In weight, when the quantity is relatively large, what terms are used? In quantities less than a kilogramme and greater than a gramme, what terms are used? In quantities below the gramme, what terms are used? What is a balance? What particulars are necessary to obtain correct results? When the beam is in a horizontal position, where should the centre of gravity be? Give a simple illustration of the principle of suspending a beam. What is the effect if the end knife-edges are not equidistant from the central knife-edge? What if the central knife-edge is not in line with the end knife-edges? What are the requisites for the beam of a fine balance in order to secure accuracy in weighing? Why should the beam of the balance be rigid and non-elastic? Why should it be no heavier than necessary in order to secure the requisite strength? What advantages have agate knife-edges and planes over those made of steel? column? What are the advantages of having the balance supported by a rigid metallic balance? What sort of counter scales was formerly in use? What has taken its place generally in more recent times? Upon what principle are the single beam, unequal arm balances constructed? Describe the double beam, unequal arm balance. What are its advantages? Describe a scale made to weigh liquids. What is the principal objection to such balances? What principle is adopted in making platform scales? What is the principle of the torsion balance? Of what weights does a pile of avoirdupois weights consist? What is meant by block weights? What is the objection to the use of a wooden block? How are troy weights usually arranged? How are iron metric weights usually shaped? What weights are generally used for analytical purposes? What is the best material and form for grain weights for prescription purposes? Why are aluminum weights preferable to brass? What are the advantages of aluminum wire weights? What measures are commonly used for measuring liquids when the quantity is more than a pint? What when the quantity is one pint or less? What effect has denting upon tinned iron or copper measures? Describe the forms of graduated glass measures in common use. Which is preferable, and why? Describe Hodgson's graduated measures. Describe Hobb's graduated measures. What is an objection to either of these, and how may it be remedied? What objection is there to using minim graduated measures? How may greater accuracy be obtained? How is a pipette used? Do the terms minim and drop always mean the same? About how many drops are there in a fluidrachm of water? Ans. 60. In a fluidrachm of syrup of acacia? Ans. 44. In a fluidrachm of chloroform? Ans. 250. In a fluidrachm of tincture of opium? Ans. 130. What is specific gravity? How much weight does a body lose by being immersed in water? How is the specific gravity taken of a solid, insoluble in but heavier than water, by means of a balance? liquids? How by means of a specific-gravity bottle? How by means of a graduated tube? How by immersing it in a liquid of the same specific gravity? How is the specific gravity taken of a solid soluble in but heavier than water? How is the specific gravity taken of a solid insoluble in but lighter than water? Describe a specific-gravity bottle. Can an ordinary bottle be used for this purpose? What are Lovi's or specific-gravity beads? What two classes of hydrometers are there? What is the difference between the one for light liquids and the one for heavy Why is the zero mark placed near the top in hydrometers for heavy liquids? What is the object of having two bulbs blown in the glass at the lower end of the hydrometer? Which is the more accurate for taking specific gravity,-the hydrometer or the specific-gravity bottle,-and why? Which is more likely to give a correct indication of specific gravity,—a hydrometer having an elongated bulb with cylindrical sides, or one having an oval or globular bulb,-and why? What is a urinometer, and how is it usually graduated? What is the specific gravity of healthy urine? What is the specific gravity of diabetic urine? What is a saccharometer, and how is it graduated? What is an elæometer? What is a lactometer? What does an alcoholmeter usually indicate? Describe Tralles's hydrometer. Describe Cartier's hydrometer. Describe Gay-Lussac's centesimal alcoholmeter. Describe Sikes's hydrometer. Describe Jones's hydrometer. Describe Dica's hydrometer. Describe Twaddell's hydrometer. Describe Beck's hydrometer. Describe Zanetti's hydrometer. Describe Fahrenheit's hydrometer. Describe Nicholson's hydrometer. Describe Mohr's specific-gravity apparatus. Describe Gannal's method of taking specific gravity of a liquid. How can a specific-gravity pipette be used to show specific gravity? What is specific volume? How can you obtain the volume of a given weight of a liquid? CHAPTER II. OPERATIONS REQUIRING THE USE OF HEAT. Generation of Heat. THE consideration of the theories which have been advanced from time to time to explain the phenomenon of heat, although very interesting and instructive, cannot be treated of in a work of this character, and the reader is therefore referred to any of the recent works on physics, which are everywhere accessible. The view which is now almost universally accepted is that known as the dynamical theory of heat, in which it is assumed that heat is produced by the constant motion of the particles composing the body, and that heat varies in quantity and kind according as the body is solid, liquid, or gaseous. It will be convenient to consider the various practical operations and appliances for generating heat under three heads: 1. Operations and forms of apparatus in which solids are used in developing heat. 2. Those in which liquids are used in developing heat. 3. Those in which gases are used in developing heat. OPERATIONS AND FORMS OF APPARATUS IN WHICH SOLIDS ARE USED IN DEVELOPING HEAT. Kinds of Fuel.