15B Furnace for the Liquefaction of Copal and Amber, 



from it. Copal thus prepared has properties different from, 

 and more extensive than, those communicated to it by the 

 common method ; and it has not that dark brown colour 

 which it acquires by too high a temperature, and too long 

 f xposure to heat. Immersed here in an atmosphere of ca- 

 loric (heat), it receives the impression only at the surface, 

 which soon yielding to the power of that agent escapes un- 

 der the liquid state from the continuance of its action ; new 

 surfaces are successively subjected to the same effect ; and 

 tbe final result is copal as little altered as possible, and 

 which can have undergone but a very slight modification in 

 its constituent principles : the force only of the connexion 

 which existed between its parts, and which opposed so 

 great an obstacle to the solutions proposed to be effected, is 

 diminished. In a word, it is possible to compose fat copal 

 varnish almost colourless, by making use of oil as little co- 

 loured as possible ; such as that of pinks prepared in leaden 

 vessels, according to Watin's method. 



In like manner also this copal, simply modified, may in- 

 crease the soliditv of alcoholic varnish in a more direct man- 

 ner than when it is employed without any preliminary pre- 

 paration. A second liquefaction would perhaps give it the 

 property of being soluble in alcohol in greater quantity; but 

 there would be reason to apprehend that the alteration in its 

 principles, carried too far, would give it no superiority over 

 those resins which are most soluble in that liquid. 



To prepare Copal Varnish with Essence of Turpentine, with' 

 out any intermediate Substance* 



Take Copal liquefied, according to my method, 3 ounces. 

 Essence of turpentine 20 ounces. 



Place the mattrass containing the oil in a balneum mariae* 

 and when the water is warm add the pulverized copal in 

 small doses. Keep stirring the mixture, and add no more 

 copal till the former he incorporated with the oil. If the 

 oil, in consequence of its particular disposition, can take up 

 three ounces of it, add a little more ; but stop when the li- 

 quid becomes nebulous ; then leave the varnish at rest. If 

 it be too thick, dilute it with a little warm essence, after 

 having heated it in the balneum mariae. When cold, filter 

 it through cotton, and preserve it in a clean bottle. 

 . This varnish has a good consistence, and is as free from 

 colour as the best alcoholic varnish. When extended in 

 one stratum over smooth wood, which has undergone no 

 1 preparation, 



