CHEMICAL NOTES SCURLOCK The Carter G. Woodson & Association for the Study of African American Life and History Library EMORY CHEMICAL NOTES A COMPILATION OF NOTES on the THEORETICAL PRINCIPLES OF CHEMISTRY designed especially TO AID BEGINNING STUDENTS TO GRASP THE FUNDAMENTS OF THE SUBJECT by HERBERT C. SCURLOCK, A. B., M. D. Assistant in Chemistry and Demonstrator of Anatomy, Medical Department of Howard University ; Physician to the Dispensary Clinic Freedmen's Hospital WASHINGTON, D. C. Beresford, Printer, 618 F Street 1902 Copyright, 1902, By H. C. Scurlock, A. B., M. D. PREFACE. I hope that these notes will prove useful to those students into whose hands they may fall. The scope of a little book like this is necessarily limited, and many things which would permit of quite a treatise can only be touched upon ; but it has been the endeavor to present the important points of the principles of Chemistry in such a manner as to be readily understood by the beginning student. In the preparation of this little volume I have frequently used the better known English, American and German text-books for ref¬ erence, as well as notes from the lectures of my instructor and friend, Prof. W. H. Seaman. H. C. S. CONTENTS. Chapter. Page. I. Matter and Force, . • i II. Heat. 8 III. Light, 14 IV. Electricity and Magnetism, iS V. Chemistry Defined—The Atom—The Molecule, . 25 VI. Properties of Atoms, 28 VII. Atomic and Molecular Notation, .... 34 VIII. Chemical Reaction—Binary and Ternary Bodies, . 35 IX. Chemical Equations, 39 X. Gases, 43 XI. Exercises 45 xii. Chemical Arithmetic, 48 XIII. Classification of the Elements, .... 52 XIV. Introductory Considerations of Carbon Compounds, 67, XV. Hydrocarbons, 7r XVI. Open-Chain Bodies and Derivatives, .... 74 XVII. Carbohydrates, 91 XVIII. Closed-Chain Bodies and Derivatives, -95 XX. General Considerations of Analysis, . . 105 XXI. Qualitative Examination of Solutions, . .107 XXII. Qualitative Analysis 114 XXIII. Analysis of Urine, 121 CHEMICAL NOTES. i. MATTER AND FORCE. Matter is any thing that occupies space, as, a stone, water or air. A substance is a particular kind of matter, e. g., a thing may be wood, brass or paper. A body is a definite portion of matter; two pieces of stone are both bodies and the same substance ; a piece of wood and a piece of stone are both bodies but different substances. All matter possesses certain characteristics which we call its properties, and is subject to certain laws which we call physical laws. The study of these characteristics and laws is the province of Physics. Physicists look upon all matter as composed of very small particles called molecules, which are separated from each other by spaces greater than their own volume, and which are in a state of constant motion. We shall see later how Chemistry explains the formation of these molecules, and how it is that we have different kinds of matter resulting from them ; for it must be evident that a tangible portion of matter is the same as the molecules that make it. Between the molecules of matter there is constantly exercised an attractive and a repellant force, and we ascribe the conditions of matter to the relative preponderance of the one or the other of these forces. There are five states or conditions of matter: solid, liquid, gaseous, radiant and ethereal, though the first three are the most common and are the ones most often described. 2 2 chemical notes. Matter is solid when the attraction between its molecules is greater than the repulsion; liquid when the attraction and the repulsion are about equal; gaseous when the re¬ pulsion is greater than the attraction—in this condition the molecules tend to fly entirely away from each other, and the body must be confined in a closed vessel to preserve it; radiant matter is that which succeeds upon the gaseous form when it becomes so far attenuated that its molecules rarely, if ever, come in contact; ethereal matter is that homogeneous form which fills the interval we call space, not only between the heavenly bodies, but also the inter¬ spaces between the molecules of other matter.* Force is that which tends to produce or arrest motion. It may be said simply that force is that which produces motion, for even the arrest of it is the tendency to produce it in another direction. As an entity inseparable from matter it manifests itself as gravitation, cohesion, adhesion, magnetism and chemism. Gravitation is the mutual at¬ traction which all bodies have for one another; cohesion is the attraction existing between molecules of the same kind; adhesion is the attraction between molecules of different kinds ; magnetism is the power resident in certain bodies by virtue of which they attract to themselves certain other bodies which come within their field of force (see Mag¬ netism) ; chemism is the force that acts between atoms, causing them to unite in the formation of molecules. Force, as manifested by the change or the tendency to change the position of bodies, does work, and its capacity foi doing work we call energy. The energy which a body exvws when in motion is called kinetic energy ; that which it possesses when at rest, by reason of its ability to do work, ouaccount of position or condition, is called potential energy. -The idea of the ethereal condition of matter is an assumption neces¬ sary in the present state of our knowledge, but not fully proven, and liable to some serious objections.— Seaman. CHEMICAL, NOTES. 3 The term rest signifies a condition of constant equilibrium with surrounding things. Energy may also be manifest as heat, light and electricity, and these are convertible one to the other. The potential energy of coal can be transformed into heat, which can produce steam and drive an engine, whose motion may be converted into electricity, which in turn may produce like motion for propelling the street cars, or which may produce the light of the electric lamp. Such transformation of energy we call the conservation of energy, since it can be changed from one form to another without loss. Matter cannot be created nor destroyed; neither can force. The general properties of matter include divisibility,- iinpenetrability, porosity, density, elasticity, inertia, etc. Divisibility means the ability to divide a larger into smaller pieces, as, by cutting, breaking or tearing. Solu¬ tion is another means of divisibility, and is that process by which the molecules of the body dissolved are separated and evenly distributed throughout the body which dissolves it„ called the solvent.* Substances like the metals are not soluble as such, ordi¬ narily, but dissolve when acted upon by dilute acids. This is called chemical solution, because the metal is then con¬ verted into a compound which is soluble. Anything which tends to separate the particles of a body facilitates its solution ; thus heat, by weakening cohesion, and pulverization, by giving greater surface for the solvent to act upon,y make solution easier. A solution which is j-S-rt ('/■:.<■; . . * The recent theory concerning solution is that substances which are capable of conducting electricity and which can be decomposed by it are, when dissolved in water, separated into ions ; that is, their components, bearing opposite charges of electricity, exist separately in the solution. The weaker the solution, the greater the relative number of ions and the fewer molecules remaining intact. Thus in a weak solution of sodium chloride, sodium and chlorine both exist separately in the free state, having opposite charges of electricity ; and there are relatively but few molecules of the salt. Such substances are called electrolytes. 4 CHEMICAL NOTES. still capable of dissolving much more of a body is said to be dilute; one which contains about as much as it can carry at its temperature is concentrated ; one which can¬ not dissolve any more is saturated. Impenetrability is the impossibility of two bodies occupy¬ ing one and the same space at one and the same time. Porosity is the property which exists by reason of the spaces which separate the molecules of matter. The spaces -are the pores. Density of a substance means the amount of matter in a unit volume. The volume of a body is the amount of space that it fills; its mass, the quantity of matter that it contains. Elasticity is the property by which a body yields to pressure or tension and tends to resume its original shape and volume when the pressure or tension is removed. Inertia is the inability to change its position unless acted upon by some external force. Among the special properties of matter are hardness, brittleness, tenacity, ductility, malleability, form (crystal¬ line or amorphous), capillarity, diffusion, etc. Hardness is the ability to resist indentation, or wear by friction ; brittleness means fragility or the tendency to break readily under pressure or a blow ; tenacity is the power to withstand tension or pulling ; ductility is the ability to be drawn into wire ; malleability is the property which gives to a substance the ability to be beaten or rolled into sheets ; crystalline form is that which certain bodies assume when they pass from the liquid state to the solid state, or that assumed by certain salts passing from solution, by virtue of an attempt on the part of the cohesive power to arrange the molecules symmetrically. The arrangement is usually angular. Amorphous form is that in which there is no such orderly arrangement of the molecules. Capillarity is a property of liquids which enables them to rise in capillary (hair-like) tubes, their cohesion beino- 6 CHEMICAL NOTES. 5 less than their attraction for the tube. Diffusion is a prop¬ erty of both liquids and gases, in virtue of which if two liquids or two gases are left in contact they will spontane¬ ously mix, even if there is a wide difference between their specific gravities. The force with which the earth's attraction tends to draw a body to itself is called the weight of that body, and it is proportional to the mass of the body acted upon. If we attempt to lift blocks of wood, stone and iron, all having the same size, we note quite a difference in the amount of strength required to overcome the force of gravity in each case. Thus different substances have different weights. The unit of weight in English measurement is the avoir¬ dupois pound, and in the French or metric system is the gram. The metric system is the one now most generally used by scientists, and is legalized in the leading civilized countries. It is used throughout this book. In the measurement of bodies we consider not only the force by which they are attracted to the earth, but also the amount of space that they occupy. The measurement of a plane surface is expressed in squares of the unit employed ; while the whole content, i. e., the product of the length, breadth and thickness, is expressed in cubic terms. Prob¬ ably it is well to emphasize here soifl^ things that may be of help to the beginning student. One gram of water at 4° C., its greatest density, measures one cubic centimeter; therefore, given the amount of water in grams it is easy to know the volume it occupies. One kilo is 1,000 grams; one liter is 1,000 cubic centimeters; these terms are, for water at its maximum density, equivalent terms. The liter is a unit of capacity or volume, and is generally used in reference to a liquid or a gas. The cubic millimeier, cubic centimeter and cubic meter are also units of volume ;. the square millimeter, square centimeter and square meter are units of area ; the milligram, gram and kilo are, units of weight. 6 CHEMICAL NOTES. 10 millimeters = i centimeter. 10 centimeters = i decimeter. 10 decimeters = i meter. 1,000 meters = i kilometer. Specific Gravity is the relative weight of a substance as compared with the weight of another substance taken as the standard, the determination being made for equal vol¬ umes, and under the same conditions of temperature and pressure for both. The standard for solids and liquids is water at 40 C. ; for gases, air at o° C. is the standard. To find the S. G. of a body insoluble in and heavier than water. (1) Weigh the body in the air. (2) Weigh the body in water. It will be less than in the air. (3) Subtract the water weight from the air weight and divide the air weight by the remainder. The quotient will be the S. G. of the body. To find the S. G. of a body lighter than and insoluble in water. It is necessary to have a heavy bod)- to sink the light one. (1) Weigh the light body in the air. (2) Weigh the heavy body in water. (3) Weigh both together in water. The weight will be less than the weight of the sinker alone. (4) Add the air weight of the light body to the water weight of the sinker, and from the sum subtract the weight of both of them in water. This will give the weight of water displaced by the light body. (5) Divide the air weight of the light body by the weight of the displaced water. The quotient will be the S. G. of the body, and is always less than 1. CHEMICAL NOTES. 7 To find the S. G. of a powder insoluble in water. (1) Weigh out a portion of the powder. (2) Pour it into a flask (which when filled to a given mark holds a known weight of water), add water to the mark and weigh. {3) Subtract weight of powder from weight of water and powder (2). (4) Subtract this remainder from the weight of water alone required to fill the flask to the mark. This will give the weight of the water displaced. (5) Divide air weight of the powder by the weight of the water displaced to find the S. G. To find the S. G. of liquids. (1) Weigh equal volumes of the liquid whose S. G. is to be determined, and water, in a tared vessel, separately. (2) Divide the weight of the liquid by the weight of the water. The quotient will be its S. G. A hydrometer is an instrument used for the determination of the S. G. of liquids. It consists of a cylindrical tube loaded at its lower end with mercury or shot in order that it will sink to an extent and float in an upright position; it ends above in a long, narrow stem, graduated to show the degrees of S. G. of a liquid in which it is immersed. Hydro¬ meters take the names urinometer, lactometer, acidometer, etc., when graduated within the ranges of variations of the specific gravity of urine, milk, acids, etc., respectively. To find the weight of a given volume of a substance when the specific gravity is known. Multiply the given volume by the specific gravity and express the result in units of the equivalent terms for water, thus: What is the weight of 400 cc. of a liquid whose S. G. is 1.32 ? 400 X 1.32 = 528.00 gins. What is the weight of 25 cubic decimeters of a stone, S. G. 5-25 ? 25 X 5.25 = 131.25 kilos. To find volume when weight and specific gravity are known. Divide the given weight by the specific gravity 8 chemical notes. and express the result in the equivalent terms for water, thus : What volume is occupied by 20 kilos of a substance whose specific gravity is 2.5? 20-^-2.5=8 cubic deci¬ meters. Of what capacity must a vessel be in order that 18 kilos of sulphuric acid, S. G. 1.8, will just fill it? 18 -f- 1.8 = 10 liters. II. HEAT. " Heat is a form of energy due to molecular vibration." Remember that the particles of matter (molecules) are in a state of constant motion, and the phenomena of heat de¬ pend upon an increase in the force and rate of their vibra¬ tion. These vibrations are capable of being transferred to the surrounding ether and to other bodies. Source of Heat.