effected in an ordinary bottle, the upper layer is usually removed by means of a pipette or syringe.

For the separation of what liquids is the Florentine Receiver used?

It is used to separate volatile oils obtained by distillation of aromatic substances with water.

How does decoloration act as a separating process, and how is this process conducted?

Insoluble compounds are formed of coloring matter when solutions of them are brought in contact with porous charcoal. Therefore by passing (filtering) a colored liquid through animal charcoal the color is removed from the liquid.

What is deodorization and how performed?

It is the process of depriving of odor by means of animal or vegetable charcoal.

To what class of substances are the two preceding processes applied?

Tinctures, oils, saccharine solutions, fatty bodies. Such preparations as deodorized opium and deodorized iodine are made by entirely different processes.

What effect has animal charcoal upon solutions of alkaloids, bitter and astringent, and what pharmaceutical importance is attached?

Charcoal absorbs such proximate principles, hence care should be used in removing coloring from vegetable solutions, that their medicinal quality is not impaired.

CHEMICAL PROCESSES.

(Treatment of mainly inorganic crystalline material.) What are solutions? Define the process of solution. Simple solutions are solutions generally of mineral salts of definite strength. Solution is the union of a liquid (the solvent) with another liquid, a solid or a gas, the combination being inseparable without the use of evaporation, distillation,

or chemical means. The union not so intimate, however, as to cause change in color, odor or taste, unless chemical combination, as well as solution takes place. (From a simple solution the solid substances dissolved can be reclaimed, unchanged, by evaporation of the liquid.)

What kind of a solution results when a change of color, odor, or taste, etc., is produced?

A chemical solution.

What solvents are used in making solutions?

Water, alcohol, ether, chloroform, etc.

How is solution aided?

Solutions of solids are generally aided by comminution.

Mention other circumstances which influence solubility and solution.

Heat usually increases the solvent power of liquids, and causes currents and consequent agitation, thus favoring the process of solution; though, as a rule, heat favors solubility, some exceptions to the rule exist, as acetate and citrate of lime. Rapid solution, when not accompanied by chemical reaction, always causes a reduction of temperature, owing to the law that bodies in passing from the solid to the liquid state have their capacity for caloric increased. When dehydrated salts are dissolved there is an increase of temperature. When a gas is to be dissolved in a liquid, cold favors its solution by increasing the specific gravity of the gas, and by counteracting the sensible heat resulting from its condensation. What effect has the presence of one salt upon the solubility of another salt?

In some cases increasing and in other cases decreasing it. A saturated solution of one salt may be a solvent for another salt-a quality of great value in the removal of impurities from certain salts.

When a salt is said to be soluble, what solvent is meant?
Water.

What is meant by a saturated solution?

A solution is said to be saturated when the substance dissolved ceases to be liquefied by the solvent at common temperatures. Therefore, the real strength of saturated solutions is dependent upon temperature.

What is meant by supersaturated solution, and how is it effected?

When the solvent retains in solution more of the soluble matter than it could under the existing circumstances dissolve, it is said to be supersaturated. It is often effected by heating the solvent to a proper degree and dissolving the substance in it to saturation, then a slow reduction of temperature (without agitating the vessel) will make an over-saturated solution, but a little agitation will start crystallization and throw out the salt in excess of solution.

What is meant by dialysis?

A separation of a crystalloid from a colloid by osmosis.

What is meant by the term crystalloid and colloid?

Those substances which diffuse most rapidly are called crystalloids (crystalline chemical subtances), those which diffuse slowly are called colloids (gelatinous substances).

What is meant by the term osmosis, and how is it effected? A simple dialyser may be made by stretching over the bottom of a sieve frame a piece of parchment or fine membrane. If into the vessel thus made is placed a solution and the whole floated on distilled water, then there is water on one side of the membrane (septum) and the solution on the other; these liquids flow through the membrane at different rates; this is called osmosis. (If the flow of the water into the solution preponderates, it is called endosmosis; if the flow of the solution, it is called exosmosis. The diffusate is found in the distilled water.)

Precipitation.

What is meant by the term precipitation?

When finely divided crystals or amorphous powders are separated from solutions by chemical (or physical) agents, this is termed precipitation. For example; when a solution of carbonate of sodium is added to a solution of chloride of calcium, a precipitate of carbonate of calcium is produced. Light will precipitate solutions of silver and heat will precipitate lime water. The agent producing the precipitation is called the precipitant. The liquid remaining is called the supernatant liquid.

By what terms are the physical characters of precipitates described?

By the terms flocculent, gelatinous, curdy, granular, and crystalline.

What is meant by the term magma?

It is applied to the moist precipitate as it is collected in a filter before it is dried.

By what means may the character of a precipitate be modified?

Hot dense solutions produce heavy precipitates, cold and diluted solutions produce light precipitates.

By what other process can very finely divided products be obtained?

By Elutriation (see Index); Levigation (see Index).

Crystallization.

What is the usual mode by which a soluble salt is obtained in crystalline form?

Soluble salts are usually crystallized from a saturated solution by slowly evaporating the solvent.

What other modes are used?

Fusion (example, sulphur), sublimation (ex., benzoic acid), precipitation (ex., mercuric iodide).

What is meant by the terms water of crystallization and efflorescence?

Water of crystallization is well defined as solid water in a combined state. All water of crystallization is expelled at high temperatures (see Exsiccation); but some crystalline substances have it so loosely held that it desiccates at low temperatures, leaving a fine powder behind; the crystal is then said to be efflorescent.

What is deliquescence?

Absorbing moisture from the air; such crystals are hygroscopic (carbonate of sodium is efflorescent, but carbonate of potassium is deliquescent).

What is exsiccation?

Driving off water of crystallization by strongly heating (ex., Alumen Exsiccatum).

AMORPHOUS.-A non-crystalline substance.

What is meant by the term mother liquor?

The liquid drained from crystals after they have ceased to form. It frequently contains much of the substance in solution.

What difference is there in the mode of washing precipitates and crystals?

Crystals are usually washed with the smallest effective quantity of cold water; precipitates, more copiously with

warm water.

How is a crystal bounded?

By plane surfaces symmetrically arranged with reference to certain imaginary lines passing through its centre; these lines are called axes.