The resins are so frequently employed in the arts that a knowledge of the action of different solvents upon them is of great value.
Dr. Sac, of Neuenberg, Switzerland, has made an extensive inquiry into the nature of different resins. The following results, as obtained by him, are given in Dingler's Polytechnic Journal: - The resins spoken of are copal, amber, dammar, common resins, shellac, elemi, sandarach and mastic. All these resins can be reduced to powder.
The following will become pasty before melting: Amber, shellac, elemi, sandarach and mastic; the others will become liquid at once.
In boiling water common resin will form a semi-fluid mass; dammar, shellac, elemi and mastic will become sticky; while copal, amber and sandarach will remain unchanged.
Dammar and amber do not dissolve in alcohol; copal becomes pasty; elemi dissolves with difficulty, while resin, shellac, sandarach and mastic dissolve easily.
Acetic acid makes common resin swell; on all the others it has no effect.
Caustic soda dissolves shellac ico,dily; resin partly; but has no influence on the others.
Amber and shellac do not dissolve in sulphide of carbon; copal becomes soft and expands; elemi, sandarach and mastic dissolve slowly; while resin and dammar dissolve easily.
Oil of turpentine dissolves neither amber nor shellac, but swells copal; dissolves dammar, resin, elemi and sandarach easily, and mastic very easily.
Benzol does not dissolve copal, amber and shellac, but does elemi and sandaraeh to a limited extent; while dammar, resin and mastic offer no difficulty.
Petroleum ether has no effect on copal, amber and shellac; it is a poor solvent for resin, elemi and sandaraeh, and a good one for dammar and mastic.
Concentrated sulphuric acid dissolves all resins, imparting to them a dark brown color, excepting dammar, which takes a brilliant red tint.
Boiling linseed oil has no effect on copal and amber; shellac, elemi and sandaraeh dissolve easily.
Nitric acid imparts to elemi a dirty yellow color; to mastic and sandaraeh a light brown; it does not affect the others.
Ammonia is indifferent to amber, dammar, shellac (?) and elemi; copal, sandaraeh and mastic become soft, and finally dissolve; while resin will dissolve at once.