—The sources of heat are principally the sun, chemic action and mass motion. It may be said that the sun is practically the source of all of our heat, not only that which we receive from its daily radiation, but also that which is stored up as energy in the fuel we use and the food that we eat. Almost all chemic action is attended by the development of heat; sometimes it produces cold, i. e., takes up heat. The first of these is called exothermic and the latter endo- thermic action. As to the production of heat by mass motion, almost every one is familiar with the fact that it can be generated by striking with a hammer upon an anvil, and that a saw becomes hot while sawing through a board. Mechanical Equivalent of Heat.—A certain amount of mechanical action can be converted into a certain amount of heat; therefore a given amount of heat can be expressed in a given amount of mass motion. The calorie or thermal CHEMICAL NOTES. 9 unit is the quantity of heat required to raise the temperature of one kilo of water one degree centigrade in metric terms, or the quantity required to raise one pound of water one degree Fahrenheit in English terms. The mechanical equivalent of the calorie, or the amount of mass motion required to generate one calorie or thermal unit, is rep¬ resented in the metric by one kilo of matter falling through a distance of 424 meters ; or in English units is represented by one pound of matter falling a distance of 772.5 feet. The Effects of Heat are (1) rise of temperature; (2) increase of volume, or expansion ; (3) change of condition of matter. When a body becomes heated to any extent it is easily recognized by the sense of feeling, but for the delicate and accurate estimation of temperature we use the thermometer. Thermometers are of various construction, but all of them depend upon the expansive quality of some substance. Mercurial thermometers are in most general use. "A thermometer consists generally of a glass tube of cap¬ illary bore, terminating at one end in a bulb. The bulb and part of the tube are filled with mercury, and the space above the mercury is a partial vacuum. On the tube, or on the plate behind the tube, is a scale to show the height of the mercurial column." There are three principal scales: the Fahrenheit, centi¬ grade and Reaumur. The graduation of a thermometric scale is made with the boiling and freezing points of water as the fixed points, between which the scale is divided into equal divisions or degrees; both above the boiling point and below the freezing point degrees *are added to the scale equal to the divisions between the two fixed points. When the bulb of the thermometer is placed in escaping steam the column of mercury rises and finally comes to a point where it remains stationary; this is taken as the boiling point of water. Placed in melting ice it sinks to a stationary point, which is regarded as the freezing point of water. If the instrument is to be graduated according IO CHEMICAL NOTES. to the Fahrenheit scale the boiling point is marked 212 and the freezing point 32, between which there are 180 divisions; if according to the centigrade scale the boiling point is 100 and the freezing point o ; boiling point Reaumur is 80 and freezing point o. Between these two points there are 100 and 80 divisions on the centigrade and Reaumur scales respectively. The Fahrenheit scale is largely in use popularly, but scientists and teachers almost everywhere use the centi¬ grade scale. It sometimes becomes necessary to translate one scale into another. Taking the number of degrees between the boiling and freezing points of the scales as referred to above, it will be seen that the value of a centigrade degree compared to a R6aumur degree is i, and a Reaumur to a centigrade is Then, to change Reaumur to centigrade, multiply the given number of Reaumur degrees by f; to change centigrade to Reaumur, multiply the given num¬ ber of centigrade degrees by f. We find in the same manner that the factor for translation from centigrade to Fahrenheit is f, and from Fahrenheit to centigrade is We have to consider, too, the 32 degrees of the Fahrenheit scale below the freezing point. To change Fahrenheit to centigrade, subtract 32 from the given number of de¬ grees and multiply by f-; to change centigrade degrees to Fahrenheit degrees, multiply the given number of degrees by f and add 32. The method between Reaumur and Fahr¬ enheit would be the same, the factors being, of course, from Fahrenheit to Reaumur, and f- from Reaumur to Fahrenheit. Considering our views of the constitution and the states of matter, it is easy to understand how heat changes the condition of matter. If the vibration of the molecules of a solid become very violent and rapid, it is apparent that the repellant power is increased, or in other words, cohesion is weakened, and the body finally approaches the liquid state, provided the amount of heat required does not CHEMICAL NOTES. II cause chemical change before that condition is brought about. The same thing is true when a liquid passes into the gaseous state. All bodies expand when they are heated. From what is said above, such would be expected to result. Some substances, however, e. g., arsenic and bismuth, expand on cooling, and so does water below 40 C. Most of our units of heat are referred to water, the heat relations of which should be well studied. Water gives off a vapor at all temperatures, which if confined exerts pres¬ sure on the walls of the container. This pressure we call tension, and it is constant for all temperatures. At o° it is 4.60 mm. At 40° it is 54.90 mm. 10 9.16 60 H8.79 20 17.39 88 354-28 30 3I-55 100 760.00 From this table it is seen that at ioo° C., the boiling point of water, its vapor tension is the same as the normal atmospheric pressure. We may say, then, that a liquid boils when the tension of its vapor is the same as that of the pressure to which it is subjected. It is well known that water boils easier upon a high mountain, where the atmospheric pressure is less, than it does at the sea level, where the pressure is greater. Latent Heat.—If we take a kilo of water at 8o° C. and mix it with a kilo of ice at o° C., we will find that the one kilo of water contained just sufficient heat to melt the kilo of ice, and that the temperature of the now two kilos of water is just o° C. It is apparent, then, that the 80 degrees of heat carried by the kilo of water were consumed by the ice in the process of melting, and not a degree was left to raise the temperature. The heat thus consumed in changing the state of matter we call latent heat. The amount of heat required to raise the temperature of 12 CHEMICAL, NOTES. one kilo of water one degree centigrade we call a calorie m the metric, and in the Knglish the amount of heat required to raise the temperature of one pound of water one degree centigrade is the thermal unit. There is also what is called the small calorie. It is the amount of heat required to raise the temperature of one gram of water one degree centigrade. It has been found by very careful experiments that the amount of heat required is not the same between all degrees of temperature, and some physicists prefer to state the de¬ grees between which the reckoning is to be made ; thus, some specify from 40 to 50 C., and from 150 to 160 F., while others say from o° to i° C., and from 320 to 330 F. The process above described required 80 calories, which would indicate that the latent heat of ice is 80. The latent heat of steam is 536 calories. Specific Heat.—The amount of heat required to raise one kilo one degree is not the same for all substances, and the ratio of the amount required to raise one kilo of a given substance one degree to the amount required for water is the specific heat of that substance. Temperature and quantity of heat are not the same. Temperature is one of the effects of heat, and is perceptible to us through our sense of feeling. The temperature of a body refers to its ability to communicate molecular vibra¬ tion (heat) to, or to receive it from, other bodies. " It depends upon the average kinetic energy of the individual molecule, while quantity of heat depends upon the average kinetic energy of the individual molecule multiplied by the number of molecules." Hot and cold are relative terms, though we are in the habit of calling any temperature which. to our sense of feeling is below the body temperature, cool or cold accord¬ ing to the sensation produced. When a hot body is placed among others of lower tem¬ perature it gives out heat until it has become of the same CHEMICAL NOTES. 13 temperature as the surrounding bodies ; their temperature is, of course, raised, even though it may not be sensible to us. Cold may be produced in several ways. Certain salts when going into solution take up heat on account of ex¬ pansion of volume and thus produce cold, e. g., water in a test tube may be frozen by stirring with it a mixture of ammonium chlorid one part and ammonium nitrate two parts, in a small quantity of water. Snow and common salt will produce intense cold. By this time it must be well fixed in the student's mind "how it is that a change of state of matter, as from a liquid to a gas, requires heat. It is well known that when alcohol or ether is placed upon the skin a sensation of cold is pro¬ duced by the rapid evaporation. In like manner any sub¬ stance which is normally a gas, and which has been compressed to the liquid condition or to a very much smaller volume than it normally occupies, when released tends to assume its original condition, and of course re¬ quires heat, which it abstracts from surrounding bodies. This fact is made use of commercially in the manufacture of artificial ice, and in the refrigerating plants now used extensively. Not only do gases take up heat upon expansion, but also on being compressed they give out heat. The heating of the barrel of a bicycle pump or of an air-tank pump is due in part only to the friction of the piston ; much of it results from the compression of the air. Above we spoke of the expansion of all substances, but the rate of expansion is not alike for the three common states of matter, solid, liquid and gaseous. Solids and liquids do not expand with the same degree of uniformity ; gases, on the other hand, do expand uniformly. For every degree of temperature that a gas is raised or lowered it increases or decreases 2T3 °f its volume. Suppose, then, that we have at o° C., a body of gas whose volume is 273 liters, and that we lower its temperature, one degree at the time, until we 14 CHEMICAL NOTES. shall have reached — 2730 C. (absolute zero). At this point all molecular motion would cease and the gas would theo¬ retically disappear by contraction of volume. But we have no such perfect gas, and it would change its condition before reaching that point. All gases can be liquefied under the proper pressure at a certain temperature, above which no amount of pressure will liquefy it; this is called the critical temperature, and varies for different gases. The absolute temperature of a body is found by adding 2730 to the observed temperature if above o° C., and by subtracting the observed reading from 2730 C. if it is below o° C. On the Fahrenheit scale absolute zero is —459.40. III. LIGHT. Like heat, light is a form of energy due to molecular vibration. These vibrations are transmitted through the ether as a series of short waves, and we perceive them by our optic nerves. The sun is the source of most of our light, even as it is of heat. Some bodies give us light because they are self luminous, i. e., they are capable of themselves generating light; others but reflect the light of other bodies, e. g., the sun is itself luminous, while the moon reflects the light of the sun. Rays of light travel in a straight line ; when they are intercepted by an intervening body a shadow is produced ; however, not all bodies intercept light entirely. There are opaque bodies, which cut off all light; translucent, which pass the rays, but in such a manner that objects cannot be well defined through them ; transparent, which readilv pass the rays of light, and things can be easily seen through them. CHEMICAL NOTES. 15 The intensity of light decreases as the square of the dis¬ tance from the luminous body increases. The candle power is the standard of measurement for the intensity of light, and is " the amount of light given by a sperm candle weigh¬ ing one-sixth of a pound, and burning 120 grains an hour." It has been estimated that light travels at the rate of about 300,000 kilometers (about 186,000 miles) per second. Rays of light striking against an object are thrown back, as a ball rebounds when thrown against a wall. This is called reflection. The angle at which they strike is the angle of incidence ; the angle at which they rebound, called the angle of reflection, is equal to the angle of incidence. Highly polished plane surfaces, mirrors, reflect nearly all the light they receive in definite directions. Rough sur¬ faces reflect light, not in certain definite directions, but in all directions ; thus they are illuminated and we are able to see them. Diffused light depends upon this general reflec¬ tion of uneven surfaces. Were it not for that, no matter how brightly the sun might shine, the interiors of our houses would be dark. Rays of light pass in a straight line if the medium through which they pass is of uniform density, but when they pass from one medium to another of different density their direction is broken. This is called refraction. If it pass from a denser to a rarer medium it bends from the per¬ pendicular ; if from a rarer into a dense, toward the perpen¬ dicular. The amount of bending or refraction is influenced by the angle of incidence and the medium. "A prism is any transparent medium bounded by planes inclined to each other." Most prisms are made of flint glass, on account of its great refracting power. When a ray of light passes through a prism it is refracted both by the surface at which it enters and at which it emerges, and if it is received upon a screen it is seen to be decomposed into several colors. They are called the primary colors, for on passing any one of them through a second prism it is i6 CHEMICAL NOTES. not broken up into other colors, and their light is therefore said to be monochromatic. There are seven of these colors, violet, indigo, blue, green, yellow, orange and red. The violet appears at the end corresponding to the base of the prism and the red at the other end of the spectrum. This separation of the primary colors depends upon their inability to be equally refracted by the same medium. A lens may be considered as formed by two prisms. There are two general kinds: (i) convex, corresponding to two prisms with opposed bases; (2) concave, which corre¬ spond to two prisms with opposed apices. Convex lenses converge the rays of light passing through them ; concave lenses diverge them. Remember that in passing through a prism a ray of light is refracted toward its base. Light is capable of initiating chemical action; that property is termed actinicism. The different primary lights produce different lengths of ether waves, and the rate per second is also different. The actinic power is greater ac¬ cording as the number of vibrations per second is greater; thus the red, whose vibrations are fewest, has the least actinic power ; the violet, whose vibrations are greatest, has the highest actinic value. The spectroscope is an instrument devised for examining the light given off by luminous bodies. The light emitted by a glowing solid or liquid will give a continuous band of the colors, continuous spectrum, but that from a gas or vapor presents a series of very bright lines against a black background. Such a spectrum is called bright-line spectrum in contradistinction to that which is observed when solar light is examined, in which a number of dark lines (Fraun- hofer's lines) are seen to cross the continuous spectrum. This is termed absorption spectrum, upon the hypothesis that the sun is a glowing solid or liquid body which is surrounded by an atmosphere containing vaporized metals, and that this vapor is capable therefore of absorbing the CHEMICAL NOTES. same kind of light that the metals which it contains would give out. The study of the spectra of bodies we call spectrum an¬ alysis. The undulations which a luminous body sets up in the ether take place in all directions perpendicular to the plane of propagation. They can,' however, be cut off in all directions except one, and the light is then said to be polarized. Polarization takes place when light is passed through certain crystals like Iceland spar and quartz ; or it may be polarized by reflection, as from the surface of water or a mirror at certain angles. When a printed page is viewed through a crystal of Iceland spar the words appear to be doubled. If the crys¬ tal is placed over a word two will appear ; and if it is rotated one of them will seem to revolve about the other. This phenomenon is called double refraction, and is due to the splitting up of the rays of light into two. Both of them are polarized. The ray which produces the stationary image of the word is called ordinary ; that producing the revolv¬ ing image is the extraordinary ray. A Nicol's prism consists of a rhomb of Iceland spar, cut through its obtuse angles, and the two pieces cemented to¬ gether after being polished. They enter into the con¬ struction of the polariscope. A simple polariscope consists of two Nicol's prisms mounted in a tube, and is used for examining substances by polarized light. One of the prisms is the polarizer; the other, the analyzer. Bodies which rotate the plane of polarized light are said to be optically active ; those which do not, inert. 