242 REPORT—1840. 
All the fixed oils may, in fact, be viewed as organic salts or com- 
binations of the oily acids, with a compound base generally 
** glycerine”’ (C,, H,, O,,), or vegetable mucilage. Most of the 
oil of turpentine found in commerce also contains more or less 
pinic and silvic acids*. Now all these acids readily quit their 
weakly positive organic bases, to form salts with the more 
powerfully basic oxides of the metals, with which they are 
used commonly in the formation of paints, as white lead, 
ochres, &c. &c.; in this combination, however, the original 
organic bases are left free to form new combinations, under the 
joint action of air and moisture, and of the metal on which 
they may be spread. The resultant action of all which is, that 
the paint, in workmen’s language, gets ‘killed’; that is, be- 
comes either more or less soluble in water, or pulverulent and 
removable by it; and in place of preserving an oxidable metal, 
promotes its corrosion. Pinic and silvic acids act powerfully 
as such, upon many bases; the former decomposes the car- 
bonate, acetate, and most of the organic acid salts of copper, 
several of the earthy acetates, and the alkaline carbonates with 
effervescence when fused with them. Yet it is remarkable, 
that upon the peroxide of copper, and several other peroxides, 
it has scarcely any action. The electro-negative relations of 
commercial turpentine, then, may be neutralized, if desirable, 
in composing a paint; but this is in every case attended with a 
diminution of its power to resist the action of water. Priestley 
first ascertained that volatile oils, such as turpentine, absorb 
oxygen or atmospheric air, and combine with them in part. 
In this they closely resemble the fat oils, and the result is 
analogous in both; they finish by conversion into resins. 
Hatchett’s experiments, and also the saponification by potass 
of oil of turpentine, indicate that the volatile oils do not unite 
directly with nietallic oxides, but receive oxygen from them, 
become acid resins, and thus form resinous salts. Thus, if oil 
of turpentine be heated with peroxide of lead, water is given 
off. The oil becomes dark brown, viscid, and at length solid ; 
the result is a compound of resin and oxide of lead; common 
resin, as Blanchet and Sellt have shown, is oil of turpentine, 
with an atom of oxygen combined = C,, H, O. Hence we 
may conclude that oil of turpentine plays no chemical part in 
the constitution of paints, but in so far as it has suffered these 
changes; in doing so its density is increased and its volume 
consequently diminished, and hence every oil-paint is full of 
microscopic pores, however carefully: laid on, as may be proved 
* Unverdorben, Poggendorff’s Annalen, vii. to xxi. 
Tt Poggendorff’s Annalen, xxix, 133. 
