cambium layer is cut the growth of tissue near the wound 

 is stimulated, and the number of resin ducts, and consequently the 

 amount of resin formed, is considerably increased. The area in which 

 additional or secondary resin ducts are formed apparently extends 

 from 2 to 3 inches above and to a lesser distance below the wound. 



1 The products resulting from distillation and their percentages are as follows: 



Losses (rosin adhering to walls of still) per cent.. 1.0 Light oil (turbulent) per cent.. 5.0 



Gases evolved do 9. Light oil, hearts do 58. 



Acid water do 3.5 Blue oil and red oil do 16. 



Rosin spirit or pinoline do 3.5 Residue, coke do — 4.0 



2 Slash pine is of comparatively infrequent occurrence, but is tapped wherever found on areas being 

 turpentined. 



