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Les cartes, planches, tableaux, etc., peuvent Stre filmds d des taux de reduction diff^rents. Lorsque le document est trop grand pour §tre reproduit en un seul clich6, il est film6 d partir de I'angle supdrieur gauche, de gauche d droite. et de haut en bas, en prenant le nombre d'images ndcessaire. Les diagrammes suivants illustrent la mdthode. 1 2 3 22t 1 2 3 4 5 6 1 i i] I «•! ( ^1 I .3 ELEMENTARY Experimental Chemisiry. — BY- THOMAS KIRKLAND, M.A., Peincii'al, Ho&mM. School, Toro.nto. TORONTO : W. J. GAGE cfe 00. .'j4 KRONT ST. WEST /^, 1/ I — -Si^-S^-^£«,»»..,.^_. ,,^^^, PREFACE. 'fflceoftheMiniBterof Uaoh & Uo. The followins: paftes contain the substance ot lectures in chemistry, delivorod to the students in the Toronto Normal .School, during the past ten years. The experiments were nmde in the lecture-roon,, and afterwards repeated by the students in the laboratory. I„ 1881-2, portions of the lectures were printed in an educational journal and n,et with such general acceptance that the author has been induced to publish tiu.u in a more extended form. It has been the author's aim to facilitate the study of chemistry by the experimental and inductive method It is hoped that the book will enable the careful student to acquaint himself with the main facts and principles of chemistry ^ -agh the medium of his own perceptive faculties, by a process not unlike that by winch these facts and principles were first established The mnaute instructions given in the descriptions of th. experiments are intended t« enable the student to ..air- a real and adequate knowledge of the things desorib.a in the presence of the things ohemselves. In cases wher. It IS impossible for every student to experiment for him- self, the author hopes that this work will enable the teacher to exhibit to his class, in a familiar and inex- IV, PIIKKAOK. P»nsiv„ „„„„„,, „p„,,n„„U „„„„,,, ,„ ,^ tllO SOIPIICO. 'n.o following, aro thn chief charactoristics of this work : — (1) Tho ox-pon,nont.s, now nurl old, havo hoen carpfullv proparo'-stions is given to dire.t the attention of the stu.lont to the n,oro important facts which rc.,uire to be in. pressed on the mind. Problo.ns, as a test of attain- ...ents, can hardly be overesti.natcl. and, therefore, a few carefully selected problems will be found at the end of each section. (r.) For the sake of completeness, facts have been stated •n the sumu,aries at the end of the sections which can- not be illustrated without the aid of expensive apparatus The book has been specially prepared for those teachers who have not a great abunrlanco of apparatus, and who .J wish their pupils to become accurate observers and sirict reasoners. Like all elementary text-books, this work is simply a compilation. It embodies in a son.ewhat new form pre- viously existing statements of well-recognized facts and principles, wiiich have become the common property o^" science. The author particularly desires to acknowledge his indebtedness to Reynolds' Experimental Chemistry from which he has introduced several experiments especi- ally in the first chapter. That errors have crept in, is probable, but it is hoped they will not be found serious, and the author will be glad to have any inaccuracies pointed out for correction in a future edition. Normal School, Toronto, April, 1886. COISTTEIS^TS. CHAl'TEK I. PAOKS. ■•Section II 1— , 8-:;j CHAPTER II. OXyOKN, HYUROOKN, NITROGEN, AND CARBON. Sec<40» / — Pr, paiMtio.i and Properties of ().\V".;ii. Manner in whl,.h Manjianese n.ox.d, .ct.. Acids. Meaning' of Te,t. Origin of Na mo Vlk^lie ' Bases and Oxuie.. Tests for Oxygen. .Smnniary and AddUlonal Facts ' 05_4i .Section 7 /.-Preparation and Properties of Ozone. Questions 4'. 44 J>i:ct,on ///.-Preparation and Properties of Hvdro.'un DifTei t Methodsot prepar,„or H.vdrogen. Sunnna.y and additional Facts'. Question" 4", ^(iO Addii:;on':rt4!^;:''^:^;iJ:;;:.:"''^P:-°f-;^:-^'^''--0S-- Sumnmryand torn^'^'yue]^^'""""- ' '^V-ationand Properti^sof Clu;>;;o;h' An;;;;pic C4— 70 CHAPTER III. CIIKMICAL CALCULATIONS. Law of Charles Umt of Vol.uno :uu;u-;'"h?*;^Sa.^-t'cn^ Composition of a Conij-ound t . t.nd its Formula. Oiven the Form ,1a of"a Compound to find its percentage Comp ) ifion .."....... 71--8I CHAPTER IV. CARBON DIDXIIIK. AND CARliOX MONOXIDE. 82—95 1 K^ ,-,- , -P''eP-ipt>on and Properties of Carbon Monoxide. Summary and Additional Properties. Questions and Exorcises ;....• 95. -100 CONTENTS. Vll. PAOKH. 8-:i-l 25—41 4-' -44 4r> -CO 60—64 64—70 ri-81 82—96 95—100 PAGBS. CHAPTER IV. KITIUC ACID, AND OXIDBS OP NITROOSK. Section T. — Nitric Acid and Nitrates. Examples of Common Nitrates. I'leparatioii and I'ropcrties of Nitric Acid. Tests {or Nitric Acid and Niliuios. Sun. nun J and Additional i'acts Secliun //. — Preparation and Properties of Nitro-^en Monoxide. Sum- mary iind Additioiuil Facts. Preparation and Properties of Nitric Kxidu, Nitric Trioxide, and Nitioj^en Pcntoxide. Second Law of Llicniical Comtiin- ation. iVtoniic thuory. iiucbtions and Exercises 101—117 CHAPTER V. AMMONIA. Preparation and Properties of Ammonia. Amnioiduin. Isomorphism. Summary and Additional Facts, liuestions Uii— j2j CHAPTEr •. WATKB. Composition of Water. Purification of Water. Relation of Water to Hea";. Hard and Soft Water. Im,jurities in Water. Naturally occurring Waters. (Questions and Exer. ises laO— 143 CHAPTER MI. THE ATMOSPIIKRR. Composition. Constancy of Composition. Diffusion of Gases. Consti- tuents of the Atmosphere, t^uostions and Exerci.ses 14o-ir,J CHAPTER Vm. MARSH QA.^!, OLBFIANT OAS, AND COMBUSTION. Section /.—Preparation and Properties of Marsh Gag 1 ja— 154 Section //.—Preparation and Properties of Ulefiant Gas 155—156 .sVc iun ///.—Preparation and Properties of Coal Gas 156-157 Section IV — Combustion. Combustibles and Supporters of Com' ustion Ucat of ComljustioM. The Composit'nn of Fuel. Combustion in a Sto\ e or Grate. Nature of Elame. Lununosity of Kiani..'. The Flame ol a Candle The Buns ;n linrner. Temperature of Ignition. Tlie Davy Lajnp. T)ie Blow- pipe. Questions and Exercises 152—168 CHAPTER IX. CHLORINE, IIYDJIOOIILORIC ACIU, BROMINE, IODINE, FLUORINE. Section i.— Preparation and Propertiesof Chlorine. Precautions Bleach- ing lowder. Tests jgn .-y 6'(!C and effects of this inity. them mouth dowii- until they become ammonia, into the I well and bring the 3, that whereas the ire now filled with le t'unblers in the •hr the influence of form a solid. in a tumbler and vill dissolve. The ■iratod. Kow mix id add to it, all at once, an equal quantity of dilute sul])huric acid (1 to 4), and shake gently ; instantly a white solid is formed. (2). TIence, Under the Influence of Chmnlral Affinit)/ liquids become solkU Exp. 5. Rub together in a m.ortar a small quantity of alum and acetate of lead ; the two dry solids become a semi-liquid. (3). Hence, Under the influence of Chemical Affinity solids may become liquids. Exp. 6. Fill a test-tube tw.)-thirds fidl of water and dissolve a small crystal of copper sulphate in it ; the solution will be nearly colorless. Add a few drops of ammonia; a beautifid blue color will be produced. (4). Hence, Under the influence of Chemical Affinity changes of color frequently take place. Exp. 7. Take a thin slice of phosphorus, taking care to cat it under water, dry well with blotting paper and do not liandle after drying. Place it on a plate and sprinkle a little iodine upon it and cover it with a wide-mouthed bottle, the two sub^^tances combine, much heat being given out. (5). Hence, Under the influence of Chemical Affinity heat is generally evolved. 6. Inference from preceding Experiments.— In the second exijcriment we see that the magnesium wire is utterly transformed; in the thu-d, the white solid formed is altogether unlike the gases which produced it; in the fourth the "white solid is an entirely different substance from either of the two liquids used ; and in tb(i sixth and seventh the substances formed are totally uidike their constituents. Hence we see that One of the most characteristic features of Chemira/ Affinity is tJie entire cliange of prnperllcs which it occasions ia tlie substances dealt witli~a change w/iich no a priori reasoning could possibly predict. 7. Difference between the Action of Chemical Af- finity and other forces. Exp. 7. I'iaee a small piece of freshly-cut phosphorus on the bottom of the a plate, and bring a piece of red-hot iron near it jiliosp' urus Ignites 4 BXPKKIMENTAL CHEMISTRY. Exp. 8. Rub a glass rod witli a piece of silk, or rub a piece of smVnv^ wax with woollen cloth ; they will attract a siispeml- 'jd rod of wood or a lon,i,' tliiii cylinder of paper. That is, Hmt and Eledricitij ad at appreciaUti distances. Exp. 9. Take a teaspoonful of finely powdered loaf sugar, and two teaspoon fuls of finely ])owdered potassium chlorate, mi.x them Avell togelher, and funa them into a little heap on a piece of card board placed on a tumbler. Dip a glass rod in sulphuric acid and bring it near the powder ; as long as there is a measure- able distance between the acid and the powder no change will take place. Now bring the acid into actual contact wiUi the mixture and it at once inflames, leaving a black mass of carbon on the plate. Exp. 10. Into a tumbler put a teaspoonful of baking soda, and the same (luantity of finely powdered tartaric acid. ° How- ever closely the solid particles are brought together by stirring or ruljbing no action takes place. Now add water and ettci° vescence immediately ensues, shoM'ing that chemical action is taking place; water added to the soda or acid separatebj does not cause any effervescence. The violent action observed on the addition of water to the mixed powders must, thei-efore, have been due to the mutual attraction of the two solids leading to chemical action ; and this could only take place when, by solu- tion, the particles of each body were endued with greater mo- bility than in the solid state, and were thus enabled to get within the sphere of each other's attraction. (5). Hence \ve see that Chemical Affiuity acts only a,t rnappreciahle distances. 8. Electricity developed by Chemical Action. Exp. 11.— Fit a test-tube with a small flat cork, in which pierce two parallel slits with a penknife, and insert in one slit a slip of sheet zinc reaching nearly to the bottom of the tube, and in the other a slip of copper foil of tliesamc length taking care that they do not touch each other. Insert in °ach f i '^ ■ silk, or rub a piece II attract a suspend- iper. That is, Heat owdered loaf sugar, issiura chlorate, mix ttle heap on a piece ass rod in suljihuric s there is a lueasuie- Mler no change will xX contact with the ack mass of carbon ful of baking soda, irtaric acid. How- iogether by stirring Id Avater and efter- chemical action is separatelij does not a observed on the 1st, therefore, have '0 yolids leading to ace when, by solu- il with greater nio- u.s enabled to get (5). Hence we see We distances, :al Action. i>t cork, in which ud insert in one le bottom of the the same length, r. Insert in each EXPERIMENTAL CHEMISTRY. 6 of the slips an end of a piece of tine copper wire about 2 feet in length, so that one wire sliall be in contact with each piece of foil. Fill the tube with dilute sulphuric acid (1 part of acid to 12 of water), insert the cork so that the slips sjiail be in the acid. Such an arrangement is a simple form of a (jalvanic cell. After tlie zinc has been a few seconds in the acid remove it, put a drop of mercury on a plate and touch it gently with the zinc in three or four places, first on the one side and then on the other, and rub it with the finger till it is all covered with the mercury. The zinc is now said to be amalgamated. Place it again in tlio acid whicli now does not appear to ad'ect it. Now join the free ends of the wire?, taking care that they are quite l)right, and observe that a gas rises from the copper. Bring b(jth wires in contact with tlie tip of the tongue, and notice llie sharp metullic tasti'. Knl) a common darning needle with a magnet and suspend it linn'znntally by a fine silk thread, pass one wire above it and the otlicr Ix-Jow, and join tlieir ends; the needle is imni(;(liat(i]y d(!fl<;ct.'d. This is the usual test for a galvanic current. (7). Hence wo see that Chemical Action may (jive rise to a galvanic current. Evidences of Chemical Affinity. From the preceding experiments we see that tiio i)iu,.f of (du-uiical action taking place between bodies, Avhen they are bi'oiight togetlior, may con- sist in the occurrence of one or more of the folJowiuf clian"-es • (1.) ^ change in tlie state of aggregation, confiding in the cm,, version of gases into solids, of liquids into solids, or solids intu liquids. These rosnlts are not however, to lie taken as evidence of chemical action, unh^ss accompanied by other phenomena not produced by simi)ly heating or cooling the sal)stances separately. (2.) A change of temperature, usuallji elecation (3.) 'Ihe formation of a new sid)stance jmssessijig physical or chemical properties, or both, differing from those of the original ■',uai(l carefully against the idea that the dements are certainly simple bodies. Chemists, at present, can- not prove them to be compounds, but it is not at all impossible that more powerful analysis may yet decomjjose them. 13. Subdivisions of Chemistry. Chomiatry occupies such an extensive sphere that it has been found desirable for the greater convenience of study to sub-divide the matter on which it treats. It is usually sub-divided into the two branches of Inorganic and Organic Ohemidry. Inorganic Chemistry was formerly defined to be the chemistry of the mineral kingdom, in contradistinction to organic chemistry, which was held to be the chemistry of the animal and vegetable kingdom, since most of the subjects included under this division were of animal or vegetable origin, This definition of organic chemistry is no longer tenable, for by far the greater number of bodies classed by the chemists as organic are neither of vegetable nor of ani- mal origin. At present there is no real difference between organic and inorganic ciiemistry, but as the substances hitherto comprised under organic chemistry invariably contain carbon, and as the number of these compounds is very larc^e it is found convenient to study them together under the head of I 8 KVI'KRIMRNTAL CfrKMIHTUY. ( ] il' i tin .No,M„„tal,, ,„„l ll,„i,. ,„„r„ i,„,„„,„„t Co,„p„u„.ir SECTION IJ. Clmniad Cmip,nmdH and M,rJ,mH,xd Mirluivs ■ L. , ■' 14. Indestructibility of Matter. Exp. 13.-T,.k„ a piece of pliosphorus al,„„t as Iar<>e as , small pea, p„t ,t i„l„ „ little „ater m a te,t-fl„. .,! „ ■cat till it ,„elt. ; tl,e„ place the poiat of „ t „ tX TT\ et ,t cool Bond the lower end of the „i.e i a pil," that ,t wl staaJ ..pvi,!,,. Select a thin, li.-ht beake a, i a Ia^«o, th„. light ,l,,.k of abo„t .600 c^bic cent 1, (abou 2| p.nts), P„t about 400 cubic ce„tia,efes (J a pu, of wate,, colored blue with lit„,„.,, i„to the b , k place ho ,v,re n. ,t, and invert the flask over the pl,o..ph„, w. h ,ts meuth reaching ahuost to the bottom of he c„lo d w„ or. In tins conddion place the whole apparatus on a pahof scales and exactly balance it b.y weights in the other pan I, about forty.eight hours it will be fonml tint tl,» ,„.i ' . into the flask as if part of the air l^d" Lef atiSS, '-,:;t color has changed fro.n blue to red. The phosphorus has evi. iTUY. Cliomislry are divulcl '111(1 No„-M,'tah ni iii^S possess a |)oculiiir ^'ity, mid lire .rood coii- ■ Non~M>:tnls are noted !■ low specific gravity, iH'at and olectriuily. ly. There exists no vo l)i;uiol)os, and t is !3 a Hutal, and what a i-e usually ,.allod tho pounds. Ocjinifn Pmporf;„„>, ; fixtures ; AviMjadm's 'ons. about aa large as a t(;st-t-;be, and gontly tliin wire in it and vire ii;to a spiral so ', b'ght beaker, and 3 cubic centimetres i centimetres (|- of IS, into the beaker, >ver the phosphorus ttom of tlie colored jparitus on a pair of the L»t.iier pan. In the water has risen annihilated, and its ohosi^liorus lias evi- I RXPEBIMKNTAL CHRMISTFty. g t't'lT"'vr;rr ''r' •' '"' ™''"'^"'™ "■- '-' >«" uostro.>e,l. N ,vurthoIos.s the apparatus wei.rlw ,.v,i,.Hv , ■""■'"'": 7""'' "-"i^l' "' «t. -13 ..f a ,,n„„ I,.„ ,v|J„ , „ ""'■ ' asses into the first Hank au.l drives tho wal.n- over into tho second. Leave tho apparatus at rest for a short time till tho tube becouK's ool.l, and it will bo found that the balanee is undisturbed. The whole wei"lit i^* just the sauio as at first. ileuco we infer that No Ions of matter takes plac", in Chemical Ikcinnpodticn. 15. Conservation of Matter. Many accurate experiments siinilar to tho foregoin- have heen made by chennsts and lave prove.l l^oyond doubt that matter is never dostroyo.l. Substances may disippear and seem to be lost, bnt the loss is only apparent. During all the chemical chaiiges through winch a substance may pass, the balance shows that the weiiht remains the same. . , The doctrine of the indestructibility of matter or as it is now^ termed the Uonsercatlon of Matter, teaches us that we can neither destroy nor create matter, though we can alter its dis- tribution, and its forms and combinations, in innumerable ways. This principle constitutes the l)a3is upon which rests tho whole superstructure of the .- -nonce of Chemistry. It i' th^ first great principle of Modern iScinnce. 16. Conservation of Energy. Energy has been defined to be "the capacity or power of one body or system of bodies when in a given condition, to do a measural)lo amount of work" ; and t hf>r bjen established during the past half-century that we can ;uer create nov destroy ene •(rv. thouyb we can change it from 10 form tc i :.cther. This is the second great principle of modern ! il KXI'KRIMIONTAL CIIKMIHTHY. n v-tiglit at tho h\. Place, tliu qile, upon the II licut tho t(!St- p(j\V(Un" will on tho silk' oi s into the Urat 1. Loiivo tho iHiu's ooltl, and I. The whole ic'i in Chemical ite exporiraenta ohoinists iiiicl !Voi' do.hnr. Exp 17 —Heat a small portion of the mixture of iron and sulphur" in a test-tube. The mixture become, pasty and then EXPEUIMUNTAL CHEMISTRY. 13 ace, showing s going on. m ciiibonate lizeJ. Then iist drop tlie ipeais. The te pni/icrtiiiii, wing hiw : — \emicaliij is nical Mix- 1 niiiny cases :hoso various ihstaiice, such jy, etc. But lem ami true will illustrate id sulplmr in -on to thirty powder results, ■ can easily be tly stir a por- iKMvy particles )iur, while the s as a distinct igiiet, and the unet, while the rtiirc- ran. easily jiartahoi of the ire of iron and pasty and then [jlows for a short time, showing that chemical action is taking place. Break the test-tube and grind up its contents in a mortar, (I) When exiMuincd by a magnifying glass no particle of iron or sulphur can be detected. (2) It is no longer attracted by the magnet, or at least very little, and therefore cor.tains little or no free iron. (3) The iron and sulphur are no longer separable by mechanical means. (4) If a small cpumtity is put into a test-tube and dilute sulphuric acid added, a gas possessing a very offensive odor is evolved, Neither iron nor sulphur alone, possesses the property of evolving this gas. The iron and sulphur have chemically combine.!, forming iron sulphide, which possesses a detinite grou]) of cliaracters which not only serve to distinguish it from the free elements, iron and sulphur, or a mixture of them, but from a!l other bodies. Hence we see that the const it v<'.iit>< of a chemical compound rannut he separated by mechanical m^an^, that its 2^foperties differ entirely from those of its constituents, and that it contains a fixed and definite quantity of its constituents. 20. Composition of Water. Exp. 13- — Take two copper wires, each aliout twenty centimetres in length, flatten an eml of each, and to the flattened ends solder a strip of platinum, aliout two centimetres long by live millimetres broad When those wires are connected with Iho wires from the battery they are usually spoken of as the /m/^.s- of the battery. Dip t!ie wires in melted paraffino, and wr.ip round each of them a thread of lamp-wick, previously soaked in parafline. Tiiis will protect the eojiper fnim the action of the acid. Take a tunililer three-fourths full of water and add to it a teii-i oonful of sulpln\ric acid for the purpose of increas- ing the conducting powi^r of the water. Bend the ecjpper wires over the sides of ihe lumlijer Mitl.at thetopsoftheplatinum strips miy be about two centime tus below the .Miiface of the water Kill two test-tubes with the acidulated water and place them over tho platinum strips, keeping,' the tubes as near to-ether as 14 EXPERIMENTAL CHEMISTKY. i^^ii possible. Connect the wires Avith the galvanic battery and minute bubbles of gas "will immediately be given off. It will' soon be seen that twice as much gas is given off from the pole connected with tne zinc end of the battery as from the pole connected with the other end ; -when the former is full the latter is only half full. As snou as the tube connected with the zinc end of the battery is full, close its mouth Avith the thuml), raise it out of the water, and examine its contents : (1). Observe that the gas is colorless. (2). Invert the tube and apply a match to its mouth ; the gas takes fire and burns with a jialo blue flame. (.')). Kciiil the tube and turn its mouth upwards and smell it ; no odnr is jterceived. Hold the tube in this jmsilion for a few seconds, and then apply a lighted match to its mouth ; no coml)usti]>Ie gas is found in it. The gas has escaped, and is, there- fore, lighter than air. iSXPRRIMEMTAr. CIIEMISTRV. 15 ;nic battery and iven off. It will off from the pole as from tlie pole )nner is full the )nnected with tlu' Avitli the tliuiul), iits: its mouth ; the pwards and smell lii.s ]>osili(iii for a to its mouth J no iped, and is, thero- The gas possessing the above properties is called Hydrogen It is considered to be an elementary body, and will be fully 1 reated of in a future chapter. Examine the gas in the other test-tube in the same way ; it will not take fire. Imniorse in it a gloM'ing splint of Mood ; the wood instantly takes fire and burns witli groat brilliancy. Hence the gas has the same characteristics as that obtained by heating mercuric oxide and is therefore Oxygen. The above process is called electrolysis and is fioi|;iently employed in decomposing chemical compounds. When the above experiment is carefully mawol loosely round the tube, and connect the wires in the coi k with the battery. The fine platinum wire will soon become red-hot and explode the gases. On raising the tube from the pad, the water will rush up and fdl the tube, showing that the two gases have united to form water which appears as vapor on the tube before it is raised from the pad. 1\ i 16 EXPERIMENTAL CII EMISTKY. lill W^ater is, therefore, composed of two gases, Oxy- gen and Hydrogen, in the proportion of one volume of the former to two volumes of the latter. When tlie composition of a substance is determined as above l)y causing its constituents to enter into combination, the process is called Si/nthem's. 21. Combination by Volume. — In the preceding experi- ment if the apparatus is so arranged tl'.at tlie gases before ex- plosion are heated beyond the temperature of boiling water and kept at the same temperature after explosion, it is found that the two volumeis of hydrogen and one volume of oxygen which were mixed together have become chemically united into two volumes of steam. It is found in other cases also that What- ever the number of volumes which enter into com- bination, the resulting compound is two volumes. 22. Physical Constitution of Gases. Ex 20. — Take two glass tubes, about one metre in length and five millimetres in diameter. Close one end of each and bend so that the short limb may be about twenty centimetres long. Fill one of them with acidulated water, colored with lit- mus or indigo, and place it over the pole from which the hy- drogen is escaping, until enough is collected to half fill the short limb of the tube. Turn the short limb uppermost and the gas will pass into it. Half lill the short limb of the other tube with oxygon in the same maunen (1). Observe that when both limbs are full of water the gases are equally compressed. (2). By means of a jiipette to which a piece of rubber tubing or a piece of fine glass tubing is attached, adjust the water in each tube so that it may stand at various heights, but always at the same height in each tube ; the gases expand equally as the water is removed. (3). If you have mercury pour an equal quantity into each tube, and observe that the gases coB.tract **> ilie sauie extent. wo gases, Oxy- of one volume itter. termineJ as above nation, the process e ])rccedi]igexpeii- i gases before ex- boiling water and , it is found that of oxygen which y united into two also that What- nter into com- vo volumes. e metre in length end of each and wenty centimetres r, colored with lit- •ora which the hy- Jialf fill the short most and the gas he other tube with of water the gases 3 of rubber tubing Ijust the water in lits, but always at nd equally as the uautity into each ke 8AQie extent. EXPERIMENTAL CHEMISTBT. 17 (4). Plunge the tubes into boiling water ; the gases expand qually. (5). Plunge the tubes into ice-cold water or a freezing mix- ture ; the gases contract to the same extent. Henco we infer that Oxygen and Hydrogen gases when comjmrcd under the same conditions are affected in the same way and to the same exfeid by equal alterations of pressure and ttmj.eratvre. VVhea tlic same mode of investigation is applied to other gases, whether elementary or compound, the following clianicter- istics are observed : — (i). All true gases obey the same law of compress- ibility. (2). Equal volumes of all true gases expand equal- ly on the same increase of temperature. The CO elusion that must necessarily be drawn from the preceding facts is, that all gases, however different chemically must be physicnJly constituted alike. Upon these facts an Italian chemist, named Avogadro, based a most important hypothesis. He assumed that all substances, solid, liquid, and gaseous, are made up of an innumerable number of little particles which he called molecules, and was thence led to the enunciation of the following hiAv : — 23. AVOGADRO'SLAW. When in the condition * of a perfect gas, all substances under like conditions of temperature and pressure contain in equal volumes the same number of molecules. The above law is considered the most important in the whole Iraiige of chemical science. It is to the chemist what the law Jjf gravitation is to the astronomer, But, like every other j.art f the molecular theory, this law owes its recognition not to any irect proof that can be adduced from experimental sources in pportof it, but to the fact that nearly all observed chemical Dhenomeua not only harmonise witli it but also find in it com- 18 EXPERIMENTAL CIIF.MISTRY. m pleto and satisfactory explanation. It not only explains thn known facts of chemistry, but is also constantly leading to new discoveries Admit this law and we at once see why gases .' re I'linally expanded by heat and why tlicy were equally contracted liy cold and pressure and why they combine by volume according to the law in Article 21. 24. Relative Weights of the Molecules of Gases. Avogadro's law gives at once the means of determining directly the relative weights of the molecules of all substances that can exist in the state of gas. For it is obvious that The ratio of the weights of equal volumes of gases, compared at the same pressure and tempe ■ ature, must repre- sent the relative weights of the molecules of these gases. Now it is found by experiment that a given volume of oxygen is sixteen times heavier than an equal volume of hvdrogen, under the same conditions ; therefore, the molecule of oxygen is sixteen times heavier than the molecule of hydrogen. 25. Relative Weights of the Atoms of Elementary Gases. Two volumes of hydrogen and one volume of oxygen comV)ine to form two volumes of steam (Art. 20) ; and by Avoga- dro's Law we know that the two volumes of steam contain the same number of molecules as the two voiunias of hydrogen, hence we have — 2 vols, hydrogen -f- 1 vol. oxygen ^ 2 vols, steam ; therefore, 2 mols. " + 1 mol. " = 2 inols. " Now in the two molecules of steam there is but one moleculeof oxygen ; therefore in one molecule of steam there can only be half a molecule of oxygen, and the weight of the oxygen corresponding to the semi-molecule is the smallest quantity of that gas that can take part in any chemical change, and fis it cannot be further divided by any chemical means it is called an atom. We shall find that the molecule of hydrogen can also be divided into two parts, and that one of these parts is the least quantity of hydrogen known to take part in any chemical action, only explains tlio tly leading to ne\v I see "why gases i re equally contracted ' volume according cules of Gases. termininj, directly ;ubstances that can that The ratio ases. compared ire, must repre- ecules of these lat a given volume 1 equal volume of fore, the molecule of ■ule of hydrogen. I of Elementary B volume of oxygen 20) ; and by Avoga- )f steam contain the anias of hydrogen, vols, steam ; mols. " but one moleuuleof there can only be iight of the oxygen imallenl quantity of ,1 change, and as it neans it is called an i^'dfogeri can also be le parts is the least any chemical action, EXPERIMENTAL CHEMISTRY. 19 and is, therefore, called an atom of hydrogen. Tt has been found con\enient to take 1 as the atomic wciijlit, or weight of a semi, molecule of hydrogen. The weight of a molecule of hydrogen is, therefore, 2 ; and since oxygen is sixteen times heavier than hydrogen, the i.iolecule of oxygen is 32, and consequently its atomic weight is 1 0. Heuc, To find the atomic weight of an elementary- gas, it is only necessary to find its weight com- pared with hydrogen as the unit. 26. Specific Gravity of a Compound Gas —Suppose that in a given volume of steam there is a certain number of molecules, then by Avogadro's Law the same volume of hydrogen will contain the same number of molecules. Tlierc- fore, the weight of a given volume of steam has the same ratio to the Aveight of an equal volume of In drogen that a molecule of steam has to a molecule of hydrogen. But the molecule of steam is made up of two atoms of hydrogen and one atom of oxygen ; its molemlar iceight is, therefore, 18, and |the molecular weight of hydrogen is 2, or the ratio is 9 to 1. Therefore, the specific gravity of steam compared with hydrogen las the unit is 9. Hence, The specific gravity of a gas simple or compound compared with hydrogen as the unit is found by taking half its molecular weight. As a rule the moleculeofan element is composed of two atoms- but in merci/i-!/, 2*'"^. and cadmium the molecule contains only one atom, and in j^hos^honis and arsenic the molecule contains tour atoms. 27. Size of Atoms. Sir William Thompson has shown that the size of a molecule of water is about one 500,000,000 th of an inch in diameter. This 'mmber is so large that it is difficult to derive any idea from it. A clear conception can be g^>t by supposing, as Thompson does, a drop of water to be magnifiecl iintil a drop the size of a pea is as large as the earth itself, •20 RXPRUIMI':>^mallnd portion of a chemical demmt that i^ l-non-n to take part in a chemical change, arid is almod inmriahlij the mmi-molecule. AtomicWeight.— Th< atomic weioht of an elom.entis the minllnd proportion, hy wrVjht, in which it enter^^ into or is expelled from a chemical compound, tJce wn;jlit of hydrogen being taken as unit)/. Molecular Weight —TJie moJecular weight of an elementor compound is the mm of the atomic weights of tlie elements comprising a violecide of it 29 Chemical Notation.— Instead of writing the names of the elements in full, chemists have agreed to use a set of symbols to represent tliem. These symb .'s, however, not only represent the particular element but al^o a certain definite quant it g of tt ; thus the letter H always stands for 1 at.)m, or one part by weight of hydrogen ; the letter O stands for 1 atom, or 16 parts by wei-ht of oxvgen. Compounds are in like manner repre- sented by writing the symbols of their constituent elements sid<; by side, and if ni-ue tban 1 atom of each element is present, Ww number is indicated by a numeral placed on the right of the syn,])ol of the element below the line. Thus, water is repre- sented by the symbol H,0, that is, a compound of 2 atoms of liydrogen with 1 atom of oxygen, or 2 parts by weight of hydro- *\<^n, +, wliich simply means and; on tiio right are ])lacc(l thu"fce express the results of experiments. Although important inferences may sometimes be drawn from the mere form of ex- pression, yet these are of no value unless confirmed by experi- ment. An exact knowledge of chemical equation is of vital impor- tance. The result of almost every experiment will be expressed by means of these equations, and the student must thoroughly master them. EXPKRIMENTAL CIIEMlsritY. 