p. • COURSE OK PEACTICAL CHEMISTRY, AS ADOPTED AT UNIVERSITY COLLEGE, TORONTO. BY HENRY CROFT, F.C.S., PROFESSOR OF CHEMISTRY, UNIVERSITY COLLEOE. TORONTO: '^^^ COPP, CLARK & CO., n ■■■■•■■ ■ ^' ■■ ' '^i^5 ;r V4f!:';i), ^-< v.:j ' ^ V IlViL^ R ERRATA AND ADDENDA. 29, 31, SI, 36, 34, 4, 35, 9. 65, 20, Page 17, line 83, for "prcscncs" read "presence" for "cliloride" rend "chlorine" for " used " read " fused " for " chlorde " read " chloride " for "produce" read "produces" for "same" read " oriijinal" 61, Under first column, read " If ammonia has been found, some salts of the above acids •will volatilise without blackening." Under second column, read " If ammonia has been found and nitric acid bo present, the salt will decompose without deflagration."* 31, Under Ferric Salts. Test 9. Tannic acid produces an intense black colour. 61, Under Group I. Ferro and fevricyanides blacken somewhat on heating ; they maybe recognized by the tests mentioned in Table I. Group II, or by those in Table III. The precipitates formed by ferricy- anides in silver nitrates is of a brownish yellow colour. 65, If a salt is given for the detection of the acid alone, without reference to the ,base, Table II. should bo used, as chromio arsenic, and other metallic acids, are not included in Table I. which is supposed to be employed after the detection of the base or metal. If arsenic or antimony has been found, their metals may have been present combined with bases or possibly with acids or halogens. Tlie solution may contain arsenious chloride or potassium arsenite, ^ ' '* I .' A ■■:■ ■' ■ : , . *. :-.'i-i^.v-: },'■■ ', ■' '\ ^ ■; . . » ■ "Vv f i , V. '" .»'-.'' . :i' V' ':"' ,■,. ^ ■•■■-■. ■ !>> ■' ■}.■'■'" H-^' •>• *:. • \" . ■ ■ '■':!.■■: -.y i^&^: ■t V.VT- ■« ^'i^ V .,::-■ ..X'. ■ i\ ■ ■■ .. . .- ^ ,,r, ' '■■■A it/&^t:;S{!i-i«>i ■.-;; X^ii K '> ■v.vU':iJ->i^ ^/jlf*?*'.. ...f*^.|£S»- PRACTICAL CHEMISTRY. RE-AGENTS. ^In the following list all the principal re-agents that are required wre mentioned by their old and new names, and by their old and now formulas. The typical formulas have also been added. The water of crystallisation has been omitted, OLD. EMPIRICAL. TYPICAL. S^phurioAcid HO. S0» Sulphuric Acid H». SO* ^h'}^' RltrioAcid H 0. N 0* Nitric Acid H. N 0» ^h}^ Hydrochloric Acid H CI Hydrochloric Acid H CI ^\ H 1 Hydrosulphuric Acid H S Hydrosnlphuric Acid H^. S H l ^ Water HO Water H» {J J Oxalic Acid HO. C 0" Oxalic Acid H«. C 0* ^*2» } 0' Acetic Acid H 0. C* H» 0» Acetic Acid H. C« H^ 0' ^' ^ 'J } ^^ Tartaric Aoid...H 0. C* H* 0& Tartaric Acid H«. C* H* 0« ^*^ ^1 } 0» Ammonia N H* This when in solution N H*! ^ may be considered as Ammonium Hydrate...N H*. HO H | f otassa H 0. K Potassium Hydrate K. HO ^ 1 Soda H 0. Na Sodium Hydrate Na. HO ^^ j BlakedLimo HO. CaO Calcium Hydrate Ca. H»0' H*}^* Carbonate of Soda Na 0. C 0' Sodium Carbonate... Na». C 0» ^^ 1 0* *Carb.ofAmmoniaNH*O.CO' Ammonium Carb..(N H*)". C 0» ,^ gP, [ 0» Chloride of Barium BaCl Barium Chloride Ba Cl« ^j*| * The salt usually employed Is really a sesquicarbonate mixed generally with iome bicar- bonate, hence ammonia is added to the solution. 