3 i8 CHEMICAL NOTES. IV. ELECTRICITY AND MAGNETISM. The true nature of electricity is not yet known to us, but we shall consider it here as one of the forms of energy. We shall study it under three heads, viz : static electricity, dynamic electricity and magnetism. It was first observed by the ancients that when certain substances, like amber, are rubbed they acquire the power to attract to themselves other light bodies ; it was also observed that this power to attract differed for different substances and under varying circumstances. For instance, if a dry glass rod is rubbed with a piece of silk and presented to a pith ball which is suspended by a silk thread, it will attract it to itself, but after a few seconds the ball will fall away from it, and if the glass rod is again rubbed and presented to the pith ball it will be repelled instead of attracted as before. But if a stick of resin which has been rubbed with a piece of silk or cat's fur is presented to the pith ball it will attract it very strongly. It will, however, fall away from the resin after a while as it did from the glass rod; if now the excited glass rod be presented to the pith ball it will attract it strongly. Thus it is seen that two opposite con¬ ditions of this peculiar form of energy exist: that condition which glass acquires when rubbed is called positive or vitreous electricity ; that which the resin acquires is called negative or resinous electricity. From experiments such as the above has been deduced a universal law of electrical phenomenon : like electricities repel each other, and unlike attract. Some substances are apparently not capable of being electrically excited by rubbing, e. g., a metal rod would show 110 such phenomena as a glass rod. Such bodies lead CHEMICAL NOTES. *9 off the electricity as rapidly as it is formed ; we call them conductors; substances which retain their electric charge, like glass and resin, we call non-conductors. Non-conduct¬ ors are used as insulators, i. e., bodies which prevent the loss of electricity from a conductor. An electrified body placed near an unelectrified one will set up in that body an electrical condition ; this is called induction. The portion of the body nearest the electrified one will be charged with electricity of an opposite charac¬ ter to that of the electrified body, while its more remote portion will sustain a charge of opposite character to that of its hear portion. These opposite conditions of electrical charge are termed the potential. If the induced electricity is led off it is possible to con¬ tinuously reinduce it, thus setting up a current. It is upon this principle that electrical machines are constructed. The older and simpler electrical machines consist of a circular glass plate so arranged as to rotate between two cushions of silk ; it is provided with a handle for turning. The electricity developed by the friction of the glass plate against the silk cushions is collected, by metal combs placed on either side of it, and conveyed to the prime conductor, which collects the charge. The electricity developed by the electrical machine may be condensed or collected. A means of collecting it is the Leyden jar; it consists of a glass jar coated inside and outside with tin foil for about a third of its height. It is closed with a cork or wooden cap, through which passes a metal rod ending above in a rounded knob ; below, it gives attachment to a metallic chain, which reaches to the tin foil covering the inner bottom of the jar. When the knob of the jar is presented to the prime conductor of an electrical machine it charges the inner coating of tin foil with the same kind of electricity as that of the prime conductor, while on the outer coating a charge of opposite nature accumulates. It will remain charged for a long time if not 20 CHEMICAL, NOTES. disturbed ; but if the two coats are by some means brought in contact the jar will be discharged. The electricity above described is static or frictional elec¬ tricity. We will now consider dynamic electricity, or the electricity of chemic action. Static electricity, just referred to, remains upon the con¬ ductors upon which it is collected unless led off, or until the tension becomes so high or the difference of potential so great that it is discharged ; i. e., the two electricities leap through the air, unite and produce a vivid spark and a sharp report. Dynamic electricity can not be accumulated in this way, nor does it leap through the air. It requires for its passage a continuous conductor. Its intensity is small compared with its quantity, while static electricity, though small in quantity has great intensity. Dynamic electricity has also great chemic (electrolytic) power; static electricity has not. Dynamic electricity or current electricity is that which is set up usually by chemic action, and which requires a con¬ tinuous conductor for its flow. It is also produced by the dynamo. It does not leap through the air nor produce a vivid spark and sharp report, as does static electricity. It is made manifest by the effect it produces upon bodies, such as the heating of a wire through which it passes, or its in¬ fluence upon the magnetic needle. The chemical cell for setting up the electric current con¬ sists usually of a glass jar in which two metal plates are placed separately in a liquid which is capable of acting upon them chemically. The metal plates are termed the elemetits of the cell and the liquid is sometimes called the electrolyte. Of the two metals, one of them is more vigorously acted upon than the other, and is termed the positive element ; the other is the negative element. The current flows only when the elements are connected outside of the cell. The direction of the flow is from the positive to the negative element; thus the negative element outside of the cell is CHEMICAL NOTES. 21 the positive pole and the positive element is the negative pole. The flow of the current through the cell and the con¬ ductor between its poles is called its circuit. The circuit is said to be closed when the poles are connected, and open when they are not. It is a prerequisite for current flow that the poles of the cell be united. It may take place through the earth as well as through a continuous wire. It is due to a difference of potential, flowing from the higher to the lower, as water flows along a pipe from a higher to a lower level. Electromotive force (E. M. F.) is the force that tends to convey electricity along a conductor, and is proportional to the difference of potential. But the strength of the current will depend very much upon the resistance to be overcome. It meets resistance both within the cell (internal resistance) and without it (external resistance). An electric cell is sometimes called a battery, but the term is most often ap¬ plied to a series of several cells connected to each other. The following description of a simple voltaic or galvanic cell will illustrate further the construction and action of a chemical cell. Such a generator consists of a glass jar con¬ taining dilute sulphuric acid in which are placed at an interval from each other two metals, a plate of zinc and one of copper. When the ends of these two plates are con¬ nected by a wire a current flows, the zinc begins to waste away and bubbles of gas collect upon the copper plate. These are bubbles of hydrogen, set free from the sulphuric acid by the action of the zinc. It will be found that the amount of hydrogen liberated bears a simple relation to the amount of zinc which has disappeared. When the copper plate becomes thoroughly covered with hydrogen bubbles, the resistance grows greater and the current strength weaker. The condition is called polarization. Under such circumstances a continuous current of uniform strength cannot be obtained. It has been somewhat over- 22 CHEMICAL NOTES. come by the addition of an oxidizing substance to the acid; it oxidizes the hydrogen and thus prevents the formation of or removes the bubbles. Potassium bichromate is uni¬ versally used as an oxidizer in this type of cell. Another means of obviating this difficulty is by using a cell having a separate liquid for each element (two liquid cells). As said above, the current flows only when the circuit is closed, and, that being true, there should be no wasting of the zinc when it is open. However, such does occur, due to impurities in the zinc. Remember that what is neces¬ sary for current flow is two metals immersed in a liquid that acts upon them unequally, and that they be connected. The presence of foreign substances in the zinc leads to the formation of local currents upon that element, and it con¬ sequently wastes away all of the time. This is overcome by amalgamating the zinc with mercury. In simple cells, as above described, carbon plates now supplant the copper. When a layer of insulated wire is wrapped around a magnetic needle and a current of electricity passed through it, the needle will be deflected from its direction. Used in this manner such an arrangement is called a galvanoscope, since it shows the passage of the current. When used with a graduated disc which indicates the amount of deflection, it can be used to estimate the strength of current flow, and is called a galvanometer. The following are the units of electrical measurement commonly in use : The ohm, the unit of resistance, is represented by the resistance offered by a column of mercury 106.3 cm- l°n&) having a cross section of one square millimeter. The ampere, the unit of current strength, which will deposit .001118 gm. of silver from a solution of silver nitrate in one second. The volt is the unit of electromotive force, and is the chemical notes. 23 force required to maintain a current of one ampere through a resistance of one ohm. The watt is the unit of power for doing work, and is the amount of pressure of one volt with one ampere. The Induction Coil.—The induction coil consists of a core of soft iron, or of a bundle of wires around which is wrapped an insulated wire, called the primary layer. Over the primary wire is wrapped another insulated wire, in several layers, called the secondary layer. The secondary wire is much thinner and longer than the primary wire. If the ends of the primary wire are connected to a cell with a make-and-break arrangement in the circuit, with every closing and opening of the circuit a current of induced elec¬ tricity will flow through the secondary wire. At the closing of the circuit it flows in a direction opposite to that in the primary wire ; at the opening it flows in the same direction as the primary. If the flow of current through the primary were continuous there would be no current observed in the secondary, hence it is necessary to have a make-and- break arrangement. Such an appliance usually consists of a metallic hammer attached to a spring, and so placed that it becomes alternately attracted by the opposite electricities and keeps up a constant vibratory motion between the poles of the cell, thus continually closing and opening the circuit. The induction coil is often called a transformer, being tised to change electricity of low intensity to electricity of high intensity, and vice versa. The common Faradic medical battery consists of an induction coil and chemical cell handily arranged for the purpose intended. The instruments to be attached to the wires leading from the poles of the battery, and by which the current is applied to the person, are called electrodes. Magnetism.—Magnetism is a power resident in certain substances, as iron ore (lodestone), by virtue of which they have the power to attract to themselves certain other bodies 24 CHEMICAL NOTES. which come within their field of force. The attractive force which they exert is manifest in all directions, and the extent of space over which a magnet may exercise its power is called its field of force. There seems to be some connection between magnetism and electricity. If an insulated wire is wrapped around a bar of iron and the current from a galvanic cell passed through it, the bar of iron will exhibit strong magnetic attraction, but when the current ceases the magnetism disappears. Again, an arma¬ ture revolved within the field of force of a magnet will set up an electric current. The dynamo is constructed on this principle. The attractive power of a magnet seems to reside near the ends (a bar magnet), and as the middle is approached a point is finally reached which is neutral, i. u- In chemiical calculations five quantities may be involved, viz : molecular weight, atomic mass, number of -atoms, per cent, and its base, 100. Any three .of these being given the fourth can be found by the following equations, in which x = percentage weight; a = atomic mass ; n = number of atoms and m — molecular weight: an X 100 x : 100 : : an \m = m = x mx 100 a : x : : m : n = n loon: x : : m \ a =■ a = 100 a mx IO0n 10 oan m : an : : 100 : x = x = m See also Chapter XII. Optical Properties.—Many organic bodies are determined by the direction or degree to which they rotate the plane of polarized light, or by the index of refraction. The former method is largely applied to the investigation of sugars. The behavior of certain bodies toward polarized light led to their investigation in that relation, from the results of which were deduced our ideas of physical isom¬ erism. chemical notes. 