23 QUESTION l)N CUAl'Tini I. 1. What is meant (a) by chemical chungo, (6) by physical change ? Give fiimiliar oxainples of each. 2. What is chemical aftinity ? How does it ditfer from other forms of force? Describe some experiments which illustrate this difl'orence. 3. Explain the terms chemical combination and chemical decomposi- tion. Give examples of each. 4. Define the terms element and compound and givi examples of each. What is the present number of elements, and what reason iiavu we for believing that additional elements may be discovered ? By what means- can the compound character of a substance be proved ? Why is platinum, magnesium, and mercury considered to be elements 1 5. The following substances are heated to redness in air — (a) platinum, (/>) magnesium, (c) mercuric oxide. What occura in each case ? 6. Matter is said to be indestructible. Explain this statement and describe experiments in support of it. 7. No weight is lost in chemical combination. How may this be shown ? 8. Chemical combination is said to take place in certain definite proportions. Expljiin this law and describe experiments in support of it. 9. State clearly the diflFerence between a chemical compound and a mechanical mixture. Two powders are given you one is a mcjhanical mixture, the other a chemical compound of sulphur and iron filings. What experiments would you make to distinguish one from the other. 10. One hundred pounds of iron filings are heated with the same weight of sulphur till combination takes place. Which element would be found in excess after the reaction, and how much of it? 11. In what proportion (a) by volume, (6) by weight do oxygen and hydrogen unite together i 24 EXPKRIMENTAL OHEMISTny, ouMnT"''"" "''''* '^''•°"'"''t'»«°"« may ^a,08 combine together with- o u^W,o,n,,u..ntn.cti..,.i„volu,a„7 Under what circ«m,ta"l invlrb;r:;;;;:,r''^ ' "^ ^"" '- ''- -'-- «^ ^^« --^^^-^'^ «- fonrl/^'l^tT^.'"^'''' ^'^'- ^•'"">«''«te the circumstanoos that UUK^ to OBtabl.h .t. Sh,.. ho. it ac.unt. for the simple ratio, i„ Which gases combino by volume. » J^;<.^"""" "'" '"""' '"'^^''""'«' '^'-'*. «<«'"- 'oeijht, and mo/.,../ar readUv""" r"" ?.' '""'"""'" ""^^^^ "^ * »"^'^^"'' ^"bstance be readily ascortaiiiod by uxperimont i 16. What rdation exists between the molecular weight of a com- pound gaseous substance and its density compared with hydro- 17. Explain briefly how the atomic weiohts of oxygen and hydrogen may be ascurtiiined. 18. Define the ter.ns chemical .vimhol., cJu^^nical formula, and chenural eqnatwu. How does a chemical e\ means of this transfer the. .dilorate to a test-tuh(! Gin. hy fin. This quantity will ahont half till the tube. Place upon the same paper about 5 grams of manganese dioxide, and transfer it to the test-tube. Place a s^mall piece of paper on the mouth of the tube to keep the thumb clean, and shake vigorously till the two substances are thoroughly mixed. Choose a sound cork, very slightly larn'csr than the mouth of the test-tul»e, squeeze it Avrll till it becomes soft and elastic, and wiili a cork-borer or rat-tail file^ bore a hole throu-h it, so tliat a glass tube may l)o inserted tightly into it. Take a piece of glass tubing, about 45 centi- meters (18 inches) in length, bend it in two places, one down- wards about 5 (;entimeters (2 inches) from the end of the tube ; the other should bo upwarcTs, and as near the other end of the tube as possible. The object of the second bend is to facilitate the escape of the bubbles of gas, by giving them a forward and upw fjentle diroction. The downward bend should uo\v', with pressure and. twisting motion, be inserted in the cork. 1 •2S KX'PERIMENTAL CII KMLSTBY. lake a large cork, bore a l>ole in it to fit the rod of t}.«. retort-stand, twist a piece of copper wire around the cork leaving about eight inches of the end free. Twist the free' lit 1 """ "'""^ ''^' ''^'■'"^^' "^^^^^ '^^ <^ovk in the tube, and arrange as represented in the Fi,"ure Take two quart and five pint bottles, fill two of then, with water, and place mouth downwards, one on the shelf of the pueumatic trough, the other in the water in the trou.-l, re.dv take the place of the one on the shelf. On gentlj Wi o- he test-tube, oxygen will readily be given ofl! When th: bottle ,s full shde it off the shelf with one hand, and with the otl.r shde the full bottle into its place. Eriug a glass plat under xts mouth while still under water, raise it out of the water, and place it mouth upwards on the table. If any of the bottles have to be kept for a considerable un.e, they should be placed mouth downwards in a saucer containing a little water winch will act as a valve to prevent the gas from escapincr ' One ounce or 28.3 grains of potassium chlorate should yield If gallons, or nearly 7.75 litres. 36. Precautions—In performing this experiment, the following precautions should be observed :— (1) lu the preparation of the mixture, care must be taken to avoid the accidental introduction of small fragments of orcrunc matter. A small quantity of the oxygen mixture shouJi be heated m a test-tube before using it on a large scale as occasionally the manganese dioxide contains lamp-black and substances of kindred nature, the presence of which would lead to an explosion. (2) When the delivery-tube is fitted into the cork, nnd the cork into the test-tube, blow down the open end of the d,.l,\ orv tube ; no air must be heard to escape, or must b,- seen to Imbble out on moistening the cork. (3) As soon as the oxygen begins to be delivered, the heat EXPERIMENTAL CHEMISTRY. 29 beneath the test-tube should be so regulated thai the evolution of the gas should be tranquil and uniform. (4) The uppermost portions of the mixture should be heated l)efore the lower, which should be heated only after the upper- most parts refuse to yield any more gas. (5) The test-tube should never be more than three-fourths full, lest particles of solid matter be projected into the delivery- tube. (6) The test-tube should be inclined at an angle of about 45°, and must never be placed upright. '^ (7) When the process is to be stopped, the end of the delivery-tube must be immediately removed from the water, otherwise the cold water is liable to go back into the hot test- tube, and break it ; and the test-tube must not be allowed to touch cold or wet objects, which would cause the hot glass to crack. 37. Manner in which the Manganese Dioxide acts. Exp. 3. — Mix one gram of potassium chlorate with half a '^ram of each of the following substances, viz. : — Manganese dioxide, MnO._j, copper oxide; CuO, ferric oxide, FcoOs, lead oxide, PbO, zinc oxide, ZuO, magnesium oxide, MgO, sand, and powdered glass Put these several mixtures into as many test-tubes, and into another test-tube put one gram of potassium, chlorate alone. Imbed the. tubes side by side in sanil to about the same depth as they are filled within, apply a grailually increasing heat, and by means of glowing splints fre(piently plunged into the different tubes, observe the diU'cience in the readiness with which the oxygen is evolved from tlie several mixtures. It will be seen tliat there is little diU'cn-iicc among the first four tubes, and tlii't tlie heat will pruli.ilily not be sufficient to cause the oxygen to be (>vnlved frn-i! the otlicr fi-.o. After all the oxygen has been given oil', aboiit lialf-Hll the first tube with water and gently heat till its contents are d ssolvcd, k-^= 30 RX^RRIMiNTAL CIIEMISTUY. •liter through a piece of blotting paper, and gently dry on hot land the black substance remaining on the filter. It will be found to bo manganese dioxide, and that it is in the same state after the experiment as at the commencement, Tlie same •a true of the next three oxides. These oxides may, however, •indergo a temporary change. We know that MuO.'is capable of taking up more oxygen and, combining with a molecule of water to form manganic acid, lI^MnO^, and it is possible that when heated with potassium chlorate the manganese dioxide may absorb oxygen from ihis substance, and pass to the state of the higher oxide which is immediately decomposed, the oxygen being evolved and the manganese dioxide returning to its original state. The same applies to the next three oxides, all of which are known to be susceptible of higher oxidation. The zinc oxide and magnesium oxide, on the other hand, which do not form higher oxides, do not facilitate the decomposition jf the chlorate, 38. Physical Properties of Oxygen. Exp. 4.— Take the first bottle fdled, which will contain a little air, but will suit well enough for this experiment. Ob- serve the physicial properties of the gas ; it has neither color, taste, nor smell. Plunge a glowing splint of wood into it ; the splint bursts into flame as in the preceding experiment. Hold the glowing splint at different heights above the mouth of the bottle ; it will not burst into flame. Leave the bottle for a short time standing on the table with its mouth open; the glowing splint will show that the gas has not escaped. Turn the bottle mouth downwards, and hold the glowing splint near its moutii ; it will burst into flame. Hold the bottle in this position for a short time ; the splint will no longer burst into '■-^ .e when pluiiged into the bottle. The gas ha« nscaped. Oxygen is, therefore, heavier than air. EXPERIMENTAL CHEMISTRY. 31 39. Combustion of Phosphorus in Oxygen. Exp. 5. — Take a quart bottle of oxygen, and adjust the deflagrating spoon by holiliiig it against the outside of the bottle, so that the little metallic cu[) may be aliout 5 centimetres (2 inches) from the bottom of the bottle, and put a little lime into it to absorb the moisture. Take a piece of phospliorus not larger than a small pea, dry it carefully with soft blotting paper, and place it on the iinio in the cup. The i)ln>sphorus must not be touched with tlui fingers after it is dry, and it should be dried only when about to be used. Place the spoon in the bottle, and touch the j)hosphorus: with the end of a lieated glass rod. The phos])horus burns brilliantly, and wiien the heat volatilizes it a flash of iiglit fills the whole vessel, owing to the points of contact between the phosphorus and the oxygen being indefinitely increased, and the bottle is filled wilh dense white fumes. The phosphorus has combined Avith the oxygen, forming the white, snow-like substance called Phosphorus Pentoxide, P2O5. The molecule of phosphorus consists of four atoms, and the reaction is expressed as follows : — Fio.4, P4 + 50, Phosphorus. Oxygon, 2P2OS Phosphorus pentoxide. 40. Acids.— Phosphoric Acid.— Pour a little water into the bottle aud shake it up , the phosphorus pentoxide dissolves in the water. Taste a few dro])s of the solution ; it is ex- ceedingly sour. Pour into it some blue litmus solution ; it will be immediately reddened. A substance possessing these charac- i^'' 32 teri EXPERIMENTAL CHEMISTRY. instics is called an acid. The phosphorus pentoxide has combined with a molecule of water ; thus : — I'oOj + H2O = 2HPO3 Phosphoius iientoxide. Water. Metaphosphorlo add. 41. Combustion of Sulphur in Oxygen. Exp. 6 — W.isli the lime out of the cup of the deflagrating spoon, and dry it by holding it in the flame of the spirit-lamp. Place in it a piece of sulphur about as large as a pea. Heat the spoon in the flame until the sulpliur melts and bogins to burn with a pale-blue almost invisible (lame, then place the spoon in a bottle of oxygen ; the sulphur burns with a much brighter flamp, emitting a I)eautiful violet-colored light. When the com- bustion is over, remove the spoon and observe, (1) the pungent sullbcating snudi of tin- ga-i'ous combination of sulphur and oxygen wnich has bc(Mi produced, (2) the seeming aksence of anything in the bottle, the product of combustion being an invisible gas, (3) that a lighted paper plunged into the bottle will be immediately extinguishcl. The gas is called Sulphur Dioxide, SO2, and the reaction is as follows : — S2 + 20a = 2SO2 Sulphur. Oxygen. Sulphur dioxide. 42. Sulphurous Acid. Pour a little water into the bottle and shake it up, 01)serve that the hand is drawi.^ into the bottte, showing that a vacuum has been produced Taste a few drops of the water; it is sour. Pour a little of it into lit- mus solution in a test-tube; the solution is immediatdv reddened. The reddening of the vegetable blue coloring-matter is called the '' acid read inn." The gas has combined with a molecule of water to form Sulphurous Acid, H2SO3 ; liius :— SO2 + H2O = H2SO3 Sulphur dioxide. Water. Sulphurous auid. 43 Combustion of Carbon in Oxvjren Exp. 7.— Cleanse the deflagrating spoon from sulphur, by EXPERIMENTAL CIIEMISTBY. 33 holdnig It in the flamo of the spirit-lamp till no smoll of suli,l,ur IS porcmved. Select a few splints of wood charcoal, place them upon tlie (lefla-rating spoon, and adjust it in a hottle of o.xyrren as u, the hrst exp,riineiit. The charcoal burns energeticilly in the gas, emitting much light and heat but little or no flamo • observe that the product of combustion is an inodorous, invisible gas. Plunge a lighted taper into the bottle ; the taper is extin- guished. The charcoal (carbon) combines with the oxy-en forming Carbon Dioxide, COo ; thus :— ° ' C* + ()., = CO. Carbon Oxygen. Carbon dioxide. 44. Carbonic Acid. Pour about half a tumblerful of water into the bottle and shake it vigorously. The hand will be drawn in, but not so forcibly as in Exp. 6 ; carbon dioxide i. IS only moderately soluble in water. Pour some of the water into a glass and taste it ; it is slightly sour. Pour some of it mto litmus solution; the solution is turned a dark-red color The carbon dioxide has combined with the water, forminc. Car- bonic Acid, HiiCOa ; thus :— . ° CO2 + Carbon dioxide. H2O Water. H3CO3 Carbonio acid. 45- Meaning of Tast. Pour some clear lime water into the carbonic acid reserved from the last experiment; the clear hqiud becomes milky, indicating the presence of carbonic acid as will be hereafter explained. Lime-water is said to be a' " test" for carbon dioxide or carbonic acid. A test is a material for some experimen ' intnuhd to hrinp out a property characteristic of the substance under examination, and bij which the presence of that body may be detected. "^ 46 Origin of name Oxygen. -In the preceding experi- ments the products of combustion in oxygen when combine cd •The number of atoms in a molecule of carbon isunlrnr,mn ^ZT. ,. (ymbol for the atom is used in equations, unknown, and In such cases the 34 EXPIMtlMKNTAL CriK\f tSTIlY. » with water formed acids. The name oxygen (from tlie Greok nxus, sour, and gennan, 1 pri)diu;e) was jjfiveii by Lavoisier, under the mistaken impression that tliis element contained a principle common to all acids. This is now known to be an error. Later re,S(jarches have brought to light a number of compounds con- taining hydrogen possessed of acid pro[ierties in whicli no oxygen is present. Nevertheless the name was not ill-chosen, for of the many hundreds of acids known there are only about six which do not contain oxygim. 47. Combustion of Sodium in Oxygen. Exp. 8. — Take a small piece of metallic sodium, scrape it clean with a knife, heat it in the deflagrating spoon till it melts and begins to burn, then plunge it into a bottle of oxygen ; it will burn with great brilliancy, and with a bright yellow Hame. A white solid c.vlhd Sixh'/nn Oxide, Na-O, is formed. The reaction is represenled by the equation : — 2Na Sodium. 2 + O2 = 'iTSTajO 0\ygeii. Sodium oxide. 48. Alkalies — Sod'um Hydrate. — Add a little water to the buttle, shake it up and taste a few drops of the solution ; it does not taste sour, but has a peculiar nauseous taste, and is soapy to the touch. Add a little to blue litmus solution ; it is not reddened, but on the contrary becomes ratiier darker in color. Dip a glass rod into liydrochloric acid, and with it redden some blue litmus solution. Pour into this some of the solution of the sodium oxide ; the red solution at once becomes blue. The solution of sodium nxidi' a -U upon vegetable colors in just the opposite way from acids, ami nil!, in fact, neutralize their action. It is called an alkali, antl substances like this, which will restore the blue color of reddened litmus, are said to have an "alkaline reaction." Tho. °,odinm oxide b.;is combined with a molecule of water, forming a substance called Sodium tlie Greok sier, under 1 principle or. Later ounds con- no oxygon , for of tho six which 1, scrape it ill it melts oxygen ; it How tiame. Qod. The le wator to olution : it iste, and is ttion ; it is ' darker in lid with it some of the ce becomes table colors ■, neutralize 3 like this, are said to ? nomhinftd led Sodium EXPERIMENTAL CIIEMISTKY. 35 Hydroxide or Sodium U,,d,ate, NaOII, bettor known by its •-•omraon name of Caudic Soda; thus :— Na,0 + H,0 = 2NaOH •odium oxide. Water. Sodium hydrate. Similarly, if we burn the metal potassium in oxygen, we f'-'Y ^'"'' ''''''" ^^•^^' ''^^'^ ^""^'^i"^^ with water to lorm Potassium Hydrate, KOH. 49- Combustion of Magnesium in Oxygen. Exp. 9.-Eurn 10 or 12 centimetres (4 or :. inches) of Magnesmni nbbon in oxygen. A white solid calle.l Maynesium Oxide, MgO, IS formed ; thus :— 2Mg + Magnesium. Oxygen O3 = 2MgO Magnesium oxide. 5C. Bases-Magnesium Hydrate. Pour a small quan- tity water into the bottle containing the magnesium oxide, and sliake It vigorously; it does not seem to dissolve in the •va er. Add some of it to blue and reddened litmus solutions • .t has apparently neither acid nor alkaline reactions Dip a |aece of wliite blotting paper in reddened litmus solution, put It into he hquid and leave it for some time; it becomes blue. Half fill a test-tube with water, and add to it one drop of nitric acid; the solution will readily redden blue litmus paper when dipped into It. Pour the solution into the bottle in which the magnesium was burnt, and shake it vigorously ; it will no longer redder. ...her blue litmus paper or blue litmus solution The .... has been neutralized. A hody possessing the characteristic ofneu.:a,ziny an acid, either partly or eutirdy, is called a base An alkali is only a base, which is freely soluble in water Acids and bases will be fully discussed in a future chapter. It may be stated bore that the characters of taste and reaction belong to all well-marked acids and bases whi<.h arc soluble iu water but they do not belong to all the acids and bases. In this case 38 BXPEHIMBNTAL CHEMISTRY. a molecule of watei' lias combincil \vith tlio magnesium oxide to foim Magnesium Ilyilrato, M,i,'(OH)^ ; thus: — MgO + H2O = Mg(0H)2 Magnesium oxide Water. M!i,:,'iie9iuin hydrato. 51. Combustion of Iron or Steel in Oxygen. Sxp. 10. — Take a piece of thin watuh-spriiifr, which may bo, obtained from any watchmaker, heat it in the Haine of a spirit- Ip.mp till it is red-hot, and allow it to cool ; it will then have lost its elasticity. Coil it into' a spiral around a glass tube clean one end with a file, twist it round a bit of charcoal, and fasten the other end to the cap of the deflagrating spoon, and plunge it into a quart bottle of oxygen, on the bottom of which there is at least an inch of water. The burning charcoal heats the steel to redness, wliich then conibaies with the oxygen burning brilliantly, forming Magnetic or Black Oxide of Iron, FegOi, and throwing out alnindance of sparks. The sparks are red-hot carbon contained in the steel, which al.^o cdinbine with the oxygen, forming carbon dioxide. Tlie oxidized iron falls to the bottom in black globules, which are so uot tliat they are apt to melfr into the glass and crack it, unless they have to pass through a considerable depth of water. The reaction is — 3Fe + 2O2 = FegO^ Iron. Oxygen. Magnetic oxide of iron. 52. Magnetic Oxide. — Pick out the black globules and examine them, as in the preceding experiments. They do not produce an acid with water under any conditions, nor do they exhibit any alkaline or basic characters, and may, therefore, be classified as indifferent or neutral oxides. 53. Ferric Oxide. — Observe that the inside of the bottle Necomes covered during the experiment with brick-rod oxide, Fe^Oa, which is called Ferric Oxide. This ferric oxide is insoluble in water, and, therefore, cannot be tested with litmus. It will, however, neutralize acids, and is, therefore, a base. 1 EXPERIMKNTAL CMKMISTRY. S? num oxide to ito. ygen. .vliicli may bo, 110 of a spirit- .ill then have a glass tube charcoal, and ig spoon, and torn of which jluircoal heats I the oxygen 'xide of Iron, 'lie sparks are combine with il iron falls to that they are have to pass ion la — globules and They do not nor do they therefore, be I of the bottle ick-rcd oxide, jrric oxide is 1 with litmus. !, a base. 54. Oxides.— Tli.i.se oxi)oriinents show that there aro throf kinds of oxides : — I. Acid producm I oxides or Anhydrides.— T\\Q^e oxidns com- bine with water to form acid,, or substances usually possussiiw a sour taste, which turn blue litmus red, and which neutrili/.r l-asic oxilcs, forming a class of comiioimds termed Salts. All the non-metallic eleinentv, with the exception of hydrogen and luorine, form one or more compounds with oxygen, which, when ;iiuted with water, yield aci.ls, and in many cases intensely powerful acids. Tiie following are of this class :— Piiosphorua \ ,-, „ peiitoxide, / ^ 2*^s y^'"** «'»th water Metaplioaphoric acid, HPO3. Sulphurdioxide.SO, " Sulphurous " H^SOg. Carbon " it " H2CO3. CO, «• Carbonic If. Indiffn-ouf Or/VA... -These oxides aro indisposed to enter nilo couil)inatio„ with ..iiher acids or bases. They usually con- tani more oxyg.Mi than tlie basic oxides, a portion of it bein- loosely combine.!, and given off on heating. The following belong to this class : — ° Manganese dioxide, MnOj. Black oxide of iron, FegO^. Lead dioxide, PbO^. III. Ba^ic Ox2^cs._Many of the indals, bv tlieir union with oxygen, give rise to oxides, the cJiaracteri.tic property of which IS their power of neutralizing acids, thereby forming salts Many of them combine with water to form a class of compounds called Hydroxides or Hydrates. The following are of this clas. •_ Sodium oxide, Na,0, yields with water. Sodium hydrate, NaOH liernc oxide, Fe.O,, " Ferric hydrate, Fe,(OH)<,. 55. Other Methods of Preparing Oxygen. From Manganese Dioxide.~By heating the manganese dioxide 38 EX P i; K I M KNTA J. CH KM ISTUY. ! ill I I t(» redness ill ,1 piece nf -iis-pipo or gun-barrol, it gives off the oiie-thii'tl of its nxy^i^en ; ilms: — • 3Mn()o Mnj,0.i O, Manpancso dioviile. Hed oxide nf niiiiiKanoso. Oxy;,'eii. From Mmiffamx'' /)/,,.,■/;/,■ and Sulphuric Acid.—Wy gently heating maiiagaiiese ilioxidi! miuI snlidiuric iicid wlicii inauganeae .sulphate and water are forniod, and lialf the (oxygen which tlie dioxide contained is disengagc.nl ; thus: MnOj + Manganese dioxide. H,,.S()^ =. MnSO, -f Hiilphmic acid. Manganesa siilphiito. U,0 4- O3 Water. Oxyyen, Bij decomiiosing Water by Kledrolysis. —This has already been effected. 56. Tests for Oxygen. (1) Exp. 11. — Fill a test-tulie with oxygon, pour into it a small quantity of a strong sohition of caustic potash, and add an ejual quantity of a strong solution of pyrogallic acid. Cut a piece about the size of a cent from an old rubber over-shoe, place it on the mouth of the tube to protect the thunih, and shake vigorously; the solution in th- tube becomes iuten.^rh, brown. This test will indicate the presence of very small quantities of oxygen. Invert the tube in water ami withdraw the thumb; the water will rush into the tube an , entirely till it, showing that the solution has absorbed the oxygon. (2) Exp. 12.— Put a few bits of clippings of shoet-copper into a test-tube. Add a small quantity of dilute nitric acid ; an effervescence begins, and the tube is filleil with red vapors. These soon disappear, and a colorless gas comes over. Pass this gas into a bottle of oxygen .standing mouth downwards on the shelf of the pneumatic trough; immediately red. vapors are formed which the water soon .absorbs. The colorle-ss gas i^ nitric oxide, II RXPRIlIMRNTAr. OUBMISTUV. dd NO wh^.h ,n,it,.s witl. ,1.,. ...y^en. formin, I.i-.I.or nitr..y.M. oxKii'.i ; til IIS : — ^^ o fO + 0, = 2N0.. N.trlco.,,,,, Ox,v,,.n. Nitrogen peroxide. aUMMARY AND ADDITIONAL FACTS. 57- History. -O.vy-oii svas discovn-ed l.y Priestly in 1774 wH heatiu. ...orcuno oxide vvifch a I, :nuug glass, decomposed the cKide mo oxygou a.ul .u.taJlio mercury. Sehe'le, a Swedish apothecary, obtained it independently a year later. It wash.,uehed by Pictet, of Geneva, in December, 1877 under a pressure of .00 atnnspheres and tha ten.perature pr'oduced i>y the evaporation of li,,„id carbon dioxide in a vacuum. f ■ .°f "rf""'-^' '' ^^"^ ^"'^•^^ '^'^"'^^I'^'^t '^'^d mo.,t im- portant ot all the elements. Ab .ut one-fifth of the atmosphere consists of ree oxygen; no less than eight-ninths of water is ormed of the same gas. It m dees up three-fourths of our own ^oches not less than four-fifths of everv plant, and about one- halt ot the solid rock. Indeed if ,.. f ^ (-i, element of the globe. ' Preponderating 59. Properties. -Oxygen is a colorless, odorless, and asteless ga. It is a littl. heavier than air, its speciHc g avity being .056. a.r bemg taken as unity, and 16, or more accu- rat ly 15-96 when hydrogen is taken as the unit. It is only slightly soluble ,„ water, 100 volumes of which at ordinary atmospheric temperature dissolve about three volumes of wat^; On the solution of this small ,,uantity of water depends the existence of hshes and other forms of animal life in the waters of rivers lakes and seas. Fishes pass water continualiy through their gxUs, ^n which the oxygenation of their blood takes place. Oxygen is a great supporter of animal life. Pure oxygen however, differs from dilute oxygen in its effpnh« on life A small animal placed in a vessel of oxygen soon dies of exces.--.e m m Ji! ';3i;w:.:.r;r 40 EXPERIMINTAL CHEMISTRV. excitement, prorlnced by a too rapid oxidation of its blood It IS equally necessary to vegetable life, being needful to the development of the buds of maturer plants, and also bein<. absorbed by thei.- roots. Henco, if much earth is piled abou't a healthy tree, the tree soon sickens; while, on the contrary 1 Its roots fi.id their way into a drain, the tree grows better than ever. In all cases in which bodies burn in oxygen, the substance' burnt combniGS with the oxygen to form new substances, and the heat and light developed are a consequence of this union The weight of the product corresponds exactly with the wei-ht of the body burned, plus the weight of the oxygen consumed The combination of two or more bodies, token accompanied by tlw development of heat and light, is termed Combustion the body burnt being tlie combustible, and tlie body in which the buruin-r takes place the supporter of combustion. These are, howeve," nierely relative terms, as will be shown when combustion is discussed. The combination of oxygen with other elements is termed oxidation. In all cases of oxidation heat is developed, but it depends on the rapidity with which the oxidation is eiiected ' whether light is also produced. Thus, when iron is burnt in oxygen, the combination of the two elements is effect-nl with great rapidity, a large amount of heat is developed within a short space of time, and the product of combustion becomes incandescent. When, however, iron oxidizes or rusts slowly no light IS produced, althougli more heat is developed than wlion the same weight of iron is burnt in oxygen, the oxide, Y^.,0, being formed in the latter, and the oxide, Fe^Ua, in the former case. Oxygen combines with all the non-metallic elements, except fluorine. All metals combine with oxygen. When metals are easily volatile, as is the case with magnesium and zinc they burn with a bright flame in oxygen. A few metals, such as gold EXPKRIMENTAL CHEMISTRY. 4| eve?';''!"; T"f '^ ""'^ '" ""*« ^^-^"y -i*h oxygen, even at tlie highest temperatures. The oxides of such nfetal can however, be prepared by indirect means. Oxygen rea.Jily combines with oils, woollen refuse cre.sv ':;:.' r:\'r; "r t '--' ^^^^^"^^^ ^^ ^^^^^ sio: ikt z Mil ,r .•"'""'■''" ^'"-^ ^^^ b^ under tho shelf of tlie trough. A straiglit tube, to tho upper end of which a small funnel ia united by a cork, may ho used instead of u funnel-tube. Pour through tho funnel enough water to cover the zinc to tho depla of about one centimetre, and try whether the joints are tight by blowing through the delivery-tube till the water rises in tho funnel, then jjroasing the connecting india-rubber with the lingers, and observing if the water remains in the funnel or descends very slowly. If it deseenils rapidly, wet the cork and push it still farther into the flask ; if there is still leakage, it may be detected by the bubbling of the water through tho cork, and may be stopped by a little sealing wax, or more conveniently by a mixture of equal parts of bees-wax and turpentine, with a little Venetian rod to give it color. Now pour through the fuunel-tube sulphuric acid in suudl quantities at a time. Tho disengagement of the gas com- mences immediately, and when it slackens it may be invigorated by a little more acid. Great care must bo taken not to add too much acid, or the liquid in tho flask will froth over. Should it exhibit a tendency to do so, pour some water down the funnel to dilute and cool the acid. If the zinc happens to bo very pure the sulphuric acid will act upon it very slowly. In that case a few drops of copper sulphate will at onco c;iu v. energetic action. Fill two bottles with the mixture of air and hydrogen which first escapes from the flask and reject it This precaution is important, as it will be shown that air forms with hydrogen a mixture whicli explodes upon contact with a light. As soon as a bottle is filled, place a glass plate or small saucer under it, lift it out of the trough, and place it on the table, mouth downwards. It is necessary to collect only one or two bottles of the gas at first, as the collection may go on while the experiments are being BXPKIllMKNTAIi CIIRMISTHT. 49 le sido, and tliiit it (loos ito the neck elivery-tubc. tubo, to tho ork, may bo lUUil OIl()llJ,'ll I centimcli'i", tlu'ougli tho len i)re3sing observing if owly. If it hoi' into tho .lie bubbling d by IV little equal parts 1 rod to give luric acid in the gas com- ) invigorated )t to add too Should it 1 tho funnel bo very pure IX that case a •gotic action, rogcn which precaution is I hydrogen a As soon as under it, lift I downwards, of the gas at iits are being One ounce of zinc is siiflicient to lib(!rato from the acid about 2 J gallons of gas, or 30 grams will furnish about 10 litres. Scraps of iron may bo substituted for zin<; ; but in this case tho gas is loss pure. It has a disagreeable odor, due to the preseneo of compounds of carbon and hydr()g(!n, but, these may be removed by passing tho gas through tubes filled with fra-monts of wood-charcoal. 68. Whence comes the Hydrogen ? The hydrogen must (iithor come from the zinc, the water, or tho sulphuric acid. It cannot como from the zinc, for that is an element ; nor can it come from tho water for that is not decomposed l)y zinc alone, and besides it remains in t' c bottle unchanged when the experi- ment is finished. It must, therefore, como from tli(! sulphuric acid. Now a molecule of sulphuric acid is represented by the formula IFgSO^. There remains in the flask, when all the hydrogen has come off, water and zinc sulphates and the formula of tho latter is ZnSO^. It appears, therefore, that one atom of zinc has replaced two atoms of hydrogen to form a molceule of zinc sulphate. The molecule of zinc, like the molecule of mercury, is supposed to contain only one atom ; hence tho re- action is expressed by tho following equation ; — • Zn 4- HgSOi = Z"SOi -f Hj Zino. Sulphuvio acid. Zinc Sulphate. Hyilro)fon. 69. Use of the Water. In the preceding equation no account has been taken of the water which was added. The water remains unchanged in the flask after the experiment is finished. Had no water been present, the zinc sidpliate formed would have coated the surface of the metal, and thus have pro- tected it from the further action of the ""id. PROPERTIES OP HYDROGEN. 70. Combustibility. Exp. 4.