-Under this head is included the very well known employment of solid fuel, as wood, charcoal, anthracite coal, bituminous coal, coke, etc. Wood is seldom relied upon as fuel in pharmaceutical operations where a regular, well-sustained heat is desired, yet from its wide distribution, ready inflammability, and comparative cheapness it is indispensable in kindling a fire. The large quantity of unconsumed carbon which is either lost in smoke or deposited upon vessels that are being heated constitutes the chief objection to its use. Charcoal is more convenient, although more costly, than wood: it ignites easily, burns readily, and leaves but little residue. On account of its ready combustibility, it is well fitted for operations requiring a quick, strong heat. Anthracite coal is probably the best form of solid fuel for general use, being the most economical: its hard, dense structure renders it difficult to kindle, but where a long-continued, strong heat is desired it is to be preferred. Bituminous or semi-bituminous coal affords a strong heat, but it is not equal to anthracite as fuel for pharmaceutical purposes. Unconsumed carbon is found in the smoke in large quantity, and this is apt to condense on the surfaces of kettles, vessels, etc., which are being heated, and the deposits of soot are uncleanly and often difficult to remove. Coke, the residue obtained from the distillation of coal at gas-works, is an excellent fuel, and may be used either mixed with coal or by itself: it is more easily kindled than anthracite. FIG. 57. B A Pharmaceutical Furnaces, etc.-Much ingenuity has been used in the contrivance of various forms of furnaces, ranges, stoves, etc., to meet general or special applications, yet in all there are certain fundamental principles of construction which must be well understood if faults are to be avoided. The elements of a furnace are the air-flue, combustion-chamber, and vent or chimney, and the relative proportions of these must depend upon the special object sought in the construction of the furnace, and the character of the fuel that is to be used. Fig. 57 represents a sectional view of a pharmaceutical furnace,-C being the air-flue, A the combustion-chamber, and B the vent. T Pharmaceutical furnace (sectional view). Coal being the principal solid fuel in use, it will be most appropriate to treat of those furnaces adapted for its combustion, and therefore the chemical constitution of coal and the theory of its combustion must be noticed. Hard anthracite, which is the best kind of coal for pharmaceutical furnaces, usually has a specific gravity of 1.550, and has been shown to consist of 94 per cent. carbon, 0.40 per cent. hydrogen, and 1.26 per cent. oxygen; there are also apt to be present 2 per cent. of water and about 2.3 per cent. of incombustible impurities or ash, consisting of ferric oxide, silica, alumina, magnesia, lime, etc. The poorer grades of this kind of coal contain from 85 to 90 per cent. of carbon. Anthracite may be distinguished from other varieties by its rich, glassy lustre, its peculiar conchoidal fracture, and its hard, dense structure: it burns freely, without black smoke, showing the absence of unconsumed carbon. Soft anthracite or semi-bituminous coal has a tendency, when broken into pieces, to assume the form of irregular cubes, and to crumble easily when pressed: it burns freely, but with the production of large quantities of black smoke. The heat produced by its combustion is very strong, and it is largely used in many parts of the United States. The combustion or oxidation of coal requires the presence of a certain quantity of air in contact with the burning coal to furnish enough oxygen to combine properly with the carbon of the fuel. The result of the combination is carbon dioxide, CO2, and carbon monoxide, CO, both of which are gases. It is very important to provide means of escape for these gaseous compounds, as they are both poisonous, and the former is a decided non-supporter of combustion. Theoretically, it has been calculated that one hundred and fifty cubic feet of air are necessary to consume perfectly one pound of coal in an ordinary furnace, but practically, because of the obstruction of the ashes, which prevents the thorough contact of the air with all parts of the glowing carbon, nearly double this amount is necessary. Stoves and ranges are now so universally used that it would be needless to multiply illustrations of them: the proper selection of such as are suited to the special uses of the pharmacist must be left to individual decision, and will depend upon the space that can be spared and the character of the work that is to be done. One important feature should not be overlooked, however, in this connection,-i.e., the addition of a boiler or water-back, whereby a constant FIG. 58. supply of hot water can be had: where stoves are used, this can generally be effected by having a circulating hot-water boiler in a convenient corner, the pipes conveying the hot water being heated in the upper part of the combustion-chamber of the stove. If sufficient space can be appropriated, a range is very useful, particularly if a sheet-iron sliding-door can be lowered over the front to enclose the space. Now, when a communicating flue, controlled by a damper, is made to enter the chimney from the top of this space, operations can be conducted here that would otherwise be impossible, noxious vapors being at once carried off by the flue. Fig. 58 represents an ordinary range which is well adapted for many pharmaceutical operations. The front has been removed, in order to show the construction more clearly. This front is of sheet iron, and is hinged to the shelf which supports the boiler; it extends half-way over the top of the range, and when the damper, F, is opened, the vapors arising from operations conducted on the top are carried up the chimney. The hot-water boiler, B, is connected by pipes, G, with the cold-water supply in such a manner that the cold water circulates through pipes which surround the combustion-chamber, and, after becoming heated, ascends into the boiler. 090 Pharmaceutical range. Fig. 59 shows a durable pharmaceutical furnace made by Mershon's Sons, which has proved very useful in practical work. The body of the furnace is of wrought iron; it is lined with fire-brick, and the top is composed of a series of rings, which permits of the use of various-sized kettles, evaporating-dishes, etc. It has two cast-iron doors, the upper one being especially useful, as it permits the ready feeding of coal to the furnace whilst a kettle or dish is being heated, without disturbing the |