71 XV. HYDROCARBONS. Hydrocarbons are bodies which contain carbon and hydrogen only. They are the simplest of the bodies which we now come to study, and all other organic substances may be referred to them as their source. They form two great classes, called the open and the closed chain series. By a chain is meant a series of atoms, usually of the same kind, joined to each other, but also united to other atoms. Carbon atoms form the chains of organic chemistry, and they are united to hydrogen atoms. Every carbon bond is supposed to have equal value, and carbon maintains its quadrivalence in all its compounds. In the open chain the number of carbon atoms that can enter into it is theoretically unlimited. We have a hydro¬ carbon whose formula is graphically expressed H 1 H—C—H I H If the end atom of hydrogen is removed, and we add another carbon atom, we shall have a body whose formula is H H l 1 H—C—C—H I I H H Such addition of carbon atoms can theoretically be con¬ tinued indefinitely, and because of the theory such a chain is called an open chain. In a closed chain the number of carbon atoms is limited, 72 CHEMICAL NOTES. and it is supposed that they are so united to each other that no more carbon atoms can enter into the ring, as it is called. Thus the formula of benzene, a closed chain hydrocarbon, is expressed graphically CH A HC CH HC CH \V CH Here it is seen that the carbon atoms are joined by al¬ ternate single and double bonds, which leaves upon each of them a free bond for the hydrogen atom. None of the carbon bonds can be loosed ; consequently no more carbon nor hydrogen atoms can enter directly into such a body. The closed chain bodies form haloid addition compounds, however, in which it is supposed the carbon bonds are freed. We shall find other series of bodies in our study of organic chemistry, but they all belong to or are derivatives of these two great series of hydrocarbons. No classification of organic bodies yet devised is alto¬ gether satisfactory, but the generalization of them as deri¬ vatives of these two series seems well founded in the present state of our knowledge. " When the general chemical con¬ stitution of a carbon compound has been rightly ascertained, it can be converted into the corresponding hydrocarbon, or vice versa." A saturated series is one in which all of the available carbon bonds are joined to hydrogen atoms, or, in other words, is one in which the carbon atoms are joined to each other by a single bond, thus I I —c—c— CHEMICAL NOTES. 73 An unsaturated series is one in which all of the carbon bonds are not so saturated; their carbon atoms are joined by double or triple bonds, e. g. : h—c—h c—h II I!! H—C—H C—H Ethene. Acetylene. An isologous series is one in which the contiguous members differ from each other by a uniform difference in the amount of hydrogen they contain. The first member is usually a saturated body ; the succeding members are unsaturated. ^ ( Isologous. A | ch, ch2. c. •i c2h6. c2h4. c2h2. 1 c3h8. c3h6. c3h, ^ c4h10. c,h8. c4h6. If the first column of the above table is read vertically we have a series of bodies in which every carbon atom is saturated ; it is a saturated series. The other columns are unsaturated. If the table is read horizontally it is seen that the first member is saturated and the following bodies are unsat¬ urated, and that each successive member differs from the preceding by a uniform variance in the amount of hydrogen contained. Each line forms an isologous series. If each column is read vertically it is also seen that the succeeding bodies differ from each other by a constant increment of both constituents. Such a series is a homo¬ logous series. Homologous bodies resemble each other in their chemical nature. We have also a heterologous series. The term is applied to a series of bodies differing in their properties, but all of them are derivatives of the same hydrocarbon. In many cases they may be formed from each other. 74 Saturated. TT . , Radical. Hydrocarbon. ch4. ch3. c2h6. c2h5. chemical notes. {Ether.) {Alcohol.) Oxid. Hydroxid. (ch3)20. ch3oh. (c2ht)20. c2h5oh. {Aldehyde.) (Acid.) ch2o. ch2o2. c2h4o. c2h4o2- The above lines read horizontally illustrate a heterologous series. We have yet other serial classifications, usually homo¬ logous, and which take the name of their first member, as, methane series, acetylene series, benzene series, etc. Remember that all organic compounds belong to or are derived from members of the two great series. While it is true that we do not know definitely the exact formula of all organic bodies, yet the results of careful experiment and the conclusions drawn from analogies seem to warrant such a classification. The facts above stated enable us to make use of general formulae which will represent any member of a given series or its derivatives, thus CnH2n+2. Cn represents any number of carbon atoms ; H2n+2 means that the number of hydro¬ gen atoms is twice that of the carbon plus 2, e.g., if 6n=C2, the body will be C2H6. Hydrocarbons form their radicals by losing one or more atoms of hydrogen. According to the nomenclature they end in yl; CH^ is methane; CH3, its radical, is methyl. XVI. OPEN-CHAIN BODIES AND DERIVATIVES. The Paraffins.—The paraffin series of hydrocarbons, called also the marsh gas or fatty series, is a homologous series of open-chain saturated bodies whose first member is CH4, methane. General formula, CnH2IH2. It is called paraffin series because the final members as known to us CHEMICAL NOTES. 75 are the paraffins, bodies which have but little affinity for other chemicals. They exhibit the three ordinary states of matter : those containing up to four atoms of carbon are gaseous ; those having from that, number up to sixteen are liquids, while those that are higher approach the solid state, until at last we have the hard paraffins of commerce. Their specific gravities increase as the molecular weight becomes higher; there is also an increase in their boiling and melting points. The behavior of these bodies toward others marks a dis¬ tinction between them and the members of the closed-chain series : (i) they are not acted upon or only difficultly acted upon by sulphuric and nitric acids ; (2) the hydrates which they form are basic (see alcohols); (3) they are not readily oxidizable. Methane, the first number of this series, occurs abund¬ antly in nature, where there is decaying organic matter, especially where vegetable matter decays in the presence of much moisture. It is a colorless, odorless gas, slightly soluble in water ; it burns, and, mixed with air, is an ex¬ plosive. Reference to the table will give some ideas as to the other members of the series. PARAFFIN HOMOLOGUES. Name. Methane, Ethane, Propane, Butane, Pentane, Hexane, Heptane, Octane, Nonane, Decane, Etc. Formula. Boiling point. CH4 (gas), C2H6 (gas), C3H8 (gas), —164° —93 -45 -fi 37 69 98 124 *5° i73 76 CHEMICAL NOTES. It is easy to understand from the above table how the paraffin homologues are formed. As stated elsewhere, the formation of such bodies is theoretically unlimited. Be¬ ginning with hexadecane, C16H34, the paraffins are solids, their hardness increasing as their molecular weight be¬ comes higher. The softer of them form the class of sub¬ stances known as vaselines and mineral or lubricating oils ; the higher ones are known as ceresine, ozokerite, mineral wax, hard paraffin, etc. It is also to be noted that their specific gravity increases with their molecular weight, but all of them are lighter than water. The paraffins can be prepared by synthetic processes, but they exist in nature to a large extent, and many industrial enterprises, using certain natural products, are the direct sources of them. Natural Gas contains^ 90 per cent, of methane, the first member of the series, and the distillation of coal produces, among other things, many liquid and gaseous hydrocarbons ; the latter compose illuminating gas, of which olefiant and marsh gases are the principal ones, marsh gas forming 29 per cent, of it. Petroleum is a dark-brown, heavy liquid, containing most of the members of the paraffin series. They are ex¬ tracted by fractional distillation. The following are some of the important products of petroleum distillation :* Cymogene, chiefly C4H10, boils at o C. ; used for making artificial ice. Rhigoline, a mixture of C4HU) and C5H12, mostly the latter, boils at 18.30 C. ; it has been used to some extent as an an¬ esthetic in surgery. Petroleum Ether, Cf)H12 and C6H14, specific gravity .665- .67, boils at from 450 to 6o° C. ; used as a solvent and in the manufacture of air gas. Gasolene, C6H14, boils at 48°-50° C. ; it is also used in the making of air gas. ■x"See Allen's Commercial Organic Analysis, Vol. II, and Redwood's Petroleum aiid its Products. chemical notes. 77 Naphthas, C6HU and C7HI6, three varieties, range in boil¬ ing points from 82° to 150° C. ; they are used for cleaning and as solvents. Benzine, C7H1G and C8H18, specific gravity .68-72, boils at 7o°-9o° C. ; used in varnishes and paints. Kerosene, composed of paraffins, C7H16 to C12H26, specific gravity .78-82, boils at 150-300° C. ; it is used in lamps for lighting. Liquid Petrolatum, Soft Petrolatum and Hard Petrolatum are described by the U. S. P. as " mixtures of hydrocarbons, chiefly of the marsh gas series, obtained by distilling off the lighter and more volatile portions from petroleum and purifying the residue when it has the desired melting point." Soft paraffin melts at 40°-45° C. ; the hard varie¬ ties range from 45°-65° C. It must be remembered that the bodies to which these names have been given are not of definite chemical consti¬ tution, but that they are mixtures of several bodies in some cases. This renders it impossible to assign a formula to them ; for the same reason it is often difficult to find specimens of them that entirely agree in their physical constants. Halogen Derivatives.—The halogen derivatives of the paraffins are substitution products, made by the direct substitution of hydrogen. The halogen derivatives of the unsaturated hydrocarbons may be both substitution and addition compounds. Chlorine and bromine act directly upon them, but iodine does not. The substitution of chlorine for hydrogen in methane gives the following bodies : CH4, methane. CH3CI, monochlor-methane. CH2C12, dichlor-methane. CH3CI, trichlor-methane—chloroform. CCI4, tetrachlor-methane. 78 CHEMICAL, NOTES. Of these bodies trichlor-methane is the most important. Corresponding to it are triodo-methane and tribromo-me- tliane, iodoform and bromoform., respectively, formed by the substitution of iodine and bromine. Chloroform may be produced in several ways. Among the more important are the alcohol and acetone methods, as shown by the equations below : (a) 2C2H5OH + ioCaOCl2 = 2CHCI3 + Alcohol. Calcium Chloroform, hypochlorite. 7CaCl2 + 3Ca (OH)2 + 2H20 + 2C02. Calcium Calcium Water. Carbon chlorid. hydrate. dioxid- (b) 2C3H60 + 6CaOCl2 = 2CHCI3 + Acetone. Calcium Chloroform, hypochlorite. 2Ca(OH)2 + Ca(C2H302)2 + 3CaCl2. Calcium Calcium Calcium hydrate. acetate. chlorid. NiTro-Derivatives.—The paraffin hydrocarbons do not form nitro-derivatives readily ; in fact, very few of them do at all. They are produced by the substitution of N02 for an atom of hydrogen. This is usually accomplished by heating the iodid of the paraffin radical with the nitrite of silver. The resulting bodies have the general formula CnH2n_rI(N02), and have an acid character. The Oeefines.—The defines are an unsaturated series of bodies having the general formula C H2n. They are able to unite directly with two monad atoms or radicals. Nascent hydrogen converts them into saturated hydrocar¬ bons. When oxidized they give rise to dihydric alcohols. The lower members are gases, the intermediate are liquids, and the higher, solids ; they are soluble in alcohol, ether and sulphuric acid, but not in water. EtJienc or Olefiant Gas, the first member of the series, is a colorless gas, having a pungent odor; it burns with a chemical notes. 79 bright flame, and to it is due in large part the value of illuminating gas. The principal members are given below. Gases. Ethene, C2H4. Propene, C3H6. Butene, C4H8. Liquids. Pentene, QH10, boils at 350 C. Hexene, CfiH12, " 70 Heptene, C7H14, u 100 Octene, C8H16, " 125 Nonene, C9H18, " 153 Decene, C10H20, " 200 The Acetylenes.—This is another series of unsat¬ urated hydrocarbons, having two atoms of hydrogen less than the corresponding bodies of the preceding olefine series. They have the general formula CnH2n_2. By the action of nascent hydrogen they are converted into the olefmes and the paraffins. With ammoniacal solutions of the salts of silver and copper they form solid, crystalline compounds. Acetylene, C2H2 is the first member of the series ; it is a colorless gas of characteristic odor. It burns, producing a remarkably intense white light. It may be produced by the direct synthesis of carbon and hydrogen, but it is usually prepared by the action of calcium 'carbid upon water, thus: CaC2 + H20 = C2H2 + CaO. Besides its value as an illuminant it is chemically impor¬ tant in that it may be the starting point for the synthesis of several organic compounds. It is directly converted into oxalic acid by oxidizing substances. The chief acety¬ lenes are allylene, C3H4, a gas very much like acetylene, and crotonylene, a liquid, boiling at 180°. 8o chemical notes. Alcohols.—Alcohols are bodies formed by the substitu¬ tion of hydroxyl, oh, for an atom of hydrogen in a hy¬ drocarbon, and are consequently the hydrates of paraffin hydrocarbon radicals. They have the general formula cnh211+ioh. If one atom of hydrogen is substituted, the alcohol is monatomic ; if two or three atoms are substi¬ tuted, the alcohols are di- and triatomic, respectively. The highest alcohols yet discovered in nature are the heptatomic alcohols. There are various isomeric monatomic alcohols, divided into primary, secondary and tertiary: PI CnH2n + i «CnH2n + i m CijH^n + i H—C—H H—C—OH K—C—OH [if—C—OH I I cJ I O I h h h cnh,n^, Methane. Primary alcohol. Secondary alcohol. Tertiary alcohol. Looking at the above representations, it is seen that in the primary alcohols the hydroxyl radical is united to a carbon atom which is attached to but one hydrocarbon radical, and that it contains the group ch2.oh ; in the secondary the hydroxyl is attached to a carbon atom which is joined to two hydrocarbon radicals, and it contains the group ch.oh ; while in the tertiary there are three hydro¬ carbon radicals joined to the carbon atom to which the hydroxyl is attached, and the group is c.oh. Secondary and tertiary alcohols are called carbinols. If we substitute in the diagrams for each of the general formulas a hydrocarbon radical, as shown below, we obtain the following isomeric alcohols : c4h9 c2h5 c2h5 I . I „ I H—C—OH w —C—OH K —C—OH I w I U I H H CH3 Normal amyl alcohol. Diethyl carbinol. Dimethyl ethyl carbinol. CHEMICAL NOTES. 