— I'ill ii test-tube with the gas, and observe that it f>0 EXPERIMENTAL CHEMISTRY. is colorless, and that it has a disagreeable smell. This is almost always the case with hydrogen prepared by this method. The smell is caused by the presence of minute quantities of cora- jmunds of hydrogen with sulphur, arsenic, or carbon ; but the gas prepared with pure zinc and pure suljjhuric acid is quite free from smell. Take a bottli- of hydrogen, hold it mouth downwards, and apply a lighted taper to its mouth ; the gas takes fire, and burns with a pale, almost invisible flame. Pass the taper further up into the jar; it is extinguished Draw it out slowly ; it is rekindled. Now turn the mouth of the bottle upwards ; the flume will pass quickly down the jar, and the gas will be found to have entirely disappeared. Hence we see that Hydrogen is a combustible gas, but does not support combustion in the ordinary sense of the term. 71. Levity. Exp- 5 — Take two bottles of hydrogen, place one on the tiil)le, mouth upwards, and hold the other in the left hand, mouth downwards. After about ten seconds, apply the burning taper to the bottle in the left hand ; the hydrogen takes fire, with a slight explosion, and burns, showing that the gas still re- mains in the bottle. Lift the other bottle from the table, invert it, and thrust the taper into it, the taper burns as in the outer air, showing that the gas has escaped. Exp. 6. — Take an empty bottle and hold it mouth down- wards in the left hand. Take a bottle of hydrogen in the right hand, and bring its mouth close to the edge of the first bottle, slowly depressing the closed end till its niouth is brouglit under the empty bottle. Place the bottle in the left hand on tlie table, mouth downwards. Thrust a burning taper into the mouth of the bottle in the right iiand ; the gas will be found to have escaptd. Now raise the other bottle and bring the burning taper to its mouth ; the gas will take fire with a slight explosion, showing that the hydrogen has ascended, and displaced the air iis 18 almost thod. Tlie .63 of com- m ; tut the :i(l is quite d it mouth th ; the gas lame. Pass 1 Draw it )f tlie bottle and the gas but does not J one on the left hand, the burning takes fire, i gas still re- tal)le, invert in the outer louth down- in the right first bottle, ■ought under on the table, he mouth of und to have aiming taper it explosion, laced the air EXPKHIMKNTAL ClIEMISTllY. 51 in tlio bottle just as it displaces the water in tilling a bolLlu at the pneumatic trough. Hence we see that llijdnxjen in much liylitw than air. 72. Displacement. Exp. 7.— Owing to the liglitius-; of hydrogen, it may bo collected by up/rard displacement. Mold 11 bottle mouth downwards, and pi;t the delivery-tube in it so Unit it may reach nearly to the bottom. In a short time the gas will have dis- placed the heavier air, and the bottle will be found full of hydrogen. To ascertain wien the bottle is full, hold a piece of snioking paper und-r it ; the smoke readily ascends through the air, bnt not through the lighter hydrogen. Exp. 8. — HvDROGEN SoAP-BunBLES. The liglitness of hydrogen may also be shown as follows : Cut a little castile- soap into thin shavings, and dissolve it in lain-water, making a saturated solution. To two volumes of this solution add one volume of glycerine. Attach to tiie delivery-tube of the hydro- gen flask, by a piece of rubber tubing, the stem of a tobacco pipe. Pour some of the soap-soluticn into a saucer, dip the bowl of the pipe into it, and let the gas blow a bubble. While the bubble is small, turn the mouth of the i)ipe upwards, The bubble, having attained a diameter of several inches, will break away, or else may be easily detached by a sudden movement of the pipe downwards. It will then ra])idly "ise. 73. Explosive Mixture of Hydrogen and Air. Exp. 9. — Take a soda-water bottle and fit to it a perforated cork without a tube, or with only a ipiill, so that, if the cork flies to the ceiling .and falls, it will do no liarm. Place some granulated zinc in it, pour in some cold dilute sulphuric acid (about 1 of acid to 8 of water), and insert the cork, but not too tightly. r- 62 KXPEK I M KNTAL C H KM ISTRY. Hold a lighted tiqx-i to tlio orifice, and in u short time a loud explosion Avill occur. Allow sulliciunt time to olapae so that the air may bo oxpollu:]. Xo ox[)l()sioii occurs, but tho gas burns quietly at tho orifice. EiXp. 10. — Take a wide-mouthed bottle, and briid a glass tube in tlio form of a siphon, so that tho shorter arm may be a littlo longer than tho bottle. Support the bottle, mouih down- wards, on one of tho rings of tho retort stand. Place tho shorter arm in tho Ijottle, the longer arm extending upwards and tied to the n.'tort-.stand. Cover tho mouth of tho bottlo witli a piece of l)rown paper gummed to tlie glass, the sijjhon-tubo passing through it. Connect the longer arm by rubber-tubing with the generating flask, and fill the bottle by upward displacement. Kemovo the rubber tubing, and the hydrogen being lighter than air, will bo siphoned up- wards, just as water is siphoned down- wards. Apply a light to the end of thi* longer arm, and hydrogen is seen to burn with its usual non-luminous flame. After a short time, however, this flame flickers, emits a musical note, at first shrill, but gradually deepens to a bass sound, until after a time distinct boats are heard, and at last, when the exact proportions between the hydrogen and the air, which enters through tho pores of the paper, have been reached, the flumo is seen to pass down the tube, enter the bottle, and the whole mass unites with a sudd.n and violent explosion, but quite harmless if the mouth of the bottle is sufficiently wide. Explosions are dangerous only when the gases are so Cvjufiued that they cannot easily escape when expanded by heat. Hence bottles should be wide-mouthed, and thin glass vessels should not be used. KXI'KIIIMKNTAr, ClIKMISTUy. 6d i time a loud e 80 that the le gas burns liciul 11 ylass nil may be a nuuili ilown- « tlio Bliorter s ami tied to witli a piece tubu passing ing with tlie le bottle T)y Hcniovo the IrogL'n l)L'iiiL,' iphoncd up- lonod duMM- 16 end of th(^ L is seen to linous flame. T, this flame loto, at first IS to a bass istinct beats between tlie jores of the ss down tlie th a sudd '11 louth cf the 3 only Avhen jscapo when ;0uthed, and 74- Precautions. From the preceding experiments we see that no light should ever be brought in contact with the contents of the bottle in which hydrogen is generated, nor with any large qnantity of the gas. untd Its non-explosive eiunaeter has been chmionstrated. This nay be done by bringing the delivery-tube within the .nouth of the test-tnbe. We have ^ n that hydrogen can be poured upwanls, therefore, the tube will ..on till with the ga. Aft..r abont ten se.^onds, remove :, ..nil hol.t-ng it mouth down- wards, and apply a light to its me. ,t . If , ,e hydrogen burns tranqndly at the mouth of the tube '. , ^..s „,ay be considered pure but If It explodes with a whistling pop. fnrther . inn,, must be allowed. 75. Cause of Explosions. The explosion of the mixture of hydrogen and air is due to he sudden expansion caused by the heat geiieratcd in the com- b.nat.on of the hydrogen with the oxygen through the mixture After the explosion of the mixture of hydrogen and air (oxyaen and lutrogen). the substances present are st,>am and nitrogen which are expanded by the heat developed irx the combination to a volume far greater than the vessel can contain, so that a portion of the gas and vapor issues very suddenly into the air around, the collision with which produces the report. 76. Heat of Combustion. w?' ^\-'^^^^ ^ ^^^^-^'^be 6 in. by 1 in., fit it ,vith a cork through which pass two tubes bent at right-angles, cue of them reaching nearly to the bottom of the tube, the oth.l just passing through the cork. Twist a short piece of conner wire into a spiral and put it in the bottom of the tube, and nearly fill the tube with pumice stone, moisf.ned -""^h "uj- ' • acid, which readily absorbs moisture, and will thorough^ Xv the gas. Attach the longer tube to the generating flask by ^S5a» 54 EXPERIMENTAL CHEMISTRY. means oi a cork, altcl to the other tuhe attacli a small glass tube, about 20 centimetres lon<^ drawn but so as to form a rather fine jet, and supported in a vertical position. If the hydrogen is not coming otF with suHi- cient rapidity, add a little sulphuric acid, and before applying a light to the jet, ascertain that the hydro- gen is not mixed witli air. Kindle the gas and note that the flame at first is of a pale bluish color, but soon becomes a bright golden, owincert!uned by Cavendish in 176G. It was named iiydrogen - / Lavoisier. It was liquefied almost simultaneously and independently by two distinguished physicists, M. Cailletet, of Chatillon-sur- Scine, and M. Pictet, of Geneva. On January 10th, 1878, Pictet succeeded in liquefying hydrogen by a pressure of 650 atmospheres and at a tcmi)erature of — 140°C. C.iilh;tot de- monstrated its liquefaction on December 30lh, iiruviously. On opening the stopcock, a steel-hlue colored opaque jet of liquid hydrogen rushed out with a hissing noise, and at the same time a rattling was heard, as if small shut or haii had fallen to the ground. This was caused by the reduction of ti'mpcniture due to its reassumption of the gaseous Btate. It is, tlu'ivlni"' oidy an accident of temperature ami [tiessurc that ])ro' il. "1 i ~oni possessing the ordinary nictiUic properties wit': ..'i"' we are (I will be riblinn, in ::il touclies nul of the 11 Husk of ! stoain to icieutly to 11 lioat the lonionts it rogeii may quite hot fjiniilia as early as .bcertiuued Lavoisier, luloutly by atilloM-sur- LOth, 1878, sure <>f 650 !aill(itot (lo- Lously. On it of liquid D siiiu'J time alien to the )cr;itnre due !i'ct'nr'> only .1, '1 t ~oin ii'' we are ar 111 Icail, silver, oi highly vdlatih; metal. KXPERIMENTAT. CHEMISTRY, 59 ■ cni>iH'A'. It is simply the vapor of a 85. Occurrence. -Hy.lrogen occurs in natun,- almost solely in a state of combiuation, altliougli it has been found in the free st.:te m small .luantitics, with other gases issuing from volcanoes. Free hy.lrogen has been found in the sun and other lieavenly bo.lies. As it constitutes one-ninth of water it is necessaruy present in large proportions in all animals and plants It IS a constituent of all acids, and forms au essential portion of nearly all organic substances. 86. Properties.-llydrogon is a tasteless, colorless ino.lc ous gas. It ,s the lightest substance known, being 1 f.-43o times lighter than atmospheric air. It burns, but does not support ordinary combustion or animal life. In burning, it produces a greater heat than an e.pial ],ulk of any known substance On combining with oxygen to form water, one gram of hydrogen yiekls neat enough to raise 34,462 grams of water from o" to 1 U., and this is terim-d its calorific power. irydrogen is only slightly soluble in water, 100 volumes of the latter dissolving only l-i)3 volumes of the former Some metals absorb hydrogen in large quantities, especially platinum and palladium, the latter taking up no less than 370 volumes of the gas at ordinary temperature. On comparing hydro..-., with oxygen, note their remarkable chemical dissiiiiilurrtv Oxygen combines with all the elements except fluorine, whereas the hydrogen compound with fluorine is easily formed and i'. of great stability. The combining power bet^-een oxy-^en and inotals IS intense, whilst thao between hjdrogen and t.als i almost nothing. Ql'KSTIONS ON HYDROOEN. 1. Give three distinct reactions by means of which hydrogen m^v be obtamed from water. Give equations for each reaction ^ Mi- ^1 ffiii ^ iwmmtt^ilmm 60 BXPERIMKJ^TAT. CHEMISTRY. 2. How is hydrogen uauiilly prepared, and what impurii^^s r..ay it contain when prepared by this niethod ? Give an expla.,.,t.o,i af. the process. . - 3. ^\iut occurs when zinc is heated with a atrou? solatior. ot caustic pi.tash or soda? Give an equation , 4 How could you obtain hyar...en fron; h,; -Irochlonc acid s 5 Name any four metals which, if dropped into liydrocMorio or dilute sulphuric acids decompose th.se acids .^ .^h 'h. tvoiUl^on ot hvdrosen. Give equacions. .,.,., ,u ■„? " G Ho^- -Muld vou prove that hydrogen is lighter than air l^ 7 A h\x>':'-y jo: of hydrogen is placed successively in air, m oxy<.en, and in' hydrogen. Satte exactly what occurs in each case. 8 What im.,L.^ . lies are generally found m hydrogen prepared by the action of arl-.k on ivou, and how may they be rem.>ved ? 9 T have two bottle, of hydrogen; I hold one of them mouth upwards, and the other mouth downwards. At the ..mration of half a minute, I plunge a lighted taper into each ga. Describe exa-tlv what you would expect to take place In each case. • 10. Describe the chemical change which takes place when steam 13 passed over red-hot iron filings. ?„„.„, 11 Describe exactly how you would show the formation of water from burning hydrogen, and sketch the apparatus employed 12 How is hydrogen found in the free state in nature ? How does'it occur in combination ? Who first obtained it pure ? 13. Hydrogen is said to be a metal. What evidence have we of this? SECTION IV. NITROGEN. Symbol, K Atomic Weight, U (14.01). Molecular Weiyht, N,, 28.^ PRUPAUATION. By Abstracting the Oxygen from 4\r. 87. By burning Hydrogen Gas. Exp. 1.— Tb - quart bottle of hydrog n;KoU it mouth EXPERIMKNTAL CriKMISTRY. Gl downwanls, and apply a lif the air, a, leaving 13 of the reparation ve all the 'hosphorus the bottle, h upwards, shed, while differ from [roin aydro- lamed. trq^porter of bottle, close itate it ; the o disHiKjuuh , Rutherford, rgh, in 1' 72. EXPERIMENTAL CHEMISTRY. 63 Schoele and Lavoisier independently proved that air is a mix- ture of tlie newly discovered oxygen and another gas which Lavoisier named azote. This azote, Chaptal in 1789 recognized as a constituent of nitre or saltpetre, and he, therefor,, named It nitrogen. It was liquefied iu 1878 by a pressure of 200 atmospheres. 91- Sources.-In nature the great store and source of nitrogen is the atmospliere, of which it forms four-fifths In the muieral kingdom, especially in soils, it occurs in small quantities as an ingredient of saltpetre and of ammonia. It is a small but constant constituent of all plants, and in the animal It IS a never-fading component of the working tissues, the muscles, tendons, and nerves, and is, therefore, an indispensable ingre-Jient of food. Nitrogen also constitutes an essential part of many of the most potent and valuable medicines, as well as some of the most dangerous poisons, such a.s quinine, morphine prussic acid, and strychnine. * 92. Properties—Free nitrogen, under ordinary circum- stances, has scarcely any active properties, but it is best characterized by its chemical indifference to most other bodies We have seen that it does not support combustion, neither does It burn. It cannot maintain respiration, so that animals perish If confined in it. Decay does not proceed in an atmosphere of this gas, and, in general, it is difficult to effect its direct union with other bodies. Its specific gravity is -9713; it is, therefore, a little lighter tiian air. It is very slightly soluble in water. Beinc. so feebly adapted for combination, most of its compounds are more or less unstable, and many are explosive. 93- Tests.-In a free state we know it by its negative chamcterj ,n con.l-inatiou as nitric acid or as ammonia, it may bo recognised by Um special tests for these bodies. m-' tl EXPBlUMril..- 0HKMI8TRY. ^ A i-^ Mixture a3 a dilueut to air, and Uses.— The'*", are conhnod to Nature aa a aa a constituent of tissue. QUESTIONS ON NITROOBN. , HOW .oe.nitro.en occur in u.u.e. MenUon .-ne g.eou. and solid bodies which ^^'^'^^^^^ discovered? 2. Wi-andbywhornwasm^^^^^^^^ j,^p,,,, 3. H .w can you obtain n^t'^""« drawings of the apparatus, the reactions by equations, -A^^o'eTand show how it may be .i Describe the characters of nitrogen, * dxsanguished from oxygen and l^^yj^^^^^^^^^ ^ produce on life 6. What effect would an atmospno and combustion 1 _______ 8 E T I >' V. CARHON. which there are several vanot; s , 3. GraphUe , ,.,„ ,„h>.tanco is capable ot making Def.-When ^fj^f,:;. having ,11^... properties. irr::iT ;» •..: .«*■-.* -«»«- ■'' *- ''-"-"- I. i.i<,KPARATION OF CHARCOAU Qc. From Wood. T ■ I . t1 ^n sDlint -' ..ood, and plunge it into a ^^P- \"7^'thi^ 1 downwards. The .ube prevents test-tube, held w^^h it^ mo' ^^ ^^^^^ ^^^^^^^^^., , .^^othered the air from getting free .^ ^^^^^^^^^^ wood uun=a. •--, ^^^ ,„i oxygen oif m li.o lorm of The bout drives the ayaio^ water, leaving the carbon be.u,:d. BXPEBIMENTAL OHBMlSlltr. G'l 96. Preparation on the large scale. -Charcoal is i)ro- pared by covering a pile of woo.l wiiii earth or sods, in which openings are made at tlie top and bottom to admit a .small quantity of air. The wood in then set on tiro, and .some of it shnvly burns. The heat from the burning wood is used to drive otf tlie liydrogon and oxygen from the re.st of the Jog.s, care bi.'iug taken that sufficient boat is not protluced to cai^se the whole mass of wood to burn. Since carbon is, under all circumstances, infusible and nou-volatilo, the charcoal retains the form of the wood, but the h k has been much reduced, and its weight does not exceed one-fourth the weight of the wood. 97. From Vegetable Substances. Exp. 2.— Take a small piece of wriiing paper, crush it into a lump, and put it into a narrow test-tnl)e; ignite the paper by holding the end of the tube in the lamp. Take a slip of blue and a slip of reddened litmus pajxT, and as soon as a white Tioke appears in the tube, dip into it the blue test-paper. Af^er a moment take out the blue paper, and put in the red . -. Observe (1) that the white pai.-r heated in the tube is . onverte(^ nto a black substance, preserving the same size and shape ; ^ hat a brown oily liquid is deposited on the sides of the tube ; (3^ that the blue test-paper turns red, and the red test-paper remains unchanged in the volatile matter given off during the ignition ; (4) that the black substance in the tube, when placed on platinum foil and strongly heated burns away without flan-, leaving nothing but a very small quantity of incombustible wliite ash. The black substance is charcov.. From tl: e experiments we infer (1) That vegetable substancea contain charcoal • (2) That they contain the elements of a volatile acid, lohich acid they produce lohen subjected to a red heat in close vessels. 98. From Animal Substances, Exp. 3.— Take a bit of -, ooll«n cloth, put it into a small >G EXPKRIMKNTAL CIIKMISTRY. • ^ 1 «1h,s of tost-papers as in tlie to«t-tubo. Pveparo .o.stenea ^s ^oj^^ _^^ P^l^ ^^^^^^^^ ^^^ ^^^ l^eceain, -Pf -;*:^; '^ ,,t tho blue paper and then the spivit-hunp, and P" "^ ^/j ^^^.,i,. ,ioth is converted mto red one. Observe (1) tlu t the w ^^^^^^ ^^ ^^^^^^^^^ ^.^^ ^^^.^^^^^ , black substance like charcoal, ^W ^^^^^^ ^^^^ ^^^^^^ ^^^p,,. i. deposited on the sules oi^J^\ll ^lue ; (4) that the ,en.ains nnaltered and the ^ d pap ^^ pUvtinum foil. ,Uvck substance taken ^-^ /^^^^^^^^^^^ ,,rnB away without ,,1 held in the flan, of ^l- ^P^^ ^ " ^^^ ^^,.,, ,,Hes. flame, leaving only a very small quan y ^^^^^^ ^^,^^ ^^^.^^ From these experiments we ^^ ^ ,,, ,/„ «o/a«t7« a doK Vma. j,„„pEBT,E8 OF OUABCOiL. 99. Absorptive Power. ^^.^^ ^ good sound coA, previously « "^P'^ ' > ; „ fe,, dro,,, :,„u,o„ia ga. T.US may be J°- ;'*;,' „,,,, or by ,>l.ci..« of ammonia into the bo lo mi <^ ^^^^ ^^^ ,„„„,„ „, it, mouth downwards, for a ^^ j^^^ ^j^^^ „j tattie containing strong ammonia^ 1-lac ^^^^ ^ ^^^^ |^^_^_.^ „„„,y.burned charcoal and cork P- ^^^^ ^^^^^ .^ ^^ ^^^ withdraw the corlt, and ";" ' » ^^, been absorbed, remaining : the whole o *"— ^^ the fact that all This power of absorb.ng '^J'^^^^ J ,^, ,„,fe„e of solid gases condense rn greate^ or -» ; ,^^^ ^ ,,„,„„„! is very porous, or possesses a m o power is proportionately great. xoo. Decolorizing Power. ^^^^ ^ ^^^^^ BXPEHIMBNTAL OrrEMISTRy. 37 or red.lon...l litmus solution, into the second a solution of ha. wood or uny other vegetable coloring matter, into the third a solntiou of potas,.iu,„ ,.,.rmanganate. Stir the solutions well with a glass rod. Fold three pieces of filtering or white hlottinc. paper so as to fit into a funnel. Pour the contents of each tumbler on a hlt.r ; observe that the filtrate is in each instance colorless or nearly so. In case the first portions of the filtrate hap,K,ns to come through colored, they may be poured back upon the filter, and allowed to pass again throuyU the charcoal. In the purification of brown sugar, the coloring n.atters are removed ,n a manner similar to the foregoing, the colored syrup being filtered through lay.,rs of bone-black. Beer or ale, thus treated, lose not only their color but their bitter taste. A solution of quinine sulphate, filtered thus throu-Mi bone-black, is deprived of its bitter taste. ° loi. Deodorizing Power. Exp. 6.— Put a f. u' drops of a sulphuretted hydrogen solution into a test-tube, add a little animal charcoal, and shake the mixture thoroughly for half a minute ; the liqui.l has now ost all the ottensive smell of the gas, which has been absorbed by the charcoal. Charcoal not only absorbs unpleasant effluvia evolved in the process of decay and putrefaction, but has the power, especially in contact with air, of oxidizing and destroying them This property is retained by charcoal for a long time, and when lost It may be renewed by ignition. Hence charcoal filters are largely used for preventing foul sewer gases from pollutin-. the air of houses, and charcoal respirators have been used to pre°vent the ingress of deleterious gases into the lungs. Trays filled with heated wood charcoal, placed in infer Led apartments, have proved very effective in absorbing noxious emanations. Charcoal filters are also largely employed fop filtering ^vatcr for drinking pur poses. In its passage through the charcoal, the water has not 68 BXPEElMfflTAI. CKEMI3TRT. ' , , u, cloruig matters removcJ, but also only the organic and soluble u.lorm. undergoes aeration. 102. Reducing Power. ,. ,„:,,it.i„„„, and draw it E,p. 7.-Heat a gl,«s t* '^J^ J'^l^ ^ ,ery srn.ll out to a „oinl. Drop nrto tl^ pc^n ^^ ^^^^^^_^ ,^ ^^„„ ,ua,rtity of -»;»- °;f ;,,f :,'i;„al red-hot in the ftaure o of wood charcoal. Hot e ^^ ^_.^^ ^^^ ^,^,j, „to the lamp, and gently ra.se *e h mi ^^ .^ ^^^^^ ^^.^^^, the ftamo withorrt takrng the f'''^ ^ t,,e carbon, and oxide will volatilize, S'".'""' J,j' ^i/^^ „f *e tube, depositing metalhc arson, on the CO p^ ^^ ^,^^^ ,„„^,„„ture rs The affinity of carbon fo o.yg ^^ ,,^_^.^, „^yj,„„, very great. " <>»'•-;: "^e.^tic state. It might almost and thus brings them rnto tire m ^^.^^^_ .^ ^^ ^^„ be said that the a,, of ^^^^ ,,„, teu.perature. the affinity of carbon for o.y„ ^ _^^^^^ ._^ _^^^^^ ^^ X03. Indestruct.b.Uty.-C a °a ^ it, forurs, is »*«'-' V'st tea, d fence posts, if charred ..Icvatod temperature. Hence ate .an ^^^^^^^^^ ^,^^^_^ „ef„re they are put into ^^^'^ J..,^, reason it is a wbeu this «f7;";X:l tterior of tubs arrd casks destined coiumon practice to ciicu to hold liquids. ^^^.^^^ ^y burning turpentme, lesm, o ^ ^^ ^^ ^^_.^ ^^,,,,„„, it carbon, with a lim.ted ^-vf^J^^,^,,,, w,ncd eon.pounds o ,Uvays retains a V""'"^'^^^ J ^os, indestructrble of carbon and >f ^'...s „ ' been employed on this account as black pigments, and has 101 „ the basis of printing mk. _^, ,„,„.„,otured from .-aU^-l----"^^^^^^^^ EXPKRIMENTAL OHKMISTRY. 69 Strongly lieated out of contact with tlic air, the variety of char- coal thus produced is called Bone-Black, and is much used by sugar refiners. 106. Graphite.— Thi^^ is a crystalline form of carbon occur- ring in massive or hexagonal plates. It is also called piumbai^o, and is more familiarly known as black-lead. It is obtained from' the earth in largo quantities, and is u.ed for the manufacture of lead pencils, and for giving a black pulisl, to iron articles, such as stoves, etc., and for protecting them from rust. 107. The Diamond.— The diamond is another form of cvystalliiie carbon, occurring in well-dehncd crystals belonging to the regular system. It is the hardest substance known. Besides its extraordinary value as a gem, it is used for cutting glass. Very small diamonds are said to have been lately prepared artificially by a Glasgow chemist. If the diamond is suspended in a cage of platinum wire, heated to bright redness, and then plunged in oxygen gas, it ])urns with a steady red light, and with the production of pure cai'bon dioxide. 108. Allotropic Forms— Charcoal, graphite, and the diamond are but different forms of the eleiiient carbon. Tliey differ in hardness, in color, in specifi.; gravity, and in many other physical propertitK. They are alike infusible, alike able to resist the action of substances which attack most other bodies, alike in being combustible, and alike in the same weight of each yielding the same quantity (jf carbon dioxide when bui'iied. 8uch phenomena as these afford strong grounds for believin<"r that our present elementary substances may have a composite structure. QUESTIONS ON CARBON. 1. Give an account of the different methods employed for preparing/ charcoal from wood. How would you demonstrate the preparation of charcoal on the ain:U! scale? ;-~t,^- , K - r„^--T iii mjLg. i m il MMUaMM^dMf .Q EXPERIMENTAL CIIEMISTEY. • i. • thvo.. allotropic modifications. De- 2. Carbon is said to ex,s xn th .U^o - p ^^.^^^^^ ^^ ^^ scribe why diamond graplntea^^d charcoa .nodifications of the element carbn ^^^^^^^ ^^ ^^^^^^, 3. How may the presence of ^"^^^ '" ^ « ^ ,i,,rcoal is placed 4. What happens when a p.ec ^jf^^^L .s standing over i„ a Jar of --"^/^^ ,/ .loll is pUced in it, what happens? mercury and a piece or uiy What is the cause of the change { solution of indigo Todt and to what useful purpose is .t applied? 0. How does charcoal ^^^^^^^^^ .^e its properties? 7. How is animal charcoal V^^'^^'Y How would you 8. Describe the allotropic f"- ^ J^'^^, ,,,, same element ^^ nrove that these different substances consist CHAPTER III. CHEMICAL CALCULATIONS. 109. Amount of Material required to produce a given Weight of a Substance. We have hitherto employed equations to express chemical changes only, but they also express tne relative quantities of the elenu.,as which form the compounds acting on each other or which take part in the changes, and hence they furnish the basis for quantitative calculations. Thus, the formatio . of carbon dioxide, by the action of oxygen on carbon, is expressed by the equation — C + Oo = CO2, which not only tells us that one atom of carbon unites with .o.a oms of oxygen to form a molecule of carbon dioxide, but also that 12 parts by weight of carbon (atomic weight of ca ■ bon = 12) unite with 32 parts by weight of oxv.et (atomi' zsi ''^rr''^ " r '' '-'' '^ -^^^^ ^^^^ aZti ies nr" ?" '^7^derations it is easy to calculate the quantities of carbon and oxygen involved in the formation of titles ot carbon and oxygen. cliox de CO,. How much oari,on dioxide by ,vei..ht can 1,. obtamed by th„. burning 15 g,.„„, „f ^^^^J "''" '='"* '» Weight ofOO, .,bt,u„.d ft„,„ ,2 «„„„ of c„bon= 44 «ra„,.; 15 4 1 = 55 71 :^^0 ; , . . ^ 91 A arams of mercuric oxide=200 grama; .. mercury requiredto term 216 grams oti^^ ^^ ^ ^^^ .. " ^" = 18-52 " B^ 3.-WUat w n,ht of oxygen can b^ obtained from 100 grams of potassium^^OorateJ ^^^ _^ ^^ ^. . o,vi4.S5'54-48=122-6 Weight of a molecule of pot .slum oWorate=3.) l_+3o 54- ^ "^ Oxygen obtained from 122^6 grams ^^lO^- ^^^ ,^ ,i 100 - r2-.i = 39 15 EXERCISE I. 1. I want 100 lb. of oxygen; how many pounds of potas^ slum chlorate must I take ? ^^^^^^ ^^^^^^^.^ 2. I require 2 kdogram. «^ ^y- ;;.^^^„, ^ , ,,,^ae, shall I oxide, (2) potassium chlorate, (3) man,, need? . „v,ifM-.,t-p 293 f^raras of potas- 3. 0„ hea«„, so,n» P;'--';"'^::: ^^ J eh.orat. were ,i„m chloride were left; ''""' ";;,„;^ ^3,,, fo„„ed ) „£ water by the action ot sodium ! .^^ ^^^^.^^^ 5. HO. "-'> JXX'".; n ev:W 1., the action of oxygen to unite with the nyui , ^°: ^wrleT;;;::":: :r he ^dea to auute ..phuac hydrogen from hydrochloric acid 1 instead of =200 grams; = m " = nw^ ■' = 18-52 " >d from 100 5 -(-48=122 -6 grams ; ■15 " tids of potas- 1 (1) mercuric oxide, shall I ^ 'ams of potas- chlorate were rmed 1 trom 70 grams misli sufficient y the action of iiluta sulphuric ^re 35 grams of Experimental cHEMiarHV. 73 t"°; ^^IfT °^'^" ^°'""^" °^ G^«^^ *° Pressure. in Art. .2, Exp. 20, we see that when a confined mass of gas IS compressed, its volume diminishes with increased pres- sure, and conversely increases in volu.ne as the pressure hmm.he. Thus, if the pressure on a given ,nass o' gas is lou led, the volu,ne is reduced to one-half, if trebled, t: one- !^lh dim " r- ^T «^P«"'--^-^ --^^ as these, performed witli diffierent ga^es, the following law has been established :- III. Bot/le's Zaw.-The volume which a gas oc- cupies is aversely proportional to the pressure to Ton^tait" "'^'''^'' "'^" ^^'^ temperature remain: This law was enunciated independently by Boyle url Mariotte; and Balton further showed that iLaLpp^^^^^^^^ the case of a mixture of gases. ^^' ^n~f^ "" ""'"'^^''^ temperature a quantity of .^as oc will It, occupy under a pressure of 24 lbs ? Space occupied under a pressure of 10 IbJ. =25 cubic feet ; (I «< 1 " 24 " = 10x25 = 10 5 (< l( (< ii=. Standard Pressure.-The average wei.ht of the atmosphere at the level of the sea, iu the la'tude oTpal t l.at of a colum,vof mercury 760 milllmefes (30 inoZ' ;„ Ex. 5. -A balloon containing 1200 cnbio metres of hydro s:.r3r:t: rtt^^^ Sp.ce occupied under pre„„re of 770 mm. = 1200 cubic metre,- 1., =770x1200 " • = 17«'i <• 74 ,,,PF,Rn.ra'»<- <='"■■"'"■"■■ „,»c,sK,.. „„j„,UcuW day, 740 „.».;»« « m a„ ,y ^^ ^^ ___^_.^^^y^ ,„„ „„,, 2 The standard pressure " ' . . „„„,,er 1 inJl es of ,.«rcury correspomls to * > ^ j^^,.^,^^^^ "t 1000 CO. of I'y''--™;: „irvo u,„e beoo,„e under the pressure of 740 mm.; "I>at w H t Idard pressure of 760 ,nm^ ^, ^.^ „,„„,!,, « cubrc 4. Ataeonstautteu,per»lu.ejra^^^^ ^^.^^ .^ „„^,„py feeturider a pressure 75 10., „„der a pressure of 'K' .te ' ,„„, ,, certain quan- 5. If, uuder the pressure o on ,^ .^^^^_^^^ ^^^^^ „i,at *^ °""^xnLru;;T::bic .revs, ^'::r;;t nli- of t^e Vo.u»e of oases to Temperature. j^^j .^es inerease FromExperlmentaO Art^22 we ._^ ^^^^^ i, e,,ual volume when l«-*"=!''7„ ;,,, ,„l„„,e of gas at 0. ;j cooled. « we ^^^^^ ^^,..^.e at a deftnrte ,nd measure *= S^ ^JJ Le in the temperature o 10^ rate, we find that fo. eael ^^ ^.^ . ^^^ ^^,,„p,e, 273 the gas expands ,lr.rd of >ts vou ^^^ temperature * of a gas at Q-O exprnds to -7* c ^^ ^^ is raised rC or ^ »Oe.e wh ^^,^^^^„„^„ ten,perature ,-0. Conversely, 273 -''^Ir.^^^^ ^7 ^^^^^ '[ "^ T'^Tf is cooled rO.; that 18, a g^ * ^^„ the scale. U „„,ery degree of '»-''»'-*'^^' tarT were maintained -t ,he same ratio of volume ^o ^mp ^^^^ ^^^^ _,^„„ ^ ,, follows that if a P«n ma.s "t ^^^^^^^^ ^ ^ "a*™''*-^ temperature of - 273 C. t wou ^^^^^^ ^^^^ ^„i ^ the point; *atis,allthemo,ecula^m ^^^.^ ^ temperature has point of no heat wou d ^^^^ ■, j, foand cou.wc"^ - never been reached , never EXPERIMENTAL CHE.MISTRY. 75 bak3 273X\ l,oloNv ZC..0 as the absolute z.ro of temperature, and the te.nperatu.es .-oekoaed from this point are called absolute poXr""' ''" "''' '"' *'' te..pc,-atu..es are evident^ "4. Coefficient of Expansion. 'Ihe fraction ..l,, by which gases increase their vol.nue at OX. ,.,. ,.„u. dc^ee of nse of teniporuture, is called the ..;///..V.i «; e^.ansion 0} ,a..s JZ U 'f r '"";'""' "^^'"^^'"^ ^''^ expansion ^gase^ we Have tlie following law : 115. Law of Chai'les. The volume of a given mass of gas, under a constant pressure varies directly as the absolute temperature. Ex. a-A certain mass of air measures 100 c.c. at OT • hnd its volume at 10°C. ' The absolute temperatures are 10° + 273° =_- 283° 17- 1 i^nd 0° + 273° = 27'^°' Vokiine occupied by the aases at 27^ — inn " i • t< "^u ^,, ^"^ '^'•?<, = 100 cubic centimetres; 283° = i%ao = 103 TiG. »« at ^^lO^Cr"^ ^'' '''"^'" ^^^ '"• '' ^^°^' ' ^'"' ^^^ ^^^"'^'^ The absolute temperatures are 10° + 273° = 283° Volume occupied at 283; = 500 cubic centimetres ; (1 1" — 500 203° = aa'sxsoo 2 8 •> = 464-6 Ex. a-A litre of air is measured at O'C. and 7G0 mm i-;^sure; what volume will it occupy at 740 nin,. at 15^5cT Ihe absolute temperatures are 0° + 273° = 273° 17- , ^ *"d 16°.5+ 273° — 2S«»'k U (( <( (< (I = J (H> 1° '' 1 " = '^'•ly'xioop it 288°.5 " 740 " = Willy ooxij) 00 .< = 1085 •34"'^'^ *« it:*! n 76 EXPEIUMBNTAI, OHBMIbTKY. EXERCISE III. 1. A -•(■rtain quantity of gas occupies 67 cubic inches when the temperatmc is 10°C., and the barometer 28 inclies ; liow many cubic inches will it occupy at OT., with the barometer at :}0 inches ? 