Copal, amber, dammar, colophony, lac (or shellac), elemi, sandarac, mastic, and carnauba wax (a resin) have been experimented upon. Amber, shellac, elemi, sandarac, and mastic swell up and increase in bulk when heated; the others fuse quietly. Carnauba wax melts in boiling water, colophony becomes pasty therein, while dammar, shellac, elemi, and mastic agglutinate. Copal, amber, and sandarac do not change in water.

Alcohol does not dissolve amber or dammar; it agglutinates copal, and partly dissolves elemi and carnauba wax; while colophony, shellac, sandarac, and mastic are readily soluble therein.

Ether does not dissolve amber and shellac; it makes copals swell, and partly but slowly dissolves carnauba wax; it readily dissolves dammar, colophony, elemi, sandarac, and mastic.

Acetic acid does not dissolve amber and shellac; it causes copal to swell; it somewhat acts upon carnauba wax, but not at all upon any other of the resins above named. A hot solution of caustic soda, of sp. gr. 1.074, readily dissolves shellac, with difficulty colophony, and has no action upon the rest. In sulphide of carbon, amber and shellac are insoluble; copal swells therein; elemi, sandarac, mastic, and carnauba wax are with difficulty dissolved, while dammar and colophony are readily so. Oil of turpentine has no action upon amber or shellac; it causes copal to swell, and readily dissolves dammar, colophony, elemi, sandarac, carnauba, and very readily mastic. Sulphuric acid does not dissolve carnauba wax; it dissolves and colors all other resins brown, except dammar, which becomes bright red. Nitric acid does not act upon the resins, but covers carnauba wax straw-yellow, elemi dirty yellow, and mastic and sandarac bright brown. Ammonia does not dissolve some of these resins, but causes copal, sandarac, and mastic first to swell, afterward dissolving them; colophony is easily soluble therein.

Rubber, Solvents for-These are ether (free from alcohol), chloroform, bisulphide of carbon, coal naphtha, and rectified oil of turpentine. By long boiling in water, rubber softens, swells, and becomes more soluble in its peculiar menstrua; but when exposed to the air, it speedily resumes its pristine consistence and volume. Oil of turpentine dissolves caoutchouc only when the oil is very pure and with the application of heat; the ordinary oil of turpentine of commerce causes india-rubber to swell rather than to become dissolved. In order to prevent the viscosity of the india-rubber when evaporated from its solution, one part of caoutchouc is worked up with two parts of turpentine into a thin paste, to which is added 1/2 part of a hot concentrated solution of sulphuret of potassium in water; the yellow liquid formed leaves the caoutchouc perfectly elastic and without any viscosity. The solutions of caoutchouc in coal-tar, naphtha, and benzoline are most suited to unite pieces of caoutchouc, but the odor of the solvents is perceptible f:r a long time. Sulphide of carbon is the best solvent for caoutchouc. This solution, owing to the volatility of the menstrum, soon dries, leaving the latter in its natural state. When alcohol is mixed with sulphide of carbon, the latter does not any longer dissolve the caoutchouc, but simply softens it and renders it capable of bring more readily vulcanized Alcohol also precipitates solutions of caoutchouc. When caoutchouc is treated with hot naphtha distilled from native petroleum or coal-tar, it swells to 30 times its former bulk; and if then triturated with a pestle and pressed through a sieve, it affords a homogeneous varnish, the same that is used in preparing the patent water proof cloth of Macintosh. Caoutchouc dissolves in the fixed oils, such as linseed-oil, but the varnish has not the property of becoming concrete on exposure to the air, caoutchouc melts at a heat of about 256 or 260 after it has been melted; it does not solidify on cooling, but forms a sticky mass which does not become solid even when exposed to the air for months. Owing to this property, it furnishes a valuable material for the lubrication of stop-cocks and joints intended to remain air tight and yet be movable.

Rubber, To cut. Dip the knife-blade in a solution of caustic potash.

Vineger, Making, from alcohol (Art us's process). Dissolve 1/2 oz„ dry bichloride of platinum in 5 lbs. of alcohol With this moisten 3 lbs. of charcoal broken to the size of a hazel-nut. Heat the charcoal in a covered crucible, and place it in the bottom of a vinegar-vat. This causes the rapid oxidation of the alchohol. reheat the charcoal once in 5 weeks.