8l These are examples of isomeric alcohols ; when oxidized they produce widely different substances. Primary alco¬ hols yield first aldehydes, and then acids when oxidized ; secondary alcohols give ketones, while tertiary alcohols give either aldehydes or ketones. Methyl Alcohol, CH3OH, is a colorless, inflammable liquid having a specific gravity of .8, and boils at 66° C. It oc¬ curs naturally in the oil of wintergreen in combination as a compound ether, and is made artificially by the destruc¬ tive distillation of wood, hence sometimes called wood spirits. '' - , / Ethyl Alcohol, C2H5OH, is a very important body. It may be produced by a few chemical methods, but the universal method of its production is by the action of a ferment upon a saccharine solution. The ferment inducing alcoholic fermentation is the saccharomyces cerevisiae, a microscopic plant. Fermentation is a process set up in an organic body by another substance, called a ferment, which is capable of changing the composition of the body acted upon, but which is able to maintain itself throughout; the products of such decomposition are new compounds. Ethyl alcohol is inflammable, and produces a higher heat than methyl alcohol; the final product of its oxidation is acetic acid. It has great affinity for water ; in fact it is almost impossible to obtain alcohol entirely free from water. By redistilling several times, followed by treatment with lime, it may be rendered 98 to 99 per cent, pure ; this is absolute alcohol. A convenient method of testing absolute alcohol is to immerse in it a crystal of anhydrous copper sulphate ; if the crystal remain white the alcohol is abso¬ lute ; if it turn blue it is not. The following is the percent¬ age of alcohol present in the ordinary alcoholic beverages : 2C2H5OH + 2COa. Alcohol. Carbon dioxid. 7 82 chemical notes. beers and porters 2-10 per cent. ; wines, 6-25 per cent. ; whiskies, 25-52.6 per cent. ; brandies, 25-43 per cent. The specific gravity of absolute alcohol at 20° C. is .789 ; boiling point, 78.3° C. Propyl and Butyl Alcohols are found in fusel oil, together with amy I alcohol; the latter is, however, itself called fusel oil. There are eight possible isomeric amyl alcohols, seven of which are known. Cetyl Alcohol, C16H33OH, obtained from cetaceum ; ceryl alcohol, C27H55OH, found in Chinese wax, and melissyl alcohol, C30Hc1OH, a component of beeswax, are examples of the solid monatomic alcohols. Diatomic Alcohols are called glycols ; they are sweet> syrupy liquids. Glycol, C2H4(OH)2, or ethylene alcohol, is representative of this class of substances. Triatomic Alcohols.—Glycerine is the type of these bodies, and from it they receive the class name, glycerines or glycerols. They are syrupy liquids, colorless, have high boiling point and are soluble in water. Their general formula is CnH2n_I(OH)3. Glycerine, C3H5(OH)3, occurs abundantly in nature, com¬ bined with the fatty acids in true oils and fats. It is con¬ sequently obtained as a side product in the manufacture of soaps. Tetra- and Pentatomic Alcohols are of very little interest. Hexatomic alcohols all have the general formula, C„H2n_4(OH)(;. The pharmacopoeial drug, mannite, belongs to this class of alcohols. It is isomeric with dulcitol and sorbitol. Hexatomic alcohols are much like the sugars in their properties. Sulpho-Alcohols or Mercaptans.—These form a class of bodies, corresponding to the alcohols, in which CHEMICAL NOTES. 83 sulphur occupies the place of oxygen. They combine with metallic oxids, aldehydes and ketones. Their union with ketones produces mercaptols, which, when oxidized, form sulphonals. Ethyl mercaptan C2H5SH is of greater interest, perhaps, than any other, entering, as it does, into the forma¬ tion of three pharmaceutically important bodies, sulphonal, trional and tetronal. ch3 so2c2h5 ch3 so2c2h5 ch3^^SO2C2H5 C2H5^^^SO2C2H5 Sulphonal. Trional. Diethyl-sulphone-dimethyl-methane. Diethyl-sulphone-methyl-ethyl-methane. c2h so2c2h5 c2Hs ^ ^ s02c2h5 Tetronal. Diethyl-sulphone-diethyl-methane. ETHERS.—Ethers are the oxids of hydrocarbon radicals. There are two classes, simple and mixed ethers. A simple ether is one which is the oxid of a single hydrocarbon c h radical, e. g., ~2 5>0. A mixed ether is one in which ^2^5 two different hydrocarbon radicals are held together by CH3 _ oxygen, e. >°- Another class of bodies, called compound ethers, are really salts formed by the linking of an alcohol radical to c h an acid radical by oxygen, e. g., ~ ^>0 ; here oxygen L.2ri3U joins the negative acetic acid radical to the positive ethyl radical. It is readily seen that this corresponds to the formation of inorganic salts. They are termed ethereal salts, or esters. Ethers are found abundantly in nature in both plant and animal life. The lower members are neutral, volatile liquids ; the higher are solids. They do not react readily with other chemicals, but when oxidized they yield the same bodies as their corresponding alcohols. 84 chemical notes. Of the large number of ethers, ethyl ether concerns us most on account of its use in surgery as an anesthetic. It is produced by the action of sulphuric acid upon ethyl alcohol, hence erroneously called sulphuric ether. This process, first explained by Williamson in 1852, bears his name, and is also sometimes spoken of as the continuous pro¬ cess, from the fact that the acid is reformed at the end of the reaction, and can convert a new portion of the alcohol into ether, repeating this continuously until all of the alcohol has been changed. The following equations explain the method : .(a) C2H,OH + H2S04 = C2H5HS04 -f H20. ■(b) C2H5HS04 + C2H5OH = (C2H5)20 + H2S04. Ethyl Ether (C2H,)20 is a colorless, mobile liquid of ethereal odor, and a sharp but sweetish taste. At 150 C. its specific gravity is .725-728, and it boils at from 34.90- 370 C., depending upon the degree of purity. Ethyl ether is much used as a solvent, especially for such bodies as fats and resins. Aldehydes.—Aldehydes, general formula CnH2I1_I.COH, may be considered as alcohols that have lost two atoms of hydrogen. They contain the group of atoms —COH, and result from the oxidation of primary alcohols, c. g., CH3.CH2OH H- O = CH3.COH + H20. Though related to the alcohols in chemical origin, the aldehydes do not resemble them except in certain physical respects. The lower members are liquids, and are more volatile than the corresponding alcohols ; the higher alde¬ hydes are solids. Aldehydes are the transition products between alcohols and acids, and form the latter when oxidized, c. g., CH3.COH + O = CH3.COOH. Acetaldeliyde. Acetic acid. chemical notes. 85 The oxidation of aldehydes takes place easily ; it may ensue upon exposure to the air. They are so readily oxid¬ ized by the oxids of the noble metals that the reduction of such oxids is considered a characteristic reaction of the aldehydes. They also easily reduce ammoniacal solutions of silver. Aldehydes are neutral in reaction, and, although they are saturated bodies, they unite by two affinities with other bodies. Formaldehyde, H.COH, is a very important substance 011 account of its energetic germicidal properties, though, ordinarily, innocuous to man. It is a gas, has a pungent odor, and is produced by burning the vapors of methyl alcohol in contact with cuprous oxid or platinized asbestos. Many sugars are polymers of this body, and from its polymerized modification formose, a sugar of the formula C6H]2O0, has been obtained. The gas is soluble in water. Formalin is a 40 per cent, aqueous solution of formaldehyde. Acetic Aldehyde, or aldehyde, has the formula CH3COH, and is formed during the preparation of ethyl alcohol. It is a liquid, boiling at 210 C., and gives off an irritating, locating odor. When three atoms of chlorine substi- ^hree atoms of hydrogen trichloraldehyde, CCl3COH, ioral, is obtained. This is a liquid substance, boiling 94.50 C. ; specific gravity, 1.502. Chloral responds to die general tests for aldehydes, and oxidizes to trichlor¬ acetic acid. It combines with water, forming chloral hydrate, a monoclinic crystalline, hygroscopic solid. Paraldehyde is a polymer of aldehyde ; its formula is (CoH^O)^ It is also a liquid, and boils at 1250 C. The aldehydes of the unsaturated alcohols correspond to the alcohols from which they are formed, just as the alde¬ hydes above described correspond to the saturated alcohols. Ketones are bodies resulting from the oxidation of the secondary alcohols. The}' contain the group of atoms CO, combining two hydrocarbon radicals. They are for the most part volatile liquids, having an ethereal odor. They 86 chemical notes. do not reduce ammoniacal silver solutions, and in this respect differ from the aldehydes, to which they bear con¬ siderable analogy. Nascent hydrogen reconverts them into secondary alcohols. A representative of this class of bodies is dimethyl ketone, CH3.CO.CH3, or acetone. It is a liquid which boils at 56.5° C., and has a specific gravity of .792. Organic Acids.—Organic acids are the highest oxida¬ tion products of alcohol radicals. They contain the group of atoms CO.OH, carboxyl, combined with a hydrocarbon radical; general formula CnH2n+I. CO. OH. The above indi¬ cated group of atoms shows that organic acids are hydroxyl derivatives, and, depending upon the presence of one, two, three, etc., hydroxyl groups united directly to CO, they are mono-, di-, tri-basic, etc. The valence of an organic acid is determined by the number of OH groups united directly to its CO. But they may also contain hydroxyl groups that are not joined im¬ mediately to CO, the hydrogen of which cannot be replaced by metals. The atomicity of an organic acid depends upon the total number of OH groups present, while its basicity (valence) depends upon the number of OH groups attached directly to CO. The relation between alcohols and acids can be seen by considering the acid to be formed by substituting an atom of oxygen for two atoms of hydrogen in an alcohol. The formula of ethyl alcohol is C2H-.OH ; substituting an atom of oxygen for two of its atoms of hydrogen we obtain C2H3O.OH, acetic acid. The alcohol radical in which oxygen replaces two hydrogen atoms constitutes the acid radical. As said above, organic acids contain the group CO.OH in combination with a hydrocarbon radical; thus acetic acid may be written CH3.CO.OH. Acids derived from the saturated primary monobasic alcohols form the series of fatty acids; they are saturated monobasic bodies. PARTIAL LIST OF THE FATTY ACIDS. Name. Formula. Melting- point. Boiling point. Where found. Formic acid, . . CHa02 Degrees. 4 Degrees. IOO Bodies of red ants and in the stinging nettle. Acetic acid, . . . C2H^p2 !7 118 Vinegar ; made also by destructive distillation of wood. Propionic acid, c3h6o2 —21 140 Urine ; perspiration. Butyric acid, . . c4h8o2 —20 162 Rancid butter ; perspiration, feces, etc. Valerianic acid, c,h10o2 —16 185 Valerian ; wood vinegar. Caproic acid, . . c6h12o2 —2 205 Rancid butter, cocoanut oil ; some varieties of cheese. Caprylic acid, . c8h16o2 14 236 Rancid butter, cocoanut oil ; some varieties of cheese. Capric acid, . . . c10h2uo2 30 270 Butter. Palmitic acid, . cltih3202 62 669* Palmitin ; palm oil ; animal fats. Stearic acid, . . c18h3602 70 287* Animal fats. * Under pressure of 100 mm. 88 chemical notes. The unsaturated hydrocarbons of the olefine series give rise to unsaturated monobasic acids of the oleic series. The acetylene series has its corresponding acids. The unsaturated acids form addition compounds with such substances as the halogens like other unsaturated bodies. Many of the organic acids can be formed by synthetic processes. They are, however, found very largely distri¬ buted in nature in animal and plant life, especially the latter. Some of them are limpid liquids, some oily liquids, and still others are solids. The higher fatty acids com¬ bined with glycerol, C3H5(OH)3, form the true oils and fats as found in nature. Nearly all organic acids unite with metals to form salts; such unions of the higher fatty acids with metals produce the soaps (which are, of course, salts); but only their salts with certain metals have those peculiar properties which characterize common soap. Acids of the Diatomic Alcohols.—The oxidation of diatomic alcohols gives rise to two series of acids—one in which two CH2OH groups are oxidized to CO.OH, and one in which only one group is so oxidized. Thereupon re¬ sults a series of acids which are diatomic monobasic, and another which is diatomic dibasic. Triatomic and higher alcohols also yield acids as their final oxidation products. The basicity of all of them de¬ pends upon the number of CH2OH groups in which oxygen substitutes two atoms of hydrogen. Lactic Acid, C2H4.OH.COOH, is a colorless, syrupy liquid; specific gravity, 1.215. Occurs principally in sour milk. Oxalic Acid, COOH.COOH, is a colorless, crystalline solid, containing two molecules of water. It occurs com¬ bined in many plants. Acids of the Higher Alcohols.—Tartaric and citric acids are the chief bodies to be studied under this group. Tartaric Acid, C2H402(C00H)2, is a solid, and melts at chemical notes. 89 T350 C. It occurs chiefly as an impure tartrate of potassium in wine casks ; it is also a constituent of the juices of cer¬ tain fruits. It is dibasic, and is derived from a tetratomic alcohol. Citric Acid, C3H4.OH(COOH)3, is also a solid ; it crys¬ tallizes with one molecule of water. Its principal source is the juice of lemons. Citric acid is soluble in water. It melts at 1530 C. It is tribasic, and is also derived from a tetratomic alcohol. Ethereal Salts or Esters.—The bodies of this class are often called compound ethers, but their composition corresponds to the formation of the inorganic ternary salts, in that a positive radical is united to a negative radical by oxygen. While, however, most of the inorganic salts are solids, most of the ethereal salts are liquid, and many of them are characterized by an agreeable odor. Chemically they are composed of an alcohol radical (positive) united to an acid radical (negative) by oxygen. The acid radical may be inorganic or organic. When ethereal salts are heated with water they split up into alcohol and acid, and when acted upon by alkalies they form alkaline salts of the acid. This is the process termed saponification. The following formulae indicate the constitution of ethereal salts : The following is a list of some of the important esters : Ethyl nitrite. Ethyl acetate. Ethyl nitrite, Amyl nitrite, C2H5.ONO. C0Hn.O.NO. c3h,(N03)3. c2h,o.c2h3o Glyceryl trinitrate, Ethyl acetate, Cetyl palmitate, Myricyl palmitate, c16h31.o.C16H33o. cI6h31.o.c30h61o. 9° chemical notes. Tlie glyceryl esters of the higher fatty acids compose the important class of bodies—the true oils and fats.* They are found in both plants and animals as proximate prin¬ ciples. Their decomposition by a metal forms a soap and liberates glycerine. 3NaOH + C.,H5(C]8H3;A)3 = 3NaC18H,A + 0,11,(011), Sodium Glyceryl oleate. Sodium oleate. Glycerine, hydrate. (Vegetable oil.) (Soap.) The most commonly occurring solid fats are glyceryl esters of palmitic and stearic acids ; the liquid fats con¬ tain oleic acid. The fats do not dissolve in water, but are readily soluble in the usual organic menstrua.' They differ from essential oils, not only in chemical formation, but also in some physical constants; they do not volatilize readily, and, when heated to a high temperature, they decompose, acro¬ lein being one of the bodies formed ; they have not, as a rule, agreeable aromatic odors, and leave spots upon paper or other absorbent substances. Oils which are glycerine esters of the unsaturated acids are capable of being oxidized upon exposure to the air, and comprise the class of oils called drying oils. Amines and Amids.—These are bodies derived from ammonia by substituting an organic radical for an atom of its hydrogen. If one atom of hydrogen has been sub¬ stituted by a radical the body is primary; if two, it is * It is not to be understood that the fats and oils are bodies of different chemical formation. The term "oils" is applied to the liquid glyceryl esters of the higher, fatty acids, and the term " fats" is used to include the solid members of the series. The higher paraffins (paraffin oils, vaseline, etc.), are not oils and fats in the chemical sense of the terms ; they are simply hydrocarbons. The essential oils differ from the true oils and fats in many particulars : (i) they belong to the closed chain series of hydrocarbons and are deriva¬ tives of the terpenes and camphors; (2) they are variable in their formation; (3) they are entirely volatile at ordinal temperatures ; (4) they occur chiefly in the leaves, flowers and fruits of plants, and are characterized by an agreeable, strongly aromatic odor. CHEMICAL NOTES. 