10 Chloride of Calcium Ca CI Chlor. of Ammonium..N II'Cl rerchlorido of Iron ...Fe'Cl' Bichloride of Platinum Pt CI" Protochloride of Tin ...Sn CI Chloride of Mngnesium Mg CI Sulphate of Copper CuO. S 0> Sulph. of Magnesia MgO. S 0» Carbonate of Lime Ca 0. C 0' Ferrocyanide of Potm. K' Cfy Ferricyanide of Potm.K'Cfdy SulphocyanidePotm KS.CyS Phosphate of Soda 1 Na'O^.IIO.POS; Oxalate of Ammonia 1 NH^O.C^O'/ Acetate of Soda Na 0. C* Il» 0» Calcium Chloride CaCl* Ammonium Chloride ...N II' CI Ferric Chloride Fe'Cl* Plntinio Chloride or p. p,^ Platinum Tetrachloride ^ ^ Stannous Chloride Sn CI' Magnesium Chloride Mg CI* Cupric Sulphate Cu. S 0* Magnesium Sulphate..Mg. S 0* Calcium Carbonate Ca. C 0' Potm. Ferrocyanide K*Cfy Potm. Ferricyanido K' Cfy Potm. Sulphocyaiiate...K. Cy S Sodium PhoBphate..Na2 H. P 0* Ammonium Oxalate(NII«)'.C20* Sodium Acetate ...Na. C II» 0' Ca> CV'f NIIM ci; FeM ci«; Ptl ci«; Sni CV'f Mk\ CA'f CO Ca Cfy) K^l Cfvl r o 1 Q, (N \\*y' ( ^ CMJM)> NaT^ }»■ NOTES ON TESTING. In tho application of re-agents some judgment is required as to tlio quantity to be employed and the manner of using them. For instance, solutions of hydrosulpliuric acid, ammonium chloride sodium phosphate, sodium hyposulphite, calcium sulphate, and some others, should be used in considerable quantities, while a few drops of ammonium sulphide, potassium ferrocyanide, &c. &c., will be sufficient to produce the result required. No more of a re-agent should be used than is sufficient to produce the desired re-action. In many cases violent agitation assists the formation of a precipi- tate, as in testing for barium with sodium hyposulphite, for magne- sium by ammonia and sodium phosphate, or potassa by tartaric acid. The test tube should be held between the first and second finger, and closed by the thumb. k< (, '". ■< ^i. -.:<'■; ■?> f, ;l' ■■ A'.. (. :.;i. ••■!; -I', ,;. .,»i-.J-,;V Vy ■• .;.■■- :''.i;'j;50 "::-^'^-'-l 'V.'^^iJ'i ^■-'■' H^tiffi'l '";'^i >"^ 11 When it is stated that a precipitnto is soluble in excess, it will be well in miiny cases to throw away the greater part of the precipitate and uso only a small portion, as othcrwiao a very larj^e amount of the solvent niny bo required (lead chroniate and oxide, calcium tartrate, &o. v», .'n.. V C2Q^ ^63 -. /' 'i:n • I , •;':'>:, ■i]:*;, V;, .hv ' Uit'S t 'vW, . ■)■■--. ;>•-. ' )'. ''!'■■ .'^i-AV,. l,i,,, t:;,u'''''iSV ^?'''; t 10 accompnny potnsslum hydrate, and moy thcrcforo bo substituted for that ro-ngont with iidviintngo, SODIUM CATinONATE. The carbonate and bicarhonnto usually contain traces of sulphato and chloride which may bo detected by adding barium or nilvcr nitrate after supersaturation with nitric acid. If rcriuircd perfectly pure, as for toxicological purposes, the bicarbonate (carbonate of the druggists) should be washed with water until the washings contain no trace of sulphato or chloride, detected as above. The residual salt may bo dried and heated nearly to fusion to obtain the carbonate. For decomposing siliceous minerals a mixture of sodium and potassium carbonate is desirable, as it fuses at u lower temperature than the individual salts. It may be obtained in a pure stato by incinerating llochello salt, the double potassium-sodium tartrate, until all the carbon is burnt away. BARIUM nVDRATE. This ro-ngent is not often required in qualitative analysis, unless for separating magnesia from the alkalies. It may bo conveniently prepared by adding a strong solution of potassium hydrate to a saturated solution of barium chloride, washing the precipitate until the filtrate contains no chloride and dissolving the residue in water and filtering. It can also bo oil lined in quantity by heating barium sulphate with charcoal, digesting the reduced mass with water and boiling with cuprio oxide until the solution gives no black precipi- tate with lead acetate. The filtered solution is usually pure, some- times of a blue colour from the presence of a trace of copper, which can bo removed by adding a few