Heats of Combustion and Calorific Values

The gross calorific value refers to liquid water of reaction, whereas the net calorific value refers to the water vapor that is formed. The two calorific values thus differ by the contribution of the enthalpy of vaporization of the water formed during combustion. 

A high chemical resistance is an important prerequisite for the use of a liquid as a solvent. Aliphatic and aromatic hydrocarbons are chemically inert and thus satisfy this requirement extremely well. 

Alcohols too are chemically very resistant but they react with alkali metals, alkaline-earth metals, and aluminum to form salts. Under certain conditions alcohols can be converted into carboxylic acids by powerful oxidizing agents. They are, however, stable toward atmospheric oxygen. On account of their reaction with isocyanates to form urethanes, solvents containing hydroxyl groups (e.g., alcohols, glycols, and glycol ethers) must not be used as solvents for polyurethane paints [14.101], [14.102]. 

On prolonged storage most ethers and glycol ethers form peroxides with atmospheric oxygen. In the case of glycol ethers this leads to acid formation due to oxidation which can be prevented by adding stabilizers. 

Esters and ketones are chemically very resistant under normal conditions, especially in the paint industry. However, it must be remembered that esters can be hydrolyzed to form alcohols and acids. For ethyl acetate the equilibrium constant K at 40 C is 2.51, and at 100 C is 2.56. 

---