2. A certain quantity of oxygon measures 155 c.c. at 10°C., and under a pressure of 530 mm. of mercury ; what will the volume become at 18°.7C., and under a pressure of 590 mm. of mercury ? 3. A glass globe holds ten litres. It i>* filled wiui oxygen at 0°C., under a pressure of 760 mm. ; how much gas will escape when the temperature rises to 15°C., and the barometer falls to 752 mm.? 4. A room is calculated to contain 3000 cubic feet of air at lOT., and under a jiressure of 30 cubic inches of mercury ; find what would be the volume of the same quantity of air if it were measured at 0°C. and 31 inches pressure. 5. 10 litres of oxygen are measured at U°F., required the volume of the gas at 15°C. 6. A flask is filled with oxygon at O'C. and 760' mm. pressure, and the flask is then tiglitly corked. The flask would burst if exposed to an outward pressure of 1500 mm. At what temperature would the oxygen exert this pressure, assuming the capacity of the flask to remain unaltered? Ii6. Unit of Volume— The Crith. One litre of hydrogen at 0°0. and under a pressure of 760"ram. of mercury weighs •089578 grams, or approximately, "0896 grams. So important is this hydrogeu-litre-weight that Dr. Hofman denotes it by the term Crith (Gr. Krithe, a barley corn, ami hence any small weight), so that " ' 1 Crith = -0896 grams. It is of groat importance to remember this number, since the weight of a litre of any other gas may be at once found by EXPKUIMEn -v. L CHEMISTUY. 77 ".-.Itiplying this number by half the molecular weH.t of the gas j thus : — o « 1 litre of oxygen = ^ x -0896 = 1-433 grams. 1 carbon dioxide = 4j* X " -= 1971 <« Ex. 9.-What weight of potassium chlorate will be required to hll a gas bag of a capacity of 20 litres with oxygen at O.C. and / 60 mm. pressure, the temperature of the room being 15°C and the pressure of the air at the same time being 750 mm.? " (1) Find the relation between the potassium chlorate and the oxi/gen given off. KCIO3 = KCl -I- 30 39-l + 35'5+48=122-6 391+35'6 43^ (2) Reduce the given volume to the standard conditions of temjierature and pressure. The absolute temperatures are 15° + 273° = 283° and 0" + 273° =:^ 273°.' Volume at 288° and 750 mm. = 20 litres • r " 1 .« = 7.^x.a litres ; J73- 760 - = ^W«^.^ litres ; = 18-70 litres. (3) Find the toeight of potassium chlorate necessary to furnish the above quantity. At 0°C. and 7G0 mm. 1 litre of oxygen =16 criths =16 x '0896 grams; r> . • u, " =26-808 r otassnni, chlorate which yields 48 grams of oxygen = 122-6 " =685. 47 grams. EXERCI.sk IV. 1. Exactly 100 litres of oxygen, at the normal temperature '^ pressure, were obtained by heatinfr ,)nf c« (I " 26 -808 and much of this salt was used 1 um chlorate: how j:;^.^. ; 1- 78 EXPERIMENTAL OHEMISTRT. i?^ 2. How much potassium chlorate must be used to yield lOU litres of oxygen at I^O'C. and 380 ram. pressur c be 1 < 3 h4 3 O » 'o < •c 2 o o u o U o Hydrogev. . ~ — — • • — ' — • ~" Oxygen Nitrogen. . . 1 Carbon..., 1 Observe that he centh bracket has no name above it : no 1 uumpound has yet Weon disco vei-ed which consists of oxygen, 82 udied. es of the nd carbon, tant com- am it will wrtions of ro formed four ele- >ne excep- l together the name I to which • I ve it ; no f oxy^reii, 83 EXPISRIMKNTAL, GFIEMISTUY, nitrogen, and carbon. We shall find that more than one coin pound belongs to each class. For instance in the fourth class. besides carbon dioxide, there is another oxide of oarbon, called carbon monoxide, CO, w.iich contains just half as much oxy- gen. So in the sixth class, besides Ns^O, there are four other oxides of nitrogen. For convenience we will discuss these subjects in the fol- lowing order : — ■ 1. Compounds of carbon and oxygen (4). '^' " " " and hydrogen (7). 3. " nitrogen and " (6). 4. ** nitrogen and hydrogen (2). 5. " hydrogen and oxygen (1). 6. A mixture of several of these substances, the atmosphere. 7- Compounds of carbon and hydrogen (3). 8. A mixture of these, or coal gas. Combustion. SECTION I. CARBON DIOXIDE. Symbol, COj. Molecular Weight, 44. 121. Carbonates — 100 parts by weight of calcium car- bonate, chalk, or marble consists of — Calcium 40 ca. Carbon 2.2 C Oxygen .!48 Og. From these and other considerations it is inferred that a mole- cule of calcium carbonate is denoted by the formula CaCO. If we compare this formula with the formula of carbonic acid, II2CO3 (Art. 44.), we see that the two formulse are identical,' except in the one case we have Ca, the symbol for calcium, and in the other we have K.,. The former may be considered as derived from the latter by the replacement of TT^ by Ca. Compounds formed by replacing the hydrogen of carbonic acid hi 'IP '^f^^'^^Sf^f^^W'^BSU BXl'EKiMENTAL CHEMISTRY. 84 a mfifal are calM Carbonatks. Most of the common metals, such as zinc, copper, mercury, act like calcium, one atom of the metal replacing two atoms of hydrogen. These metah an' called dijaih. Others, such as potassium, sodium, and silvci-, replace the hydrogen, atom for atom. Tliese are called monads. Bicarbonates. — When only half the hydrogen of the acid is replaced by a metal the resulting compound is called a bicarbonate. Thus, NaaCOa is sodium carbonate, and NaHCO„ is sodium bicarbonate. SYSTKJIATIC NAME. COMMON NAME. Calcinin Carbonate SotUuin " Hydrogen Solium Carbonate..., Potassium Carbonate Hydrogen Potassium Carbonate. Maguesium Carbonate Lead Carbonn*' Copper Carb Miale Chalk, marble, limestone.. Barilla, washing soda. . . . Bicarbonate of soda, baking soda Potash, pearlash . FORMULA. CaCOg. Na2C03. VaHCOa. KoCO-,. 'Saleratus IKHCO3 M agnesia . . White lead. Malachite . , MgCO:l. PbCOa. CuCOg. 122. Properties of Carbonates. (1) All carbonates are insoluble in water except potassium carbonate, K.,CO; sodium carbonate, NaaCOg, and ammonium carbonate (NH4)2C03. (2) All carbonates evolve carbon dioxide, CO2, when hoated to redness, except the alkaline carbonates, such as potassium carbonate and sodium carbonate. (3) All carbonates effervesce on the addition of any strong acid; the escaping carbon dioxide is without smell. (4) All bicarbonates are decomposed by heat. 123. Calcium hydrate. — If calcium carbonate is heated to redness it loses a molecule of carbon dioxide, and there is left a molecule of calcium oxide or quicklime; thus : — CaCOa = CO 2 + CaO Calcium carbonate. Carbon dioxide. Calcium oxide, or lime. 84 EXPKRIMKS-IAI, CIIKMISTHV. 86 Ihis change is ide.itictl with that which takes place in a iime-kUn when li.a. is ui 1 1. I.y hui'uiu. limestone. When water ,s added to lime it . >:n!M>uM witii a definite amount of It, oG parts by woi-ht of lime witii 18 pa.-ts by weight of water tornung ccUeiutn lujdmfe, a white powder familiarly called slaked lime ; thus :— CaO + H^O = Ca(OH), ^•""'- Water. Calcium hydnite. 124. Lime-water.— If this calcium hydrate is mixed with about 700 times its volume of water it dissolves, forming a clear solution which is familiarly called lime-water. This lime-water IS alkaline, turning red litmus blue. It quickly absorbs car- bon dioxile from the air, and is used in medicine, and in the aboratory to detect the presence of carbon dioxide and car- l)onic acid. 125. Preparation of Carbon Dioxide. Exp. 1.— Take the n])paratus usod for the preparation of iiydrogen, place in it some marble broken into lumps, an! pour in enough of water to cover them. Fit to the flask a delivery- tube, as in the figure, and secure the flask on the retort-strad h sail 86 KXI'tCRIMKVr.\r. CIIKMI il-ur. Ill, sii(!li a height that the loii^'(!(' linili of tlio lul>,. ni.iy reach nearly to tlio table. Place the delivery-tuli." in a li,iU,|,., cover- ing the mouth with a disk of canlhoard with a slit in it lor the tuho. Pour ill hydror.hloric acid, IICI, in Miiall (luantiti^a at a time, until a brisk eli'crvescencw is set up. After the lapse of half a minute, pass a liglited tai'.er into tlie botth- ; as it approaches tiie bottom it goes (mt. There is evidently some gas collecting there. The reaction is expressed by tlie folhnving e(piation : — CaCO;, + 2HC1 = CaCI.. + H,0 + CO, Calcium ciiiboiiate. Hydrochloric acid. Caloiuni chlorid.;. Water. Carbon (ll"\idt!. This reaction takes jilaco in two stages. Th(« iirid exchanges its hydrogen for the calcium, producing calcium elilorido on the one hand, and carbonic acid on tlio other ; thus : . CaCOy + 2HC1 =. OaCla + H.-COa (1) The carbonic acid, at the moment of its formation, breaks up into water and gaseous carbon dioxide, the latter of which escapes with brisk etfervescence ; thus : — ■ HaCOa == H^O + CO, (2) A cubic inch of marble will yield about four gallons of the gas. 126. Metathesis or Double Decomposition. The re. action expressed byecpiation (1) consists merely in an inl(!rchan<'e between the hydrogen atoms of tlie acid and the metallic atom of the uar))onate ; and of the dilfereiit modes of chemical action, this is by far the most frequent. It has received the name of Metathesis or double decomposition, and consists simidij in the excJiamje of the elements or group of element^ in one body fur the elements or group of elements in annther budij. PROPERTIKS. 127. Neither Burns nor Supports Combustion. Exp. 2.— Plunge a lighted taper into a bottle of carbon dioxide ; it is quickly and decidedly extinguished, and the gas does not burn, its power to extinguisii liame is not owing to % EXPKUIMKNTAL CHICMISTRT. 87 any chemical aa.ou of tl.., ,as, hut i.s „..,rely owing to the exclusion of iitnios|»h(!nc oxy;,'('n. This property of carbo.i dii.xi.lo has led to its h,m>.. u.o.l to oxtu.M-.sh (ir.s in .nines, un,I in the "Chon,i..al Fin, J-Vtin ^'M.slH.r" ,t uflunls a ready ni.-an^ of extinguishing lires in their early stages. 128. Heavier than Air.-The density of carbon dioxide K.s ahvady he.n shown hy the method of collecting it. It nnv be furlh(!r shown as follows :— - ° y Exp. 3. -Take a wid.-nn.uthed bottle and plaee in it a Jghted taper P.ring the n.outh of a bottle of the gas close to he edg.. of t ,. bottle, and pour the gas over the taper, not auectly over the centre of the bottle, but at its edge, since the gas receives_ a forward as well as a downward inxpnlse whilst the bottle 18 be.ng inverted; tl,e taper will be immediately ex inyuKsluH 1, showing that the gas has been poured from one bottle into the other. The molecular weight of carbon dioxide (At. 2G). I.ut hydrogen is U-47 times lighter than air • carbon d.oxule is, therefore, about 1^ times heavier than air. ' 129. Solubility in Water. Exp. 4.-Half fill a bottle with cold water, and fill the olaer half wiih carbon dioxide by displacement. No^v tightly close the mouth of the bottle with the wetted palm of the hand and shake It vigorously for a short time; the bottle will adhe're to the hand, owing to a partial vacuum being produced by the combu.ation of the gas with the water. The reaction is as follows : — CO3 + H.,0 = H,C03 Carbon tlioxido. Wuter. Carbo.no acid. Invert the bottle in water, and remove the hand; the water 11 rush m and nearly till the bottle, sliowing that the whole the carbon dio.xide has Ik-cu ab.sorbed. Water, at conrr -, w 'i* 1 88 BXPERIMKNTAL CHEMISTRY. : if i ;i temperatures, absorbs its own volume of the gas, acquiring an agreeable acidulous taste, and sparkles wlien agitated. Its solubility increases if the temportituru is diminished or the pressure increased. 130. Acid character. Exp. 5. — Fill a tost-tube to the depth of about two inches with a solution of blue litmus, place the delivery-tube in it, and pass a stream of carbon dioxide throuj^'h it for a short time ; the color is changed to a wine-red, ditfcriiig entirely from the pure red produced by the action of sulphuric or hydrochloric acid upon the litmus. Boil the reddened solution ; it becomes blue again, the carbon dioxide pa-!sing off with the steam. Hence, Carbonic acid is decomposed into carbon dioxide and water, by hoilin;/. 131. Action on Lime-water. Exp. 6. — Half- fill a test-tube with clear lime-water, place the delivery-tube in it, and allow the carbon dioxide to bubblti through it; the solution becomes milky. The carbon dioxide first combines with the water which holds the calcium hydrate in solution, forming carbonic acid, which then combines with the calcium hydrate, the calcium of the hydrate and the hydrogen of the carbonio ucid exchanging places ; thus : — (1) (2) OO3 Carbon dioxide. -f H.O Water. H.COa Carbonic add. Ca(0H)2 + ^2-v.3 Calcium liylrate. Carbonic acid H,CO, r= CaOO 3 + Calcium carbonate. 2H2O Water. The calcium carbonate, being insoluble in water, gives the milky appearance. 132. Calcium Bicarbonate. Exp. 7. — Continue to piss carbon dioxide through the liquid in the test-tube; the turbidity disappears. Tlie calcium BXPEHIMKNTAL OHEMISTUy. gg carbonate comblno. with a molo.Ue of carbonic acul, forming oalctum bicarbonate, whioii is nuhiblo in water • thus -1 OaC03 + H,003 - H,Ca(C03), Oalcltim carbonate. Carbonic add. Calcium bicarbonate. Jal^^m Bicarbonate, like Carbonic Aci,, has neoer yet been H^CaCCO,,), = CaCO, + H,0 + PO Calcium bicarbonate. Calcium carbonate. WaL. Carbon divide. This oxperiinent explains the origin of the incrustation which 3 deposited u.ul. kettles and stea.n-hoilers. The calciun. Incarbonate :s decomposed as above, leaving the insohible car- from k ;V\^°"^- -'^.-'- «^ the vessel. It n.,v be removed from kettles by pouring m a little ton of and filtered. When carbon dioxide is passed through the filtered M«id It becomes turbid ; what is the composition of 'the BubslTce which causes the turbidity ? Give an equation. 3. Express in symbols the action which takes place between hydrochloric acid and chalk, and describe in word! the ^1^3 which occur and the proportions by weight of each constituent dioxide.''"" ' '""' '"^ '^'"'^'' P^°P«^"«« of «*rbou 5 What is iime-water. and how is it made ? What happens when carbon dioxide is led. into it (a) in small quantity. (6)Te Jes " Express all reactions by equations and ofyTenT"'" "^^ '"" ""' "'^'^" '^°^^^« °-«^«*« «f ^'^'bon ihl'I^ ""T "'*".ri "^'""^ '' °"'''°" ^'"^''l^ constantly entering the atmosphere withdrawn from it ? "'"ering * 100 EXPEBIMENTAL CHEMISTUY. 8. Describe the composition of ordinary baking-powder, and explain its action in raising bread. 9. What volume of carbon dioxide measured at 745 mm. and 15°C. can be obtained from 150 grams of marble containing 3 per cent, of silica ? 10. What weight of carbon is needed for the formation of 88 grams of carbon dioxide ? What is the volume of this weight of gas at 0°C. and 80 inches barometric pressure ? 11. A substance has the following percentage composition : — Carbon 27 "27, oxygen 72 73 ; what is its formula? 12. How is carbon monoxide usually prepared ? How would you prepare it from carbon dioxide ? Give an account of its properties. 13. A litre of carbon dioxide is completely reduced to carbon monoxide by hot carbon ; what volume of carbon monoxide is obtained ? What volume of oxygen is needed for the complete combustion of this carbon monoxide ? 14. Explain the production of carbon monoxide. When coals 'mm in an ordinary stove. '4 tnposition :— When coala OPIAPTEU IV. SECTION I. NITRIC ACID. Symbol HNO3. Molecular Weirjld^ 63. 151. Nitrates.-It has boon ah-ea, and liiosdy clo.se the mouth of the tube with lino dry shavings or dry hay. Boil the nitric acid, and the shavings take fire° the acid is docoinpoaod into nitrogen tetroxi.I.., water, and oxygen, the latter uniting with the shavings. In the same way .sulphur and carbon when boiled in nitnc acid are oxidized to .sulphuric and carbonic acids respectively. 156. Action on Organic Substance. Exp. 5.— Dip a piece of white wool or a piece of white flannel into dilute nitric acid, and gently dry it; the wool is stained yellow. In the same manner horn, skin, silk, are stained of a yellow color by dilute nitric acid. 15y concentrated nitric acid many organic substances are changcl into compounds of great practical importance, such as sawdust into oxalic acid, cotton into gun-cotton, benzol into nitro-benzol, and glycerine into nitro-glycerine. Exp. 6.— Put a drop of nitric acid, a drop of hydrochloric acid, and a drop of sulphuric acid on a piece of black cloth ; the cloth is colored red by each of tlie acids. Now put a drop of ammonia on each of the spots ; the red color produced by the hydrocloric and sulphuric acids disappears, while that due to the nitric acid remains. Although the red spots produced by nitric acid cannot be obliterated by the application of ammonia, they should always be wetted with it, or a hole will nrobablv result. * "^ 101 EXPKRIMl.NTAL CriF.MISTUY. 157. Action on Metals.— Tho ivution of nitric acid on metals varies with tho f»'»*en-,'th and concentration of tlio ncid. With liighly concentrated acid, nitro{,'un tutroxide is disengaged. Exp. 7- — Pour a little strong nitric acid on a few scraps of copper, or any other metal excc[)t gold or platinnm ; deep yellow or ruddy funici^ of nitrogen tetroxide are produced; thus: — Ou + 4F1N()3 = Cu(N0.,)3 + 2N0a + 2110^ Copper. Nitric Acid. Copper Nitiute Nitrugeii Tutroxide. Water. This reaction takes place in two stages ; thus : — (1) Ou + 2HNO3 = Cu(NO)3 + Ha The hydrogen immediately attacks another portion of tho nitric acid and nitrogen tetroxide is evolved ; thus : — (2) H, + 2HNO3 = 2H,0 + 2NO2 For the action of dilute nitric acid on iiiutals see nitrogen dioxide. 158. Action of Metals on Acids.— There is little doubt that in all cases the metal simply displaces the hydrogen of the acid forming a salt. If under the condition under which the experiment is made, the acid has no tendency to enter into reaction wi'h the hydrogen which is displaced, tlio hydrogen is evolved j but if the acid can enter into reaction with the hydro- gen, the products of this secondary reaction are obtained. 159. Commercial preparation of Nitric Acid. Sodium nitrate is preferred to potassium nitr'i^o ou the manu- facturing scale, because it is cheaper, and aiso ii rl a "iven weight of it can be made to yield a larger qrantifcy of aoid than can be obtained from the same weight of nitre. Only half the quantity of sulphuric acid is used, but a much higher tempera- ture is required. The reaction is expressed by the following aquation : — 2Na''f03 + H2SO4 = NagSO^ + 2HNO3 •3ot<;r"r' a.trate. Sulphuric acid. Sodium sulphate. Nitric acid. •V^ KXl'KHIMENTAI, (MIKMISTUf 1 i- i6o. Tests for free Nitric Acid -f ':iirs;=:':;;::s:>:; *.■■— 101. Tests for Nitrates. (1) The premliiijr tests implv to nitr.itp« it f 2N0 + o, = 2N0, If aix molecules of Ferrous Snh.lmte (IF„ qn stead of tl,e three atom, of Jj"! /' '''''"'' "'■ »™.excc,. that instead o C SO .te wUi' ^ T^^' '^ ""■' oules of Ferric Sulphate, 3Fc,(S0 ) f ' "™ *"° "°'°- is in exees. the nitric oxi,l„ • ,n,l ■ , "™'" ™'P'""« by heat and othetwise uistab L T^ IT''" '"T°"' delicate te„t f„. nific acid and nifa iL"! hti "r't^ conducted as follows :— '"^uuion. It may be iLXp. 9. — Dissolve a small rrvc-fTi ^p „;i o»e..rou, s,,,hate in a t^M i , l^t^.'^-^™'"''™ sn,all ,„anti,, „f s„lp,„,rie „cid do™ it do 1",';'' f" " acid falls to the bottom of the t„b. „.,M *° '"=">'>' .empefatu. of the ,i,„id 'a "tZ w.r '{ "''"^' '"° iwo layers of liqnidslviolet, red Z™T IZT T ""= l»oportio„s and conditions, ''■ ''""■'''"■g to i'>«e iVtfrtc Acid may be distinmi.ho^ f ■» the 6™,„ „>«, „,«„.,^„„ <,rfS"ott """"' ""^S'^-'S . : .^luuuion oj suipnunc acid. • For metiiod ol obUlning ooefflcients oelhii^ E«» lit mm 106 EXPKrUMENTAL CHEM ISillV. II iiown as far back alchemists it was The nature of its SUMMAliV AND AUDlTIONAr- KAOTS. 162. History. — Li(iui(l nitric acid wii as the seventh century. In the time of known as miun foriis—a name still retiiine constituents was siiown by Cavendish in 1785. 163. Sources. — Its principal source is potassium nitrate, found in large ([uantities in certain districts in India, and sodium nitrate which occurs in immense ipiai'tit:(!S in Peru. It is found in the atmosphere after thunder storms, and in the dried leaves of cerliun plants. Nitrates form whenever organic matters are decomposed at a temperature of from 20T. to 30°C. in presence of water and alkaline carbonates. 164. Properties.— Pure nitric acid is a colorless liquid, but in commerce is usually found of a yellow color, from the presence of the lower oxides of nitrogen. It possesses a peculiar but not a very powerful smell. It absorbs moisture from the air with avidity. It is an extremely corrosive liquid, an intensely irritant poison, and acts very destructively on organic bodies, communi- cating a yellow color ti) such as contain nitrogen. Strong nitric acid has a specitic gravity of about 1-5. With very few excep- tions, it oxidizes all elementary substances, converting them into oxides, acids, or nitrates, as the case may be. It acts on all metals exce[)t gold, platinum, and a few of the rarer metals. Nitrates greatly promote vegetable growth, intensifying the color and increasing the quantity of nitrogen of the plant to which they are supplied. Their effect when in excess is to favor the development of foliage at the expense of fruit. Sodium nitrate is extensively usetl as a fertilizer. 165. Uses. — Nitric acid is extensively used for etching on copper, as a solvent for tin in the preparation of valuable mordants used b» dyers and calico printers. In medicine it is prescribed as a tonic, and is used in surgery as an energetic caustic. *il EXPERIMENTAL CIIEMISTUy. 10. SECTION II. NITROGEN MOJTOXIDE, „„ MTROVS OXIDK PREPARATION. by' hea^ *' ''"°'"P°^W°n of Ammonium Nitrate '"•"■"""I. mi „ test-tabe six i" oh w U? T"","^ "■" """"' umlei- the shelf „f the n! ■ * "'"' "^^ ^""^ '"V dip «'I' fu.o» into a cloar 1 „ ,, I ff , '°"'" «'="">' "■"" "« Ammonium Nitrafn k t ^ "HgO ^'trate. Nitrogen monoxide. Water Olio oz or SO ^* "^outh upwards on the table. 167. Precautions, specially toward, L 1 '," ,"'" "'"r» '» «" «« retort, raodemtei "" °I""'""™' "« h»at must be ~ :: tt itr,:;; ;r '«'°. "■= t-u,,. ti„ the ."-..0. the ..tit i:: a e;::;::::!:;^^^^^^^^^ """"-« "■» n 108 EXPERIMENTAL CHEMISTRY. :S4 of the steam, the water will be drawn into the hot retort, and crack it. PROPERTIES. i68. Supports Combustion. Exp. 2. — Plunge a glowing splint into a lonttlo of the gas; the splint bursts into flame and b'lrns nearly as brilliantly as in oxygen, but the gas itself does not take tire. Exp. 3. — Pour the gas from one bottle into another, and test both bottles with a glowing splint of wood. The taper is rekindled in the bottle into which the gas was poured, showing the gas is so much heavier than air that it can displace the lighter air just like liquid. Exp. 4. — Burn a small piece of phosphorus in nitious oxide, taking the same precautions as when burning phospliorus in oxygen. When the white fumes have somewhat subsided plunge a lighted taper into the bottle; the taper is extinguished. In this respect the gas in the bottle resembles nitrogen. Now add a little blue litmus solution, and shake it up; the litmus is reddened, as when phosphorus is burnt in pure oxygen. The burning phosphorus has decomposed the nitrous oxide, uniting with its oxygen to form phosphorus peul oxide, and setting the nitrogen free ; thus : — ION.,0 -\- P4 = 2P2O5 + ION, Nitrous oxide. Phosphoms. Phosphorus peiitoxido. "J Nitrogen. Exp. 5. — Place a piece of sulphur in the deflagrating spoon, just light it, and plunge it into a bottle of the gas ; the sulphur is extinguished. Had this gas been pure oxygen, the sulphur would have burned with increased brilliancy. Hold the spoon in the flame of the spirit-lamp till the sulphur is well kindled and then plunge it into the gas ; it burns with considerably increased degree of brillianfn', and the prndnr^t of combustion is found to be sulphur dioxide. Probably brown vapors may t'hat subsided EXPERIMENTAL OnSMISTRT. jQg make their appeaiance in the hnfH« • tu the higher oxides of nitrogen ' " '''''''' '^ °"^ °*' The extinction of the fp^Ki,, i taming one-l„,lf ofL 1 .'"'"* "'*"■■' '° " S'^ ™"- H oa„ i...,f »,„«:; rioXjr/v' ""'™ "^^^ •Wgl. ter„p„rat„re is .-equirei ' " " »°''"''"el.V 169. Solubility in Water. Wng the mouth of the U e „,t .t" "''""" ''"*'^- ^"^ ha... the «te„i3e. iltl" t TMr'rto a'T™ ^f nitrous oxide from oxygen Po„r .1 ! distinguish ta.te it; it has ac,„i«l a s JZh 1! T ""Z" ^ '"^ »" smell. ^"eetishtiite ami a famt agreeable SUmiABT AND JDI.ITIOBaL PACTS. 170. History.-Nit,.„„, oxide was discovered hy Priestley i„ '•"l-H.v as the tem|,3.-,t,„, rC It t 't '"^'""'""'■»' P.«ure „f about 50 al.uos or. • ..t ov", "^ '"""""^O by a a.«l even fiweu by the „ i',: l' ° '".,"' » "°'»'-'<»'' "q-W. When liquid nitrous oxi li ib' 1 ""'i'. "''"'"'''"■ evau,„,,M in vicno a ■ ■ °''*°" J'""'?'''''" and lin-n , , '"•'""™" "' l«mperature, estimated at -140 G. IS ,ro lueed whieli is lo.er than that vihiol, h^beeu no EXPERIMENTAL CHEMISTRY. obtained by any other means. It readily supports combustion, but all combustion in this gas is simply combustion in oxygen, the burning body not uniting with the nitrous oxide but with its oxygen. The most remarkable property which nitrous oxide possesses is that of causing loss of sensibility when inhaled. When re- spired for a short time it produces a singular species of transient intoxication attended in some instances with an irresistible ten- dency to muscular exertion, and often uncontrollable laughter ; hence it has received the name of ''laughing gas." It is now frequently used as an ansesthetic for producing insensibility to pain, more especially in the extraction of teeth. Great care must bo taken that the gas used for inhalation is free from chlorine and nitric oxide. Nitrous oxide maybe distinguished from oxygen as follows:— (1) It is much more soluble in water. (2) It is much heavier. (3) It does not form red fumes with nitric oxide. (4) When phosphorus is burnt in it the residual, nitrogen is identical in volume with that of the original gas. SECTION III. NITRIC OXIDE, NITRIC TRIOXIDE, NITROGEN TETROXIDE, AND NITROGEN PENTOXIDE, SECOND LAW OF CHEMICAL COMBINATION. JSitric Oxide. Symbol, NO. Molecular Weight, 3C. PREPARATION. 172. By the reduction of Nitric Acid. Exp. i.-— Take the hydrogen bnti.l<". ;uid place it in about W -lams of copper clippings, cover tliem with warm water, and EXPERIMKNTAI. criEMisTnr. Ill xs follows:— pour down the funnel-tube a little strong nitric acid. Eirorves- cence almost immediately begins, the flask is fill,,] „,th red lumes which soon disappear, and then a colorless gas is pro- duced which may be collected over water in tl)e usual way Ihe reaction is expressed by the following equation :_ 3Cu -f. 8HNO3 = 3Cu(N03), + 4H„0 + 2N0 copper. N.tricAcid. Copper Nit.a,e. Wat;. titrio Oxide. This reaction takes place in two stages, thus :— WgCu + 6HNO3 = 3Cu(N03)2 + 3H„- (2) 3Ha -f 2HNO3 = 4HaO -f 2N0. PROPERTIES. 173. Supports Combustion. Exp. 2.— Introduce a lighted taper into a bottle of the "as • It IS extinguished. Place a small piece of phosphorus in thrdo- flagrating spoon, touch it with the end of a warm wire, and just as It begins to burn plunge it into the gas; it is immediately extinguished. Now let the phosphorus burn briskly for a short time, and again plunge it into the gas ; the phosphorus burns onlliantly. In the first case the temperature was not suffi ciently high to decompose the gas and render its oxy<.en aviil able. In the second case the gas was decomposed, phosphorus pentoxide was produced, and free nitrogen left. Similar ex periments may be tried with magnesium wire, charcoal, and sulphur. ' 174. Affinity for Oxygen. Exp. 3.-Withdraw the glass plate from a bottle of the gas and observe that red fumes appear when the gas meets the air The oxygen of the air combines with, the nitric oxide to form" nitrogen tetroxide ; thus : — ^ 21S0 + 0, = 2N0, x.imc Oxide. Oxygen. Nitrogen Tet;oxide. Pour a little water into the bottle and shake it up with the Ill 112 EXPRRIMEXTAIj CHEMISTKY. gas ; the water combines witli the nitrogen tetroxide to form nitric and nitrous acids ; thus : — 2NO2 + H2O = HNO3 + HNO, Nitric oxide. Water. Nitiio acid. Nitrous acid. If the quantity of oxygen present is only equal to one volume for four volumes of nitric oxide, nitrogen tetroxide is uo longer produced, but nitrogen trioxide is formed ; thus : — 4N0 + 02 = 2N20a Nitric oxide. Oxygen. Nitrcsjeii trioxile. 175. Oxidation of Nitric Oxide by pure Oxygen. Bxp. 4. — Half-iill a bottle with nitric oxide, and leave it mouth downwards in the pneumatic trough, Half-fill a similar bottle wit'i pure oxygen. Bring the mouth of the bottle con- taining the oxygen under the mouth of the bottle containing the nitric oxide, and pass the oxygen very slowly into the nitric oxide. As each bubble of oxygen comes in contact with the gas, brown ruddy fumes are produced. Shake the bottle from time to time, taking care to keep its tnouth under the water ; the watar rises in the bottle, showing that the gas is being absorbed. Continue the addition of the oxygen, and Ultimately the bottle is entirely filled with water. The two gases here combine to form nitrogen tetroxide, which combines with the water to form nitric and nitrous acids. As nitric oxide entirely removes the oxygen from a gaseous mixture, it was much used by Priestly, Dalton, and other chemist in the analysis of atmospheric air ; but the results are not found to be trustworthy, in consequence of the formation in uncertain pro- portions of other oxides of iron. 176. Absorption by Ferrous Substance. Sxp. 5. — Pour a solution of ferrous sulphate into a bottle of the gas and shake it up ; the hand is strongly drawn into the bottle showing that tho. g;is is .absorbed, and the ferrcms .sulphate becomes black. A definite compound is formed, the formula of EXPERIMENTAL CilEM18TRV. Dne volume wJiich 13 CFeSO ) "NTH Ti • • X, which oci.. iX^ ,^'Z::^^ «^f - of the d.-k .n, nitric oxide is drive,, ^ff , ' ^ ''^" '^'-^^"^ ^'-l'"''! and j^^^_ off, ami a somewhat brownish solution is Symbol, iVr,03. i/oZe.,.u/.. fFe.^^^. 76. PREPARATION. .■..'oXMi"'tu\f:;;;,":n™ °' »'^»'"°- -w-. as,03, liqmd. Tlie reaction is— ' '^^^^''^ ^ ^ue 2HNO3 + AsoO, 4. 2H O N2O3 + HoO = 2H1VO Nitrous anhydride. Water. mUonl^^,, T-n- Nitrous Acid, HNO . Nitrons acid is an ill-defined, unstable compound WI •. hydrogen is replaced by a metal a class of "tT" I " ^ . ? " formed. Observe that the acid end n. '"^'^'''*' ^^ -ding in ite; and that an a d li ,^^1" ^"^ '""^ ^ ^^^^ a salt terminating ia -ate termmation -^^ gives NITBOGEN TET.OXIOE OR ..x.OOE. PEROXIDE %n6o^,iVr03. Molecular WeicfU, j^e ^^^Z::^"^' '''-'' P^'-^-tl, d^ lead nitrate is pb(N03), = 4NO3 + 2PbO + o N'troge. tetroxiUe. ^ead oxide. ^ ox^/en. Lead nitrate. r ^4 EXPERIMENTAL CHEMISTRY. Nitrogen peroxi.le i« a li.iuid at tho ordinary atmospheric tern- porature, but at - ^C. it soliditiea. NITROGEN PENTOXIDE OR NITRIC ANHYDRIDE. Symbol, N._,Or,. Molecvlar fVc.ight, lOS. Tliis sub.tauco is obtaiiiod when dry chlorine ga. is conducted over dry silver nitrate : — 4A'^Cl + 2N2OS + O, Silver nitrate. Chlonne. Silver chlcrile. Nitrogen pentoxide. Osy^en. It is a solid b . ly, very unst,il,le, combining with water to form nitric u-'id, and is, therefore, an anhydride : - N.Os + H.O = 2HNO3 Nitric anhydride, H2O Water. Nitric acid. li'ii We have seen that there are five oxides of nitrogen, which are represented by the following foriuuhv:— N3O, NO, N2O3, NO2, N2O5. Two of these, N„03 and N.O^, are anhydrides of distinct acids. Aaalo-y and th"eir place in the senes would seem to indicate that the formula of nitric oxide should be N3O,, and that of nitro.^en peroxide N,0, ; but this is contrary to the molecular weigSt, according to Avogadro's Law (Art. 23). Possil>ly when the erases are condoised it may be found that their molecules may^ossess twice their ordinary weight. With respect to NO^ this seems to be the case, for when the gas is cooled down its density increases from 23(H = 1) to nearly 46 when close to its condensing point ; the latter number gives the molecular weight 92, and the formula N^O^. 178. Second Law of Chemical Combination.-From the study of the preceding compounds we see that :— (1.) Nitrogen monoxide contains 28 parts by weight of 1 ; ii.irts of O. to EXPEIIIMENTAI. CIIEMISTItr. eric tern- )E. ouducted Oxygen. water to 115 en, which inct acids. )o indicate nd that of molecular sibly when molecules set to NO2 1 down its close to its ular weight on. — From cht of N to J'JZTr '™""° "■" " '' ""''^ "^ «■■«'■' "' ^ '" 04 par ™fT '""°'''"'° """'""" '^ P"* '■>■ -«'■' "f ^^ '» Whilst that „f tlic oxjscn ,3 increawj by successive a,l,mi„,„ „ of 28 parts of ,„l,.