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may be tested by inverting the instrument and seeing that the mercury descends to the lowest part of the tube.

What is a blow-pipe, and how is it used ? A slightly conical, gradually tapering metallic or glass tube, covered at the smaller end, and having a minute orifice at that end for producing a blast. When used, an unremitting current of air is forced through the tube from the mouth, by keeping the cheeks distended with air and constantly supplying fresh air from the lungs, as needed.

Describe the nature of the blow-pipe blast. Ist. It has an intense heat. 2d. When used with a luminous flame, the interior of the blow-pipe blast, owing to the carbon not being wholly oxidized, has the power of reducing oxides. It is, therefore, called the reducing flame. The outer part of the blast has the opposite or oxidizing property, and is called the oxidizing flame.

What is the blow-pipe used for in Pharmacy ? Used for bending and working glass, testing fusible chemical substances, in soldering, etc.

What is a Crucible, and for what is it used? A crucible is a cupshaped vessel, intended to withstand a powerful heat. Clay, plumbago, porcelain, iron, silver, and platinum, are some of the materials employed for crucibles. Platinum ranks first, plumbago second, the Hessian crucible next, though quite inferior; then comes the more fragile porcelain and wedgwood crucibles, which must be gradually cooled, to prevent breakage.

What eight processes in Pharmacy require the application of high heat ? 1. Ignition. 2. Fusion. 3. Calcination. 4. Deflagration. 5. Carbonization. 6. Torrefaction. 7. Incineration. 8. Súblimation.

Describe each of these processes. 1. Ignition consists in strongly heating solid or semi-solid substances to obtain a definite residue. Ex. The official quantitative tests for purified sulphide of antimony, phosphoric acid, etc.

2. Fusion is the process of liquefying solid bodies by heat. Ex. Melt. ing of iron or lead, or of wax.

3. Calcination is the process of driving off volatile substances, such as gas or water, from inorganic matter, by heat without fusion. Ex. Magnesia, lime, etc., prepared by calcination.

4. Deflagration is the process of heating one inorganic substance with another capable of yielding oxygen (usually a nitrate or a chlorate); decomposition ensues, accompanied by a violent, noisy, or sudden combustion. Ex. Salts of As and Sb made by this process.

9. Carbonization is the process of heating organic substances without the access of air, until they are charred. The volatile products are driven off, but combustion is prevented. Ex. Charcoal is made in this way.

6. Torrefaction is the process of roasting organic substances. The constituents are modified but not charred. Ex. The roasting of coffee. Torrefied Rhubarb is obtained in this way. It loses its cathartic properties by this process, but retains its properties as an astringent.

7. Incineration means the burning organic substances to ashes in air. The ash is the part sought. Ex. Determining the amount of fixed matter in organic substances by burning them and examining the ashes.

8. Sublimation is the process of distilling solid volatile substances from non-volatile substances. Ex. Camphor is separated from strips of wood from the camphor tree in this way.

What various forms of apparatus are used to modify and control heat? The water-bath, salt-water bath, sand-bath, oil-bath, glycerinbath, etc.

Limit the range of the several forms of bath. The water-bath can only be used for temperatures below 100° C. (212° F.). Saturated salt solution boils at 108.4° C. (227.1° F:), which degree limits the range of the salt-water bath. Glycerin may be heated to 250° C. (480° F.) without much inconvenience from the Acrolein, which is produced when that substance is raised nearly to the boiling point. The oil-bath is designed to furnish a regulated temperature below 260° C. (500° F.), and the sand-bath may be used at any temperature.

Upon what theory is Steam used in pharmaceutical operations ? Matter exists in three forms: solid, liquid, and gaseous, depending upon the degree of distance between its molecules. Heat is but another name for molecular motion (possibly atomic motion also). Increase molecular motion, and molecular distance is increased to give room between the molecules for that motion. Cohesion holds molecules together. Heat, therefore, works against cohesion. If water is heated until its molecules are driven far apart, it becomes steam, and its molecules are now in very rapid vibration. If brought into contact with a cool surface, that is, a surface of slower molecular vibration, it imparts its motion to that surface, and the steam is condensed-its motion is lost, and it returns to the condition of fluid again. But by imparting its heat (motion) to the surface with which it came in contact, this surface becomes heated. The molecular motion of the surface becomes as great as the steam when equilibrium is attained and the temperature of the surface remains constant. As hot steam can be transported long distances by appropriate pipes, it becomes a convenient means of heating surfaces at a distance from the fire, and the pressure of the steam being under perfect control, the temperature may be regulated with great exactness.