drops of ammonium sulphide, boiling and filtering. The solution absorbs carbonic acid rapidly from the air, and must be kept in closely corked vessels. It may also bo prepared by heating the carbonate with charcoal and extracting the mass with boiling water. CALCIUM HYDRATE. The solution is useful in the detection of carbonic, tartaric and citric acids; it is prepared by pouring water over slaked lime, allowing the mixture to stand for some hours, frequently stirring. The first washings should bo rejected, as they often contain potas- 20 siura hydrate. Tho solution is filtered with as little exposure t( air as possible and preserved in well corked bottles. CALCIUM CARBONATE. The perfectly pure salt is sometimes required, and may be pared by dissolving chalk or marble in dilute hydrochloric adding ammonia until the liquid is alkaline, filtering, and pre tating the filtrate with ammonium carbonate. The snowy v precipitate must bo well washed and dried. CALCIUM CHLORIDE. The solution is obtained by digesting dilute hydrochloric with the above carbonate until perfectly neutral, and filtering, should not be coloured by ammonium sulphide, and should evolve ammonia when boiled with potassium hydrate. BARIUM CHLORIDE AND NITRATE. These two salts can bo purchased in most drug stores, and be purified by repeated crystallization. They sometimes cor traces of lead and iron, which may be removed by hydrosulpb acid or ammonium sulphide. One part of the salt may be disso in fifteen parts of water. The nitrate is often preferable to the ( ride, and it must be remembered that both, though tolerably sol in water, are difficultly soluble in both nitric and hydrochloric a POTASSIUM CYANIDE. May be obtained at the photographic establishments and at i drug stores. One part of dry salt must be dissolved in four pan water, but the solution cannot be kept for any length of time v out decomposing. POTASSIUM FERROCYANIDE. May be purchased sufficiently pure, and dissolved in twelve p of water. The solution remains unchanged. POTASSIUM FERRICYANIDE. l^Iay be purchased in some stores, or may be prepared by pas chlorine into the above named solution of ferrocyanide until a ( of it no longer gives a blue precipitate with ferric chloride, but ( a brown colour. The solution should be contained in a large be ■ ■,"-. r 21 which can be closed and shaken from time to time to aid the absorption of the chlorine. No more of this gas should bo employed than just sufficient to produce the above change. The solution is concentrated to crystallisation ; the salt must bo dissolved in water when required, as the solution is apt to decompose, POTASSIUM SULPHOCYANATE. Can be purchased in some drug stores, or may be made by fusing at a gentle heat, in an iron crucible or pan furnished with a cover, 40 parts dry ferrocyanide, 17 potassium carbonate, and 32 sulphur, until the whole mass fuses tranquilly. The heat should then be raised to faint redness. Boiling alcohol of 80 per cent, extracts the sulphocyanate from the cold mass, and yields crystals on evapora- tion.