„ge„ to 17 of oxygen. If the „,„„u„t of three times 16, or 48 parla; and so on. The same law hoM, good ,n every series ot chemical compounds, and hence w Ire led to the following law, which is known as Dnltou's sLZ law of Chemical OmiUnaHon .■— 179- IMW of Multiple Prnportton—When an element unites with another in different proportTons . .h:,'^:..''"'"'"'""^ ^™ ---"'y multiples Of 180. Atomic Theory._To explain the facts which are X .ssed by the laws of combining proportions, D.alton revived liat s known as the Atomic Theory. Ancient philosophers vere divided n, opinion on the question of the finit or i fi I d visihihty of matter. The Epicureans held that matter Zt capable „ ,„fi„,te division, and even if we possessed the moc hanical .appliances to make the minutest po.ssib e sub, li u we slionW at length reach a point at wliidi the narli,.! ,' resist all attempts to effect a furtbe. -!, 1 ' i^ '"" 1 o lu uncct a luitlier subdivision. Thesp ulH mate particles Dalton called atoms, and he assumed (1) T, „t ,' matter consists of ultimate and unchangeable particlel or aC u -^ IH 116 EXPEKIMRNTAL CIIEMISTKY. (2) tlmt atoms of the same element have a uiiifoi'iii weiglit, but that in tlitfereut elements they have diirr'rcnt weights ; (3) that the combining niunl>ors of du-mi>''''y rei.iTsent those relative weights ; and (4) that between those different atoms there are attractions, which unite them by juxtaposition in the formation of cheniical compounds. Dalton maintained that if these ideas are accepted, the laws of detinite proportions and multiple pro- portions follow as necessary consequences. Tliis theory has been of gtvat service in the modoru development of the si^xnce ; but it has been gradually extended and altered, until uo-at it assumes a quite ditferent form from that which it had at f.rst. QUESTIONS AND EXER0I3E3 GIT NITRIC ACID. 1. How is nitric acid usually prepared, (a) on the arnall scale, (6) on the large scale? . . 2. Describe in detail the composition and properties of nitric acid. Describe the experiments which illustnue its properties. 3. Point out in what respect nitric and sulphuric acids have similar properties, and on the other hand, what differences there are which enable you readily to distinguish the one from the other. 4. Describe fully what takes place when strong nitric acid is added to copper. Give equations. 5. What happens when nitric acid is added to caustic potash, ti. sodium carbonate, and to gold respectively ? Give equations. 6. You prepare hydrogen by the action of zinc on diluted sul- phuric acid. Why cannot you prepare hydrogen by the action of zinc on diluted nitric acid ? 7. What are the distinguishing tests of nitric acid, and how may these tests be applied to the detection of nitrates? 8. How many pounds of nitric acid are obtained on distilling 400 Ihs. of sodium nitrate with sulphuric acid ? 9. How much nitre and sulphuric acid shall I need to prepare nitric acid enough to neutralize exactly 6 lbs. of chalk ? 10. Calculate the percentage composition of nitric .cid. 11 Express in symbols what takes place when ammonium nitrate is subjected to heat. eight, but ; (3) that ie rehitive there are formntioii ihese ideas iltiplo pro- hoory has le SL'i.uce ; til u.j.v it at first. by c.l,e„uo,lL,.. ' """■'«"'*'«' W by I.hy.»l te,.i,'(6i 13. If 100 litres of nitrous nvwi,. „^ r^'n posed intr> free oxy«en and "T. " ?" ""'^ ^"^ '"'"' ^'^ ^'''^■ occur? ^^ ^"'^ '"'"•»"^"' ^^»^t increase in bulk will H. Give the name and chemical formnlH nf fi, u . ;y ••-» action „f d„u.o ,n.,.ic „ci.l ,, ™ t"' WM ":"'"' '"T" ,11 scale, (6) 13 of nitric perties. Hcida have ences there a the other, trio acid is c potaah, to [itions. diluted sul- he action of nd how may listilling 400 i to prepare ? lid. nium nitrato CrTAT'TEK V. ri AMMONIA. Siimhnl, NH^. MoUmlar (f'eirjhf, 17 Whilo thoro are tivc compounds of nitvo-cu aii.l oxygen, there is but ono knowu comround of nitrogen and hyd^)^en. Analysis has shown that this compound is made up of one volun.e ot nitro-en combined with throe vuhunes of hydr.>-(M., tlm four vohimes of the elementary gases bein- condensed to two volumes; the fonnula of its molecule is, therefore, NH3. PREPARATION'. 181. By the reduction of Nitric Acid or a Nitrate by Nascent Hydrogen. Det—An element is said to he in the nascent t-tate at the iiiffant it is set free from comhination. Exp. 1.— Add a little fine granulated zinc or zinc filinf,'s to a stron.' solution of caustic potash in a test-tube. On boiling, hydro-en is given off (Art. 81). Now add a little potassium nitratl or free nitric acid. If the latter is used it must not be in sufficient quantity to neutralize the alkali. On heating the test-tube, the pungent smell of ammonia is readily recognized, and a piece of red litmus paper, held in the mouth of the tube, is rendered blue, showing the presence of alkaline vapor. Ono vvxrt of the nascent hydrogen, developed by the action of the zinc and the caustic potash, deoxidizes the nitre forming water, whilst another portion of it unites with the nitrogen of the nitrate to form ammonia ; thus : — -{- KOH Potassium hydrate. KNO3 -t- PotassH'.in nitrate. 4n2 = Hydrogen. Aniinonia. 118 2H2O Water. state at the 119 BXPEniMENTAL CHEMiaTRY. 'estate. Tl„s\™ i'::T','' '" "'" "■"^'"' ^'"'" ""1 in tl,o alon,H whid, „„ ™„e •',/!"''''''"*'' ''^ *" '"'''"ted partly e.,,™.,., Z ^^ , ' :::;:, "'"' ';-'°™ «''7 h«vo Ex,,eri„„„e proves that „i," .i;! T ?;:/°™ "'"'"""- Substa^c'es "^""""P-"-" "f Organic Nitrogenous tioned contain nitrcvrp,, „„ , , , ^ ^ ■•^nhstiinces men- "f contact -vitl/ i ° . " , ,'^f °-"""' ">"•'■'■• »"™ l-tedout matter is destroveil, and ,,L J "'\'""'''' "' ""s original -■-i..it,»:uairi:::e;:;s:::Si;,:r'^^^^^^ chtia^ ^:ar::r -t;,^r „t, t"""°-» d'H'ing t])e process «f .?o«f.uetive di^- ™°'"' '''^'''' tl iiR nian!!f;i<'( un; of coal iition, ill the coul to fi as. unites M-ith tlio hyd; caiiied on di onn ammonia, which is dissolved in o ■ogen present water alontr i 120 EXPEBIMENTAL, CHEMISTRY. ii I I with Other products formed at the same time. This hquor is boiled with milk of lime to liberate th.; ammonia which distils over and is received into hydrochloric acid, forming ammonium chloride or sal-ammoniac, NII4CI; thus: — KH3 + HCl = NH.Cl Ammonia. Hydrochloric acid. Sal-ammoniao. Exp 4— Take 15 grams (about | oz.) of powdered sal- ammoui'ac and about twice this quantity of slaked lime, mix well together, and introduce into a dry flask, fitted with a cork and <^lass tube bent twice at right angles, the longer limb being sufficiently long to reach to the bottom of the bottle in winch the <^as is to be collected. Apply a gentle heat, taking care to move the spirit-lamp to and fro under the flask, the flame never bein- allowed to rest in one place, otherwise the flask is apt to crack, the substance to be heated being a solid of low conducting power, and not a Uquid which would distribute the heat by con- vection. The gas coiues off at a comparatively low temperature. It cannot be collected over water, as it is very soluble in that liquid, but its molecular weight being 17, its specific gravity compared with hydrogen is 8^ (Art. 26) ; ib is, therefore, only about half as beavy as air, and may be collected by upward displacement. To ascertain when the buttle is full, hold a piece of red litmus-paper near its neck and slightly above its mouth ; if the gas is overflow- in-, it will (piickly restore the blue color; or hold a glass rod moistened with hydroch one acid in the same ,.la, v, and ^vbite fumes are produced. 1' dl six EXPERIMENTAL CHEMISTUy. "f tlw gas. "'■ °' '" S™"'« "ill yii-ll 12J litres PROPERTIES. 185. Is lighter than Air. Exp. 5.— T.ike a dry bottlp .,n,1 t. a«.„,, to t,.e i,..-,,, „i t, fc t r"" ;' " "■«" «"■■■ litmus-paper. Take a bottio .,f ' '■' °' """stoned re,l '■-" of tL em,,., I ottt „i 7'T'' "■■'■"« "« "■™'l' "..«1'' "f I>l»'e; the water rises tL'^lf,':"'""^ ."•'*'''■'"" *« ."la- would gradually fill it if the „ , ,° ' '™"","« ''''"= "««">. and «.« bottle gent,, hastens the^rLe rZ"" """ "'■-■ '""""■»" ^irn'oft;:::!' ■: :::?"-' -"'"°'' -^ ''-vi„g .^e so,. Exp. 7.— Take a large bottle fif- if -, -^i. well saturated with paraffine and fif '7/''^''''^ sound cork about 20 en,. ,..„. endingi n L L f '' "^'' ^ ^"^^^^ ^""^^ tUo bottle. Twii a pie^e of n o/T "^" ''""'^ ' ^•"- ^"^'> I of moistened lamp-wick rouud the h 122 EXPERIMENTAL ClIEMISTllY. tube just below Uio point, Fill a bottle with iv.l litnin-snlunui,. Now mi the luvge bottle with iunmonia, wet the liuui)-wiek, inscit the cork, and place the tube in the bottle of colored water The anuiionia will be absorbed, a fountain will be formed, the red snlution bee(Muing blue under the action of the ammonia. 187. Ammonium Hydrate. Exp. 8.— Take a little water in a narrow test-tube, and place •i small "rubber baud arouiul the tul)e to mark the height of the water. Place the tube in cold water, and pass ammonia into it; the gas is absorbed by the water, and when saturated it will be' seen^'tbat the water has increased to the extent of abr.ut one-half its volume. This solution of ammonia is colorless, hiw a very characteristic and pungent smell, and strong alkaline reaction. The great solubility of ammonia gas in water, accompanied as it is by "a considerable evolution of heat, is commonly regarded as due to true chemical combination, a new body being formed which closely resembles potassium and sodium liydrates in its highly alkaline character, and in its power of neutralizing acids and forming salts analogous to potassium and sodium salts. Hence the liquid may be regarded as a hydrate of a monad radicle, NH4, which acts like a monad metal, and is called ammonium. The reaction is— NH3 + H2O = NH^OH Ammonia. Water. Amiuoiiiuui hydrate. If ammonium hydrate, the liquor animonvvoi the druggist, is heated in a test-tube, almost every trace of the gas is removed ] ^^''''*~ NH.OH = NH3 + H,0 Ammonium hydrate. Ammonia, Water. This is the readiest method of obtaining gaseous ammonia for the study of its properties. A slight elevation of temiierature -;nHices to decompose it, and nearly all the gas is expelled before th'^ r^uid reaches 100°C. 12.3 KXPERIMKNTAT, CIIUMIstkY. 188. Combustion of Ammonia. .nisi . T,;, tl '\ "' '^^'-^''tly on]a,,..l and th..,. extin- '■--='1 to a ].i,l. te,npe,aturo ' '""' '^""^"' ^^^'«" Exp. 10.— Put a small ouinfifv nf i; + 30„ _ OXT 4NH3 Ammonia. Oxygen. Nitrogen. 6H2O Water. bytrM'liX'""' "'" '' '""""'' '" •■'° ■"--'*«- °' ™y-n uj' uic loiiowiiig jin-angonient : -Voeii Exp. 11. — Take a short tiibp nho„f q /■■ , . ammon,a, it burns as in the Jast experin J a1 'f ' '•' ment may be made with a smaller sLnl ' 'f ^ " '"P^"- out tl. tube delivering .bo anuno.;im3:'^[ '"7"^ •^. f-1 lowering it into a bottle of oxy.en Z annlv i !' to It just as it enters the n.outh of the botul ^^"^ " '°^" 189. Combination with Acids. As m i.t,'ht be expected fmm its ammonia combines with acids, neutralizinAhe strong alkaline ch sni laracter, perfectly. ir: i^-.r23:?sftw«^ai«B*>* 124 ^;xl'^:!ll^l knta r^ chemistry. Exp. 12. — Gently licut a wule-inouth bottle, pour into it a small qiuuiLity of hydrochloric aciil, cover with a glass plate and shake it well. Place this bottle mouth downwards on a bottle of ammonia; on withdiawing the glass plate, the gases combine, disengaging nuich heat and forming a white solid, ammonium (■hloride, NH4CI, in which the acid and alkali have neutralized (iach other; thus :— Ammonia. + HCl = NH4CI Hyilrochloric acid. Ammonium chloride. Exp. 13 — Fill a dry bottle with carbon dioxide, and place it mouth downwards over a bottle of ammonia ; a white cloud appears. The gases combine, forming carbonate of ammonia, a salt which occurs in commerce under the name of "salts of harts- horn," and which, with the addition of some perfume, forms the contents of the so called smelling bottles. It rapidly vaporizes, exhaling the odor of ammonia very strongly, and heuce called sal-volatile. 190. Ammonium. It was stated (Exp. 8) that liquor ammonire may be considered a hydrate of the monad radicle, NH^. This radicle has never been obtained in a free state, but it can be obtained combined with mercury as an amalgam. Exp. 14- — Put a small quantity of mercury into a test-tube, gentle, heat, and add a few siuidl pieces of sodium; the metals combine, forming a semi-fluid mass called sodium amalgam. I'our out this amalgam before it gets cold into a tumbler one- third full of a cold saturated solution of sal-ammoniac. The amalgam immediately begins to swell, increases to about 15 times its original volume, becoming light enough to float on the liquid. This mass presents a brilliant metallic appearance, and since mercury is not known to unite with any non-metallic suVjstance without losing its metallic appearance, it seems fair to .'I* pour into it a lass plate and Is on a bottle uses {joml:)ino, 1, anuuoniuui ire neutralized ilorido. ide, and place a white cloud if ammonia, a salts of harts- me, forms the dly vaporizes, I heuce called be considered icle has never ued combined to a test-tube, n ; the metals um amalgam. I tumbler one- moniac. The to about 15 to Hoat on the )pearance, and f non-metallic t seems fair to KXPKIifMKNTAL CHIvMISJ Uy. 126 conclude that tlie soft m.IM io ,., n ' ' ^'<^>:^u!^::^u:u:^^::7'^'""'"--"'y«''' ««li„m tend to confirm thi» vi„J, °' ''°''"""'"' "'"' 191- Isomorphism. Tiie roseniblanee of the qiltq nf o :;- ■■■' .-.""i-^. .,.0,, .tr^Cf 1 Thr;:r,'r-''°" °' ""'"'■ Uio crystallino form of tl,„ .t, , "" »"->' <""<» toxturo. color .K, l,,! I' S7"-;; ^'^^ - -" - «.eir salts are mixed, neither „l tl L ' k ' '" °' "'"* '>"' Wi,ou the soLuion is ev— ' "f!""'"'' ""' "^ "-"■ poso,l of the two salts „ « ' ^/ ''''f ^ "''""-^ «- com- Bo.ii.. which are thus ca "i'^ ':;tX;::'t "ir"""'""-^ proportions, without alteration of the c™t 1 i " f " ' '" "" tsomori,l,ous. orystalime form, are calloci Sl'MMART iND m ITIOSaL PaoTS. itsiTuoo"'::hir^™:™ ;:: in"' r.'-° "'"'-"-"^ - state in 1774. Scheele in 1777 d 1 " "" "'° "•^''™>'» nitrogen, and i,s true eoml H„ ' "'"^ """ " "'"^'"""t ...out .78. The «ri.i:7«:r„n::rt:;'r','- '^«"°"- that It is derived from Jupiter A J. ^^o'ne consider the Lybian desert sal-amm i : ^7^1^ :'''' '''''^'' ■"" ■ pounds, was first prepared. Ti e .ame h«T ""'""'"' ^•""- hartshorn, was adopted from thpT- . ^^^^^^''"rn, or spirits of hy distiiii;, the h:!:^:;r t!r;:r ^^ -' '- ^"■^^— 193- Suurces — Amm cipally in the form of onia is found in tl carbonat le alnio.splK.ro, prin- '"' "^ ""''y -^'"'ilJ quantities. It fg ti, ' ariiSMW-'^ 126 EXPEIUMIONTAI. OUBMISTUY. present in nmnurc, of which it forms one of the most essentia constUuents, in all fertile soils, and its salts arc found u> the ju.c s Jphnt u a in nu,st animal fluids. It can be synthetically It^d by the direct combination of its elements by the sden eL re discharge passing through a nuxtuve of nitrogen and t^^Jn The source from which amnmnium salts are now ^:^Ii. the watery li.md which distils over ur the manu- facture of coal gas. 104 Properties.-Ammonia is a colorless gas, of a pungent smell and allavline taste and reaction. It does not support com- b son or respiration, and is only feebly combustible. It is d "s ived bv wLor with great avidity, much heat being developed and reat i^icrease of volume taking place, one volume of wate dlsolving about 700 volumes of the gas. It is easily li.uehed by c luUrcthig It into a tube plunged in a mixtiue of erys.ai.ed calcium chloride and ice, which gives a temperature of - 40 , at a temperature of -TS^C. it becomes solid. iQc Uses.-In medicine its applications are numerous ; its pungent odor is reviving and stimul.'ing In the arts it is used for producing artificial cold, for the production of carbonate of Zuiov the production of aniline colors, and m tl^ manufacture of i di.^o. On account of its alkalinity it is used for removing llse^from cloth, and in restoring colors which have been ian.ed by acids. In nature it furnishes nitrogen to plants^ Its aU^applied as manures have produced most benehcia effects. Plants watered with a very dilute solution of ammonia have far Lpassed in luxuriance similar plants supplied with ordinary water only. iq6 Tests —If salts of ammonia are rubbed together with slaked' lime or caustic potash, and the mixture then gently w rmed in a test tube, with the addition of a few drops of water Uro ammonia is liberated in the gaseous stat- and is i-ecognized (1) by its characteristic odor; (2) by turning moistened red nost essential 1 ill the juices synthetically V)y the pilent nitrogen and salts are now in the nianu- , of a pungent t support com- iisti))le. It is jingdevelopctl ilunio of water jiisily liqneKed of crystidlized re of - 40°; at numerous ; its s arts it is used of carbonate of he manufacture id for removing ioh have been I to plants. Its eneticial effects, mionia have far i with ordinary id together with u-e then gently I drops of water, nd is recognized ■ moistened red EXPERIMENTAL OUBMISTfly. jgj, ">; iiqnia a sat„...ea s^,: " ^^.^ ^;' ™'-^ "dd to -<• o,,id» just ceases to redissoivn^ d T^ ""'" "» causfc |,„t,«l,, previously dissolved iu a lit! . *''"'" "^ "lake up the total volume to inn V "'"' ""'""'•i water; finally add a wd" ,! , ?"'""""' "'"' ""''"'"J tion, allow to'staud I : d aT oTL or"';"*- f '•'""' '°'- must uot be filtered throur:! '" ^ f' '"l"'f ,'"'■ "- It apidicable to amm„,u„,„ Iwdratf » '"^ '^** 'o^' ''^ liquid to be tested should bfb . n'l T"'""""" '"'"• »» white plate. If ouly a tr,- „ "' * ' ™''°' ='"'"""8 O" a .-ni. a yellow ;S .• ^ ut^s :^:t''-'' -"^ '-^ a browu precipitate is formed. ■°'" luautities QoEsrio™ «,o EMaois.8 oj, imo^^ <^<^^V:::^:^^ZIS:' ---- -^ «™»»ia, De.erib, 3. Enumerate the prinoipal properties of ammonia, i» pa,."r;r ^iX-fa^d xi:"t 'rr^ -'■» »—»'» water! ''"'"''"''. Mroohloric aeid, and 128 EXPERIMENTAL CHEMISTRY. What is Nessler's test 7. How is ammonia usually tested for ? and how is it used ? 8. An alkaline solution (which you are told is either potash or ammonia) is saturated with hydrochloric acid, and evaporated to dryness ; how would you ascertain (a) by physical tests, (6) by chemical tests, the nature of the product ? 9. How would you distinguish a mixture of three volumes of hydrogen and one volume of nitrogen from ammonia, which is a chemical combination of the same elements. 10. The salts of ammonia are conceived to contain the radical ammonium. On what grounds is this assumption based ? 11. What volume is occupied by 100 grams of ammonia gas ? 12'. 29 cc. of ammonia are decomposed by a series of electric spark", and the mixed gases are exploded with 30 cc. of oxygen. What volume of what gases remains ? 13 How much ammonium chloride must be used in order to get 100 gr.ms of ammonia t How many cubic centimetres of hydrogen will th3 ammonia contain ? 14. 100 cubic centimetres of ammonia are completely decomposed by a series of electric sparks, yielding 200 cc. of mixed hydrogen and nitrogen ; an excess of oxygen is next added, when the volume of mixed gases is found to amount to 290 c. c The mixture is now exploded, vhen 65 cc. of gas remain. Show from these data^that the symbol for ammonia is NH3. 15. A body yields, by analysis, 4375 per cent, of nitrogen, G-2.-. per cent of hydrogen, and 50 per cent, of oxygen. Wliat is 1 - ;or inula and its name ? 1^%^ ^&^0^ ressler's test CriAPTEli VI, WATER. SymhoJ, n^O. Molecular Weight, IS. oomposition-(a) synthetically. It Ims already been shown (Art. 20) tlmt water is conn,oscd of two vol„n.o.s ol hydrogen and one volume of oxygen. Exp. 1 -The above experin.ent can be varied by adniittinc. hydrogen ,nto the eudiometer and noting the volume; t^ care not to more than about half-fill the tube with the !a «; Press down the mouth of the tube on a piece of india-rubber" pad of blotting paper, and explode the gases. When the tube has coul-1 a,„ ,,^ ^^^^^^ ^^^^ ^^^^ ^^^^ ^^^^^^^ ^^ u gas. If 100 volumes of hydrogen and 75 volumes of oxy.en b admitted, the gas which remains will be found to oc 'C 25 volumes. Hence 100 volumes of hydrogen have combined vih oU volumes of oxygen. Hydrogen. "' """"'"" °' ^""P" "'^^^^ by (b) analytically. igg. By Electrolysis. This has been fully described (Art. 19). 200. By decomposing Water by red-hot Iron That water is made up of hydrogen and oxygen in the pro- MMi ■iMhi \M) ICXI'KUIMKNTAI, CI1EMI8THY. ^k portion of 2 parts by w.ight of hydrogen to IG parts by weighu of oxygen, may bo shown by passing steam over a^ye.gUcd quantity of rod-liet iron. The water is decompose.l, the byih-ogon passing over in a free stafs and an oxide of iron i^ fanned The hydrogen may be measured and its w.-ight estimated, Nvhi sfc the weight of the oxygen in eombination witli tlie iron may also bo determined (Art. 82). 201. Pure Water. Tlio preceding oxpcrimenis nave shown that ptn-o water is composed of hy.h'og mi and oxyg.n. P.ut the water whieli oecurs in nature is neve: absolutely pure. It may be obtained m a pure state by the following methods :— 202. Purification oi Water. Exp. 2.— (1) DistillaHo7i.—lhxU-i[\\ a moderately large sized retort with water, place its neck in a large Hask, and place the flask in a pan of cold water. Cover the flask with a ch)lh or with blotti ig paper, anc . pour cold water from time to time upon it. Place the retort ujion wire-gau/;e (111 a ring of the retort- stiiiul, and boil the water. As fast as the water in the retort is converted into steam, the vapor will pass over into the cold receiver, and will there be condensed again to the liquid state. Reject the first portion of the water that comes over, as it contains carbon dioxide, ammonia, and many volatile substances which the water may have held in solution. Observe that the pure tcater obtained by distillation in the preceding experiment is colorless, inodorlcss, anc..ce.s lou'er than fresh wntov n,v i i matters are to a "rent extoni- oifv, i JJissolve.l 203. Relation of Water to Heat. (1) Expamwn and Contraction. Exp. 3.— Take a small thin flask fit If «,;n »-..ich „„.« a 3n,a,. ,iass tube ab o^t ft ' " M 'u'T'!' -nth coll I,„i|e,| ,,„,„,, i„,„,.j ' °"S- 1" I the flask are „„ air.bui,blc, e„ta„..|e,l beneaU it t ° """' •"'"' ""•"" '."tile until the small tu°b„ is b u ., '," l""" " ''"' "■= fl»sk, and the li,,,,!, slo,.,, Hses in t , t be ' , J"; "' '''° '•■•■"'""'« ''. "^. This ,„,„,„,,, „,,„,. ,„,;^^ i r; b t^' saoMhi 132 EXI'EHIMKNTAL CHKMIrtTllY. Stances. It may be .said t.. l..; ii I'lw of luituro that inoignnic substances expand when heated. Kcxt immerse the Hask in a mixture of sn(.w or pounded ice and half its weight of eonimon sdt ; or a mixture of sulpliate of soda (Ghuiber's s^alt) and hydrochl(aic aci<»>) said to U Thi on., , /• "'"^'"'^''"''■" «^ '/-' fon., it i. "«J- ovation.. It hus'boon o,.n l'. . " """' "' tains tho boilin- is lowored VV f r ''""'"^"'o' niouu- " lowoieu 1 h. U,i- every 51)0 foot. Who n ice at OX' iiiolN i> ,.l.. i •s ro,,uiro,l to ohango tho state fro„/ solhl > 'T'''' "' ''''' «i-l«"n of as its /...,, ,,,, ^;' ; • '" "1'>"1 ^vator, an.l is -'•■'i. tins amount of h..afvhir ""' '^ '"""'""^ i" the li,i,.i,l fonn and i tl or o '^'T^ '" '^'^'^J' ^''" "'"''t-' >^ ovolvoa or ro,K,;.:d ::n!!;:^;'"^' '"""'^^^^ '^^^ ^^'^"^%. (4) Lateiit Ilmt of S(uu,, of the fi,-P 7 . ' ""tu-,thstandi„g the continuous action ^^^^:: ^ ."";rr: ''tt ^^"^""- '^ '- •-" to raise 5.3" -.an of '- !.'"'"' ''*"'P""'"''« '*« '^ wotdd ^ata, ,.,t ; r, ° T r -'''"' "^ ^-"Pe-turo. 7',, unit 1 i ' '■ ■^''■'' ^'^^ ''^"'""^^ "'"'/^ a theru.al unit L.,ng the amomf of heat roquived to rai^e a it . water thmnnh PC Wl.on .. . ^ " "- ^^ ^^^^<^ " "nd ,re„,l,f ,,f 204. Water as a Solvent W«fo.. • *i. gaseous, w'iii ' are absolutely insoluli >ie in it. Ao a I'uie, tho 'l! :s 134 EXPERIMENTAL CHEMISTRY. power of water to dissolve solids increases with the temperature while the solubility of gases is greater at low ihaii at high tem- peratures. 205. Impurities in Water.— Natural waters are never free from dissolved impurities. They contain gaseous, liquid, or solid impurities, varying according to the source from which they are derived, and the nature of the soil or rocks over which they have flowed. If water containing carbonic acid percolates through cretaceous rocks, the carbonic acid combines with the insoluble calcium carbonate, forming soluble calcium bicarbonate (Art. 132). Of the solid matter dissolved in drinkable waters, the greater part is usually made up of calcium salts, generally accompanied by small quantities of magnesium salts. 206. Lime in Water. Exp. 4.— Half -fill a test-tube with water, add a little lime- water, and pass carbon dioxide through it ; it first becomes milky and then clear again. Now add a solution of ammonium oxalate, (NH4)2C204, or oxalic acid, H2C2O4 ; the water becomes turbid. Again, half-fill the test-tube witli water, and add a little plaste"r of Paris, CaS04, shake well and filter. Now add ammonium oxalate or oxalic acid, and the water becomes turbid. Hence, ammonium oxalate or oxalic acid />s a test for lime. Six grains of lime per gallon will yield a .-light turbidity, 16 .rrains a distinct precipitate, and 30 grains a large f)recipitate .soluble in nitric acid. If the water contains calcium bicarbonate the reaction is — H,Ca(C03)2 + (NH,),C,0, = CaC.O, -f 2NH,HC03 Calcium bicarbonate. Ammonium oxalate. Calcium oxalate Ammonium bicarbonate. 207. Hard Water. Water that contains an excess of calcium or magnesium salts is said to be hard, while one not so chai'gud is said lo be soft. feXPERIMENTAI. CIIEiMISTBY. 136 208. Action of Hard Water on Soap. acids coiiihne with q,..!, nn-7 * i . ^""^*^ "le idtter. Iheso irafe. »/,« ™,,B,„ ,„,,„„ ^„^^ .^ ^^^^^^^^ ^^^_^_^ ^^^^^^ Exp. 6.-HaIf-iill a test-tube with wit, r , • • cium bicarbonate i„ solution, and carl Hvld r" """' "' the solution becomes milkl So ^ /"''"''''' ^' ' soluble bicarbonate into the LoIuL ^II^^ ^''' ^^ IS expressed by the following equation :-l ''''^^^" H,0a(C03), + Ca(OH), = 2CaC03 + 2H O Zfa,.?«e.. ../«•«/, ,„a^ f,e got rid ofhy hoilincj or by the a,1,m ■ of hme^^oater, is called " Te,a^.oranj Hardnl" ''" ! ij, 136 EXPEHIMr^NTAL CnEMISTIlV, 210. Permanent Hardness. Exp. 7. — Sliiikc up a little caloium sulpliate (Plaster of Paris) witli water and iilt<>r. 'I'he water now contains calcium sulphate, which is solul'le to the extent of one part by weight in about 460 parts of water, wliile calcium carbonate is only soluble to the extent of 2 grains in a gallon (70,000 grains). Boil a portion of the water ; no change is observed. Add lime- water to another portion ; it still remains clear, the lime re- maining in the water. Water which rainiot be ma soft by hoiling, or by the addition of lime-water, is said to be '' rennanentln Hard." 211. Total Hardness— Degree of Hardness. The term " total hardness " implies both temporary and per- manent hardness. In expressing hardness in degrees, it is to be understood that e\ ery degiee of hardness represents 1 grain of calcium carbonate or its e.piiva'ent in soup-destroying power, in a "allon of water. TIuh, water tliat has a hardness of 10 dcrees contains 10 grains of carbonate of lime in a gallon. Most chemists now, however, estinuite the hardness in 100,000 erains of water. A soft water is one below six degrees of hardness ; a water of 8 or 10 degrees is moderately soft, while a water of 20 degrees and upwards is hard A good drinking water should not have a hardness of more than 15 degrees. A very hard water is injurious for drinking purposes, because its power as a solvent for food is impaired, and because it is absorbed by the stomach with greater difficulty than a soft water, thus giving rise to indiges- tion and dyspepsia. 212. The Softening of Hard Water. (1) By Distillation. This method is chiefly, if not solely, used for the preparation of fresh from salt water, for the supply of ships at sea. When freshly preparc-l it has a vapid and uu- KXPRRrMENTAL OHEMISTRV. I the addition m in 100,000 f 20 degrees Id not have a "- objection, „,„, be re^ al'l;;'";. ""•*-- ; both „, bonate, „,„i ,„,„,„„, „,„^,,_,^ ^ ^ ' g soluble so.liun, bicar- This action take, place .,1„„,,,,,„,, ,, ="""» >'«.,ta.... '•^■;.|.on.Nre, As the .„,,;,„, . ri;'!"'''' ™P«'.' »' a hi.he. »»' ^ ;.us softenc, cannot be Zx " .''° .""'"""'-"t ta.te, the waste of soap. " ""'"Jressos, who thus avoid ».M^w£).i^„':;tTnrxtLin'" »"■'■•'- ■■- -i..«o„ »i"ble calcinn, carbonate precipitated J " '°'-"'^'' ■"■" "'• -.„..„,.... ,.,„„i^„a.^ "c..„°»S,„„+ JO,SO, Water containing sn]., „r Sodium sulphate. --. i..tead:;':x,::;;:^;;:;;-of;o..cdinthesa„e '■"" )""»»""■» ""Aonatc, n,„y be nied "'^'"''' '"'«'' ™- '-dness of wati whic, is' ' " ™^ •^'-'■■« '° 'bat pa,t o, the *» of in,e, aagnesia, and i™ f,7"- »' "- bicarbon "■•"".g frou, s„|p,„i,3, ^ •" " not applicable to that boiled, the bicarbonates a^^ Xr'"'""'"'« ^--tonate carbonates being l«cipit„. J „ "'^.f^'-'l^eJ, llie insoimj ">-toa„., Ebullitinn fo. half T ^^ "^^ -Lciled with' tne same kind of "'ifo, *! ' Process is aiinI,'o-M . - -ate. u. ti.e preceding, and to the 3!"' "uo same extent. M: 138 EXPERIMKSIA'- ClIKMiaTBlf. L; rtl.vs« scale in n»n,evo.H ,.1:kcs, being appl.e'l t" tl- entire water m¥S "^ '=°™''"' '""'"• •21, Lead in Water.-Aa Lad a,.t, as a omnlntivo ,.o,son it, X PV0.1UC0 serious results if laken into tl,e sjsten,, even ; V m nute quantities, for a leu.t,, of tin.e. It ,s, t .ereto re^ „ cre'at impn-tunee tl.at suspecte.1 w:,tor should be care n ly ^^^^rZr:^^:^^^--^ -•«. l,,,lrate wlncU Us tw." Potable water always contains a eertam an.onnt of 'sn solution, and tl,e corrosive action on lead depends upon salts msoiu • j y ,,,,„„t. Salts of tbe nature -"^^^ik '- "- -!-'• "I^"" ""-"" X'TL s ;: as 2 earboltc and snlpl.ate, by for„,in, an sthl W n on its surface, ei.i.er retard or „lt„setl,er prevent :2:::::::^^^'^^^ ^ --«"■ A-,-e.inds :; ;tt.ble matter forn, insolnblo con.ponnds «,th lead. vlx> 10 -Boil 100 e. e. of water, acidulated with a few ,rn!!f 1 vdrocldovic .aeid. and add sulphnretted hydrogen water Ar 19 If '' brown or blaek coloration u prodneo;!, the * of lead may be inferred. This bl.ck eolorat.on .s lead r:;re,Pi;a'rv waters kept in lead Cisterns can be uret with which do not yield some trace of lead. ORGANIC IMrUUlTIES. ,,i. T^iatter mav bo either of vegetable or animal The -g-- j;^^\ ;;; ,,. u. most injurious; but water ^^'f ' t vl^ ^ab^ quantity of vegetable matter, partly contanunga y ons 1 ^^^^.^ .^ ^^^.^^^^ unwholesome. i'^^^^l^"""\7\rted for organic matter by the following Water may be testeu lui ^ „ methods : — 13d laPSKIMESTAL ClIEMlSinr. ''■«"■'«! ...■ mi„ ,v„t„, , "„ 7 ■""■" '" «'« »-mc. stee with ^™atc ,„|,„i„,, p,,,„„ ' !■» '■'.;« .|..m,tity of „o,,„,,„. "■ '"o P»P=.-, a„J „„,„ ,, , f'" »■ ■■ I'y -Jo o„ a shoot of ; ■clM,uay.,poo,„,,,,,,: ,^ *"■» ■-woo,, «- 'wo ,,„J «o- l-lacc ,,,,,i,„j,_ „,^.,.^ i^' 7'"''" i'l^'-- If J«co]„,,,tio„ »'-oo, .,„o|, a, „,„j^., ' ,t ■• 'Y"---"'- Ti.o,.„ „,, „t,,,, ,; ' -W .■.-l,.oo t.,0 sa, "f' :'.:"';''"°"«i '.^■■•»go„,,v,,L l'-o„co of „u,,.,,, i„jj^^ - organic „„.tte,.. T,„ °ao. two „,, ,„i ,,,, ^^ .IttT'r "'''"''"""'■ "■" =ol„,.at,o„ is „wi„„„ ,„ ,,„ ^ -^ ' ■ ■ onl„,a,y water. T,„ ! '"'«>'™ "f "'" l«m,a„,,„,ate. A sot If' ""'T '"''"" V -- ..„..os Of po™a„„Lr,s ^ -:-:;- -^^-S^^:,s:::----.-orisa,wa,s "7"' """;; -™- '» "%hi: :,:tati:ir:,:7 ^"'"""' »ol»Ue i,-. a,„„o„ia Good ^te ,,' ^r"*"""" P'<^«'P"'>'o ''""OSS. '"•""' '''»»M only yi,M „ ^';._,|^^ (3) Anmonia-The prosenoo of f^ amn,o„- ■ 'n.oammon,a,„con8i(!o,.nl,|o ! 1 y ^^Q EXPKaiMENTAL CHEMISTRY. Ma water shouM conuui vtiy may be detected as follows :— Ext. 13 -To a test-tube half full of w.ll-water add five or Exp. A-^- /Y , ,.. .cfQ) A yellow or brown color ,ix drops of Nessler's Test (Ait. iJo;. a j indicates sewage contamination. iTA Naturally Occurring Waters. ■ i,r , , Tho natiu-e and amount of matorial in (2) SP""'J'^'^'":'-^''^Zl of the strata through which ">""« ^'nt":t : l:: conru,on>, occur are (1) the ;liX:atejr::inatc, of »Hu,n..a.a^..u.^> ^ .„„,atc, of calciun. ««-'- l^ tl .»cous corr- amount of salts, it is u,u. ^ ^^^^^^.^^ ^ *- "'"":ir:i'o;:::: :« tte::f!:ictah,e „.,„, .crivea irtroCLt.*- of the country which has hccn drarncd by the stream. U^ Sm Waier.-Tim usually contains about 3i per- cent by „. t /rs^stanccs in solution, the one wlnch^« present rn by fir Ihe largest quantity beh.g common salt, tsaCl. QUESTIONS AND EXSECrSIS ON WMEH. 1 Water is »id to he . compound of oxygen and hydrogen; ^t'-^iitr^lirlf «::::--i"ed h, th. eudlomeier , Good pot- ts presence add five or brown color a\ of natural washed out ammoniacal 3 kinds. material in ,rough which r are (1) the sium, (2) the Hi carbonates, caseous con- ioxide. ain a smaller king purposes in solution a 3rigin, derived .s been drained ^ per cent, by s present in by and hydrogen ; the eudiometer? EXPERIMENTAL CHEMISTRY. 