ELISHA MITCHELL SCIENTIFIC SOCIETY. 25 



is supposed to give to the pale Rosins their transparency and lack 

 of color. But in distilling ''yellow dip" and "scrape" no "spir- 

 its" is left in the Rosin. The effort to expel the spirits com- 

 pletely may cause too high a heat in the still, with consequent 

 darkening of the Rosin. 



Again, as "yellow dip" and scrape are exposed to the air 

 longer than virgin dip, having to traverse oftentimes several feet 

 of " face," oxidation products may arise, and influence the final 

 color of the Rosin. 



Again, there is always much more foreign matter mixed with 

 yellow dip and scrape than with virgin, and the heat of 160° C. 

 for an hour or two, in the presence of water, would doubtless 

 extract from these pine leaves, bark and chips more or less of 

 their coloring matter, which might well aifect the color of the 

 Rosin. The New York Standard Rosins are divided into 12 

 grades, viz., from the highest to the lowest: 



W— G— Low No. 1 . 



N— Extra pale. F— Good No. 2. 



M— Pale. E—No. 2. 



K — Low pale. D — Good strained. 



I — Good No. 1. C — Strained. 



H — No. 1. B — Common strained. 



These grades are used at Wilmington, Charleston and Savan- 

 nah. But at Wilmington the arrangen^ent, while essentially the 

 same, has some minor points of difference. 



Considerable experience is required before one can grade 

 Rosin, and very few can do it without having the standards at 

 hand, so as to compare constantly. After some time these 

 "standards" acquire a lighter color, due to exposure to light, 

 and this fact complicates the matter still farther. The higher 

 grades of Rosin are worth from two to three times as much as 

 the lower grades, and of course much interest has for years been 

 manifested in the question of the possibility of bleaching the 

 lower Rosins. Exposure to strong sunlight does raise the grade 

 a degree or so in the course of several months, but this is not 

 continuous. The main difficidty, I apprehend, is in our igno- 