91 secondary, and if three, it is tertiary. The substitution of hydrogen by an alcohol radical (positive) gives an amine; the substitution by an acid radical (negative) gives an amid. /C2H5 N- C2H5 -h XH Ethyl amine. /CftO N—H XH Acetamid. N—C2H5 xh Diethyl amine. /c2h30 N—C2HSO xh Diacetamid. /c2h5 n-c2h5 c2h2 Triethyl amine. c2h3o N c2h3o xc2h3o Triacetamid. The lower members of the amines are gases, while the higher are liquids. They behave in many particulars like ammonia, are strongly basic and unite readily with acids to form salts. The amids may combine with both metals and acids, but the bodies formed by such combinations are not very stable. xvii. CARBOHYDRATES. The carbohydrates occur widely distributed as products of plant life, and they also enter into the vital processes of animal life. They receive the name carbohydrates from the fact that they are composed of carbon combined with hydrogen and oxygen in the proportion of water. Chemi¬ cally, they may be considered as the aldehydes and the ketones of the hexatomic alcohols, the former termed al¬ doses and the latter, ketoses. These, like other aldehydes, form acids as their final oxidation products. For the most part they are white, solid bodies, and characteristic of them is the ability to ferment or to produce bodies which will 92 chemical notes. ferment. Many of them have the power to reduce the oxids of certain metals, and many also rotate the plane of polarized light, while some are optically inactive. The old classification separates them into glucoses, sac¬ charoses and starches. The new classification, into mono-, di-, tri- and polysaccharids, serves the purposes of the chemist better, in view of recent discoveries made concern¬ ing these bodies. We shall, however, present them to the beginner under the old classification. The Glucoses.—The glucoses have the formula C6H]20G. For the most part they are white, crystalline bodies, soluble in water, and of sweetish taste. The final products of their oxidation are saccharic and mucic acids—two isomeric bodies. They form ester with acids ; their organic esters are the glycosides, bodies which when heated with alkalies or acids are decomposed, glucose being always one of the products formed. When heated with phenyl-hydrazine, CcH5.NH.NH2, dissolved in acetic acid, they yield a class of crystalline bodies called osazones. The}* can be separated by this reaction and identified. Ghicosc.—The principal sugar under this class is glucose. It is commonly known as grape sugar ; it is dextro-rotatory, and reduces Fehling's solution, which may be used both for its detection and its quantitative estimation. Fehling's solution consists of (i) copper sulphate, 34.64 gins, dissolved in 500 cc. of water; (2) Rochelle salts, T73 gms. dissolved in 500 cc. of sodium hydrate solution having S. G. 1.114. Equal parts of the two solutions are mixed wdien ready for use, diluted and boiled. A solution of glucose added to it while boiling precipitates cuprous oxid, a bright, yellowish red substance. Ten cc. of Fehl¬ ing's solution are reduced by .050 gin. of glucose. Glucose occurs very abundantly along with fructose in many fruits, and it is also found in small amount in some tissues of the animal body. It is the sugar which is found in the urine in diabetes mellitus. chemical notes. 93 Fructose is found in most fruits and juices ; it is laevo- rotatory. / The Saccharoses.—The saccharoses have the formula C,2H22On. When heated with acids or under the influence of certain ferments they produce bodies belonging to the glucoses. The more important ones are siicrose, or cane sugar ; lactose, or milk sugar, and maltose ; the first of these does not reduce Feliling's solution, but the latter two do. Another point of distinction is that cane sugar and milk sugar are not directly fermentable, but form sugars by in¬ version that are fermentable ; maltose is directly ferment¬ able by yeast. The fact that milk sugar and maltose reduce Feliling's solution indicates that they belong to the aldoses. They produce osazones with phenyl-hyrazine, and their oxidation products are monobasic acids. Cane sugar does not produce an osazone. Sucrose or Saccharum.—This substance is the sugar which is so largely used as an article of diet. While found in many fruits and plants, its principal source is the sugar cane and the sugar beet. It is crystalline, easily soluble in water, melts at i6o° C., and its specific gravity is 1.606. When boiled with dilute acids it takes up a molecule of water (hydrolysis), and yields a mixture of glucose and laevulose (invert sugar). It is dextro-rotatory. Ten cc. of Feliling's solution are reduced by .0475 gm. of it when inverted. Lactose, or Milk Sugar, occurs in milk and occasionally in certain other animal fluids. Its crystals form rhombic prisms, and it is soluble in six parts of cold water ; it melts at 2050 C. It reduces ammoniacal solutions of silver, and its inversion yields glucose and galactose. It is dextro¬ rotatory, and .0678 gm. reduces 10 cc. of Feliling's solution. Maltose.—This sugar is formed from starch by the action of diastaste, a ferment produced during the germination of grain from its albuminous portion. Taking up a molecule 94 CHEMICAL NOTES. of water it forms needle-like crystals; it loses its water of crystallization at ioo° C. It is dextro-rotatory ; .0807 gm. reduces 10 cc. of Fehling's solution. The Starches.—The general formula of this class of bodies is (C6H10O.-)n. They are amorphous substances, and are very slightly soluble in water. They are not capable of the chemical reactions shown by the glucoses ; however, they split up into members of that group by hydrolysis (boiling with dilute acids), or by the action of ferments. The principal bodies of this class are starch, dextrine and cellulose ; these may be considered as the chief mem¬ bers of subdivisions of the starches bearing their respect¬ ive names, and which contain other bodies. To the group dextrines belong that class of natural bodies known as gums. Starch.—Starch is found in the cells of plants. As commonly seen it is a white amorphous powder, which, when examined microscopically, is found to be composed of circular or elongated granules, which present a laminated structure. It is insoluble in cold water, but when heated with water its granules swell up, burst and are partly dis¬ solved. This forms starch paste. Boiled with dilute acids it forms dextrine and glucose, and under the influence of diastaste it is converted into dextrine and maltose. Dextrine.—As indicated above, dextrine is a product of the action of dilute acids by boiling or of ferments upon starch. It is a yellowish-white powder, soluble in water, which solution rotates the plane of polarized light to the rip-ht. It does not reduce Fehling's solution. o 0 Gums are natural products occurring in plants. They are amorphous, transparent, odorless and tasteless bodies. Some of them give perfectly clear solutions with water, while others produce a sticky mass with it which cannot be filtered through paper. They are dextrines, belonging to the aldoses, their oxidation products being mucic and oxalic acids. CHEMICAL, NOTES. 95 Cellulose.—Cellulose occurs as a white amorphous pow¬ der, insoluble in the ordinary solvents, but soluble in am- moniacal solutions of copper. It forms the principal part of the woody fiber of plants, from which it is obtained by treatment with potash, hydrochloric acid, water, alcohol, ether, etc. It yields a series of esters with nitric acid, under the joint influence of sulphuric acid, forming first the dini- trate, C12H1808(N03)2, and going as high as the hexanitrate (containing six N03 groups). The tri- and tetranitrate dissolved in alcohol and ether is collodion. These nitro- celluloses, as they are termed, are usually made from cotton, it being nearly pure cellulose ; hence the hexanitrate is.tjie body called gun cotton. XVIII. CLOSED-CHAIN BODIES AND DERIVATIVES. The constitution of the benzene chain is explained on page 72. The bodies belonging to or derived from it are variously termed benzene, aromatic and cyclic compounds. Reference to the page referred to above will show that the benzene ring, as it is called, is a hexagonal figure in which the six atoms of carbon which compose the body are united to each other by alternate single end double bonds, and that their free bonds are joined to hydrogen atoms. Remember, as stated elsewhere, that this is one of the two great classes of hydrocarbons. The idea expressed by the benzene ring is a theoretical conception of the chemist, but the behavior of the bodies of this class is such that, although it cannot be said how the carbon atoms forming the ring are united to each other, it seems certain that they form a nucleus into which no more carbon atoms can enter. 96 CHEMICAL NOTES. On page 75 some of the differences between the open and closed-chain bodies have been pointed out. It is well to note also that only in exceptional cases can the members of one series be changed to members of the other. Substitution and Addition Compounds.—Substitution compounds are formed by the substitution of an atom or radical for an atom of hydrogen in the benzene ring; such a radical then becomes a side chain. Addition compounds are produced when the side chain takes on other atoms or radicals. Benzene Isomers.—The isomers of the benzene hydro¬ carbons are formed by the substitution of a paraffin radical for a hydrogen atom in the benzene ring. When two such radicals are substituted for hydrogen atoms they may stand in three relative positions : they may be contiguous, as at 1 and 2 ; one angle may lie between them, as at 1 and 3 ; or there may be two angles between them, as at 1 and 4. 6!M2 5V/3 4 This is also a theoretical arrangement of the chemist, in keeping with the notion of the constitution of the benzene ring and the formation of its derivatives. The bodies formed in this manner all take the same chemical name, to which is prefixed the terms ortlio-, para- and meta-, according to the position that radicals forming them occupy in the ring. If in the first position (contigu¬ ous), ortho is the term prefixed ; in the second (one angle between), para ; in the third (twTo angles between), meta ; thus, ortlio-cymene, para-cymene and meta-cymene. Benzene Homologues.—The benzene homologues are formed, not by adding to the nucleus other carbon atoms, as in the open chain series, but by the substitution of CHEMICAL NOTES. 97 hydrocarbon groups for one or more hydrogen atoms of the ring. The following homologous bodies are formed from the first member by the substitution of CH3 for the hydro¬ gen of the ring: Name. Formula. Boiling Point. Benzene, c6hc, 80.5° Toluene, c7h8, hi. Xylene, c8h10, 142. Cumene, c9h12, I53- Many of these bodies are derived from coal tar, one of the substances formed during the destructive distillation of coal, which also gives rise to other technically important bodies. Among them may be mentioned liquid hydro¬ carbons, tar water, from which ammonia is obtained, coke (gas carbon), etc.* When coal tar is distilled it separates into a heavy and a light oil. The latter contains benzene and some of its homologues. They are separated after treatment with sulphuric acid and potassium hydroxid by fractional distillation. The benzene hydrocarbons are volatile liquids ; they react to sulphuric and nitric acids, and oxidation of their side chains produces aromatic acids. Benzene, QjH^, the simplest of the aromatic compounds, may be obtained in crystals from the light oil of tar by a process of chilling. Its crystals melt at 6° C., and it is commonly seen as a colorless mobile liquid of a somewhat ethereal odor ; it boils at 80.5° C. Benzene is inflammable, and produces a very bright flame. Its chief use is as a solvent. This body must not be confused with benzine. Benzine is a mixture of hydrocarbons belonging to the methane series, obtained from petroleum, while benzene is * Illuminating gas, composed chiefly of gaseous hydrocarbons of the methane series, is a product of the distillation of coal. 8 98 chemical notes. a definite chemical compound of the closed-chain series, and is obtained from coal tar. Halogen Derivatives.—The halogens readily substi¬ tute the hydrogen of the aromatic bodies. In the benzene homologues they may take the place of the hydrogen of both the nucleus and the side chain; in fact, some of the benzenes unite directly with the halogens. The reactive relations of bromine, chlorine and iodine to them are anal¬ ogous to their relations to the paraffin bodies. Nitro-Derivatives.—The nitro-derivatives are pro¬ duced by the substitution of N02 for an atom of hydrogen of the nucleus. The di-, and tri-nitro- derivatives are the principal ones; they are, for the most part, yellowish liquids, whose color is deepened by the addition of ammonia. Nitro-Benzene, C6H5.N02, is a liquid, specific gravity i.20, boils at 205° C. There are three isomeric dinitro-benzenes having the formula C6H4(NO)2. Amido Compounds.—These are bodies formed by the substitution of the benzene radical for the hydrogen of ammonia, producing, as in the paraffins, primary, secondary and tertiary derivatives. They are organic bases, and unite with acids to form salts. The primary phenylamines give up their NH2 for OH, thus yielding a class of bodies called phenols. The following are homologous amido compounds: Aniline. Toluidine, Xylilidine, Cumidine, c6h,nh, c7h7.nh2. c8h,nh, C9hu.NH2. Aniline, amido-benzene or phenylalanine is of some im¬ portance. It is a colorless liquid ; faint, peculiar odor; boils at 183° C. ; specific gravity 1.036. Sulphuric acid chemical notks. 99 and a solution of potassium dichromate added to it produce at first a red color, which after a while becomes blue. Aniline forms substitution products in several ways. Perhaps the instance which concerns us most is that in' which acid groups substitute the hydrogen of the side chains, forming a class of bodies called anilids. Chief among these is acetanilid, C6H5.NH.C2H30. It is a solid body and occurs in colorless, odorless scales. It is practi¬ cally insoluble in cold water ; melts at 1120 C. Diazo and Azo Compounds, benzene derivatives, contain the group —N = N—. Diazo compounds are formed when the above group of atoms unites a benzene hydro¬ carbon radical to an acid radical, as C6H5—N = H—N03v diazo-benzene nitrate. In azo compounds the group —N =N— unites two hydrocarbon radicals together, as C6H5—N = N —C6H5. Bodies belonging to these two classes are not important in medicine; however, they claim a place in industrial chemistry, especially in connection with dye compounds. Hydrazines are bodies derived from hydrazine, or diamid, H2N—NH2, and are formed by the replacement of hydrogen by a hydrocarbon radical. There are both open and closed-chain hydrazines ; the latter are of more importance. The hydrazines resemble the amines in their chemical nature. They are not affected by the presence of reducers, but they oxidize quite readily. Phenyl-hydrazine, C6H5.NH—NH2, claims some notice, since its introduction as a test for sugar in the urine, with which it forms crystalline compounds called hydrazones or osazones. It is a solid, occurring in colorless crystals, which melt at about 128° C. Antipyrin (phenyl-dimethyl-pyrazolon) CuH]2N20, is a derivative obtained by the action of phenyl-hydrazine upon aceto-acetic ester. Phenols.