141 After exploding a mixture of oxy^^en anci h.^ water was obtained, and 11 -5 c c of f . ^ '^^'"' "01^ gram of temperature was 15^0. and the pressure 7r.n" '"'"'"''^- ^^e of the mixed gases. '^ "^ ^^^ """• ' «"d the voh.me 3. Explain how the action of hydrogen on used as a means of determinintr fhi "'^'P^'" "^'^^ n^'iy be Ber.elius and Dulo:: 1^5 r^"''^ "' ^^'^^■• contact wxth ].ydro.c„. The sidual . ^'""' ""'^'' '^'^' "' and 12-107 grams of water were obtlT'p?'"'^' ''■''' S'-"^^> the percentage composition of water '^'"'''^ ''"^ ^^"« ^^ta 4. What are the characteristics of nnm . water be obtained in a pure state? hT """"l"'' '""^ ^°^ "^^y obtained from sea water ? """^ drinkable water be as a piece of solid iron I '""^^^''ted accordnig to the same rule 6. What is meant by the boilinnr ,, • ^ , pressure of the atmos'pl re affecTthr? "'^^^^ ""^'^ ^°- *he bods ? "'*'''* *^^^ temperature at which water Two thin flasks are filled with wnf,.,. j in boiling water and the o th" L a e '"''' "^^ ^"« '« P'^^ed m each case ? "^'^^^ "' -^ ^^e^-^^'ng mixture. What occurs 7. What is meant by the tprm ;,„^j the earthy impurities fvl^tVr Ltt^r '^^ 'T''' ' ^^^ water and of deposits in boilers and JTT "^"'' °^ ^'^'•'^»««s in What is meant by sayin^ that a "" '""^^ ^^"'^ ^^'"oved degrees of hardness ? ^ ° ' ^'^'^" '^'^^^^^^^ of water is 10 8. Some hard waters can be softened h^ K t cannot. Explain the cause of this and d ^^.^•^'"=' ^^h"«t others for softening waters. ' ^''^ '^"'""^^ ^"^ other methods 9. A sample of water contains in 100 000 n . .n cum carbonate, 5 parts of calcium J^'T ^Tl"' ^^ P"^*« ^^ ^^l" -!t ; what is its hardness, a, 7 lo ^j^ ^^ "'' ' P-*« "^ common re ueed by boiling the wat'er for 'Z X^^" '''' ^^^^-ss be If. oupDosiiior a '^"'•ta-'n wat • ' bonat. i„ ,he g.L„, .,„ .ha, ni: LtX^ ^1"' "' ""°""" ""'- " <^quation represoiif.s t|,e (; Ik MmM J ^2 EXPERIMENTAL CHEMISTRY. ■vction of a solution of v.-ap on calcium carbonate, 2NaCi8H350.4 CaCO Ioa(C,3H,,0,).+Na,C03. What weight of soap must be added to th^wat'or'iefore a pormaueut lather can be produced '"n^^w^^yC-enco of lead in waters be accounted for, anyhow Luld you distinguish orgamc matter of vegetable ong.n from that of animal origiu ? OHAPTER VII. ATMOSPHERIC AIR. CONSTITUENTS. 215- Oxygen and Nitrogen ti gasos respectively present in the air'„,avt ^T"'l'? "' '^''' ways :-- ^"^ '"^^^ ^e estimated in various (1) By Withdrawing the Ovva«« r volume of Air by Phosphoru^. "^^ ''^^^ " ^^^^" This can be done, as already shown in f},. ^Vitrogen, either by the active combust n of nh T'^";'"" '' or more accurately by the slow n T P^«''^PJ»0"'« Art. 88) (Art. 89). In the'latL ease tL 2 "I " '' "" '^''^ ^^^^-^ end of a copper wire In 1 , ^^''^[''^^ "'«y be hxod on the to the samJLel ^i^hintTw^^ttrtt^ T' '' ''^^''^' to the requisite extent it wilTl ^"'' ^^ ''^P'-'^ssing it theairin\hebotti:ts'i::ta:er ^'" ^'^"^ ^^^^^^^ °^ Pitlh" ^'^°^'^"^ ^^^ ^^^^- With Pyrogallate of in S;tt::Sl\t:: iiti?:"^ ; ""'''- ^^-^ -^ ^^ -- india-rubber bands. F:::Z:^'^TJ!' iT '' ^'"^^ solution of pyrogallic acid till ^h.^ . T ^ ''' *"^^ '^ ^^rong full. Wash the^ube;;! "it : " T^^"" ^^ '^'""^ -^-^hird Py^-o.allic acid, and agi^.: ^o .^^ [T^f^ «'7^:>^ the Miistio potash till on wfn,H.. • ="," " «rong solution of Me above the first l:S"a° " ,^."''"''' --' »tand a on the momh of the tub^ shak it n T' "' '"'^'^-'-^ier li ivH SSSSB 144 EXI'KBIMKNTAL OIIKMISTUY. Mil I ^,,1, ,„„i .,„ ,.ijusti„,' t],o water to the same level withm an.l without th. tube, th.. wutov should stand a little above the «eco„d ring, showing that about ono-tifth of the .ir has been nbsoibcd. This one-fifth is oxygen, which has Um absorbea bj' the pyrogallatc of potash. (3) By the Eudiometer. Exp 2— To 100 volumes of air in the Endimrotor add 50 vclumes of hydrogen and .xplode. The 150 volumes will shm.k (steam being condensed; to 87 volumes ; therefore, 150-87 = 63 vols. loss. Of these G3 vols, one-third is oxygen ; there are, therefore, 21 volumes of oxygen in 100 volumes of air. (4) By drawing a measured volume of Air over red-hot Copper, and then weighing the Copper Oxide produced. Exp 3.— Take the hvdrogon bottle, press the fnnnel-tul.e no.rly to the bottom of the flask, and add a little water to cover the end of it. Attach a drying-tube, tilled with calcium chlorade, and connect this with a tube of hard glass filled with bnght copper turnings. Bring the copper turnings to a red heat, and then pour water through the funnel-tube to expel the air and cau'^e it to pass over the red-hot copper, which combines with the oxygen to form copper oxide. The nitrogen may be collected in the usual manner. This experiment illustrates the principle of the method adopted by Dumas and I'.oussingault in their precise determina- tion of the composition of air by weight. They passed a given volume of air (1) over calchcm chloride, then (2) over caustic potash, and finally (3) over ignited copper reduced from its oxide, severally contained in glass tubes accurately weighed before the experiment was commenced. The increase in the we iaht of the calcium chloiide indicated the moisture, of the EXPKIUMENTAL CJIEMISTUy. j^g caustic pntasl. ful... tin, carl.n,, .li,.vi,lo -unl . f H the oxygen. sovenUly containe.! in ' ;^ '. ^'; "^^^^ ^"^« upon. The rosidinl ,.. • »i • i • v«^'">'u <>f air oporatod wiuci, «,„.„ the nil- ;!,,'' ;,'i;;r"r '," "'° "•"'"'■' °' ™ «ive the ...Us or r::,:::.:;:::;;;;::!::'-"'-'^'»>- By weight / ^'troA'en yg.gjj^ numbkrs. By volun.olJ.^itrogen :; y^.jf 23 ^o^yg'^"-- 20-9U ;.;;.•;;; JJ 216. Constancy of Composition. but JittJe variation. Awrn. Smii\ h , f ''' '""' '''"^■' •■"Hi nioni.tains, is as lii-rh as '^O'QQQ .. Scottish mo-.rs "'7'^ '"-» I e,«,:„;:„-.i„r ,.r; ::;:i,.:''-;" '"^ "'° iislinv x-i 20-82. This «„,«f.,„. ""■'"■'''""'r, it may sink "... volu,„eof „.,y,.e„a,dtrv , "'"="' «°»'l""""l "' '-■-'-- "..i-:i I ;i;r::t^^^^^^ ^"^'"-^ /IX Tf O ■'"LIS . y) It pun. a,r were a definite compound nf mtrogen .t should be absolutely eonstazTh. '^°'" ""'^ ^t IS not quite constant, and. thereto , ZT'"''- ""''' cient proof that the cases arp nnf ! ''^''"'' '' «"«- together, as the constit':: s ^ a ^^^^^ '^' ^^^^ ""--d variable proportions (Art. 17) '^"'^^^""^^ ^^^^J^ occur in in- 146 EXPEUIMENTAL 0I1EMI8TRT. Ill i 11 .-volution of heat, and ultcmtion in properties and volume, usually vttendant on chemical cunihi.iation, are perceived ; nevertheless, tlie mixture is actually identical in composition mih atmos- pheric air and possesses all its proi)ertie8. (3) Were air a compound it should dissolve in water as such, that is, the proportion of oxygon and uitrogen in dissolved air should be the same as in undissolved aiv j but if a mixture, the more soluble constituents should dissolve the more readily, and, therefore, more oxygen than nitrogen sho.M dissolve, since oxy.'en is uiore soluble than nitn^eu. Experiment shows that the hitter is the case. If water which has been recently boded, and then allowed to cool out of eontact with uir, be shaken with air and the dissolved air be then expelled by boding, and coUectrd, 11 will contain 32 instead of 21 per cent, by volume of oxygen (4) The oxygon and nitrogen in the air do not present a simple ratio to the atomic weights of these elements. 217. Diffusion of Gases. The uniformity of composition of the atmosphere is partly ,lue to the operation of winds, but it mai.dy depends upon DIFFUSION, by which iiases mix in ojqnmtioii to yraoitahon, and tohen mixed remain so. This may be illustrated by the following experiments ; — Exp 4 —Fill a ^^^^^^ """^^^^ carbon dioxide, and leave it mouth upwards. In about half an hour introduce a burning fujcr • it will not be extinguished, thus proving that the gas h,s escaped from the vessel. The carbon dioxide, though hea^ier, has dijfn^cd into the air above, although the latter is ^'"Diffusion between gases takes place if they are separated by a porous partition. A partition made of plaster of Pans ;s very euitable for experimeiiLs ou ditlusKiu. the latter is BXn.;itlAli;NTAf. CIIEMISTuy. u- ''■"i», »o ns lo form „ |„v„r , „, ,' ""' " """ l''»»'«r "f "'" f =1 ..|.»n ,t, an, i ;„ 'l':;! ' """■ ""«"■ J"- lifl«l. Leave tho A^, „L :,. ■ "'" '"""«' "■'-" '•" ™»ily cork., a,„l l„,.v„ it for , ,'. " ^ """ " "''"" ""■- ^"'aM Now la,,t tl,„ rin, „f Ih! 1 1 ' '° "■' *" '^'^ """-onghiy. -..«.. to ..,t ini:^.:::::'^:^:!:';:::^ "" "■ tl.o nm. Wlicn this kyci- l,o, nnrf,.,! , , "" '"""'■' «"*er with „ p«. of »,^i , ' 1' : : ^.^ '""*-''. ""ko it tl.o.. l.eat tl„, whole u„ifo„,„; "l "'! l"™' " "P'"'"'"'"!' i Now place tho f„„„el gt,„„ !,',! , ' " """ *<> I'"'"'"''. «ii it With carho„aioi,:t. :::;:r",,: ^•',t-'""'°' •^"" with the gl„., pI„io, ,,,■ II,; o,„, i ™ ' , " " '"=""'""■ The carbon ,lioxide will „" "l ,'? ""'' """""^ <■><" Pl»lo. >.ut the lighter air flowXr:: , "■"."^■" ',"" P'^'- "«. the volume of the g.., eontai,::; ^ li:: f ^' ™"- « that buhblos of ,™ e,eape f.o,,, the e^d f ?"''T™°"' rise through the water A.»-,i„ „i. J , ° ''""'°'' »"'! position. a;,l while st il eovl d wtt """"' '" "" "?"»'" hyarogen b, displaoeme: , d^^ : tl '";" "" " """ lighter g„., Will .litruse out^rds n o're pM| ^r'" ,7'';' ' ""' enters inwards. The volume of the -a, i^ e il '° '""'" and in the course of a '.:„ seconds M 7 ' ■^""'"'"^'"^ the height of the funnel. "'" "^'■■' '■> '"'™t half For the experiment with carbon diovi,!. .1, . aip only a few n.illimetres into the we.: t°J:Z:y unnecessanly the escaping gas-bubbles With T ""' ube must dip somewhat deep;, or the end i wouh"'™, "'° the surtace of the water when the latter rises in ZtZt"'' 148 EXPERIMKNTAL CHEMISTRY. IP'* ■ Graham found that hydrogen diffuse, four times as fast j oxvcren Now, the densities of these gases are as 1 . 1 6 , but oxygen, x^o , applies to the diffusion their diffusive rates are as 4 : 1. il^s appiu- of all "ases. Hence wo have the following law :- Griham's Law of Gaseous Diffusion.-^ dip^nve ra?es^ft.o n>a.s.s of aas in coniact are inversely proporUonal different :Uhts as those which form the — ^ ^ ^^ uniformlv distributed instead of forming layers with the heavust a the boUom. In obedience to this law the heavier gases are lipenedto rise, and the lighter ones to fall, until the propor- tions of them are all the same throughout. 218. Ozone.-The presence of ozone in the atmosphere may be detected by ozone paper, as in Art. 61. The general facts regarding ozone may be stated as follows :- (1) More ozone is present during the night than durmg the day, and most of ail is found at day-break. (2) More is found on the sea-coast, and specially when the wind is blowing from the sea. (3) More is found in the country than in towns. In country air it does not amount to more than to one volume m .00,000 volumes of air. . (i\ It is invariabW formed when water evaporates, and this is probably the main source of atmospheric ozone ; atmosphenc eleclSity and tl 3 action of aromatic plants and flowers may be reckoned as minor sources. 210. Aqueous vapor. Hlit) 6-Bring a tumbler of cold water into a warm room, or put a few piece; of ice into a test-tube ; moisture is ,oon de- p. .ted on the outside of the glass. A given volume of air can- not take up more than a certain quantity of aqueous vapor and as fast a? : 16 ; but J diffusion le diffusive 'opovtional ses of such •e are kept he heaviest \x gases are the propor- =phcre may eneral facts during the J when the In country in 700,000 es, and this atmospheric ,vers may be warm room, ) is soon de- LC of air can- is vapor and thon it is said io 1,0 .v«^,,,,,^,,^ .n, ''"^-b- on the to,,,.,.,,,;: ^v,^ T'^'y ^"'-" "P 'depends '»'^' '^^'-'t 6 o,,,-,„ „f , ; ^2 *'""i';"'"^"''^ "f' «0°i^; there -- .rain to the ,al]on " I^I '" "'/''"'' -"- ^-^ of air, or ^^-t io„g and .sevent,.on h "'"'^ ^■""^ ^^venty-fiv,. -^i^ ^-Mt would .Ik', ;;\:^ "''-^t- to n,ak-o the .'up.oous 1 / > '" ""^ ^'"' ' '"""'^ "f ,t-ni.erature ..re only 40"f' " ""^ """ *^^' ^'^^'•- If the fle-'ee the necessity of .s„no]v r' ' "'"^' '^ ''^ "''t 60F. ^^'-' it is .used in^ea,::::!:!:::^ '"'^^^^"- ^« ^'- ^^tu^sphere (Ta!:'""^ facts respecting n^oisture (J) A,r rarely contains its fuJJ,,,t,„,., ^• except ,n very cold weather, or i . v T"""' '' °^«^«^"^-« (2) The n.ost comforfdde 7 ' '"^"■""' '^^■^^■ ^0 per cent. More t ' s '^1^ " "'""'"" '^ ^'^ ^^ to "''''^«t less causes too ^^!^ '^^ ^^''^'f ^ ^-^ the hody, •"'-^J' -> ,..,+ • j -l.on d,„xide ,,ei„. ,,«„ „ff, ^^ ' T" n'" '"''^ "'"'"■■ P«o,.co ,„,lica.e.| i„ the „.„.i „, ^ " """="'«' "'Kl it^ Carlon ,lioxi,le is, tl,ere'„„ „ ,.' ... ri.« ave,,,.. a,„„„„.' of mJZ^T'""'""""""^'^^'- 'woo,, 3 „„J 4 ^,,,1, ^ Toooo ■"'"■" "°""'" "'■"■« to. C or 7 volumes in 10 000. Wii 'e amount en may rise as hf the au..unt a present existing in the air. Accor.ling to Dr. Parkes, an em.nen authority on this subject, air - -^-'^"^ ^^' ^ ^'^ "^^^ aioxiae exceeds .OG per cent, or G volumes ni 10,000 lenc^ in a sanitary point of view it is exceedingly nnportaut to a..er- tain when this amount is exceeded. Yov tins purpose Di. Angus Smith gives the following method :— Ext) 8 -Take a bottle of clear white glass having a well- fitting stopper, and when quite full containing as neady as possible ten and a-half fluid ounces of water. Fdl the bottle :^th the air to be tested by putting a glass tube to he bottom and sucking out the air. Now pour into it half a fluul ounce of clear linre-water, insert the stopper, and .hake vigorously for a short time. Let the bottle stand so that the air bubbles may vise, and observe whether or not turbidity or opalescence is pro- duced If the liquid does not remain bright and clear the ai ■ examined contains more than G volun.es of carbon choxule m 10 000 volumes of air, hut if no turbidity is piydueed the sample tested may be considered wholesome, the carbon dioxide l^in. in this case taken as the measure of its general purity. Dr Smiih proposes the following rule as a practical application of this method :-"Let us keep our roon.s so that the air gives no precipitate when 10| oz. bottle is shaken up with half an ,„„ce of clear lime-water." In order that the air in an occu- M ro, may not contain more than "OG per cent, o carbon dioxide :i,000 feet of fresh air must be introduced per hour for each person, and about twice this volume for every gas burner (.at consumes three cubic feet per hour. Fortunately this re- newal of air takes place to a considerable extent in most roonis, even when the doors and windows are shut, by the chinmey, by cracks and crevices in the doox-s and windows, and especially t^,ro^,,,U vv.U. Most building materials are i-orous when dry EXPKRIMENTAL CflEMISTRY. 151 , but become nearly air fio-l-f i 1 , ""J '"i-iii^lit Avliei) Wat n fcl^ercfore render room. Loh ^"'"'^ ^^'^^^^^ ^''^'"P an.l ; fashioned white.vash ^''^ ""^^^"^^^^^^^ '^^^ t),; oJd- 222. Ammonia. Exp. g.-mi a bottle Avith frnol. • «'"all quantity of NessJer's J • '"'" "'"*^^' '-^^^^^ *« it a ^-;tbe.L.,,;s::t--;-^^^ tlie i)re«ence of ammonia ^ ^^'''^ '°''^^' ^"'Jicatii,^ ---f min, amounts to !2;;^:':,:r'"^'' ^^ ^'- -I by the greater part of the .n't,:; .V ^h IT"""' ^^'^^'^ ^'^-•° "nation of seed and other ^nnLJlit I ''^"^''' ^°^ *'^« f«^- '-'^bJo to assimilate free li^,, ' """' ^^"•^^-«' P^-ts bein, 223- Nitric Acid. This substance is alway, present Jn .1. . 1"antitios. It is a source of ,1 Y ^f "^^'^^''^re in small -d sulphuric acids are H^Ti^l '' f'"'''- «"^l'hurous ^viiere coal is burnt. "" '^''^ atmosphere of town.s 224. Organic Matter. * J- he atmosphere also of* particles of Ju,t, ,,,„•,,, J"™'; ™"»"' "rganic vap„« ,„j ""■"■ak T|,„,, „„,|,.^^ ■ the g„,„„ ,f p,^„j^ 1'" Wactio,,, „,„, .ir „,,;„, ' °l««ata of f„„„o„tati„„ a„J fitatio,, «.,o„gh cotton 1 :". *""' ""™' «'*-■ by bo kft i„ contact for «»; Wt^J' ^ :''' " ''^ -'«J-oc. n,,' '"eat. etc, without the i ,,,«;,„..!" ""'"■ "'"J-'oeof w fr J'^ii a iviy of li.rhfc om solid particles 'y'lfc is allowed to ^•<^iiig the slightest ch pass throuffl > »o relloction is noticed ange. ' air til us freed aud the spa. Il 1 II' ^ 1 il t i i"if 1 EXPERIMENTAL OHEMISTRY. 152 appears perfectly empty, the motes which in ordinary air reflect the light being absent. QUESTIONS AND EXERCISES ON THE ATMOSPHERE. 1. What are the two chief constituents of airi By whom and when was each discovered ? . . ,, • • ii 2 Name the bodies which are always present in the air in small quantities, and those which are occasionally present 3. Describe a mothod for recognizing with certainty each con- stituent of the atmosphere. , . , ,„jo ri„« 4. Is air a mecimnical mixture or a chemical compound 1 Give reasons in support of your answer. , ■ a y.r ^h. 5. How niay the composition of air be ascertained by the eudiometjr^^^ phosphorus be used to demonstrate approximately the proportion of oxygen and niv-rogen present in the air ? 7 Desciibe fully how Dumas and Boussingault determined the composition of air by weight, and sketch the apparatus required for *^8 Tn ^analysis by Dumas and BoussingauL h3 copper employed gained in weight 1-4094 gram. Find the nu .ber of grams of air used and of nitrogen obtained. , ^. v -^ .,„i.f 9 In a well-ventilated room the amount of carbon dioxide ought not'to exceed 6 volumes in 10,000 of air. What weight does this correspond to per litre of air, and how much calcium carbonate would it precipitate from lime-water 1 10. A man inhales 18 cubic feet of air per hour. What weight of oxygen does he consume in 24 hours ? ^ 11 A man exhales 1,122 cubic inches of carbon dioxiae per hour. How many men, at the same rate, would be required to produce 2 240 lbs. of carbon dioxide in 24 hours I ,. ^ , ' 12 Give a short account of what is known about the solid matters, organic and inorganic, found floating in air? What impurities docs rain water extract from the air ? What weight OJJAPTEK SECTION I. ^^Ilh Marsh-gas is the simnh.i """^ ^^^ study two of them j, -hich one atom of It '""''' '' '^''"^'^^ a.d h ^ ? '' ^- ^o-uia is, thoLrrcnr'' " ^^-^^ ^^°- «' fe PBEPJiiailON. "5- From Sodium Act^t ^^Pl~UUto.,Zt '"" ^'""•"" Hydrate ^"t'«- The reaction is-, ^ "'""^ ^^ ^^'«"^ stoppi,,g up ^^^^ Sodium acetate. s„h- = NaoCO PROPERTIES. 226. Burns but does nnf Ezp. 2.-l.otioe tuJilZ\y^''' Combustion. a«s89>M»n»».»«i««««»,«m : 164 BXPBKIMENTAL CHEMISTRY. 227. Lighter than Air. Exp. 3. Pi^'ve this by pouring from one bottle into anothwi as in Hydrogen, Exp. 5. Sin.-e the moleoulur weight of tho gas is 16, its density ccmpared with hydrogen is S; it is, therefore, the next lightest body known. 228. Products ol Combustio I. Exp. 4.— Pour a little lime-water int, the bo! tie nf.ed in the I,«-t evperi.'iient, and shake it up ; the iime-water becomes turbid, shovvitr.; the presence of carbon dioxide ; carbon is, therefore, one of );.-• constituents of the gas. While the gas is coming off pass it tiucagh a urying-tube, ignite it and hold a cold body in the tlame; Tt soon becomes bedewed with moisture, showing that hydrogen is another of the constituents of :.he gas. 229. Explosive Mixture with Oxygen and Air. Exp. 5.— Mix in a soda-water bottle one volume of the gas and twice its volume of oxygen, cork the bottle, wrap a towel tightly round it, and shake it well, take out the cork, and apply alight to its mouth; a sharp explosion occurs, carbon dioxide and water is formed ; thus : — CH4 Marsh-^as. + 20 2 . = COo + 2H2O Carbon dioxide. Water. Oxygen. If air is used instead of pure oxygen the mixture also explodes, affording the same products, but it will require ten times its volume for complete combustion. Marsh-gas is very abundant in nature, being produced by the decay of submerged vegetable matter. It is the principal part of the gas which escapes in bubbles when the muddy bottom of a stagnant pool is disturbed. It is found ir coal mines, where it is known under the name of "fire dam^. ' When mixed with iiir and ignited, it causes the violent ex- :is in coal mines. The pv ■ "ct of combustion, the [w . "nn^ > ft of which is carbon dioxld.: .> called "after-damp" or ' ^oi-. ..lamp." EXPmuMENTAL CilKMlSTBy. 1 into another ;ht of the gas is, therefore, ie Tif;eu in the comes turbid, therefore, one lining off pass I body in the showing that and Air. nie of the gas wrap a towel irk, and apply irbon dioxide 2H2O Water. also explodes, ! ten times its oduced by the principal part ddy bottom of mines, where en mixed with in coal mines, vhich is carbon 165 SECTION II. ETIfCNE, OLEFIANT GAS nn trr. GAS, OR HEAVY CAIIBUEETTED HYDROGEN. ^^-Ha//,. Moke,,,., W.;kt, ,S - important constituent oJ ^T''' '' "^^ — iva U i, PREPAKATION. Exp. l_To tl,e hydro^Pu fl.,.!. «. f'']' '' -■ of .u,p,„„,, aci., I : ■ , '^""^ '''' p-^^ '^^"-"^' 20 c. c. of alcol.ol. and on . : " ' '"' "'"^ '''^^^^^ ""-^ture into a tl.i.k n.ud The f '"'" ''"^ *^ '^^"^^^t the ventfrothin. an.i if the sulp, ,r; Z' "''^'"'^^ "'^^^ *« Pre- «I>.<^Pensed witl,. >,^,,, ..,„t v , , ^' '' ''" 1*^"'« ^^ W be -cl may be collected ov^ L 1"'' "f '" '^ ^^^'^ ^^^^^ ;;-l abstracts the elen.nts ^ ' '"'^^ ^^^^ ^he sulphuric thus:— '^'^^'^^ ^i'^>in the alcohol, C^H 0- Alcohol. fi,„„,„.... *.. ^:iH4 ^ '■ ^""te sulphuric acid. - rnoPEUTIES. 230. Combustibility. After th„ e„„,b,„,.„„ ,, „,;%7 " '""s'y '..mi,.,,, „.:„, E^p. 3.-1^ ill V and down through a series of vertical pipes called con- densers. In the hydraulic main and condensers the gas is cooled and the greater part of the tar and ammoniacal liquor are con- densed and separated. It then passes through a box filled with perforated trays containing slaked lime. This is called the lime purifier. In passing through the lime the gas loses its carbon dioxide and sulphuretted hydrogen. 233. Composition of Coal-Gas. Coal-gas thus ^luritied is a mixture of combustible gases and s?j: i "^fmnxTM. cnBinsTnr. KIWI'S whicl, ,„„^ l,„ ,,i,,., . . , 'W : '"' '■■"■•■ with', ;, : , ;: ":;:; *«-. «■.: (,) T„o,e «amo, an,l ,„„ t.,n„ed ,«,«,; '"•'' '"'"' "■■"' » "o.,-l„mi„„,„ 234- Water-Gas. Tlie following proa-ss „f „ , • .v«- i.cc„ s„coe,.r,„,,; ;,„,,,;:; ,;;;f."'"""'""""s o-a i.,, ,■„ ,oce„t btoam from a boiJer ;« n • , ^"•y'^ temperature. Tin's <";?.'/"'" " ^"'""'^^'^ ^"^ hoat.I to . f:!--^"^"^ ^ea.ot;,.t;r;r ;' t-: i-'^-'-t: : I't'aetioij -tort containing red-lHHantl!^;r'';' ''""'" '^ '^'^^ occurs:-. ''^"tl.rac.te coal. The fuJiowin-. Carbon. + H3O Steam ss called am- i^lie carbon monoxido n,„l i,„ , ™- ''oP' ».te,.ol, hot,i„to" ■ rS """""" »"<>"- reeor. SECTION IV. COMBUSTION. ^35- Combustibles anH q. siibstaiicec), such as phosph «Jso seen that oi'us, sulphur, carbon great niany etc., burn readi] •\.jr 168 XI'ERfMKNTAL CriEMlSTUr. in oxy:,'en. In tliese cdsos oxyj^'on is said to bo a supporter of combustion, while tlio IkxIIos llicmselveH avo said to he com- buHlilile. But in reality there is no did'ereneo in the part played by the two bodies. The -' ' ' ehanf,'e is nnitnal, and the terms are ruoiely relative, as the following exijeriments will show : — Exp. 1. — Place the materials for making oxygen in a te.st-tube and connect with it a glass tube drawn out to a rather wide jet. Fdl a large bottle with hydrogen, and hold it mouth downward.s. Now heat the tulir gently, and when the oxygen is coming oil freely apply a light to the mouth of the bottle containing the hydrogen and thrust tlie jet into it. The flame will follow the end of the jet in its u[iward progress into the jar. In this case oxygen is the comlmstibie and hydrogen the -yupporter of com- bustion. Exp. 2. — Take an alcohol limp, and by spreailing its wick make a large flame. The centre of this flame is dark, aiul is lilled with the vapor of alcohol. Now send a gentle current of oxygen through the jet, and slowly pn.'-b it into the edge of the dark centre of the aluJiol flame. Thv jet of oxygen will take fire while entering the flavie and continue to burn with a very distinct d pretl\ light. In this lit'.le flame the oxygen is the combustiiji.. and alcohol the su])porter ; while in the large flame around it the alcohol is the combu.stible and the oxygen of the air the supj^torLer. The fact is, both are equally combustible. 236. — Heat of Combustion. It has been shown by nur ; >us and careful experiments that when the same weigh' '' the -iune substance burns to form the same products of cor ^ti a constant aniuunt of heat is in- variably evolved, win .'rtn> ombination takes place slowly or quickly. Thus 12 parts by weight of carlj unite with 32 parts by weight of oxygen to form 44 parts by weight of carbon dioxide, and in this act of union the quantity of heat emitted is 1 axipporter of \ to 1)6 com- \i\ p.'iit I'hiyt'd liial, and tho oi'iiueiits will in a test-tiil)e tlier wide jet. ii downwards. is Cdniing oil ontaining the ;11 follow the In this case it»y/er of coni- iling its wick dark, aiid is le eurrpiit of 3 odge of the ^en will take 1 with a very ixygen is the e large flame carbon dioxide, because the ot ^I "''^.«^^^^'"^' -^^l^-^ Wing '^on f'i...tp™ ,', '"""no..ly is „„., tl,„,.„f„„, , °' '«; "»tio„, Tl,„ ,■„;„,,„,, »"' must 1» du- ,„ ,, """ '0 solid imrliclcs ,„ ,1, „ •"o'H, »)ut stroiiL' V ho..,f,.,i ,1, . '" chlorine with «Pom,,„„K ft ,-3 i„,„,,,,:, ,';""-. From tl,es„ „„, X 'ho same k,„d „f „„,„„ "■ T'"^' ''""ovo, 1,„,.,, ^^ J^ ^^^ . (2) Onthedensiiu nfth t Exp. 6 -Eu, ^"'■^'^'^^^^^^^ Gr«.... ''t burns with a brillVf ''^ ''^'''''°'" ^" ^ bottle of chlorfn Jtnsityof which is 18-9 v •^^"^°'"oric ac d, HPl J"™' in o.x,,,„„ ,,„, /^ ~ /^o; ;« know that ,„d,f„^i (lo„s,ty of ivl.ich is 9 Tl, , ''S'"' 'orn,i„g st„n„ Tu Alcohol b,„.„s with a f.e',Iv,n„ ■ ,. ^vhen oxygen and Jiydroa." ^" ^'•^"'^^''^nd has shown tl. atmospheres fh« y'^'ogeu are burnt i,„der « n ''"'^ and arC ) ^ ^'^' '''' *° ^ iumin.,r fl ' ^ '''"'^ «^ ^^ "'"^'^ ^'^^^ ^i^b very ]u„,i,,,3 •;;'; f ""^- i^hosphorus flames m consequence of |-:-aK3-E7j^?"'-«**«i»i»««Wfc^ ~V sats ••'iWifTiTigMMI 102 EXl'EHlMKNTAIi criKMIhTRY. 1 ( the formation of vory dense vapors of pliosi.honi.s pontoxide and arsenic tvioxide during the conibu.stion. The hiniinosity of an ordinary flame is materially ail'ected l)y the pressure of the atmosphere in which it burns, a diminution of pressure causing a loss of illuminating power. The light emitted by a burning candle at the top of a mountain is much less than that given i\t ihe bottom. If the light of a given tlame, burning in the air when the barometer stands at 30 inches, be represented by 100, each diminution of one inch in the height of the barometer will reduce the luminosity by five. This is not due to any dilference in the rate of burning, for the amount of fatty matter, wax, etc., consumed remains constant. It, therefore, ajipears that a certain relation exists between the luminosity of a tlame free from solid particles and the density of its constituents ; the hrinhted flames contain the densest vapors. (3) On the presence of solid j^trtieles within the area of Coin- Imdion. Exp. 7.— r.urn hydrogen from a wide jet, and gently blow into the tlame a small quantity of finely divided charcoal iron lilings, or zinc oxide ; the flame becomes luminous, 'iherefon^ a fecUij illumiiiatinij flame increases in luminodty hij injecting solid 2>articles into it. On the authority of Sir Humphrey Davy, it was long con- sidered that the luminosity of a flame depended entirely on the presence within it of solid incandescent particles. Now, although there is no doubt that the presence of solid particles may bring about the luminosity of a flame, there are certainly flames which emit an intense light, and yet do not contain any solid particles. Arsenic burns in oxygen with a bright light, and without the immediate formation of a solid substance. No Sdlid matter is separated when a mixture of nitric oxide and carbon disulphide burns. The blinding light of burning phosphorus in oxygen was formerly explained by supposing that the pliosphorus flame »t oxide and losity of an ;ure of the aire causing y a hnriiing tiat given nt ig in the air ited by 100, rometer will ly diinn-ence 31", wax, etc., lat a certain lO from solid jilted flames irea of Com- gently hlow larcoaL iron 'i he reform, bij injecting as long cun- tirely on the iw, although !S may bring lames which lid particles, without the 11 <1 matter is II disulphide s ill oxygen )horus flame 163 OS of phosphnru. pontoxide, lUit tlii.^ is EXPERIMKNTAf. CHKMISTHY. contained solid jiarti =41. The Flame of a Candle. '■'"' i' i« ch, .,.,1 L " ,". ''f '-^ " >■""- '"'-•. »...! ok„,v„ «"iWo„Iy„t the „.,,:„; ■';-"-«--! .•tk.c,.,„„s "f tl,o ft,„,„. Tl,e i„f, ,., , "'"■" ""-^ "'" """^■'- l'""i°'« of the caudle, "; r'V" '"■""';■ '""■" "- -''ole lla,„e i' «een to co„si.t of „', , ' '"^ °'""""'™' *' 1 , . ^" ^i Win distinct narts- n\ Ti, •J-k inner cone surrounding the ;■ T ^ '\ made nn of fl,„ " i^ne Avick. Ihis is ' w)n-..K fi , '^^'y'lt, iuinmous cone in »'i of carb(jn, wliidi 1 '^'dod an.I omits a bri-l liaine IS a It li-d Ueconics intensely leeblj lunnnous mantle. (i) s :irroun «. wliicli may be 164 EXPERIMENTAL CHEMISTRY. rill liy burning a little bit of sodium in its vicinity, when it is colored strongly yellow. This cone consists of the final products of combustion of the constituents of the luminous zone mixeil with atmospheric air heated to incandescence. The flame of alcohol appears to be differently constituted from that of a candle ; but it has the same number of zones, although their relative areas are very different. The internal cone is very large, in consequence of the great volatility of the alcohol ; the luminous portion is very small owing, probably, to the simple manner in which the alcohol is broken up and con- sumed. From the feebly illuminating power of this cone the mantle appears largely developed. Frankland considers the luminosity of flame to be due entirely to the dense intensely heated hydrocarbon vapors. Recent re- searches rather tend to support Davy's liypothesis. Heated surfaces as well as cold ones beconie covered with soot when held in an ordinary flame, sc that the deposit of soot does not result merely fi^m the condensation of dense hydrocarbon vapors. If a rod is held in a luminous gas flame soot is de- l»osited only on that surface against which the issuing gas im- pinges, and not uniformly on the rod, as it should be if the soot wv)re the vapor of heavy hydrocarbon condensed by its cooling action. The most conclusive evidence for the existence of solid particles in a flame is afforded by the fact that although lumin- ous flames which are free from solid particles cast no shadows on a white screen when exposed to sunlight, ordinary luminous hydrocarbf)U flames, under similar circumstances, cast distinct shadows in the same way that these flames do which undoubt- edly owe their luminosity to solid particles, showing that they too contain solid matters. The luminosity of ordinary flames used for illuminating purposes is therefore probably due not only to the ignition of very dense hydrocarbon vapors, but also to the presence of solid intensely heated particles of carbon. vhen it is ,1 productfi jue mixed ;onstituto(l of zones, le intoriial lity of tlic •obably, to p and con- s cone the Lie entirely Recent re- . Heated soot when t does not ^di'ocarbon lOot is de- ng gas ini- if the soot its cooling ce of solid igh luniin- shadows ' luminous 3t distinct 1 undoubt- ; that they ary ilaraes y due not s, but also arbon. EXPEBIMKNTAL CUEmSTRj, 242. The Bunsen Burner. If air is Jet into the interior of a fl becomes non-h.minous, and does nlTT • '°'''°''' "'*^ ^^"^^ principle is seen in the Eunserb 1; wM ', "^' '''' ^^- surmounted by a wide brass tube a 2 T '"''''' °^ ''^ J'^^ several holes for the admission of a r Tl " '' "'^'^'^^ ^''^ the wide tube in such pronortioii th.Ml u '" '"^ ^'' ""^ "^ 't non-luminous flange. Tli hZorf ^^ ''" "* *^« *«? ^^^^h in laboratories for heating purpos ''>" " "'"?"'^"^ ^'"^^^^^^^^^ -ith a smokeless Hani' Teal 'n'"" '°' '""^"'''^^"- arrangements for heating by .as .re Z fl^'f^"^'' and other ' more or less modified to s.fit n' T "''' ^'"^^^^ burner., the holes, the gas burns u nix d " f/' '•""'""^- ^'^ ^^-"^^' smoky flange. These facts irns, T, '"' "^'^ "^'^ ^-''^ary that the oxygen thus C^IJ^"^' T^^^-^ ^'^ assuming hinos at once with the carbon Th' ' f '' "^^ ^'^'^^ -- if not incorrect. If, i„«tead of mixi 17 ^^f '^^ '' "'"^"^^^'^^0 indifferent gases as nitrogen Z dfo V ''' '^"^'-^^-' «"«^^ -e employed, the flame "ik^.v.