Amorphous substances, optical

In a similar way, the video disk reconverts the signal produced by the Kerr effect on a thin film of an amorphous substance such as Tb-Fe sputtered on a substrate disk made of plastic or glass. The Tb-Fe film functions like a perpendicular magneto-optical memory... 

The solutions of all proteins are optically active. Most proteins are amorphous substances. Some have been obtained, however, in crystalline condition from pumpkin, hemp seed, castor seed, and Brazil nuts. Edestin, a well characterized protein which occurs in a number of seeds, can be crystallized from a warm 5 per cent solution of sodium chloride. Other proteins which do not occur in nature in a crystalline condition have been crystallized. Egg albumin, after precipitation from solution by ammonium, sulphate and acetic acid, assumes a crystalline form on standing. 

Rosin family s most common form of adhesive is colophony, a hard amorphous substance derived from the oleoresin of the pine tree. This material is applied in solvent solution form as a hot-melt mastic. It has poor resistance to water, is subject to oxidation, and has poor aging properties. Plasticizers are usually added to reduce its brittleness. Bond strengths are moderate and develop rapidly. These materials are used as temporary adhesives in bonding paper and as label varnishes. They are also used as components of PSAs based on styrene-butadiene copolymers and in hot-melt adhesives and tackifiers. These materials have been largely replaced by synthetic-resin adhesives. One specialized form of rosin adhesive is Canada Balsam, covered by the obsolete Military Specification MIL-C-3469C, titled Canada Balsam. This material was intended for cementing optical elements. 

Before these results were published, polymer physicists and chemists mainly investigated only two phase-states, amorphous and crystalline. At the present time, along with these two states, the third phase-state of condensed systems, i.e. the liquid crystalline state, became very important. Here the situation turned out to be the same as in the case of low molar mass liquid crystals. In spite of the fact that historically the low molar mass substances in liquid crystalline state had been known for about a century, the intensive study of their properties began only after they had found an important practical application owing to a sharp change in optical properties of liquid crystals in electromagnetic fields (for visual displays) and as sensitive temperature indicators (in medicine). 

White crystalline, amorphous, or syrupy substance salts are optically active melts at 214°C (417.2°F) insoluble in water, soluble in alcohol, ether, and chloroform. 

---