10 OLEOKESINS OF SOME WESTERN PINES. 



pletely removed by extraction with chloroform in a Soxhlet appa- 

 ratus. The weight of trash obtained, subtracted from the combined 

 weight of trash and rosin after drying, gave the weight of the rosin. 

 The percentage of water originally in the oleoresin was obtained by 

 difference. 1 



VOLATILE OIL. 



The oil for examination was secured by distillation with steam. 

 About 500 grams of this oil were fractionally distilled, using a 12-inch 

 Hempel column, and the specific gravity and refractive index of the 

 fractions were determined with the Westphal balance and Abbe 

 refractometer. The detailed method of fractionation is given in 

 Bulletin 105 2 of the Forest Service. 



The methods employed in the chemical examination of the volatile 

 oils will be discussed in connection with the determination of their 

 various constituents. 



ROSIN. 



The grade of the rosin was determined by comparison with the 

 standard rosin cubes used in the naval stores trade. 



The specific gravity was determined by means of a salt solution 

 of such density that a fragment of the rosin, free from cracks and 

 bubbles, remained suspended in it, neither rising nor sinking. The* 

 solution was maintained at a temperature of 15 C. and its specific 

 gravity determined with a hydrometer. The specific gravity of the 

 rosin was considered equal to that of the salt solution. 



The acid number was obtained by dissolving from 1 to 1.5- grams 

 of rosin in 95 per cent alcohol and titrating the solution directly in 

 the cold, with a N/2 alcoholic potassium hydroxide solution using 

 phenol-pthalein as the indicator. The number of milligrams of 

 potassium hydroxide required to neutralize 1 gram of the rosin repre- 

 sents the acid number. 



The saponification number was determined by treating from 1 to 

 1.5 grams of powdered rosin with 25 cubic centimeters of N/2 alcoholic 

 potassium hydroxide solution. After heating the solution for one- 

 half hour on a steam bath, and then cooling, the excess potassium 

 hydroxide was determined by titration with a N/2 sulphuric acid 

 solution using phenol-pthalein as the indicator. The saponification 

 number represents the number 'of milligrams of potassium hydroxide 

 neutralized by 1 gram of rosin. 



Rosin does not contain esters but contains a small proportion of 

 bodies having the nature of lactones. The measure of the latter 



1 The water may be conveniently determined directly as follows: 100 c. c. of dry redistilled turpentine are 

 added to a given weight of oleoresin (approximately 100 grams) and 100 c. c. of turpentine distilled over 

 by direct heat. The distillate containing all the water is collected in a graduated funnel. On standing a 

 short time the distillate separates into two layers and the amount of water is read off. 



2 "Wood turpentines, their analysis, refining, and composition," by L. F. Hawley. 