—A phenol is a body in which the monoatomic group OH substitutes an atom of hydrogen in a benzene IOO chemical, notes. hydrocarbon. They are mono-, di- or triatomic, according as they contain one, two or three OH groups. They cor¬ respond in this particular to the fatty alcohols, and are analogous to the tertiary alcohols in that they can not be oxidized to ketones nor acids. They are acid in character, and the hydrogen of their OH groups will give place to a metal. Phenol (carbolic acid), C6H5OH, is the first of the series -of monatomic phenols. In its normal condition it occurs in colorless crystals, which melt at 420 C., and boils at 183° C. Exposed to the air it diliquesces and assumes a red color. Nitric acid forms compounds with phenol; trinitro- phenol is picric acid. Sulphuric acid unites with carbolic acid to form phenol sulphonic acid, the sodium and zinc salts of which (sodium and zinc sulphocarbolates) have a place in medicine. Pyrocaiechin, resorcin and hydro-quinone are isomeric diatomic phenols, having the formula C6H4(OH)2. The first of these forms ethers with methyl. Its monomethyl ether is the substance known as guaiacol, and is the chief con¬ stituent of creosote. Pyrogcillic acid is a triatomic phenol, formula, C6H3(OH)3. There are bodies in which oxygen substitutes two hydro¬ gen atoms of a closed-chain hydrocarbon. They are called qiiinones. Aromatic Alcohols are bodies in which OH takes the place of a hydrogen atom of the side chain (cf. phenols; see also " Substitution and Addition Compounds," page 96). They are analogous to the fatty alcohols and are isomeric with the phenols. Their oxidation products are ketones and aldehydes and, finally, acids. Benzyl alcohol, CBH3.CH2.OH, is an example of the aromatic alcohols. Phenol Alcohols contain an OH group attached to the nucleus in addition to the OH of the side chain. chemical notes. ioi Aromatic Aldehydes.—These bodies are also anal¬ ogous to the corresponding bodies of the fatty series, and are characterized by the group COH. Benzaldehyde (oil of bitter almonds), C6H5.COH, is an example of the aromatic aldehydes. Aromatic Acids may be considered to be formed by the substitution of COOH for an atom of hydrogen in a benzene or by the oxidation of their side chains. Their basicity depends upon the number of COOH groups they contain, as is the case with the fatty acids, to which they correspond in many particulars. The hydrogen of their benzene nucleus can be replaced by other atoms or groups. The aromatic acids are white crystalline bodies, and dis¬ solve with difficulty in water. They may be sublimed without decomposition, and when heated with soda-lime hydrocarbons are produced. Benzoic acid, C6H5.COOH, is a monobasic aromatic acid, found free in a few resins, gum benzoin, coal tar and the urine of herbivorous animals. It is obtained in white needle-like crystals or scales, which melt at 120° C. and boil at 250° C. Heated with lime it yields benzene and carbon dioxid. Phthalic Acids, C0H4(COOH)2, are dibasic aromatic acids. Phthalic anhydride is C6H4(C0)20 ; when heated with phenols it produces phthaleins. Phenol-phthalein, much used as an indicator for fixed alkalies, belongs to the phthaleins. Phenol Acids.—Aromatic oxyacids, in which the OH group is united to the nucleus, are termed phenol acids. Salicylic acid, C6H4.OH.COOH, is a phenol acid. It occurs naturally as methyl salicylate in gaultheria, and is obtained in crystals which melt at about 156° C. It may be sublimed, forming needle-like crystals. Gallic acid, QH^OH^.COOH, is a tetratomic monobasic phenol acid, found in gall nuts, tea, etc. It crystallizes 102 chemical notes. in fine, silky needles, and at 220° C. begins to melt and decompose. Tannic acid also occurs in gall nuts, tea, etc. It is a colorless amorphous substance, and is very soluble in water. Other Cxosed-Chain Bodies.—This section includes bodies that are not described in the previous chapters. The scope of this set of notes does not permit of a description of all chemical bodies, and this chapter is added to call the attention of the student to certain bodies, and he is directed to consult a text-book in reference to them. Naphthalene Group.—The naphthalene hydrocarbons may be considered as formed by two benzene rings having two carbon atoms in common. They are, then, bodies con¬ taining two condensed benzene nuclei. CH CH AA HC C CH I II I HC C CH vv CH CH Naphthalene. Napthalene, CJ0H8, the first member of the series, behaves very much like benzene in many reactions. It is obtained from coal tar, in white, shining crystals, which are easily volatilized and which possess a peculiar, characteristic odor. Its crystals melt at 790 C. Naphthalene is the substance largely used as " moth balls." Anthracene Group.—The anthracene group is formed by the union of three benzene rings joined to each other by doubly-united carbon atoms, hence spoken of as three con¬ densed benzene nuclei. Anthracene, ChH10, is the first member of the bodies of CHEMICAL NOTES. this series. The following formula, while not showing the union of the three condensed benzene nuclei, expresses the constitution of anthracene : /CH c6h4x i )c6h4. ch Anthracene is a derivative of coal tar, and may also be produced by various synthetic processes. It crystallizes in colorless monocHnic tablets, which exhibit a striking bluish fluorescence. Its crystals melt at 2130 C., and the liquid thus obtained boils at 360° C. Furfurane, Thiophene and Pyrrol are closed-chain bodies containing less than six atoms of carbon, and seem to form a transition step between the paraffin series and the benzene series. The following formulae show the formation of these bodies : ch = ch ch = ch ch = ch I )0. I /S. | ;NH. ch = ch ch = ch ch = ch Furfurane. Thiophene. Pyrrol. It is to be noted that the bodies shown above form alco¬ hol, aldehyde, ketone and acid derivatives, as the other groups that we have studied. Pyridine, CGH3N, and Quinoline, C9H7N, are two basic bodies, formed by the entrance of nitrogen into the ben¬ zene and naphthalene rings, respectively. In their chem¬ ical behavior they resemble the benzene bodies. They are important as being the basis of many of the alkaloids. They form homologous series, like the other bodies that have come to our notice. Alkaloids.—This class of compounds occurs naturally as the physiologically active principles of certain plants. Chemically, they are closed-chain derivatives, containing nitrogen ; they are strongly basic, and unite with acids to form salts. There are two classes of the alkaloids, liquid CHEMICAL NOTES. and solid. The liquid alkaloids contain no oxygen, but the solid ones do; the latter forms the larger class. Volatile Alkaloids, Liquid. Non-volatile Alkaloids, Solid. Piperidine, C5H,N.H6. Conine, C8H17N. Nicotine, C10HUN2. Atropine, C17H23N03. Hyoscyamine, C^H^NO^ Hyoscine, C17H23N03. Quinine, C20H24N2O2. Cinchonine, C19H22N20. Cocaine, C17H21N04. Morphine, C17H]9N03. Physotigmine, C15H21N302. Strychnine, C21H22N202. Aconitine, C33H45N012. Terpenes.—The terpenes, of which oil of turpentine is the type, are hydrocarbons found in certain plants. They are isomeric bodies of the formula C10Hlc or (C5H8)n. Camphors are closely related to the terpenes, with which they are found in the secretion of plants. Chemically they are oxygenated bodies. Ordinary camphor is a secretion of the Laurus camphor a^ a tree idigenous to China and Japan. The resins are also related to the terpenes, from which they may be formed.by oxidation. When a resin is found dissolved in essential oils and in turpentines the product is called a balsam. Essential Oils.—This class of bodies is somewhat vari¬ able in their chemical formation. Perhaps most of them are camphors and terpenes, while others are esters, alde¬ hydes or ketones. They belong to the closed-chain bodies. Essential oils, called also volatile oils, occur principally in the leaves, flowers and fruits of certain plants. They are volatile liquids having fragrant odors, and do not leave a grease spot upon substances like paper. (See page 90.) When oxidized they yield resins. chemical notes. XX. GENERAL CONSIDERATION OF ANALYSIS. Analysis seeks to discover the constitution of matter by separating it into its elementary constituents. As ordin¬ arily understood it means the discovery of substances pres¬ ent in bodies, whether each element is separated out singly or not. There are two general kinds of analysis—qualita¬ tive and quantitative, which include all other kinds. Qualitative Analysis determines what substances compose bodies. Quantitative Analysis estimates the quantity of the substance under consideration. The determination of a number of compounds which together make up a body is called proximate analysis, and the separation of it into its elementary parts is called ulti¬ mate analysis; e. g., proximate analysis shows bone to be composed of calcium carbonate, calcium phosphate, sodium chloride, etc., while ultimate analysis determines that calcium, phosphorus, carbon, oxygen, chlorine, etc., are the elements found in it. Again, we have inorganic and organic analysis, which differ from each other widely. Their difference can not be discussed at length here. (See page -66.) To establish the identity of inorganic bodies qualitative tests usually suffice ; but for organic bodies quantitative tests are of more importance. Alcohol and ether are organic bodies, containing, as do hundreds of other substances, carbon, hydrogen and oxygen, so that merely proving the presence of these elements does not prove the compound. On the other hand, in inorganic chemistry it is often only neces¬ sary to find what elements are present in the substance examined to know what it is ; e. g., we find a body com- io6 CHEMICAL NOTES. posed of sodium, carbon and oxygen ; we know that it is sodium carbonate. The behavior that bodies exhibit toward one another under certain conditions often makes it possible to use one substance as a test for another or for several others. When a chemical is used as a test the term reagent is specially applied to it. According to the reactions of the metals with different reagents Fresenius constructed a table, arranging them into analytical groups, which serves as a splendid scheme for the systematic examination of solutions of salts. The use of the analytical table and the subsequent sepa¬ ration of the metals from one another depends upon the process of precipitation. Berthollet set forth the chemical law that zvhenever on mixing substances in solution a compound can be formed zvhich is insoltible in the menstruum employed., such com¬ pound separates out and appears as a precipitate. The solid substance, then, which is formed is the pre¬ cipitate ; the menstruum in which it is formed is called the supernatant liquid, or after filtration, the filtrate. When an unknown salt is taken for examination several points are to be noted : 1. Color, odor, solubility and form (crystalline or amor¬ phous.) 2. Reaction. Acid substances turn blue litmus paper red ; alkaline substances turn reddened litmus paper blue, and neutral substances do not affect it at all. 3. Ascertain if the substance is organic or inorganic, by heating it on a platinum foil in the flame of a Bunsen burner. Organic substances burn, usually, and leave a black residue, i. disease it may fall as low as CHEMICAL NOTES. 123 1.005 and rise as high as 1.060. Urine is a solution of the excreted salts of the body in water, and the specific gravity represents the relative amount of solids contained in it. The specific gravity is usually ascertained by the urin- ometer, which is a hydrometer graduated within the vari¬ ations of the specific gravity of urine. The instrument should be tested as to its accuracy of reading. A small cylinder, deep and wide enough to allow the urin- ometer to float freely, should be nearly filled with the urine to be tested ; then immerse the urinometer in it, release, and allow it to come to a stand ; it must not be anywhere in contact with the cylinder. Observe that the urine rises upon the stem of the instrument, forming a meniscus; the reading is to be made on a line with the urine in the cylinder. To make an approximate estimate of the solids con¬ tained in the specimen examined, multiply the last two figures of the specific gravity by 2.33 (the coefficient of Haeser); the product expressed in grams will give the amount of solids in 1,000 cc., and if it is desired to esti¬ mate the quantity in 1,500 cc. this product may be multi¬ plied by 1.5. To find absolutely the amount of solid excreted, pour 100 cc. of the urine into an accurately weighed evaporating dish and evaporate over a water bath ; then place the dish and its contents in the drying oven and dry to a constant weight. The difference between the weight of the dish and the weight of the dish and residue together will be the amount of solids in 100 cc. of the urine, from which the amount of daily excretion can be calculated. Reaction.—Urine is normally acid ; however, after a cold bath or after a meal it may be neutral or even slightly alkaline. The reaction is best tested by litmus test paper. Acid urine turns blue litmus paper red ; if alkaline, it does not affect blue litmus paper, but reddened litmus paper is turned blue by it. 124 CHEMICAL NOTES. Alkalinity of the urine when voided usually indicates decomposition within the bladder, or it may be due to the excretion of an excess of alkaline salts. The alkalinity results from decomposition with the formation of ammonia, if after drying the paper turned blue by it becomes red again, and is said to be due to volatile alkalie; if after drying the blue is permanent, it is said to be due to fixed alkalies. Sometimes urine reacts to both blue and red litmus; such a condition is termed amphoteric. When urine has stood exposed to the air for some time it undergoes decomposition by the micrococcus ureae, by which its urea is broken up into ammonia carbonate, and it becomes alkaline in reaction. The Sediment.—Normal urine, when freshly voided, de¬ posits no sediment, but after standing until thoroughly cool it begins to deposit a flocculent, whitish-looking sediment. This sediment consists of mucus and is normal to all urines. When ammoniacal fermentation sets in, it be¬ comes very cloudy and quite a large amount of sediment is thrown down, consisting principally of the phosphates which are precipitated in alkaline medium. The cloudi¬ ness results mostly from the swarm of bacteria which mul¬ tiply rapidly in the decomposing animal fluid. In strongly acid urine there sometimes occur reddish, sand-like grains ; it is uric acid. There may also occur (in strongly acid urine) a pinkish, mealy deposit which dissolves on heating; it is composed of amorphous urates. Pus produces a yellowish-white sediment; blood, a dark brown. Urea.