In what two forms is steam used for heating? Steam without pressure, and steam under pressure, or superheated steam.

What advantage has the latter ? "Steam under pressure is hotter because more heat is required to raise water to the condition of vapor against increased pressure.

In what way may steam under pressure be used for evaporation ? By means of jarketed kettles. *

How may the heating surface be increased in such kettles ? By combining the kettle with a steam coil.

For what other purposes are steam coils used ? For heating apartments, drying ovens, evaporating dishes placed upon them, and for boiling water, by placing a steam coil in the water.

OPERATIONS REQUIRING HEAT. What is Vaporization? The operation of increasing molecular motion by heat until matter assumes the form of vapor or gas.

Explain what is meant by the various terms, Evaporation, Dis

* For various forms of jacketed kettles, boilers, etc., for using steam in pharmaceutical operations, see Remington's “ Pharmacy."

OPERATIONS REQUIRING HEAT.

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tillation, Desiccation, Exsiccation, Granulation, Sublimation. In the vaporization of liquids, when the object sought is the fixed part, the process is called evaporation, when it is the volatile part that is sought, it is called distillation. If solids are vaporized, when the fixed part is sought, the process is called Desiccation, or Exsiccation, and when furnished in a granular condition, Granulation ; but if the volatile part is sought, it is called Sublimation.

What 'is Ebullition, or Boiling? A violent agitation in a liquid produced when it is heated from the fluid to the gaseous condition. The heat acts first on that portion of liquid resting against the heated surface, converting a portion into steam, which rises in the form of bubbles, which break on the surface of the liquid.

What is meant by the boiling point of a liquid ? The temperature at which it boils. Each liquid has its specific boiling point as well as its specific weight. Liquids evaporate more or less at all temperatures, hence there seems to be no specific evaporating point, but there is a specific point where ebullition commences.

What is meant by the tension of matter? The molecules of which matter is composed repel each other, but are held together by cohesion and atmospheric pressure. Matter is, therefore, said to exist in a state of tension. The repelling force may be heat; at any rate, by increasing heat, or molecular motion, the repelling force is increased. Heat, there. fore, is a force working against cohesion and atmospheric pressure, to separate molecules apart.

How may advantage be taken of the knowledge of tension to increase the rapidity of evaporation? By removing the pressure of the atmosphere from a liquid and increasing its molecular motion, viz. : heating it, evaporation is hastened.

What important factor plays a part in the evaporation of a liquid in the open air ? The degree of moisture already in the air.

In evaporating liquids at the boiling point, temperature, pressure, etc., being equal, what determines the rapidity of evaporation? The amount of surface exposed to the heat.

What determines the rapidity of evaporation under like circumstances below the boiling point ? The amount of surface exposed to the air.

How would you apply this knowledge ? By selecting suitable vessels for evaporation, and employing various devices to increase the heating surface, or the surface exposed to the air, depending upon the method of evaporation chosen.

What is a Vacuum Pan? A covered evaporating pan, with an air pump, condenser, etc., for removing the pressure of the atmosphere while conducting the process of evaporation, thus enabling the liquid to boil at a lower temperature.

What is an evaporating chamber ? A species of “fume-closet,” built into a chimney breast, provided with gas-burners, etc., for conducting evaporation.

How would you protect a vessel from unequal heating by the fame when evaporating by direct heat ? By a piece of wire gauze between it and the flame.

How would you evaporate a liquid to a fixed weight ? Use a tared dish, and weigh both dish and contents when required.

How would you evaporate to a fixed volume ? Use a graduated evaporating dish, and evaporate to the required volume.

How would you mark the evaporating dish to determine the required volume ? Dishes may be bought already graduated, or graduated in the laboratory, either by marking the dish on the inside or pasting a strip of paper to the inside, marked with the required measure. A strip of wood placed across the top of the dish, perforated in the middle for a glass thermometer, can be used for graduating purposes, by tying a string on the thermometer to indicate the desired level.

What is a Hood ? A contrivance connected with a chimney to place over evaporating dishes, etc., to conduct away vapors.

What is a Grommet? A circular bit of rubber hose upon which a round-bottomed dish may be placed to keep it from turning over.

What is meant by Spontaneous Evaporation ? The evaporation of a liquid at the ordinary temperature of the atmosphere.

