244 REPORT—1840. 
with it, as the drying oils do. This substance can be obtained 
in any quantity cheaply ; all the resins possess the property of 
gradually combining with water when long immersed in it, and 
forming a porous compound, analogous in all respects to the 
substance thrown down by water from a solution of resin in 
alcohol, or from its combination with an alkaline solution. 
When the latter is precipitated by an acid a true hydrate is 
formed, consisting of an atom of resin and eight atoms of 
water. Even copal, after having dried as a varnish, is gradually 
acted on in this way by water, and becomes pulverulent. Re- 
sinein, however, does not seem to be capable of forming a 
hydrate, and therefore offers decided advantages as an aquatic 
paint. 
200. Reichenbach has lately shown* that Eupion (Cg; Ha) 
may be obtained by distillation of rapeseed oil. Naphthaline 
and Paraffine are both soluble in the latter; and these, from 
their stability of constitution and other properties, only require 
a suitable solvent to form the most valuable bases for paint. 
Naphthaline can be obtained in large quantity, in fact it is a 
drug with those who distil naphtha from coal-tar 5 and Laurent 
has shown+ that Paraffine may be obtained in abundance by 
distillation from the shale of the coal formations. In the com- 
bination of these with solid materials, the principal object to 
be held in view to obtain a durable paint is to choose a metallic 
powder or peroxide least liable to be acted on by the agents 
most obnoxious to paints, viz. air, water, carbonic acid, and 
hydrosulphuric acid, and at the same time capable of intimate 
combination with the organic base. 
201. But ina paint, or rather varnish of Naphthaline or Paraf- 
fine, no solid inorganic substance is necessarily included. The 
only other component needed is a suitable vehicle to cause these 
substances to spread and hold them upon the metallic surface. 
This obtained, a varnish covering, more durable than any known, 
would probably be produced. This is rendered almost certain 
by the facts already adduced by Mr. Prinsep’s and my own ex- 
periments. In these, coal-tar laid on the iron hot is immea- 
surably superior to every other covering. Now coal-tar in this 
state consists of naphthaline enveloped in asphaltum ; when coal- 
tar is exposed to this temperature, naphtha and other volatile 
matters are driven off, and the results of an imperfect destructive 
distillation, in which hydrogen is lost, while naphtbaline is a 
product, remain on the iron a bright and solid varnish. This 
not only gives the key to the only true method of applying 
bituminous matter as a varnish, but it indicates the cause of the 
* Jour. fur Pract. Chim. i. 377. + Annales de Chimie, lv. 218. 