—Urea forms about 50 per cent, of the total solids of the urine and is a very important substance in that it represents the nitrogenous waste of the body, or, in other words, is the measure of the bodily metabolism. No exami¬ nation of urine is complete or at all satisfactory unless it takes into account the daily excretion of urea. Normal individuals excrete about 30 grams of it in 24 hours, with a CHEMICAL NOTES. !25 variation of perhaps 10 per cent, of this quantity on either side. When urea is acted upon by an alkaline hypobromite or hypochlorite it is decomposed, free nitrogen being liberated. The determination of urea depends upon collecting the nitrogen set free from it in a graduated vessel. One cc. of nitrogen represents .0027 gram of urea ; this figure multi¬ plied by the number of cc. of nitrogen liberated will indicate the amount of urea in the quantity of urine taken, from which the amount in any given quantity can be cal¬ culated. (NH2)2CO -f- 3NaBrO = 3NaBr + C02 + 2H20 -f N2. Hypobromite and hypochlorite solutions do not keep very well, so that it is best to prepare them as required. The compiler of these notes generally employs sodium hypobromite. There is kept on hand a 40 per cent, solu¬ tion of sodium hydrate ; and bromine is kept in one ounce bottles. When an analysis is to be made, 1 cc. of bromine is added to 50 cc. of the sodium solution and shaken up. Bromine is a very disagreeable substance to handle, on account of the heavy, suffocating fumes which it gives off. Immediately after withdrawing what is required at the time, the bottle must be restoppered and the stopper paraf¬ fined. It is best to keep the bottle covered in some sub¬ stance like chalk. The determination may be made in a nitrometer, or it may be conducted in a flask fitted with a funnel tube and a delivery tube which leads to a graduated tube (eudi¬ ometer), in which the gas can be collected by upward displacement. Several ways have been devised for the estimation of urea. A very handy and much used instru¬ ment for this purpose is the Doremus ureometer. It con¬ sists of a tube closed at its upper end. At its lower third it is bent at an acute angle, thus forming a longer and a shorter arm ; the longer is upright and closed, and is gradu- 126 CHEMICAL NOTES. ated to indicate the number of cc. of nitrogen liberated,, milligrams of urea in one cc. of urine, the percentage, or grains per fluid ounce. The shorter arm is expanded into a bulb. To use the instrument, the sodium hypobromite solution is poured into it so that the long arm is filled and so that the solution rises above the bend of the short arm. Then,, with the small pipette which accompanies the instrument, measure out i cc. of the urine to be tested ; pass the pipette into the tube and under the bend of the short arm in such a manner that the disengaged gas will rise in the long arm. Now gently press upon the rubber bulb of the pipette and slowly force the urine out of it; set the instrument aside and, after ten minutes, read off the results of the reaction. The liberated gas will depress the solution in the long arm, and the reading is made as indicated by the graduation at which it stops. If the tube is graduated in c,c. multiply .0027 gm. by the number of cc. of nitrogen as shown ; the product will represent the amount of urea in 1 cc. of urine ; the amount of daily excretion can easily be estimated from this. Chlorids.—The chlorids of the urine respond to the usual test with nitrate of silver. A rough estimation as to the elimination of chlorids may be made as follows: Pour into a test tube 10 cc. of the urine to be tested ; add to it about three drops of nitric acid, and then pour in a 5 per cent, solution of silver nitrate solution until there is no longer a formation of the white precipitate. Let the tube containing the urine set for a few minutes. In urines in which there is normal excretion the volume of precipitate will occupy about one-fourth of the volume of the liquid ; if it occupy more than this there is increased excretion ; if less, decreased. If it is required to make an accurate estimation of the chlorids, 5 cc. of the urine should be diluted with 30 cc. of distilled water and titrated with a decinormal solution CHEMICAL, NOTES. 127 of silver nitrate, using a 5 per cent, solution of potassium chromate as the indicator. Phosphates.—The phosphates of the alkali metals are called the alkaline phosphates, and of calcium and magne¬ sium, the earthy phosphates. The earthy phosphates may be precipitated by the addition of an alkalie, and in this manner an approximate estimation of the excretion of phosphates can be made. Take a test tube 2 cms. wide, and fill it to the height of 5.33 cm. with the urine; make it strongly alkaline with ammonium hydroxid, and warm. This will cause a precipitation of the earthy phosphates. Set the tube aside for 15 minutes, after which time examine it. If the precipitate rises to the height of 1 cm. the excretion is about normal; if higher or lower than this, the amount is increased or decreased, as the case may be. For the purpose of this test it is well to mark off the measurements on a test tube with a file or other instrument, or paste on a graduated paper scale, and always keep it convenient for use. Uric Acid.—Uric acid bears more or less a constant re¬ lation to the quantity of urea in the urine ; it has been variously estimated at from 1 : 30 to 1 : 60. It is detected chemically by the murexid test, as follows: A portion of the urine to be examined is evaporated in a porcelain evap¬ orating dish ; the residue thus obtained is moistened with nitric acid. Evaporate the acid and add ammonium hy¬ droxid ; the presence of uric acid will be indicated by the formation of a purple-red color, though other substances are said to give the same reaction. Quantitatively it is estimated as follows : Put 200 cc. of the urine into a conical sedimentation glass, and add to it 10 cc. of hydrochloric acid ; set it aside for from 10 to 24 hours, at the end of which time upon the sides and at the bottom of the glass will be seen the accumulated " grains" of uric acid. Filter the urine (after gentle agitation, so as to free the uric acid from the sides of the glass) through a 128 chemical notes. dried, carefully weighed filter paper. Dry it in the drying oven and then weigh. The difference between the weight of the filter paper and that of the filter paper and the uric acid will represent the amount of uric acid in 200 cc. of the urine. The amount of daily excretion can be calcu¬ lated from it. Albumin in The Urine.—Proteids are organic bodies elaborated in the animal system as metabolic products which serve a physiologic end. They are never excreted as waste products, and when found in the urine usually point to some pathologic condition of the kidneys or the general system. Chief among the proteids that may be found in the urine is serum albumin, and while it is a mooted question with some whether it ever occurs in healthy urine, its presence is always to be regarded as indicative of a kidney lesion. Tests for Albumin in the Urine. Heat.—Fill a test tube one-third to half full of urine to be tested, and heat over a Bunsen burner or alcohol lamp. If albumin is present a whitish precipitate will form. If the urine is at all alkaline a white flocculent precipitate of earthy phosphates will be thrown down, so that should a precipitate be obtained the specimen should be acidulated with a few drops of nitric acid and again heated. If the precipitate then clears up it is due to phosphates; if it persists it is due to albumin. Nitric Acid Contact Test.—Put about 3 to 5 cc. of con¬ centrated nitric acid into a test tube, and then add to it a quantity of urine so that it will float upon the acid. This may be done by pouring the urine gently down the inside of the tube or by introducing it by means of a nipple pipette. If albumin is present, a dull white ring will appear at the point of contact between the two liquids. The reaction is slower and less pronounced when the quantity of albumin is small, than otherwise. The Ferrocyanid Test.—This has proven a very satis¬ factory test with the author. The reagents required are a CHEMICAL NOTES. 129 5 per cent, solution of potassium cyanid and acetic acid, 50 per cent. Pour into a test tube 10 cc. of the urine to be tested and add 2 or 3 cc. of the ferrocyanid solution ; shake the tube so as to mix its contents well, and then add a few drops of acetic acid, 50 per cent. The presence of albumin is indicated by a diffuse, white cloudiness through¬ out the contents of the tube. The reaction occurs in a very short time,—from one-half to one minute. Purdy's Test.—The reagents required are a saturated solution of sodium chlorid and acetic acid, 50 per cent. First filter the urine, then fill a test tube about two-thirds full with it, and add about one-sixth its volume of the sodium chlorid solution. To this is added 5 to 10 drops of acetic acid, 50 per cent., and the test tube is inclined over the source of heat, so as to boil the upper inch of the contents. This is continued for about half a minute, and if albumin is present the reaction takes place in the por¬ tion boiled. (See Purdy's Practical Urinalysis.) Urine in which albumin has been detected should be examined at regular intervals, the value of such exam¬ inations being to determine if there is an increase or a decrease of it. Albumin may be determined quantitatively by the use of Esbach's albuminometer. It is a graduated tube—so graduated as to read grams per liter. The reagent required is composed of picric acid, 1 gm. ; citric acid, 2 gms. ; water, 100 gms. The letter U upon the tube indicates the height to which it must be filled with urine, and the letter o ' R shows to what height the reagent must be added. When this is done it is closed with a rubber stopper, slightly shaken, and set aside for twenty-four hours. The height to which the precipitate rises is read as grams per liter as shown by the graduations. The quantity never exceeds 2 or 3 per cent, by actual weight. A convenient method is to attach a paper scale to a test tube graduated so as to show the height of the column of 10 chemical notes. urine, and if albumin has been detected the tube and its contents may be set aside until it has fully precipitated and settled to the bottom. It may then be estimated as follows: The column one-tenth full = .1 per cent, albumin, one-quarter .25 one-third . 5 one-half 1. full 2. to 3. Both this and the Esbach method are sufficiently accurate for clinical purposes. It may also be estimated by centri¬ fugal analysis. The only accurate method of quantitative estimation is by gravimetric determination. For other methods, and for the differentiation of the proteids, the student is referred to a text-book on the subject. Other substances sometimes react with the tests for albumin, e. g.> oleoresins. They can be differentiated by the fact that they dissolve 011 the addition of alcohol. Blood in the Urine.—Blood in the urine is easily detected by its histological characters with the microscope, or by the spectroscope. However, haemoglobin, its red coloring matter, can be detected by chemical reaction. The reagents required are a freshly-prepared tincture of guaia- cum and ozoned turpentine. These two reagents are mixed in a test tube and the urine containing blood is added to them ; a blue ring (at first greenish) is formed at the point of contact. Pus in the urine will give a blue color also, but the presence of ozonized turpentine is not essential for it; it further differs from the blue of haemo¬ globin in that it is discharged if the urine is boiled. In the above test hydrogen dioxid can be substituted for the ozonized turpentine. Bile in the Urine.—Tests for bile in the urine are not always satisfactorily applied. Rosenbach's modifica- chemical notes. tion of Gmelin's test answers very well. Allow about 200 cc. of urine to pass through a pure white filter paper ; then place a drop of nitric acid upon a portion of the paper which is saturated with the urine. If bile is present a play of colors appear—green, blue, violet and yellow. Not much importance is attached to the test unless the green color appears first. Sugar in the Urine.—For the detection of sugar in urine, use has been made of that property of certain carbo¬ hydrates by which they reduce the oxids of certain metals ; thus there are the copper tests (Trommer's, Fehling's and Haine's) and the bismuth test (Bottger's). As a qualita¬ tive test the author has used Haine's reagent with satisfac¬ tion. The solution keeps well and the reaction is decided. The following is its composition : Copper sulphate, . . 2 gms. Distilled water, . • J5 Dissolve and add Glycerine, . . 15 After mixing thoroughly add Liquor potassae, . -150 To apply Haine's test, pour about 5 cc. of the test solu¬ tion into a test tube and bring it to the boiling point. Then add 8 or 10 drops of the suspected urine. Boil momentarily, and if sugar is present a bright yellowish-red precipitate will fall. The Fermentation Test.—This is a very accurate test, and may be employed as a corroborative of the other tests, or where only a very small quantity of sugar is present. It depends upon the fermentation of glucose by yeast, whereby it is split up into alcohol and carbon dioxid, and is conveniently performed in " fermentation tubes ordi¬ nary test tubes over water may be used, however. Three tubes are filled, as follows : 1 contains the urine to be ex¬ amined and a small piece of yeast; 2 contains a solution 132 chemical notes. of grape sugar and yeast; 3 contains normal urine and yeast. The tubes are to be left in a warm room for from 8 to 12 hours and then examined. Gas will be found in 1, if the urine contain sugar ; gas in 2 and none in 1 shows the urine to contain no sugar; gas in 3 shows that the yeast is faulty. Quantitative Estimation of Sugar in the Urine.—For this purpose Fehling's solution is generally used. (See p. 92.) It is best conducted in a white porcelain evaporat¬ ing dish. Dilute 10 cc. of the solution with water and bring it to the boiling point. Add the urine slowly from a graduated pipette until the precipitation of cuprous oxid ceases and the blue of color of the solution is discharged. Ten cc. of Fehling's solution are reduced by 0.050 gm. of glucose. Test for Acetone in the Urine.—Pour a few cc. of the urine to be tested into a test tube and add to it a few drops of a fresh solution of sodium nitroprusside, followed by a little strong ammonia. If acetone be present a red color is produced, to which, if acetic acid be added, a purple color will succeed. Another test for acetone consists upon the formation of iodoform. The reagents required are a solu¬ tion of potassium iodid in tincture of iodine, and a 5 per cent solution of sodium hydroxid. Pour 10 cc. of the urine into a test tube and add a few drops of the above solution ; if acetone is present a precipitate of iodoform will be thrown down. Examination of Urinary Sediment.—To obtain sediment for examination, a sedimentation jar may be filled with urine and set aside for several hours ; then the greater part of the liquid may be removed by cautious decanta- tion, leaving the sediment practically undisturbed in the bottom. A better means of obtaining it is by the centri¬ fugal machine, now so largely in use. It saves the time of waiting, and the possibility of change occurring in the CHEMICAL NOTES. J33 urine. Besides this the centrifuge can be used for esti¬ mating the volume percentage of such ingredients as the chlorids, or of albumin, when it is present, etc. Chemical means are not much employed for the exam¬ ination of urinary sediments, unless it be in the case of calculi. The microscope is far more valuable for the exam¬ ination of urinary sediment, and more expeditious. Crys¬ tals of urinary salts are quite as readily distinguished by the microscope as they could be by the most careful chemical analysis. Besides, there are other characters that chemical analysis would not reveal. For all practical purposes the microscope should be used for the examination of the sed¬ iment. Blood and pus, though yielding reactions to chem¬ ical tests, are readily recognized by their histological characters.