^w'' " ^^^'^'-^^^-- acid a.flammable gases, such as hydro-^ror arl, '"^'"'"'"°"^' ^^'^"^«t the same effect. If the n.ixed :a es ' / '"''''''''''' P^-^^^e ved-hot platinum tube, the flam: alri '"''"' "^^°"°'^ « appears, therofo.e, that a luminll tl 17^ '""i"""- ^^ luminous m three ways- /D hv ^ '^ rendered non- the too rapid oxulation of 1 sepa^^t j'^ f^ ''"""^ ^' (^) '^^ vapors. ''^^''''^'^ -carbon or carbonaceous 243. Temperature of Ignition. Id order that any combusfiKl. u . m-stbel,eaW to a carta If;'"''"",'""^ •""". ■■'""... ne t«„„erature a, „Uck «» a '' Tt ''"'" "' "'»' ''-'■ t.:mrature ofi„UUo„, ^ th ^Z^. ■"" '' «*" «« »A'-«, This te,„,x.,,,h„, va„V " I r'*r'"™ ''■'' """ ™»- il*u.phoru« takes fire at about GO^C %;in- '"^■^^'"'^««- ' ^^'"Jst a jot of c<)al..,a.s ■I 1 1- 166 EXPEUIMKNTAL CUEMI«TRY. cannot be lighted with a piece of red liot iro)i. Whenever bodies are cooled below the teniperaturo of ignition they go out. Exp. 9.— Make a small helix of copper wire, and place it over the flame of a burning candle ; tlie flame will be immediately extinguished. The metal so rapidly a1)stracts the heat from the gases in the llame that their temperature is reduced below their kindling point. If, however, the helix is previously heated to redness, the flame wall not be extinguished. Take also a piece of fine wire-gauze, and press it down over the flame of tlie candle ; no flame is seen above the gauze, but instead of flame a cloud of smoke. Hold the gauze over a gas jet, light the gas above it, and gently raise the gauze ; it may be removed several inches, and yet the inflammable gas below does not take fire, the flame burning only above the gauze. 244. The Davy Lamp. The Davy Lamp is an important application of the principle in the preceding experiment. It is simply an ordinary oil lamp surrounded by a cylinder of wire-gauze. If this lamp is intro- duce 1 into an explosive atmosphere of fire-damp and air, com- bustion occurs within the lamp, but the flame produced by the union of the gases is prevented from traversing the gauze, owing to the rapidity with which the burning gases are cooled down in contact with the metal. If, however, the gauze should becf)me heated, its action ceases ; it allows of tlie transmission of the flame, and is powerless to prevent an explosion. 245. The Blow Pipe. The lilow-pipe is an instiument which serves to direct a stream of air into a candle or coal-gas flame. In its simplest form it is a tube drawn out to a jet and bent at right angles near one extremity. The introduction of Llio air within the flame at once destroys its luminosity by effecting a more rajnd combustion of the carbonaceous mattor. I li iver bodies out. lid place it nniediately it from the below their f heated to ilso a piece ime of tiie [ of flame a gilt the gas ved several ike fire, the 16 principle iry oil lamj) lap is intro- id air, corn- iced by the the gauze, i are cooled auze should ransmission Q. to direct a its simplest ight angles within the more rapid EXPEniMEWTAL CHEMISTRY. .^T -nes of „,e ca' dll .^ i Lr""'"'^; ^l- throe ,„.i„oi,,„i one, exton.lin,, so, e t " t ""'J"""""""'' ""'' "'« ">"<«• contain, air „ ■,,, ^t;!: ^ " '^,7'° ■' ''" '"°-'"'"- Tlm portio,, 0, a, „„„'?";! "": '«»; '» ">. metallic state. Now i,o,d the disoot: ■ ii; tfsho "', "r '■*""^^«'- "-We poim of the ,l„„e ^the ,1a A col ■ "'" '"^'°"" "« - 'lue to the oxidation of tW let "l! l''^^"''!""'"- This eiTeet 0J:«Uzmjflamr. The bh.w ra„„ ■ ' ' ''" '"" '" "''""' «w "-' i" tl,e .leteetio o Tod s harr?"""'«'^ "■'''"' ■"*- oi"".i!es nnder its infiaonces *'° "'°*"'* «''<»"'=al Q0.=ST,0.-S AKO .XERCsra OK C„A,™ „, .■~ nUo n^an- MnCl^ •^I'H'Sfanous clilorido. MnC]^ Man-ancse tetrachlo.ide. + 247. and 7- From Sodium ChloriH^ n>r Sulphuric Acid. '^''^^' Mangan Chlorine. iiixp. 2. -Mix 30 ^se Dioxid( ^'rams of sod m ' "'""'■'"« "■•■ii, «,, Hfinio 170 EXPERIMENTAL CHEMISTHY. :|| I amount of manganese dioxide, and transfer the mixture to the flask used in the kvst experiment. Now mix 38 grams of water with 60 grams of strong sulphuric acid, allow the mixture to cool, and pour it through tlie funnel-tube into the flask. In this case hydrochloric acid is first produced by the action of the sulphuric acid on the salt : — • NaCl + H2SO4 = HCl + NaHSO^ Sodium chloride. Sulphuric acid. Hydrochloric acid. Sodjiifc hJtUosen . ulphate. The hydrochloric acid then enters into reaction with the manganese dioxide, as before, but the manganous chloride is converted into manganous sulphate and hydrochloric acid by the sulphuric acid. The following equation expres.ses the final result but does not take into account tliat there are several stages in the reaction : — 2NaCl Sodium chloride. 3H.,S04 Sulphuric acid. MnOa Manjjriincse dioxide. = CI2 Chlorine. + 2H2O Water. + MnSO^ + 2NaHS0., Manganous sulphate. Sodium hydroi,'un sulphate. 248. Precautions. (1) Its action on the lungs is extremely irritating and injurious ; therefore, the greatest care must be taken to avoid inhaling it. (2) It should be prepared in a cupboard communicating with a flue, or out of doors ; or, if it must ))e prepared in a room, collect it over warm water and not by displacement, covering every bottle when full with a well-greased glass plate. (3) As soon as the gas is collected, throw away the water in the trough. (4) Should a little of the gas get into the lungs, pour a little alcohol into a test-tube, warm it, and inhale the vapor. A little ammonia sprinkled on a warm plate will get rid of the gas in *l»i» i><\/^>lll linm^r,,,, ^uiphate. ancse dioxide. iiXPKniMENTAI, CIIKMISTnv. 171 PR0PKJJTIB3. '«• Solubility in Water ■"t e ,v,ti, the h„„d, ,„., „,„,";„ .?'"" "" "«"•* <" «- - ;-ovi„g tl,o h„„„ „„:,, '■ : °;f 7 ';- '«l«n piaoe „,„ c-xp. 4— Pl„„.e „ |,„,,„i , ^onne i «,» t„,„,, ,„„,,,, ,,,.„'; ™^ -;i-' "Ho a sm,,il bonfe „f Exp. 5.~T«l;e a piece „f i ^->1 't -a. the ena so as to l^tM^^^ff ''"?" "'* *^ ^ i^^. :'"'l connect it l.y , p,-,,, ^^ r.l 1. ,V ''"'^'^'^^ ^'^ ^'^'^' ^"^e -l^ I'y.lrogen. When the ai "''"° "'^'' '"^ '-"le evoJv i;'-.eitintoa,,ott,eofei::>:;::tV'^^^ b -n wuh a sonK.vhat lununous L . ' "'"^ '^"'^^""^« to of hydrochloric acid. '' "'' «'^"'fe' ^«' «-hito fumes Chlorine, therefore n)iiof u »i'.«- f.-o„. t„e f.ii„,vi,,„:;::::;t"»''« *-'■-«-. a. -■« Exp.^6.-T„te a .,tr„„. „„, iiiid uuoLher of the ,!;!!"'";' .'"""•= "' =w™„e -- »'- or -.-.ivo,.,, ,,,,;;;:,: '"outh to 172 EXPEIUMENTAI, CKKMISTHY. month, and kocping tliom cIo«e togotlior invert tliom several times so as to tliiiii)ii;i[lily mixthein and cover with glass plates. Remove the cover from one of the jars and apply a flame ; an explosion results, and acid fumes of hydrochloric acid are pro- duced. Close the second bottle with a well-greased ground glass plate, and bring it into ditFused daylight ; the yellow color entirely ilisappears, and the bottle will be found full of hydrochloric acid gas. If the bottle had been exposed to direct sunlight almost instant combustion would have taken place with ex- plosion. Exp. 7- — Moisten a strip of blotting paper with warm tur- pentine and plunge it into a bottle of chlorine ; a cloud of black smoke is at once produced, iiccompanied by a momentary flame. The turpentine is coinpo-cd of carbon and hydrogen; the chioi Mi) combines with the hydrogen, setting the carbon free ; fhv.P .-- CoHie + 801., = IGHCl -f 100 Turpentine. Chlorine Hydrochloric acid. Carbon. Exp. 8. — Fill a long-necked flask, with water and saturate it with cidorine. Place it moutli downwards in a bowl of water and expose it to direct sunlight ; in a short time bubbles are seen rising, and a (piantity of colorless gas collects above the liquid. Invert the flask and test the gas with a glowing splint of wood ; ihe splint is rekindled and therefore the gas is oxygen. Add litmus solution to the liquid in the flask ; the litmus is reddened. The chlorine has combined with the hydrogen of the water, forming hydrochloric acid, and setting the oxygen free. 251. Bleaching power of Chlorine. Exp. 9. — Moisten a piece of nuiddei >lyef fi ho,„e.e,„,„ „f ,„„,,„ ;, '" "'.°""» '»■""■■• .l...«n,l» .,„ Exp. 10 —Will ,■ ", iM.iii,.,.. Hence as a rnio AIi,i,n-a/. r / ^ Exp. J2.-p„„ ,„„ I, '"^taiiic antimony in ^aj 'iU ^, ^ ^^ IMAGE EVALUATION TEST TARGET (MT-S) fe /> .'!'/ 4' :/. /a 1.0 ^i^ I.I ? lis IIIIIM M 2.2 11:25 III 1.4 m 1.6 riluiugi-cipiUL Sciences Corporation 23 WEST MAIN STREET WEBSTER, N.Y. 14580 (716) 873-4503 •1>^ V qv :\ \ ^*-■"»■ °-»^-» ■■" ti. Kg + 2HC1 = oK-p, This very important acid has recoivp,? fl. p n • ■^P>rits of salt, muriatic acid chTrhv/ ^'^"" "''"'^'^ Hiloride. ' •^'^^oiohyJnc acid, and hydric '"IJition of a diop of sil™ rn ! f .«l'l»"l.olog,.a|,l,y. ""'"P^uiKls arc used i„ ,„„,|i„i„„ SECTION IV. IODINE. ^yn^ol, I. Atomic ^Veiqht 1^7 dor- n5.;. Pnm^X RATION. 267. From Potassium Iodide <5M1r^t, • * • Manganese Dioxide. Sulphuric Acid, and Exp. 1. — Dissolve a few crv^f.lo .4; v, ^ • water i„ a t,,t.i„he, „„d add a, f'""""" '"''■''''' '". "' color is i„„„ediatoi; produced and H ""'"' " '"■""" the liquid. Alio/tL mHi I . '''" "' »1"""" frou, liquid Ann], „ ' 'r r '° "'''"■''"• »"'• l'<"»- «lf tl.c the tube i„\,acM,r.'„rell:™-'°^ 7 '"« "" I'"''' of loduie IS widely distributed throu»l, ni'tur. . ■ qua.„,.ties, aud always in con.binati ; ,1' ""i ' ' '" ™'"" sodium, and magnesium. It occurs in ,7 f"^"'"""'. water, from which it is s»,n°ated .f. .?"''°""°-^ '" ^'=- -weeds. Thescsea-wccd; :»;,;::';;■■'''''•• ''^ ™*- -h called ,,,, whiC. contains l::,' I '^od -'.'.rtrf '^ "" -»-. M«I„ etc. The kelp, „,., preHiaina,:; r^ 1 I't 182 I! ! '■I EXPKRIMICNTAL CIIEMISTUV. lieatod with manganese dioxide and 8ul[)hiii'ic acid, and yields iodine just as potassium bromide yielded bromine. Tlie reactions are similar. Iodine acts as an irritant poison, but in small quantities is used in medicine to reduce glandular swellings, etc. 268. Tests. — Dissolve « few grains of potassium iodide in two or tliree litres of water and a little clear .solution of slarcli paste. To this add a little free chlorine or a few drops of chlorine water, to set free the iodine, stir it, and a beautiful blue tint will be observed. The blue tint will disappear on heating, but will return on cooling. SECTION V FLUORINE. Symbol, F. Atomic Weii]ht, 19 {19-1). This element has, perhaps, never been obtained, and :ortainly has not been satisfactorily examined, in the free state ; for as soon as it is liberated it attacks and combines with glass and almost every substance with which we are acquainted. It is the only element that has not been combined Avith oxygen. It commonly occurs combined with calcium, forming the mineral fluor-spar or calcium fluoride, CaFg. It is also found in the enamel of the teeth, in the bones of mammalia, and is said to have been detected in the blood and in milk. 269. Hydrofluoric Acid, HF. Exp. 1. — Make a small cup out of a piece of thin sheet-lead, place in it about 10 grams fluor-spar, add 15 grams of strong sulphuric acid, and apply a gentle heat ; fumes of hydrofluoric acid will rise, which are extremely irritating to the eyes. The reaction is — CaFa + H,,S04 = CaSO^ + 2HF Calduui fluoride, Suli'hiu-iu w'ul (Jivlciitm «iiliihivtu. Hyikofluorie aokl. I and yields lio ruautioiiH nantitios is n iodido in )n of slai'cli of cliloi'iiiu il blue tint loating, but id iortainly tato ; for as .li glass and I. It is the in. orming the also found lalia, and is I sheet-lead, IS of strong liydrofluoric eyes. The 2HF f'drofiuorii-' acid. EXrKIUMBNTAL CHBMI8TRT. jgg EXD2 W '' '^"^ ^'^'^^ "«* ««t "P"" lead. -- to cut ,.ito through to tl Xs ' Wr r: '' ''''-' J'^'«le" cup, waxed side downwmh 1 . '''"*" "P"" *].o •■e'"ove an.l dean with a r^ d , S '' '' ^"' ' ^'^^^ '"'""*-S ;;i'^ ^0 found eorroded . .:;e;Sr L:, *^ ,^''"^\^-i-^tine ; i; the design will renuun engraved on tl- " - " "'"^'' ""' - en„loyed in this way to e cTtlL ' ", "';"• ^^'^^-«"-- acid eudioineters, etc. ' graduations on thermometers, 270. Comparison of the Group. one is present all are prient Thov" n ' '''" ^^^^^- W'-- the single compound wh d Ich olf" ""r' °^^"'^"^^' -^ aci.!. Their nitrogen eompoun a «:::;"• ' '^^^•^""^" '^ ^ a renK.rkable sequence of properties in 0^^ ^''^^ ^^'"^it ^^-avity, and in atomic weighir '"^ '°^^''' ^" ^P^^i^c QtrESTioi^s Ai.n exercises ok chapter « 1. Express in 8vmbnl« h,^ .. "^i-TER vc. 0W«ri« acid ta heafed rth l;r„r J"'* °°™- "■» M„. proportion, by .,i«h. „f ^.r:,:^-' dtl'd u"'"' "" "'"■™ .cij.^S,:i;r^::r,„- -^^^^^^^^ =»„ d. ,., Planation. ''^Periments m proof of your ex- 4. Explain the action of chlorin« fn^ caustic potash. ""^ ^"^ "P«" slaked lime, (6) on 5. What is chloride of hme? Evnl^Jn u • how It is applied in bleachin. cotton fT '* " P''"P^'^» and «tains of lamp-black or of ni rate "sV;^^^^^^^^^^ ''^'^"^'^ ^^ -P- means ? Why so ? '^'^^' *^ ^- removed by these 184 EXPKIlIMr.NTAL CUKMISTRY. G. Chlorine will bleach vo^etablo colors. How is this action of chlorine usually explained ? 7. Describe the effects produced by chlorine on the followinj{ substances : — Indigo, copper foil, powdered antimony, powdered charcoal. 8. State the useful applications of chlorine in the arW, 9. How much salt is recpurod to make 28 litres of chlorine ? 10. Sketch the apparatus rei^uired for preparing small quantities of hydrochloric acid. 11. How may hydrochloric acid be prepared from its elements ? Describe ditiorent ways of effecting the union. 12. What volume is occupied by 78 grams of gaseous hydro- chloric acid ? 13. How many j^ramf* of hydrochloric acid can be obtained from 100 grams of salt ? 14. How would you prove that hydrochloric acid gas contains chlorine and hydrogene ? 15. How is bromine prepared ? In what respects do th« chemical properties of bromine resemble those of chlorine ? 16. Where does iodine chiefly occur 1 Give a short account a its preparation. 17. In what substances is fluorine found ? You wish to te.t in aqueous solution for hydroflueric acid. Describe how yra would do 80. .y '{w lis action of CHAPTER X. SBOTION I. PREPARATION. 271. From Iron Pyrites. a ^fz t:^:; iHTizi'f:':'' r^' -^ p-* ^^ into tl^e tube with the thumb .at'n' ''"''''''"^ ^'^« '"«"tJM,f orovvii liquid. This hquid is tho ll '"'"'"■^ ^ ^«''d'«I^ Iron pyrites. Ma.n!' * + ^3 Ma,.net.c pyrites. Su,ph"„_ 272, From Native Ore. Almost all tlio sulnhur of n .";-,i w.lh oa,.tl„ „„„ otl,„, i™„„ il^'^if ""'°™ " i» found l"t w,tl> a small ,,„a„tity „f ,„„ ' ' . ^ '' °" i^ Placed in a allowed to smoulder; the sidphu , el ^ ""' '"'"''"■-^ "".i <» the pit. wta„3 ij j^ ,^j,_^^,';;;» "-'t» aud eolleet. on lhefl„„r liJ5 186 EXPERIMENTAL 0HEMI8TEY. 4* % 273. Refining Sulphur. The crude sulphur is meLed in an iron retort, the vapor pass- in" into a large brick chamber, where it is condensed at first into a light crystalline powder termed /owers 0/ sul^fhur, just as aqueous vapor fulls as snow when the temperature suddenly sinks below 0°C. After a time the chamber becomes so hot that the sulphur condenses in the liquid form, and collects on the floor, whence it is drawn off and cast into cylindrical moulds, in which state it is known as roll sulphur or brimstone. 274. Liquefaction. Exp. 2. — Heat about 20 grams of roll sulphur in a large test-tube; the sulphur begins to melt, and soon forms a clear mobile liquid (120°('.) On continuing the heat it darkens, gets, thicker, becoming so viscid (at 220°C.) that the test-tube may be inverted for a moment without spilling any of it. On further heating, it again becomes clear, especially as the boiling point (440°C.) is approached. When this point is reached, slowly ponr the sulphur into cold water ; the mass of sulphur in the water is translucent, plastic, and can be moulded by the hand into various shapes. In this state it is termed plastic or amor- phous sulphur, and is used for making moulds of coins, etc. When dry, it gradually loses its plastic properties, becoming opaque and brittle. 275. Allotropic Modifications of Sulphur. (1) The Crystalline Odohedra. Exp. 3- I'^t about 1 gram of flowers of sulphur into a test- tube and pour over them 5 c.c. of carbon disulphide. Loosely cork the tube, and hold it in warm water for a few minutes, shaking occasionally ; part of the sulphur is dissolved. Filter the liquid into another tube, and pour a little of it on a glass plate, and leave it to evaporate ; small, transparent crystals of sulphur soon apitear. When examined through a magnifier the«e crystals are easily recognized to be right rhombic octohedra. EXPERliiENTAI, CHEillSTRy. 187 (2) The Oblique Prismatic. been formed on the surface Z " 'T ,"' ' "''^^ ^''"^^ ^''^^ a heated glass rod, and ^u. o, t Z '1" '^ '""'^ «^-^' -'^^^ H"id. On removing th. cru t ' , , '^'l'^^'"'"' ^^^ich is still -ucible is found lin^d l^t^tf f' ''^ ^"^^"^^ ^^ «- of sulphur. In a few day h^ 1 7 "' ^'™«^^'^ -^^tals and are spontaneously con e ' in t! " '"^ ^'^'^ ^^^-^^'--y octohedra. "^ '"^^ ^^^ aggregation of minute (•^) The Amor ^otis. l'^™ in tl,c sulpha vaL V , i T""' ""■"' "'" '"'o "iH into c.,,..„„s sulphiJe Cu S ""■""'^'^'"='^"«'^. ^"'K oonvcrkj '^'"' l'l'"'ged into sul],hur vano 1 " '^^ I "'"' ^^'''^" '"^^^ed Exp. 6.— Mix a small (luaiititr „f ,„ q"»"Hty of »di,„„ ca,.|,„Lr i 1 «''"»»■'""'■> equal " 'hu, f„r,„„,,, ,„,, ,,„.; ,„ ;"-'''° '''"";!"Pe; »o,liu,„ „„p,,M^ quantity of ,„,,,„ J " "' ;=''t .Ivor co„, TIto s„,allest a brown «tai„ „f .^.Ui^^^^^X'^ ''^^ *» '"nation of ---.eo,..i,.,uH„ao,ifr:t"::i;:;;',„x,;^'he 188 BXPEUIMKNTAL CHEMISTRY. SECTION II. SULPHUR DIOXIDE. Symbol, SO^. Molecular Weight, 64* PRKPARATION. 279. By burning Sulphur in Oxygen. The combustion of sulphur in oxygen has already been de- scribed (Art. 41), and its . 'ribustion in air needs no special description. Neither of th^se methods affords a convenient source of the gas for experimental purposes, though the combus- tion in air is very useful when we desire to diffuse a quantity of the gas through the air of a room. 280. By the reduction of Sulphuric Acid. Exp. 1- — Introduce into the hydrogen flask 30 grams of copper clippings, add through the funnel-tube 60 c. c. of strong sulphuric acid ; arrange the flask for collecting the gas by down- ward displacement, and set it on a piece of wire gauze on the retort stand. Heat the mixture, and when effervescence begins take away the lamp. The gas coming off has the unmistakeable odor of the gas produced by burning sulphur in air or oxygen. The rate of the filling of the bottle mny be ascertained by means of a lighted taper, as in carbon dioxide. The reaction is ex- pressed by the following equation : — Cu + 2H2SO4 = CUSO4 -f 2HaO + SO2 Copper. Sulphuric acid. Copper sulphate. Water. Sulphur dioxide. This reaction takes place in three stages : — (1) The displacement of two atoms of the hydrogen of the -:n1i)linric acid by one atom of copper; thus : — Ou -+- IlaSO^ = CuSOi \ Ha Copper. Sulphuric acid. Copper sulphate. Hydrogon. ady "been de- ds no special a convenient I the coinbus- a quantity of 30 grams of 3. c. of strong gas by down- gauze on the scence begins uniistakeable ir or oxygen, led by means action is ex- ■ SOa ilphur dioxide. rogen of the •oa;on. H2SO4 -j. J£ _ Sulphuric acid. HydJen '\,,^'^^^ + ^aO /q\ Ti , S-'Iphurous add. WuL- (3) TJie breaking up of tl.p . , , ^J'o-xide an'"- tlie chimney be lin.itcj a, f-.n „ , I , '° •■'"' ''"I'l'Ir I" 'hat the chteney .houU I tZ tl, t " " "''" °-»"«"' tep full of the g„, „„„, „,^ w. ', 1^1, " " t" " "'"^ •» kmdhug temperature of the soot ° °°°''"' '"''<'>'' "'o 282. It is heavier than Air. Exp, 3. — piacj ^ buniitia tn„ • "bottle of eulphur dioxMl :,poT:;° T T''' """'^ »■"' P"" The molecular weight of the L isCU T' '' °^''"S'">'h,,i. ■^ V=3. (H = I, or more ^C:::'X:;TZ:'' ''"''' 283. Solubility in Water. Exp. 4. —Invert a bottle of f}i« wards in water -r,' ,-u ? ^''^^' P''^^^ i* mouth -I .-, .^aier ..rxu Withdraw the nkfp • ti -'-"^^n 'lovva- «- Shp the haud beneath the Jo2 ^ft Zi ""' '" "'° " oocwe, remove it, 190 EXPERIMENTAL CIIEMISTRT. / 1 • ' .1 ;1 I'. shake briskly, and again place it mouth downwards in water, repeating the operation till the water has nearly Filhul tlie bottle. Water at 0°C. dissolves about 68 times its bulk of the gas. Now add a little of this water to litmus-solution ; it immediately becomes red, showing the presence of an acid. Sulphur dioxide is, therefore, an anhydride, as has already been shown in the experiments on oxygen ; thus : — SO2 + H2O = H.SOg Sulphur dioxide. Water. Sulphurous u id. This acid is so unstable that it is decomposed completely by boiling into gaseous sulphur dioxide and water. 284. Reducing Action. Exp. 6. — Add a few drops of potassium permanganate, KMnOi (Condy's fluid), to some water, and then add sulphurous acid; the beautiful purple color is destroyed. To the bleached liquid add a few drops of barium chloride ; a white precipitate insoluble in acids is formed, showing the presence of a sulphate. The sulphurous acid has deoxidized the permangiinate, forming sulphuric acid, which has combined with the metals forming sulphates. Exp. 7. — Place a few violets, pansies, or red roses in a bottle of sulphur dioxide ; the color is soon discharged. Now dip the flowers into a very dilute solution of caustic soda or sulphuric acid, and the color reapjiears if the action of the bleachin<^ a^ent has not been too long prolonged. The manner in which the sulphur dioxide acts in this case is not well understood. It may be that the dioxide becomes sulphuric acid in the presence of water, the liberated hydrogen combining with the coloring mat- ter to form colorless compounds ; thus : — SOo + 2H2O = H2SO4 + Ha Sulphur dioxide. Water. Sulphuric acid. Hydrogen. Thus the bleaching action of sulphur dioxide, in this case also, is thought to be a reducing one; just the opposite to that of chlorine, which is an oxidizing action. - ■aPEniMBHTAL OHBMlSIRr. 'loes not, like chloiinc ,ll ** , '''""^ ™n,pou.,j3. It 0/ the ,el J„ CO t;l;; Ztj'' ! '"""^ ■ '"'" '■="™J-«™ »'kaiino soap, is an iUnZt o " 'tit" E „': " n ' """■ "- restore tho color in so,„e cases. iCL Z ""f ''°'"'" "''«' to oxidize the sulphurous aci,l I 7, "'P'"* """'■' '' bleached rose be LgZo^l^/jTV: '"'"■ ^''"'' « = vapor o( red fu,„i„,. nitric "at" "^ " chlorme ,,„s, or i„ th„ '0 -pHurie acid, a^d the\::itr jr^stlotr' '-' pin:f'd;„°rei/r;o:frf:u,i"""''f ''"P----S..- ™.p.«.ed,„rprevr„t:;t:::r^::,tt\:dr'T''""^ fermentation. Sulnliur f?inv,vi« • , "" ^°^ stopping a». is often e^pio,'::^".*;^:;: t : t:^, *'''f' -: disease, have been treated. For this nr„r ,t °'"""°"''"' oarefully closed, and a quantit/o( nlplZ d „ ^ °'"""' "" in the room by throwim, sulnh,,. , [ '"'' " Senerated an iron vesae,,' After twrnXbu^te™""' ""f""'^ ^ and cleaned out °™ ">»"»"' may be opened 286. 1-iquefaction. Exp. 7.— Pass a stream of snlnhnr diovM. ■ . mmersed in a mixture of po„n-'-d il T , '" ° ''"-"''"= the gas is condensed into a' Iriess Iwie r '• ,'" ^'"^' P"*-' ture of - 10-0. To preserve "t , Z T"' "' " '™P™- sealed up. For this purp^It ke , ' ""f""" " ■""»' ^ one end, heat it near thTot he 'nd Tf *""' '""'■ *»» *» just admit a son,ewhat «ne deliveryTu"'';" °? '"' " ^^' "a.0. part o. .. .he .ith' t^I M^pltrt; tit Mil s !' 192 EXPKUIMKNTAL CUKMISTUY. as to seal it. Tlio sulphur dioxide will remain liquid in the closed tube. The pressure exerted by its vapor is rather less than 2 "5 atmospheres; heucc it can be liquefied at ordinary temperatures if subjected to such a pressure. 287. Sulphites. Sulphurous acid, like carbonic acid, contains two atoms of hydrogen, both of which may be replaced by metals; it is therefore a dibasic acid. It forms two series of salts called sulpJiites, in one of which half the hydrogen is replaced by a metal, and in the other the whole of the hydrogen is replaced. The first series of salts are termed acid sulj^hites, and the latter normal eulj)Jiites. Ex. : NaHSOa is acid sodium sulphite, or hydrogen sodium sulphite, and NagSOa is normal sodium sulphite. > 288. Tests, — (1) All sulphites are decomposed by dilute sulphuric acid with elTervescence if the solution is strong. The escaping gas (SO2) smells of burning sulphur. (2) When a small quantity of a sulphite or of sulphuric acid has to be recognized, the following is the best test : — Add to a few pieces of granulated zinc in a test-tube some dilute hydrochloric acid till there is brisk effervescence. Then pour in a little of the liquid to be tested, and hold a lead acetate paper in the escaping hydrogen. Any sulphite present will be reduced by the nascent hydrogen and converted into sulphuretted hydrogen, which will stain the paper ; thus : — ■ H2SO3 + 3H2 = HgS + se^o Sulphurous acid. Hydrogen. Sulphuretted hydrogen. Water. SECTION III. SULPHURIC ACID. Symhol, H^SO^. Molecular Weight, 98. Sulphuric acid is the most important and useful acid known, probably the most important of all the chemical compounds that nearly ull the other acid, .re nv , '^ ' ""''"^' "^ ^^ PREPAKATION »d^s:n/„~'!' :,';':!;:^:' "'■"■'■" -'"«. —e the 3topp„ TO. are P-duoe/'V' ;!;:;,''" ''^'"'""' °' ^'^ -r red fu„,„, , ■,„ ,,i,„„„ ■. T' "'" ^'°W»'' .-"'d sl.ake; the "'-ir; thoi, L„« :" 7; ">« *W-- and „,,,„„ *aki„„ will, ,„„^ more sTl',' ?'"' ^'^ '™'»ved by "•.a-Kes can he ..„pe„te., Z^^^Zjl^^L """ f "'^ »' «' nar,c oxide. Now test the lin,,,-. T„ t f "^'^ '''""'8° ■>' "Idoride, followed by hy,h-o jw ,"'° """"^ ""'' t»*.m fo^ed, ,-,KUcath,g the — V ^ ,i:,.;:'"'T?"»'-= ttr ""' '■- '"»-- ^-" Cd ;: x^.j:x 2N0 Nitric oxide. ^2 = 2N0„ O^ysren. Nitric oxide. iiien the nitric peroxide reacts with the .„! i thus:— "" tlie suli^hurous acid; '«*pi;;,„,.+ 3„,^f2»« = ,.,tfj„. + NO The reproduced nitric oxide then takes , , , "* liil exi'b:i{imental ciiemisthy acul is roqiiii'cd. The sulphur dioxido formed is conveyed to n liirge U'adeii cliainber, into wliicli steiiin and air are also continu- ously admitted. At tlie back of tlie furnace in wliieli the pyrites is burnt, a small vessel is placed containing the materials for making nitric acid. Sulphuric acid is formed in large quantities, and dissolves in the stratum of water with which the bottom of the chamber is covered. The reactions which occur are but imperfectly understood; the nitric acid is, however, apparently decomposed by the sulphurous acid in such a manner that nitric oxide is produced ; tlms : (1) 2HNO3 + 3S0., + 2H2O = 2N0 -f 3H,,S0i Nitric acid. Sulphur dioxide Water. Nitric oxide. Sulphuric acid. The nitric oxide combines with the atmospheric oxygen, which is admitted into the chamber ; thus : — (2) 2N0 + Oo = 2NO2 Nitric oxide. Oxyjfcn. Nitric peroxide. This nitric peroxide is no sooner produced than it is reduced again to nitric oxide by the sulphurous acid, which is oxidized to sulphuric acid ; thus : — -f NO, = H2SO1 + NO Nitric peroxide. Sulphuric acid. Nitric oxide. The nitric oxide again absorbs oxygen to form the higher oxides, which again enter into reactions with the suljjhurous acid, and so on continuously, the nitric oxide simply acting as a carrier. Theoretically, therefore, a limited quantity of nitric oxide should suffice to produce an indefinitely large amount of sulphuric acid but practically this is not the case, as a certain quantity dissolves in the sulphuric acid on the floor of the chamber, and a certain amount escapes with the nitrogen. The sulphuric acid thus produced is very dilute, and in order to convert it into the sulphuric acid of commerce it is heated in glass or platinum retorts until a large portion of the water is driven off. (3) SO2 + Sulphur dioxide. H2O Water. convoyctl to n } iilso contimi- cli tlio pyrites iiiiiterials for rge quantities, the bottom of iderstood; the he sulphurous -I ; tlms : — Sulphuric acid. )xygen, which le. it is reduced Jh is oxidized h NO Nitric oxide. ligher oxides, ous acid, and : as a carrier, oxide should dphuric acid, tity dissolves and a certain and in order r is heated in the water is KXri.;rilMi;NTAL CllKMiSTRy. 195 290. Affinity for Water. m«t.,n, will, a small l.„ ,, , T •' ' "' "•"'■•'■• '""I »'"' «"> aopam e out, which have the o„,„p,»iii„„ , f^, „' n'*: ' aci.l. On w„,ki, : I, ' „ „ t ■ -"'""u""'"' "'""■« ""'Pl'""' i« cooled byitso™ , ; „''° "'; "V'^ha-ted and the water as the vapo" produce, at oT "'f"' I ""'''""' "'"'''"<'■■ »'"• the evapolati^n IZlZ VZ^^Z^^f:"' """""'' -"• water is lowered to the freezing point '""P"-'"™ of the mell; XZr ^■""""""^^ ""'-"-^ *a Ele- the'^'ne ! Tlll^tir'l:' If ° ^™ "'" ^""'■""■■■« -«-■ and the reaction is!! '"™ '' """''»'"='' <>' ""ody fibre, Wocrfyflb,.. Su.,hu,l„dd Cats, + H,SO„6H,0 Exp. 4.-Make a stron syrTof ,„:;'• '"';-* «■ abont one-half as much of stro'JL ! ' '""^ """ '"'" " into a buit, ,„„ss of porous cluu^r Th eS™ ■ ""™''^' Oi2H„.,(),j Sus:ar. Sulphuric acid. Carbon. ^2SO„liHaO Diluto Sulphuric acid. '*» i>,* 106 RXPKRIMKNTAL OriKMISTUV. 292. Sulphates. The salt? formod by ropladn- the hy.lrogoa of sulphuric acid l.y u u.otul are tortnod 8uli>hahs. As tliis acid, like .sulphurous acid, 18 dibasic, two series of sulphates exist. By displacincr (Hie-half of the hydrogen acid sulphates are formal, and normal mlphatos are produced by displacing the whole of the liydrogen. COMMON SULPHATES. SYSTEMATIC NAME. Sodium Sulphate . . Potassium " Magnesium " Calcium " Zinc Copper Ferrous COMMON NAME. Glauber's salt. } FORMULA. NaoSO. MirSO^ CaSO^ Epsom salt / Alabaster, irypsuui, plas I \ tor of Paris ! VVhito vitriol "' I y„sn i31ue vitriol CuSO Green vitriol or copperas FeSO* 293. Properties of Sulphates. (1) All sulphates are soluble in water except barium sulphate, lead sulphate, strontium sulphate, and calcium sulphate which is a little soluble. (2) Barium chloride or nitrate added to a solution of a sul- phate in wa^er gives a white precipitate iusolublo in hydrcchloric acid. 8 E C T I O N I V. SULPHURETTED HYDROGEN. Symbol, H^S. Molecular Weight, SJ^ PREPARATION. 294. By the action of Acids upon Sulphides. Exp. 1.— Fit up the apparatus for the preparation of hydro- gen, attach a small fljvsk as a wash bottle, and place iu it a little KXPERIMENTAL OnEMISTRT. jgy «"Jl>hunc aei.1; the ,as ^ • i,' ," 'f ' ""^^^ ^'-'^'^y of -ter, and «„ t,n-oo "o. ZZuL ''T' T''' '''' -"" FeS + K«n Tho roact.oa is- Ferrous .u,ph„o. Sun^u^lZa ^, ^"^^' + H,S ferrous Bulphato. Sulphuretted hyclrojfon, PnoPEU'l'IES. 295. Acid Character. «-' «.e ga, „„. feeu„a:l,;':;|,„';;L? "°'' ™'" "■"• *-"'■« 296. Combustibility. =«lpl.«r is depositor, „,. Ti ,/:,"",'; -'-="i*«l, »...! 2H3S J_ Q Sulphuretted hydrogen. Oxy.e'n. " Su.p^hu "^ ^^^^ 297. Solubility in Water. ottlo underwater and withdraw elv'T" ''f' "'-^-^ ^'- sl^owing that the gas is soluble in ^v. rooms. A little chlorine lihoratod from chloride of lime Uoudorizos an atmospli(u-e rendered otfonsivo by this gas. 299. Action on Metals. Exp. 7.— Place a drop of suli)hiir,.ttod liydrogen water upon a bright piece of silver ; .the metal quickly becomes black. The reaction is — + HaS «= Ag^S + h; Sulphuretted hydrogen. Silver sulphide. Hydrogen. It is on ti.is account that silver plate is so easily blackened by the air of towns, whicli is usiiiilly contaminated with sul- phuretted hydrogen. An egg spoon is always blackened by the sulphur from the egg. Silver coins kept in tho pocket with matclies become black. The black sulphide thus formed may be removed by rubbing with strong ammonia or a solution of potassium cyanide. 300. Action on Metallic Salts. Exp. a— Dissolve a small crystal of If^ad nitrato or acetato in a test-tubi> half full of water, and m drops of sulphuretted hydroge . aif.-i black ; thus : — Pb(N03)2 -f- H„S = Lead nitrate. Sulphuretted hydrogen. t,ead sulphide. Nitric acid It is in this manner tliat paints containing white lead (car- hMni>t.p. of lead) are darkened by exposure to the air of towns- lis solutioi 'K'.! a few Uie solution becomes PbS -f Lead sulphide. 2HN0., BXraiUMBNTAL C|/B«ISTl,V. , „„ Poiiilii.gi,, whethm- in ,i| ,„ „ , into dasso... "'"'' """^ '«' wparatiiig m„t„jg lead ncelato, tartar o.i.rtio ,i,7o ,^1, " ' '"'"^' ""'l'''"'". Add a few drop, ..n^^^Z^^'^l":"'"' '""■'"' '"l"'"'' appnratim, wasliing the Ion,li„„ ...i , . " "™'-'™'i"g 01;.crvc and tab,,,! tiL t";!|";f ""'° ''"'™"" «'' ^lutio,,? .1.0 ad,lit,o„ of I, •,l,.„ol,K,;;„" ; ,""' -7 «"IiA".o> „*;,„„, O'».vo and tal„,lat<, tl,o "„„ ' """ ^ "'""•°"-' l-d,.„g„„. .I.-P3 of hydr„„i„„,,eacn,.a„„„b,„„j^Vo :::„;;:' ■■' '""• 301. Poisonous Character— WJ ;..;-wiu,ac™.d..a.w„,„,„eofai::,;:i:t;'::^::::: i.o'";olreH3':;r,-;r:,;;lr'r"''"'''^' '-'■■»- -^ I«-ul acetate. ° "^ ''" l''^P^'f "moistened itJi 1. In what condition and i„ wh.f l v.- § ^:!uM^«K f: 200 EXPERIME5NTAL CHEMISTRY. Ill oxyj';; HLr s' ^'^" ^"'^'^"^ '-- ^«^ ^" ^^^' ('') ^" and su^tV" ''""'' '"" corresponding compounds of oxygen 7. Express by equations the reactions which occur when strong sulphunc acid xs heated with (a) znercury, (6) sulphur, (c) copper' 8. Explain the bleaching action of sulphur dioxide 9 How may the process for preparing sulphuric acid be iUus trated on the smell scale ? Sr tch the apparatus 10. Explain fully the theory of the formation of the sulphuric acid m the leaden chamber. Give equations to represent the rT actions supposed to occur. JJ" Zt^l ^"7" "'^'" '"^P'^""" ^°'^ '' ^'^^ '^P^'^^ to the air ? as sugaT? '' '°*'"" of sulphuric acid on organic matter, such 13. A sample of vinegar is supposed to be adulterated with sul phunc acid. How would you ascertain the presence of sulphurt acid in vinegar ? "'i^uuuo 14. Enumerate the chief properties of sulphuretted hydrogen ? 