This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
When sugars are heated without the addition of water a point is reached at which they change from a crystalline to a liquid state. This is called the melting point.
Mackenzie states that the melting point of sucrose is 160° to 161°C. Impure solutions of sucrose will give variable melting points. After sugar is melted and cooled slowly it forms the hard amorphous sugar sometime? called "barley sugar." The amorphous form of sugar like the amorphous sulfur slowly reverts to the crystalline form. If sucrose is heated above the melting point brownish-colored substances called caramel are formed. In the presence of moisture, caramelization may begin at temperatures below 100°C. Caramel is composed of a number of substances, decomposition products of sucrose with loss of water.
Maltose melts at about 100°C. Having a lower melting point than sucrose it decomposes more easily by heat.
Dextrose crystallizes as the hydrate, C6H12H1O, that is, one molecule of water is combined with the molecule of dextrose. When heated slowly it loses this water of crystallization between 50° and 60°C. Perkin and Kipping state that the melting point of the hydrate is 86°, and that of the anhydrous form is 146°C.
The melting point of levulose is 95°C.
Sugar and other substances are used constantly in cookery processes. Therefore, it is desirable to know something about the properties of solutions.
A solution is composed of two parts: one, the solute, is the dissolved substance; and the other, the solvent, is the substance in which the solute is dissolved. A solution is a homogeneous mixture. This means that it is uniformly mixed or alike in all parts.
A solution may be a gas dissolved in a solid, a gas in metal; a gas in a liquid, air in water; a liquid in a liquid, alcohol in water; or a solid in a liquid, sugar in water. It is to the class of solids in liquids that many of our solutions in cookery belong.