What is Distillation? The operation of separating one liquid from another, or a liquid from a solid, by vaporization and condensation, the volatile part being the object sought.

About how much water is required to condense steam at 100° C. (212° F.)? About twenty-five times its weight of water, at 20° C. (68° F.).

Describe the two typical forms of apparatus used in distillation. Ist. The alembic consists of a head or dome, in which the vapors generated in the body or cucurbil are condensed and run into a gutter at the base of the dome, and are carried off by a pipe. The use of the alembic in its original form is nearly obsolete. 2d. The retort consists of a long-necked flask, with the neck bent at right angles with the body of the flask. When the flask has a tubulure, or orifice at the top of the body, for the purpose of introducing the liquid to be distilled, it is called a tubulated retort. Other materials, besides glass, are used for making retorts.

How would you select a retort ? For very volatile liquids a deep retort is preferable. The bottom of the neck should form an acute angle with the body. The tubulure should be situated well back, to admit a funnel without striking the bottom of the neck. The neck should taper gradually, permitting the use of a rubber ring, to form a tight joint between it and the condenser, the ring being made tight by forcing it up the gradually tapering neck. The glass should neither be too thick nor too thin, well annealed, and free from scratches, bubbles, and imperfections.

How would you improvise an ordinary flask for distillation ? Select a flat-bottomed flask, with a wide mouth, to admit a large-sized rubber stopper containing a wide, bent tube, to act as a neck, a thermometer, and a safety or changing tube. The joints are made tight by luting them.

What is a Lute ? Various pastes, which harden when dry, and serve to make joints vapor-proof, are called lutes. Flaxseed meal poured into boiling water and stirred into a paste is generally used.

How may glass tubes be connected with each other ? By rubber tubing, or pieces of bladder moistened and wrapped around the proposed joint, and tying with strong linen twine.

OPERATIONS NOT REQUIRING HEAT.

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What are Receivers ? Glass vessels, usually globular in shape, for receiving distillates. Three kinds are used; plain, tubulated, and quilled. The tubulure is to prevent explosions, and the quill to allow the distillate to escape, for the purpose of measuring it as it condenses.

What are Adapters ? Tapering tubes of glass, used to connect retorts with receivers.

How would you charge a retort? A plain retort should be charged with a long-beaked funnel, reaching well down into the body of the retort. Place a funnel in the tubulure, to charge a tubulated retort.

How are retorts supported ? By retort stands, of which there are several patterns.

What is meant by bumping, and how may it be prevented ? Certain explosions occurring in a liquid when it is boiled. It may be prevented by placing some pieces of broken glass in the retort.

What is a Liebig's Condenser ? Two long tubes, the smaller inside the larger, and sufficient space between them to allow the free circulation of water, are kept in place by rubber rings between them at each end of the apparatus. The inside tube is longer, to allow it to be connected at one end with a retort, and the other end with a receiver. The apparatus is inclined at an angle on a stand, and, when in use, cold water is circulated between the tubes, entering at an orifice situated at the lower end, and escaping at a similar orifice situated at the top, thus condensing the vapors passing through the inner tube.

What is a Still? Various forms of apparatus embracing the principles of the alembic and retort, either singly or combined, used for distillation, are called stills. When the neck of the retort is prolonged into a coil and immersed in water to condense the vapors, it is called a worm.

What is Sublimation? The process of distilling volatile solids. The product is called a sublimate.

Describe the product: ist. Cake sublimate ; 2d. Powder sublimate. When the volatile product condenses at a temperature but slightly lower than the condensing point, the deposit is made slowly and a large cake of crystals is produced. But if the vapor is condensed rapidly in a cold temperature, a powder results. Retorts and hoods of various patterns are used for sublimation, or the vapor may be condensed in chambers specially arranged for the purpose.

What is meant by Desiccation? The operation of drying medicinal substances.

What are the three objects for drying medicinal substances ? 1. To aid in preserving them. 2. To reduce their bulk. 3. To facilitate their comminution. The operation is effected by various forms of ovens and drying closets, described in works on pharmacy.

OPERATIONS NOT REQUIRING HEAT. What is meant by Comminution ? The process of tearing drugs to pieces or reducing them to powder.

Name some of the processes for comminuting drugs. Cutting, rasping, grating, chopping, contusing, rolling, stamping, grinding, pow. dering, triturating, levigating, elutriating, granulating, etc.

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