ETHEREAL SALTS
When acids are brought in contact with alcohols under certain conditions a reaction takes place similar to that which takes place between acids and bases. The following equations will serve as illustrations:
KOH + HNO3 = KNO3 + H2O,
CH3OH + HNO3 = CH3NO3 + H2O.
The resulting compounds of which methyl nitrate (CH3NO3) may be taken as the type belong to the class known as ethereal salts, the name having been given them because some of them possess pleasant ethereal odors. It will be seen that the ethereal salts differ from ordinary salts in that they contain a hydrocarbon radical, such as CH3, C2H5, C3H5, in place of a metal.
The nitrates of glycerin (nitroglycerin). Nitric acid reacts with glycerin in the same way that it reacts with a base containing three hydroxyl groups such as Fe(OH)3:
Fe(OH)3 + 3HNO3 = Fe(NO3)3 + 3H2O,
C3H5(OH)3 + 3HNO3 = C3H5(NO3)3 + 3H2O.
The resulting nitrate (C3H5(NO3)3) is the main constituent of nitroglycerin, a slightly yellowish oil characterized by its explosive properties. Dynamite consists of porous earth which has absorbed nitroglycerin, and its strength depends on the amount present. It is used much more largely than nitroglycerin itself, since it does not explode so readily by concussion and hence can be transported with safety.
The fats. These are largely mixtures of the ethereal salts known respectively as olein, palmitin, and stearin. These salts may be regarded as derived from oleic, palmitic, and stearic acids respectively, by replacing the hydrogen of the acid with the glycerin radical C3H5. Since this radical is trivalent and oleic, palmitic, and stearic acids contain only one replaceable hydrogen atom to the molecule, it is evident that three molecules of each acid must enter into each molecule of the ethereal salt. The formulas for the acids and the ethereal salts derived from each are as follows:
| HC18H33O2 | (oleic acid) |
| C8H6(C18H33O2)3, | (olein) |
| HC16H31O2 | (palmitic acid) |
| C3H5(C16H3102)3 | (palmitin) |
| HC18H35O2 | (stearic acid) |
| C3H5(C18H35O2)3 | (stearin) |
Olein is a liquid and is the main constituent of liquid fats. Palmitin and stearin are solids.
Butter fat and oleomargarine. Butter fat consists principally of olein, palmitin, and stearin. The flavor of the fat is due to the presence of a small amount of butyrin, which is an ethereal salt of butyric acid. Oleomargarine differs from butter mainly in the fact that a smaller amount of butyrin is present. It is made from the fats obtained from cattle and hogs. This fat is churned up with milk, or a small amount of butter is added, in order to furnish sufficient butyrin to impart the butter flavor.
Saponification. When an ethereal salt is heated with an alkali a reaction expressed by the following equation takes place:
C2H5NO3 + KOH = C2H5OH + KNO3.
This process is known as saponification, since it is the one which takes place in the manufacture of soaps. The ordinary soaps are made by heating fats with a solution of sodium hydroxide. The reactions involved may be illustrated by the following equation representing the reaction between palmitin and sodium hydroxide:
C3H5(C16H31O2)3 + 3 NaOH = 3 NaC16H31O2 + C3H5(OH)3.
In accordance with this equation the ethereal salts in the fats are converted into glycerin and the sodium salts of the corresponding acids. The sodium salts are separated and constitute the soaps. These salts are soluble in water. When added to water containing calcium salts the insoluble calcium palmitate and stearate are precipitated. Magnesium salts act in a similar way. It is because of these facts that soap is used up by hard waters.