618. CONIFERS. 



The surveyor of the forests of this district, which is one of the richest 

 in Plnus Abies, has informed one of us that from 790 to 850 quintals 

 are collected and exported to Basle, Zurich, Aarau and Vaud. The 

 pitch is worth in loco (1868) 100 to 110 francs (£4 to £4 8s.) the hosse 

 of 6 quintals. The quantities collected in other parts of Switzerland 

 are even less considerable. 



Description — Pure Burgundy pitch, of which we have numerous 

 authentic specimens, is a rather opaque, yellowish-brown substance, 

 hard and brittle when cold, yet gradually taking the form of the vessel 

 in which it is kept. It is strongly adhesive, breaks with a clear con- 

 choidal fracture, and has a very agreeable, aromatic odour, especially 

 when heated. It does not exhibit a crystalline structure, although, as 

 we have frequently observed, the resin on the stem of the tree is dis- 

 tinctly crystalline. 



Burgundy pitch is readily soluble in glacial acetic acid, acetone 



_T 1_-J-- -T-^1__l 1 •__ . 1 _ _ 1_ _ 1 _ P hr-' L / „— A.O/7A\ *rr^H 



) 



7 



its solubility in these liquids is considerably altered by the presence oi 

 water or essential oil; and still more by the formation of abietic acid in 

 the resin itself. The same influences also affect the melting point. 



The crude resin of Pinus Abies, '^ deprived of essential oil and dis- 

 solved in one part of absolute alcohol, was found to deviate a ray of 

 polarized light 3° to the left, in a column of 50 mm.; the essential oil 

 deviated 8-5° to the same direction. The oil contains a small amount of 

 an oxygenated oil. After treatment with sodium the oil which remains 

 does not form a solid compound if saturated with hydrochloric acid. 



Chemical Composition— The investigations of Maly mentioned 

 at p. 607 afford a satisfactory elucidation of the chemical properties of 

 the pinic resinous exudations. They all, according to that chemist, are 

 mixtures of the same amorphous resin, C"H'''0^ with essential oils of 

 the composition C'"ff ". These terebinthinous juices are collected and 

 sold either in their natural state as turpentine, or deprived more or less 

 completely of their volatile oil, in which condition they are represented 

 by Burgundy Fitch, and finally by rosin or colophony. 



The turpentines flowing down the stems of the trees gradually lose 

 their transparency if allowed to dry slowly in the air, becoming at the 

 same time harder and somewhat granular. This alteration is due to 

 the incorporation of water, which at last is not only mixed with the 

 components of the resinous juice, but to some extent combines chemi- 

 cally with the resin so as to transform it into a crystalline body having 

 the characters of an acid. The fact is easily observed if clear drops oi 

 the turpentine of Pinus silvestris, P. Abies or P. Pieea are collected in 

 vials and kept perfectly dry. Thus treated these turpentines^ remain 

 transparent, but the addition of water causes after a short time tnt. 

 formation of microscopic crystals of abietic acid, rendering them mor 

 or less opaque. _ , ^ 



If turpentines are collected before they lose their essential oi by 

 evaporation and oxidation, and before they have become crystaliin ' 

 they can be retained perfectly transparent by distilling off the volatu 

 oil without water. The distillation beimx most commonly carriea 

 ivitk water, the remaining resin is opaque 



i=) 



1 Collected by myself.— F. A. F. 