15 How would you prove that sulphuretted hydrogen is a com- pound of sulphur and hydrogen ? j o » c v,om 16 8 grams of sulphur are burnt in air, what volume of sulphur dioxide IS formed ? ^ 17. Howmuch copper and sulphuric acid are required to make 1000 grams of sulphur dioxide ? 18 16 litres of hydrogen diffuse through an apparatus in 100 minutes, how much sulphur dioxide will diffuse under the samP conditions ? 19 What weight of iron sulphide will be needed to yield a litre of sulphuretted hydrogen at 0" and 760 mm., and how much air will be required to burn this gas completely to sulphur dioxide and water ? 20^ An unknown volume of sulphuretted hydrogen requires 110.34 c.c. of chlorine for complete decomposition. What was the volume of the sulphuretted hydrogen ? CHAPTER XI. SECTION I. ^HOSPHOKUS. ^ ^^' ^'^''''^<'r Weight, F^, js^^ PREPABATION with water or treated with .1 u "'' ^'« «>"^er boiled ^-^^^tin. The, are ti.en IX^tt ^^""^ *^ «'^^-«^ the P-dered and digested with d lute if ^ "'^' '''''^^ ^ ^^el, "^S reaction takes place :- "^P^^""" ^''^d. The follow- Bone ash ' Suln! ^'^^* = OaH.rPO ) ^ ^ W-,, a„Jova,„,,J,, JITJ'TVT "■» '--""We '» heated to ,.ecl,«.s, th„,;_!'^ ' °"'' "''""I' »« »lid residue Caic:.,n: Superphosphate r», • ^^^'^^3)2 + 2B Ck Tbis salt i, .,„ ,„ ~ ™ 7""'* ^-' over and ,s collected in „tcr :_ "'" '""'Vl'orua pa.« 30a(PO,); Calcium inetaphosphate. + 100 = Charcoal. '. + Jt^2^' + "CO Phosphorus, PROPBRTiEg Great care ia ro/m;.. 1 • IV catch I ^ '" ^^Ponnientincf with nh , ty catch hre even when lvi„., on , ,.£ P^°'P^^«^'"«. Calcum Phosphate. Carbo„ wonoxide. ■»a.v catch «,.;:,:, r°'""°""'«"' ^iept and cut It und «f water. 201 ^ paper; it should 202 EXPERIMENTAL CHEMISTRY. 303. Inflammability. EjXp. 1. — Pour a small quantity of carhou (lisuli)lii(le into a test-tube, and add a small piece of phosplioius; it rapidly dissolves. Place a piece of blotting paper on a ring of the retort stand, and pour a little of the licjuid upon it ; the carbon disulpliide eva])onitos, leaving the phosphorus in a minute state of division in which state it ignites spontaneously. Exp. 2. — Put a piece of phosphorus the size of a small pea on blotting paper, and sprinkle over it some soot or iinely powdered charcoal ; it melts after a short time and spontan- eously inflames. 304. Phosphorescence. EjXp. 3. — Put into a bottle a quarter of an ounce of ether and a piece of phosphorus tlio size of a small pea, cork the bottle and let it stand a few days, frequently shaking it. P(.ur some drops of this solution on the hands and rub them quickly togetlier ; the ether rapidly evaporates leaving the phosphorus upon the hands in a state of minuie division. The more finely it is divided, so much the more easily does it combine with the oxygen of the air. During this combustion it diffuses a white smoke and a faint light, causing the hands to shine in the dark ; hence its name {Fftos, liglit, and few, I cx'Ty). Exp. 4. — IVfoisten a lump of sugar with the solution of phosphorus in ether, and throw it into hot water, the surface of the water will glow in a dark room. 305. Combustion. Exp. 5. — The combustion of [jhosphorus in oxygen has already been described (Art. 39). The combusti(jn may also take i)lace under water. Put a piece of phosphorus about the size of a small pea into a wine-glass and ])our hot water upon it until the glass is half filled; the phosphorus melts, but does not ignite, as the access of oxygen is prevented by the water. Rut if air is carefully blown by the mouth through a glass tube upon ilphiile into a is; it rapidly 1 ring of the b ; the carbon minute state f a small pea oot or iinely and spoutau- unce of ether )ea, cork the ing it. P(,m' them quickly e phosphorus 10 more finely ;ombine with it difru8(3s a 3 to shine in cviy). e solution of the surface of oxygen has ion may also •us about the water upon it but does not water. Rut isa tube upnii EXPERIMENTAL CilKMiSTRV tJie bottom of the ch,, . ; ■ 203 in the darlc. ^''''' -^^-^- wiii ensue. .,,, , ^.^^^^ 3o6. Combustion with Chi. • sulphur and ,.-,. I ^^"Osphorus — .pi back a"aiii (n fi, "'a" '-enineratiipn t^ ■ ' "•^""- 308. Lucifer Matches —v. , -t clipping the ends of the* wf^lf "'''^^^'"'^ -'"- "'-^do hy Phospliorus, and either n,-f ""^^ " P«ste of .,,„„ . \ ^ ";» p'.o.p>,o„. i,:i:vrrTf '"'•■'''""'''■ '" •:: ;;;■ l.l.ori,8 is intense o„„uI , ^'"^ '"»" "' tl,e lju,„i,„. , explosive co.„l,„,,ti„„. TlJZf: """"''°'' •»'"■ will 309. Action of P),osnh„ "^ '"■'"'■ pl>'«l.l.om i» „ ,,„„,.2?'^ °™' ^^ ^ Poison -_, „. ,. ^ P^i^J^^ffWUMW"*"** " Ft S ' (1 204 EXPERIMENTAL CHEMISTRY. few hours, or when given in small doses, of producing a remarkable train of poisonout,- symptons lasting for many days or oven for M'eeks. There is no gT^.nl antidote. Giving an emetic and ad- ministering at tlie same time some thick gruel containing chalk or magnesia, the former to suspend the particles, and the latter to neutralize any acid products formed, constitutes the best method of treatment in case of poisoning. Above all, the administering of oils or fatty matters must be avoided. Tests.— Phosphorus is easily identified by its odor, by its property of fuming in the air, and by shining in the dark. COMPOUND OP PHOSPHORUS AND OXYGEN. OXIDES. P2O3 Phosphorus trioxide. P2O5 Phosphorus pentoxide (( CORRESPONDING ACIDS. Hypophosphorous acid H.PO Phosphorus acid H PO.^ Metaphosphoric acid HPo'' Pyrophosphoric acid ! ! !h. P. O^ Orthophosphoric acid H. Po' It will be seen from the above table — (1) That there is no anhydride for hypophcsj^liorous acid. (2) That phosphorus pentoxide forms three acids by com- bination with 1, 2, or 3 molecules of water respectively. (3) That although hypophosphorous p.cid, phosphorous acid, and orthophosphoric acid severally contain 3 atoms of hydrogen in the molecules, nevertheless they differ as follows :— (a) In liypophosphorous acid, only 1 atom of hydrogen can be replaced by a metal (monobasic). (bj In phosphorous acid, only 2 atoms of hydrogen can be replaced by a metal (bibasic). (r) [n phosphoric acid all 3 atoms of hydrogen can be re- pl' ■>! by a metal (tribasic). ig a remarkable ys or oveu for smetic and ad- itaining chalk md the latter utes the best bove all, the ded. odor, by its lie dark. EN. ACIDS. BjPOa H^POo HP03 H,P,0, H3PO, reus acid, iids by com- vely. (horous acid, of hydrogen Irogen can be ogen can be I can be re- ^^PKHIMKNTAI. CnmiSTRY, S !■; C T I X II 205 Symbol, Pjf Molecular Jf'eiyht, 34. PREPARATION. bydissolving40grains ofcausticsodainllO c- ^•- of water. Pour a few drops of ether upon the liquid in the flask, then dose the flask with a cork carrying a long de- livery-tube. Place tJie flask on the wire- guage, on the retort stand, and immerse the end of the de- Jivery-tube in warm /;:■■ "^^S- - ., ^ater m the pneumatic tronfflTa^d /^^^^^-^^^e in war.n ;"-f fi-t passes out, canyZ^X t^^i]' " ''''''' ^^'^^^ *^- gas m then evolved, each b bbl f '\"^^ ^^^ ^'^ '^^ Aask; a "'^ water into tl,e air slt.„ f ^''"'''' ''^^ '' ^^'^^^ ou ot -.of White .uoke. r^Xt^-^--' -^ Produces;' J'ho.sphon,,. So„i„n. ir.vdrate Sf == S^^aH^PO, + pjj ^t-i '■...). + 40„ >''irogen ; thus :— = ^.0: r- --. 3H„0 Water. 206 tXrERl MENTAL CHEMISTRY. i I 11 |l 1 ! ii 1 '11 1 !! Pliospliui-etted hydrogen when imi(>, is not spontaneously in flammable. When preparcl us uhove it contains a little of the vapor of another compound of phosphorus and hydrogen, P2H4, wViich is spontaneously intiainniiible. 310. Precautions. (1) Care must he tak(>n to expel all the air from the flask, otherwise a dangerous explusion will result. This may be done by passing coal-gas, carbon dioxide, or hydrogen, through it, or by a few droi)S of ether. (2) If convenient, the flask may be heated in a vessel con- taining a strong solution of salt. This will guard against the ignition of the phosphorous ' . case the flask sliould accidentally break. (2) The sodium hydrate must not be too concentrated, otlier- wise there will be a tendency to boil over. (4) During the experiment, currents of air in the room must be avoided. (5) When it is desired to stop the evolution of the gas, add some boiling water to the water in the pneumatic trough, with- draw the lamp, and allow the hot water to be slowly tlrawn into the retort. QUESTIONS AND EXERCISES ON PHOSPHORUS. 1. What is the chief source of phosphorus and its compounds ? What is the most abundant phosphate found in nature ? Name other naturally occuring phosphates. 2. Give the details of the process employed for the preparation of phosphorus from bone-ash. Represent all reactions by equations. 3. A piece of bone is heated (a) in a covered crucible, (6) in an open tire. Describe the substance obtained in each case, and state which would contain the larger proportion of phosphorus. 4. Compare the properties of the two varieties of phosphorus. How would you prove, in spite of the great difference in properties, that the common and red phosphorus are modifications of the same element 1 I n KXPERIMRXTAL CflKMlSTRY. 207 phospl.orus in the skeleton P"'''?''**'^- Calculate the weight of 8. Phosphorus vapor is 4 42 tlm^a „ i. molecular weight. ^' *' ^^^^^ =^3 air, find its 9. Calculate the formula of » », i, i per cent., phosphorus 2"";^^":^" '"'""" "^°'"™ ^^'^^ 10. How is phosphuretL r '"'^^'"^^■^^P'^^'^^"*- properties. HoV r^.TlJlt'^^^^^^ Describe its Phosphuretted hydrogen^tsi :! 12x7 "' " '' ^'*^^^ "^ SECTION in. ARSENIC. -Sj/mfto?, As. Atomic Weiaht 7^ ;i-f 7 7 ,., «'i?/if, 75. iV/«/ec«?«,. Weight, As^, SOO. PREPARATION. 3ti. From Arsenic Compounds. of charcoal. Heat the chare tr^^rt" '' f^ " *'"' 02; arsenic wi„ be deposited i„ Tri, "on ,"" ^7 '' ''■■'■ ti.e tube, presenting a brilliant" III" f ° ""'' °' reaction is— metallic appearance. The 2As,0. + 60 = ., . , _ Arsenic trioxide. Carbon . * + ^O Commercial arsenic i.s prepared byTeatin. ''^^''"'""°"'"''"^- enware tubes in a furnace It i. n -f f ^ ""'"' '" ^^''^^h- charcoaL The arsenic thus nil r/l l?^"^"-^""'^ ^^^^ ductor of heat and electricity." In ^^1^'''' '''''' '''^- j in nature it occurs in small 208 EXPKIMMENTAr- CHEMLSTBY. i i i -; M '■ t .L Id quantities in the free state, hut much more commonly in a state of combination witli iron, cobalt, and other metals. Traces of arsenic occur in all mineral waters, and it has been detected in sea-water. PROPERTIES. 312. Odor and Volatility. Exp. 2.— Repeat the la&c experiment and note that on the application of heat, an odor resembling {/arlic, is developed. Close the mouth of the tube and heat the mirror ; the arsenic readily volatilizes Exp. 3.— Break oft the end of the tube, hold it at an ang's of 45°, and heat the mirror ; the arsenic combines with the oxy- gen, forming arsenic trioxide which condenses in minute octahedral crystals on the colder portions of the tube. Arsenic readily oxidizes in warm, moist air, forming "fly powder," which is probably a mixture of arsenic, and arsenic trioxide. It is used in the manufacture of shot, to faciliate the lead assuming a globular form. 313. Arsenic Trioxide.— This is the white arsenic of the druggist, and is the source of most of the arsenic compounds. It is formed when metallic arsenic or arsenical ores are heated in air. 314. Arsenious Acid. Exp. 4. — Boil a small quantity of arsenic trioxide in a test-tube ; it appears to be insolul)le. Add a few drops of lit- mus solution, it is slightly reddened. Arsenic trioxide is, therefore, soluble to a small extent in water. One grain requires for solution 50 grains of cold water, and 12 "rains of boiling water. The reaction is — AS2O3 -f 3H3O = 2H3A8O3 Arsenic trioxide. Wati^r. Arsenious acid. This acid, like carbonic acid, has not been isolated in a pure state. mm nmoiily in a ther metals, 1 it lias been 209 ) that on the s developed. the arsenic ; at an ans'a ath the oxy- in minute I be. arming "fly and arsenic to faciliate •senic of the compounds. s are heated 'ioxide in a irops of lit- trioxide is, One grain 12 grains of 3 d. id in a pure B.Vr-RtUMRNTAL orrKMisruv. 315- Scheele's Green. « formed. Tho co,npo,iti„r„f H '^ •' " ^"""' P'-'^-Pitete by tl.e formula. C„Ao",l ","'""'''""' '^ "P™-"^ -ti«cia, fl„„e.. .a,„p-shLe l„IL';,'i:r"' ^"^ ™"-P»P-. the poison i, meohanioally do aohp,l « "' "'°'' ''*<"■ -.palpable powder, a sljlp ',":'/";'-"«-»-, an every breath, sometime, givin" i 1 1 '" '"''"'""' "' poisoning. ** " """ '" asgravated oases of 3i5. Detection of Arsenic. »ont^-t,!-~^:!,;: ,';:: ::,.:? r """="- "»"-'^">-. -ap« -r lajorof ch„,l„;, an,;;,:!! tE: TTT t'""' °°"" >''"' " arsenic >vill be obtained, or crvsi;iV „f .1 "°° °^ '"°'""'° deposited on the eoUer p'arts of ' e „ t" T'' ^"' "= arsenical. "^ ^"^^' '^ the pigment is wif b^wi,fd~fre tlf ::;t,*° ^-'r » » '■"'« a„.moni„, colors that eontain copp:;:!: rrte^r"" "'^"'''- «-" 317- Reinsch's test. iixp. 8. — Intiodiice some of tha from wall-paper, into a tost-tube a Id dll-r .''f"''' '"'^^'^^^ and place in the tube a slip of brl, t l^ycU-ochloric acid, becomes dark colored from the de T"' "' '^'' ^"PP"' metallic arsenic. Dry the col T '' "" '^' ^""-^'^^e of ^MsofblotUngpape?:;: X^,--^;^^ -s.ayhemorefullyexamine;;;S:li;::^:t-:- 210 BXIMOIUMKNTAfi OUrailSTIlY. Ill » 1^ i i • 11 ■' IF tlie next experimout. Tliis is known as Koiuscli's test. The presenco of organic matter tloosiiot inttu-foru with it, but as the greater part of the arsenio remains boliind in combination with the copper, it can bo employed only when the quantity of arsenic is consiihirablo. To avoid mistakes, the; hydrochloric acid and copi)or should be examined in ))recisely the, same way, witliout the suspected paper, so us to render it certain that the arsenic was not derived from them, 318. Marsh's test. Exp. 9. — Fit up tiie ))ottle for Ltcnoruting hydrogen with the drying tube, as in Kxp. 11, Art. 76. When the air bus escaped, light the hydrogen and hold a pit'cc of white porcelain or stone-ware in the llame ; a circle of small drops of water is formed upon it. Dissolve the white sublimate of the last ex- periment in boiling water, and add through the funnel-tube ; the flame becomes bluisli-white, and on holding the cold porcelain in it, a black or irnwn shining mirror is deposited. This is Marsh's tefit. The pre-ience of the minutest trace of arseidc can be ascertained with perfect certainty by it. Tiie gas is arseniuretted hydrogen, AsII^. Great care shoukl be taken not to inhale any of it, as it is exceetlingly poisonous, and one to which some chemists have already fallen victims. 319. Arsenic distinguished from Antimony. Exp. 10. — Pour upon the black stains a solution of bleaching powder ; the stains will rapidly dissolve. Repeat Exp. 9, sub- stituting a little tartar emetic for arsenic trioxide ; black spots are deposited on the porcelain, but they have a sooty ap- pearance. They consist of metallic antimony. Pour upon them a solution of chloride of lime ; they remain unchanged. This distinguishes antimony from arsenic. 320. Antidote. — Dilute ferric chloride with about twice its volume of water, and add sodium or r .monium hydrate in sli"K-esia is also an antido v T "''" "'^'■'"- ^'"'^'"-l soluble compounds .vith arsenic ut '"'"'""^'^-^ ^'•""' '»- ^ the sy^ten.. An en.et . H '^' J^"""^:^ '^^ "'^-'Ttion « «"!• of warm water should f V'"''"""^"' "^ '""-^tard in "^ ^•''■-''••"''^ -''' ^-'Ji-d i.;^^^^^^ 321. Arsenic and SulDhur a. • r pounds witl. sulphur ... ,, ^ v '' ^'™' ^''^ ^"O"'- -''•te Indian m-e, ^4i.H J o;^f ^iT "' "" "^^-^-ts of «;7^^V«.«^ As,S3, the coloring in.redie "' T^ ^'"''^ ' ""^^ King's yellow. ^ "'fe'cdient in the pigment called QUESTION.S AVD EXERCISK«I nw . 1 FTn,^ ^ A'i'WC.iaES ON ARSENIC. " Rein,„h'. lest ! » "™""'' ''"''™ " " Marsh'. le,t," ,„d ohL:,r °°™™ "'"° "-"'« '-«» « haaeea in „..,., „,^ 4- What is Scheele's ereen an^ u • • eentage of arsenic does i' co'la"? " " '* ^'^'^''^ ' ^'^^t per- 6. What is the best antidote to nr. • • 6. A room 15 feet Ion. 10 If^-?"'' ^^'""^"8 ^ with a paper containing a 8 grain; t' s . '^ '^^^ ''"^'^' '^ —'J foot. How much arse;:ic L ZTL 1 rfom ;' ^™^ '^' ^^^^^ ..''"''-■ oiled _»V,a, and is the only known 7 "'.°°"'P°""'' '» "Iso '■oth in a c,y.talli„e and i^ anl f "' f ''■"'■ ^ "-« ^tal. amethyst, and oain.g :,; ; " 7'"""'/°™- Hock „ry.. "ne variety; agate. eha,:ed .yT ,' ^ "e °''', °' """ "■•^»"'- opa areinnst™tien.„f.oa:;i;r:;:™''-. ''^«. and 327. Soluble Glass. "^ ■Exp. 1. — Heat a common flmf o* " .ed-hot, in,n,e.e it in eolVtaJT;: '" 'u' "'"' *" " mUnence, and diminishe, the inten, I J ■""'*" "°°""S » fl.nt can be easily redneed to I « ,". v ""'"' ""' '"""'- clean iron ladle four gran,> „f I, ' ? . " """"''"•' """ ■" a " '"'' '>''""''"■•»'* eight grams ot ^n ' \ 214 • EXPERIMENTAL CHEMISTRY. caustic potash, and sixty grams of water for some hours; supplying of fresh water occasionally as the other evaporates. Pour tiie mixture into a bottle and let it settle. The silica dissolves in the potash solution and forms with it a thick fluid, potassium silicate. Sodium carbonate may be employed in- stead of caustic potash, but greater heat is required. These soluble silicates are often called soluble glass, and are employed for hardening soft building stone, and for the artifical prepara- tion of hard stone from sand. 328. Silicic Acid, H4Si04. Exp. 2.— Add hydrocldoric acid to a strong solution of potassium or sodiuni silicate. A white gelatinous mass of silicic acid is deposited. If this jelly is collected on a filter, washed well with water, and dried, a white powder, consisting of pure silica in the amorphous state, is obtained. Almost all springs, as well as plants contain small quantities of soluble silicates. If spring water is evaporated, silica will be found in the insoluble residue ; if a plant is burnt, silica will be found in the ashes. Grasses and different kinds of grain are particularly rich in silica, which is to them what bones are to animals. Silica is the substance to which the stalks of plants owe their firmness and stiffness. If there is not enough potash in the soil to render the silica soluble these properties will be wanting in the stalk, and it will readily bend. The horse-tail plant (Equisetum) contains so much silica that it has been used for polishinf wood. In its natural state silica is so hard, as to produce sparks with steel, and is quite insoluble in Avater and acids, except hydrofluoric acid. 329. Silicates.— The silicates are very numerous and very complicated. Among important silicates may be mentioned felspar, mica, hornblende, comi on slate, soapstone, and other compounds of frequent occurrei e. The different varieties of some hours ; er evaporates, e. The silica i a thick fluid, employed in- uired. These are employed ifical prepara- ^ solution of aous mass of d on a filter, er, consisting all quantities 3d, silica will burnt, silica ent kinds of ) them what o which the If there is soluble these will readily ns so much )duce sparks icids, except 'US and very 3 mentioned B, and other varieties of EXPERIMENTAL CHEMISTRY. glo clay are silicates of aluminium Pi • S'licates, especially those of tl'.P i r '' ^ '"'•^"*^"''*' °^ ^'^"«"s ^"'.-'-d by the fui/oTJl ;: :^ x^^^^^'- '''''-' «il^cate of soda and lime FlZ T • ^^"^^'"^^"^^'-^^^ i« a bottle-glass is a silicate of sod? /'•" " ^ ^^'^^'^ «^'-t- ^na and oxide of i.on and it t '"'' ''^''^''' ^^^^ alun. owes its green color. " *' '^"^ ^'^"«^ ^^at the glass QUESTIONS ON CHAPTBR xil •Mher it ,s glass o, diamond " "'"'<" '>J'*«">io«l testa, m CHAPTER XIII. il ACIDS, BASES AND SALTS. 330. Properties of Acids. -We have seen that acids possess the lollowing properties : (1) They have an acid, or sour, taste (Art. 40). (2) They change blue litmus red (Art. 40). (3) They act upon metals, hydrogen being evolved, and its place taken by the metal, (Arts. 66, 68, 157, 280). (4) They act upon metallic hydrates, forming' neutral sub- stances and water. The first characteristic applies only to soluble acids. This rnay also be said of the second ; and besides, copper sulphate, a umuiium sulphate, and many other salts of the heavy metals change bUie litmus red. The third may be asserted .f alkalies' (Ar . 81). In the fourth we have a characteristic which applies to all acids. 331. Definition of an Acid. An acid is a compound, contamnxj one or more atoms of hydrogen, which heroines dis- placed h,, a metal whm the latter is presented to the compound m the/orm of a hydrate, water hehig evolved. HNO3 + NaOH = NaNOa -f H O H2SO, + 2K0H = K^SO, + 2H O 2HC1 + Ca(0H)3= CaCl, + 2H;o.' The hydrogen capable of being so displaced is termed th.^ dis placeahle hydrogen. An acid containing one such atom of hydrogen is said to be monohasic, two such atoms, dibasic &c 332. Bases.-The term base is applied to three class'es of compounds : — 216 m that acids Ived, and its neutral sub- acids. This )er suljihate, leavy metals, c' 3f alkalies, ristic which I compound, becomes dis- ie compound O. 2O. med tlie dis- ch atom of dibasic, &c;. ee classes of expe'-rimkntal chemistry. (I) Certain compoundq nf . . , ^^^ -Me H,,,, ,,„J^_.^;* 0, eta. .,h „.,,„,„ „ ^^^^^ -^-.m hydrate, Gaml &c ' '' '^ "''""' ^^^^'-^0. NaO,/ These 1 "'"'""' ^^3, &o. ^ '' "''"'"«' "" *i , These salts often nn<,«o. 339- oasic Salts — -R • nation of a normal ^alt ^I'' ' *'^ ^«''™'^^ bv t\ >l W r » CHAPTER XIV. ATOMICITY OR QUANTIVALENCE. 340. Atomicity. — We have seen that an atom of chlorine combines v.'ith only one atom of hydrogen, (Art. 260), and that one atom of oxygen combines with two atoms of hydrogen, (Art. 29). An atom of chlorine, tlierefore, may be said to be equivalent to an atom of hydrogen, while an atom of oxygen is equivalent to two atoms of hydrogen. Similar relations may be observed in the other elements and compounds. We have seen also, that an atom of sodium replaces an atom of hy- drogen, (Art. 66), and that an atom of zinc replaces two atoms of hydrogen, (Art. 68). This power is called the atomicity of the element. The word quantivalence is also used to express the same idea. Hence, the elements may be arranged in groups according to the number of hydrogen atoms with which they combine, or which the replace in a compound, thus : (1) Monads, combine with or replace one atom of hydroo^en. (2) Dyads, " « « two atoms of hydi'oaen" (3) Triads, " " « thrr.n -^ •= " (4) Tetrads, " «' " four (5) Pentads, " " « five (6) Hexads, " " «« six 341. Variation in Atomicity.— The degrees of atomicity of the elements are not invariiible ; thus, sulphur in SO. is a hexad, in SOg, a tetrad, and in HoS, a dyad. Nitrogen in NH^Cl, is a pentad, in NH3, a triad, and in N^O, a monad. The circumstances under which the variation takes place cannot well be defined, but the extent or rate of variation is governed by the following very simple law, to which there are only a few exceptions : — When an element chanaes its atomicity, either incrcasinq or tHmiidshinijf the chamje in hi/ two di-ijret'.i at a time « ;oni of chlorine . 260), and that 3 of hydi'ogen, y be said to be -torn of oxygen p relations may ids. We have Sa •*• * = 3 ■ 221 hydrogen. nitrogen. oxygen. ->22 EXPERIM ,NTAL CHKMlHTItY. X = a. 4a J/= 3* 2a Substituting these values in the equation and dividing by a we have — ° ' 3Cu + 8HN03 = 3Cu(N03)2 -f 4H2O + 2N0. As another example of a still more difficult charactov take the ordinary test for a nitrate, viz., add ferrous sulphate to the nitrate, then add sulphuric acid, and a black ring will be formed. (Art. 176.) The products arc potassium sulphate, K2SO4 ferric sulphate, Fe.(S04)3, water, IlaO, and the black brown liquid, (FeS04)2 NO. Hence, the equation muy be written as follows •— aKNOa + m.SO, +(;FeS04=(.K,S0^+xFe2(S0,)3 P ,. „ ^ . +^' -•k to admit air. a short wi ' ,"; 't' '!' ^''« -''« of the eork to prevent evaporation when h T L" " ""''' «^^^' *he 351. Bottles -All ^ '' '"^^ '" "««• Lottie. tho.eoiij;::^;:;:t-:;^ ""^y bo of 200 to 2r.O cc 6 « ° ' '■'' '^"P''^^^- Thoso ammonia etc. Dry reagents' shou .1 1 T'^ """^'"''^^ ^"^ "«id«. - (I to 2 oz.) wide.n.;;.hedto L 7 ", ^^'"'^' '^ ^° «^ plainly labelled with the name an f ^'^^ '^«^^^« ^^^onld ho contained in it. ' ^"^ ^"^"'"^a of the substance 352. Bottles, pourine frnm r bold the bottle in the right uZ'Z^^ T"''''^ ^''"^ ' ^'^'h palm, remove the stopper Jit 1 /'^^^'''^ ^°-« '^ ^k t -ieft hand, and poul. the iJ^^^J^ ^-"•^'' fi".ers of the thumb and index finder ho k'''"'"^' ^'^'^ between ^'-P adhering to the lip "o" ^ tt2' b f"' '" "^^" ^^^^^'' «- «toi)per, and replace the latter in its phtce^ '^ '^ '''^^' *'"' 353- Corks. — All rovi-c. »;, 1 1 ■ « boanl „r„„ t„e ta,i ' „t::^' „^! '*-^ "^ ro.,i„, „,„„ "■».■■ Ste,u„i„g also softc, 1° ,™t ^ f ""°" ">« "'"»" 354. Glass, Manipulation of T f "°™- tl.o 1„„,|, fl„,„e, tur„i„g it oo„sla.?t ;T " '"'*• ''o''' " "' ' ti.e flame, and slowly bonj it t„ .h, P"""' ''■°" '"'"""e it f,,„, " lart'o and tl.in walled, or it it i, ,„^ ? "■'"■ " "'« '"be angle, it should be bent at sevel ' . ' ""■°"«'' » '■■"•«« sion, till the desired angle is obtli„e7 ^-^^ ""'"'' '" ""='='='- Glass tubing is cut by niakir, , .u- of a file at the desi-ed point, an3 the'Tr:!! ""'" '"^ »^S« then steadily drawing the two it 1'B**'*' 226 EXPKKIMKNTAL OHRMIHTHY. pDrtioiia !iii;iit, and at the sunie time, applyinf,' tlio lateral pressure U8 if attciiiiitiiig to lii'iiJ the tuhe whero tht) file mark was made. To close a tube at one end, heat it as before, and removing it from the tlanie, draw apart the portions on each side of the heated point ; finally, melt down the pointed ends in the flame ; on blowing in at tiio open end of the tube while the other end is red hot, a bulb will be made on that end. To cut glass, take an iron rod about 10 inches long, and \ inch in diameter, and insert one end in a wooden handle. With a pointed piece of soap trace a line whore the cut is to bo made, and make a notch in the glus-i with a file. Heat the iron red- hot and apply it about 1mm. from the end of th(! notch, till a tine crack begins to creep towards the rod ; then sIon* ly move the rod along the traced line and the crack will follow it. If it is a bottle that is to be cut, apply the rod to one end of the notch for about 5 seconds, and then quickly apply it to the other end and hold it till the crack begins to creep towards it, and then move it as before. To bore a hole in glass, make a thick paste by partially dis- solving camphor in turpentine; nip off a short piece from a rat-tail file, and keeping the ragged end wet with the paste, a hole -can be bnml by strong pressure and a twisting motion. 355. Litmus Solution. -Boil the litmus in water, adding more water from time to time to replace what is boiled away° add a few drops of sodiui.i hydrate solution, and a drop or two of carbolic acid to prevei t, decomposition. 356. The Metric System— For an explanation of this sy-stem, see the Canadian edition of Hamblin Smith's Arithmetic. The following rules are useful in chemistry :— A centimetre = 392708 in. = j^ in. nearly. Hence, to convert centimetres into inches, Multiply by 4 (tnd 1 eject the last figure. A millimetre — 0393708 in. = ,-^q in. nearly. Hence, to cnnvert millimetres into inches, Multiply by 4. ami point oj the last two figures. eral pressure ■k was made, roinoving it side of the n the fliimo ; 10 other end lonjf, and \ iidlo. With to bo made, ho iron red- notch, till a tlowly move )w it. If it of the notch je other end it, and tlien )arti!illy dis- iece from a the paste, a motion, ater, adding oiled away ; irop or two tion of this Arithmetic. «-ihon dioxide, pre,,ara't"ion of ! ! ' ' ' ' «?, ,; propertiuHcf.... S action on llmo wa"tor 88 formed by the co;„' '*'* bum Ion of carbon In ticcompoBitlon of hy K.owlnK' p|a„tH., («) bymaKneHlum... ,,, 83 i;4 (;« (ii) iU Hi 84 ri 1 ' toatx lor Carbon monoxide, preparation- and 'c „ I'lojiortlcHof, ni 1 tests... l-harcoal, preparation of ^^ ab.sorbs gascN '.',', adeodmiziny-n^.j,,;;," ,., . , "■ rcduciiiij ayini I.emistry, dinned. Ciiemical combination latent. 'J 1 1) ■>H) ri equations notation . . , iionne, preparation 00 m 04 m 08 (J7 1 6 !2 V21 cf 2(1 232 INDKX. PAQB Chlorine, acids and oxiri(>porters of' com' DUStlOlI Combustion, definition of; ordinary.' .' Corl7 157 41 225 224 l> Definite proportions ... . n l>etection of arsenic .... ona Diamond ''™ Diffusion of ftases ".'.'.'.'.'. i?) *'***'"•* u3 Electrolysis of water . . '14 Klement, definition of ....'].'.'.' g " nunil)er of 7 inpirical forniulaB ....'.'.' 220 EiHiationd, chemical, calculation 'of ' ' 71 h-tchiny on glass |gj Explosion of oxyKsn and hydro'eeii ' 51 Experiment, definition of .........,; ; J 159 160 160 182 220 119 203 159 F Flame, definition of " luminosity of ..'. " structure of Eluorine Formula), empiricai Vatioii'a'l,' 'jfr'aphic h ree trasts exist as molecules * riction Miatehes Fuel, composition of ... i .'!.".'; 1.".' '.' ' Gas, illuminating- jgg Glass, compo-sition of ....[ ] [ [ ] .' .' " ' 204 " niaiilpulation of .. . 2''5 Graphite ,";„ Graphic formulae .'. 22O H Hard water II,^drogen, preparati'oil au'd pro'nort'iis of " liquefactioM of. . .' .' .'.'.'.,'" " precautions in niaJiVn'^' product of combustion . " ' standard of apeciflc if ra\ itv arseniuretted " phosphuretted " sulphuretted .' 134 45 58 53 54 19 210 205 196 PAQg Iodine, preparation and propcrlie^of 1«1 Indestructibility of nutter......!.? 10 K Kindling temperr ure 243 Lampblack .... ,,„ Lan-hiMffgas ....■.'.■.■.'.■.■.■.■ ■,,,, Law of Avogadro " Boyle ...; " Charlcx .....'.' 7, Lead, action of water on . 1 'u ." testing for i-^ Lime, caustic ... La " slaked S? " water ff Limestone tl Litmus, soluti n . .' m,n Luminosity of flame.. '.'.'. i^q 111) 17 7.J in 153 Mars-h gas . . . Magnesium, combustion of'. I i' i" ox.vgen '.'.'.'.'.'.'.'. 3.5 in carbon dioxide 89 [ Manganese dioxide, manner in which It acts „(, Mercuric oxide... i! Molecule, definition 'of '.'.'.'.'.'. go Multiple proportions, law of ..." .' .' ." ." .' 115 Pt Nascent state Nitrates, common .'.'.'.'.'.'...'...'.'." " !' . presence of, how dete'ted'.'. Nitric acid, prep irationand prop, rties Nitrogen, preparation' and 'properti(28 Nitrogen mon'oiide,' pr'e'paVa't'ioii" 'a'n'd properties of Nitrogen monoxide, dis'tiiigiiiVh'cd from oxygen Mtrous acid 119 101 105 102 60 107 110 113 preparation and pro- defiant gas, peities of j^rc Order list of chemiciiis .' .' '.".'.',. ,' ' .' ' " ' 228 " apparatus 22 » Oxygen, preparation '.'. 2.1 " supports coiubustio I ...... 31 " liquefaction of 31) " precautions in making ..' '>h Oxides 7 37 Ozone, preparation and properties cf. 42 Phosphor:is, preparation and proper- ties of 201 rAUB I proportie-of 181 ■tur 10 243 OS no 17 7.i 75 l:?8 1.18 88 84 85 84 220 160 Of )xii1e ler in whiuh of 153 2 35 89 2!) 25 20 115 119 101 dote tud . . 105 1 prop, rties 102 I properties 60 iration and 107 itIiiKuished 110 113 1 atid pro- 1:5 228 22J 2.1 io 1 81 39 kin^' .... 28 37 perties i,f. 42 id proper- 201 INDEX. Pho8phon.s, red ,arlety 'Zl Phosphorescence 204 S°8P{|o™s pentoxido ." 202 PasterofParis 1 rmmbajro . 136 Pneumatic troughs 69 Potassium chlorate 224 :: Er'^«'''°-Vge„fi.om 'II permanganate.;; J"i lo9 233 PAoa $ uantivalenoe uioklime . . . ' Q 218 84 Bational formula Reduoinfi. flame 220 neplaomg, power Sulphur ,Ilo..ide, preparation Of jgg ., properties of . . . ; ' ' i|| S-'PijHesaeida/rnS".; £ a..i 1. . '^sts for. . -^92 oulphurio acid 192 ;; preparation!; }at Su'Phates.conC"^" ■■■■■■■■'■ m «,.i u tests ... 196 Sulphuretted hydrogen; preparati -''''* o' 196 " « .properties.. 197 poisonous char- " ., acter jgo Symbols, chemical *^" '• 109 Synthesis, definition ot'. ?o 16 8 167 218 T Safety lamp . . . Hoi' ^"'^'ches" ;;;;;■• Baleratus . Salt, definition of Soheele's green... ""• Shot, arsenic added' Vo;. Silicon"; Soap, hard andsoft";;"" boda water Sodium, carbomte oioarbonate..;" chloride . hydrate .."■■■ Q„,, . , nitrate .... ' " ' Solublegflass Stearic acid .^„ Structure of flames:; 186 SuljJhur, preparation of 169 action of hejt on ?85 187 . 166 . 203 ■ 84 217 209 208 213 213 135 94 84 84 177 84 101 21s I'^^^^ot Atomic weights Tetrad elements ^ Temporao^ hardness in waier; Triad elements! ; ! ! 227 218 135 212 218 Volume, combination by . Mr 16 Water . composition of density at 4°c. hardness of impurities of properties of pu;e::;:::::;; relation to heat J* gas . . 131 157 129 132 138 130 134 134 130 Zinc, granulated. Z 47 IJ.,; t' 'I f i. / ♦ fill 1 , ^^Bi^B' ■ hI IB ^^^B