A Collodion is a solution of pyroxylin (gun-cotton) in a mixture of ether and alcohol. It is a highly inflammable liquid. When applied to a surface, the solvent evaporates, leaving deposited a transparent, tenacious film.

Prepare the official Collodium as follows: In a bottle place 2 Gm. pyroxylin, add 12.5 mils alcohol; thoroughly shake the mixture; then add 37.5 mils ether, and shake this mixture until the pyroxylin is dissolved. Cork the bottle tightly, setting it aside until the liquid has cleared; then decant the clear portion, place in a suitable bottle, and cork tightly.

All these operations must be conducted away from the vicinity of any flame.

Prepare the official Collodium Flexile as follows: Tare a small bottle, and into it place 19 Gm. Collodion, 0.4 Gm. camphor, and 0.6 Gm. castor oil; shake the mixture until the camphor is dissolved.

This preparation should be kept in well-stoppered bottles, in a cool place, and well removed from the fire.

Properties of Collodia,............................................................................................................................................................................

Paint one knuckle with Collodion, and an adjacent knuckle with Flexible Collodion. On flexor surface of forearm, paint comparative areas with the two in the same way.

Collodia are used as adhesive protectives; also to render cotton dressings more concrete and impervious. They are being in part supplanted by the new flexible paraffin dressings.

There is one other official Collodion: Collodium Cantharidatum. This is an obsolescent preparation, well deserving complete discard.