* Ammonium sulphocyanate may be made in a few minutes by boiling ammonium sulphide with hydrocyanic acid until the solu- tion is colourless and inodorous. MAGNESIUM SULPHATE. One part of the officinal salt may bo dissolved in ten parts of water. The chloride obtained by fully saturating dilute hydrochlo- ric acid with magnesium oxide or carbonate may be used instead. FERROUS SULPHATE. The salt may be prepared in a very pure state by (dissolving the residue left in the bottles employed for making hydrosulphuric acid. The solution is boiled, filtered and evaporated rapidly to crystallisa- tion. The crystals should be dried rapidly and kept in well corked bottles. It can be obtained in a still purer and more permanent form by precipitating the above solution by excess of alcohol. FERRIC CHLORIDE. The solution is obtained by dissolving iron nails or wire in dilute hydrochloric acid, continuing the heat until no more hydrogen is evolved even with excess of the metal. Chlorine is then passed into the solution as described under potassium ferricyanide until a * Although an iron crucible is universally rccommoniled, a common earthenware one will answer equally well, indeed is rather better, as the irou pot is often melted if too much heat tie employed. 22 drop of it gives no blue colour with that salt. The fluid may bo diluted to twenty times the weight of the iron dissolved. The offi- cinal tincture of iron often contains ferrous chloride, the presence of which may be detected by potassium ferricyanide. The solution must bo perfectly free from excess of acid, the least drop of ammo- nia should produce a permanent precipitate. SILVER NITRATE. The commercial salt, especially that used by photographers, is sufficiently pure and may be dissolved in twenty parts of water. LEAD ACETATE. The commercial salt may be dissolved in ten parts of water. MERCURIC CHLORIDE. Corrosive sublimate may be dissolved in from sixteen to twenty parts of water. CUPRIC SULPHATE. The commercial salt may be re-crystallised several times and dis- solved in ten parts of water. A very pure salt may be obtained by dissolving the residue left in the preparation of sulphurous acid from sulphuric acid and metallic copper, filtering and evaporating to crystallisation. STANNOUS CHLORIDE. Concentrated hydrochloric acid is boiled with excess of tin filings or tin powder (obtained by rubbing melted tin in a mortar till it becomes solid) until no more hydrogen is evolved. The solution should be filtered and kept in bottlos with a small piece of metallic tin. It is rather apt to decompose by exposure and oxidation and consequently becomes useless. A white precipitate shows that the change is taking place. PLATINIC CHLORIDE. This salt, also called platinum tetrachloride, is obtained by dis- solvmg the metal in nitro-hydrochlorio acid and evaporating in a water bath until acid vapours are no longer evolved. The residue may be dissolved in ten parts of water. H:l i ■ ':,^i-. >r ,,'" . i: ' • ■;;;.• 1 . : '','K- ■ V • ' '(- ■■, ,; t:>; .-KO'^tA:. 23 AURIC CHLORIDE. The salt formerly called torchlorido of gold nay bo obtained from the photographors and dissolved in thirty parts of water. It is not absolutely required as a re-agent. SODIUM PHOSPHATE. The ofiScinal salt contains small traces of sulphate which may be detected by the imperfect solubility in hydrochloric acid of the preci- pitate produced by barium salts. The salt may be prepared by digest- ing burnt bones with two-thirds of their weight of sulphuric acid for twenty-four hours, diluting, filtering, washing out, adding sodium carbonate as long as effervescence is produced, filtering and evapo- rating to crystallisation. The salt thus obtained always contains some sulphate unless repeatedly crystallised. It may be dissolved in twelve parts of water. AMMONIUM OXALATE. Add ammonia to a hot solution of oxalic acid in two parts of water until the liquid is alkaline and allow to cool. The mother liquor drained off from the crystals will yield more of the salt on evapora- tion. Dissolve in twenty-four parts of water. SODIUM ACETATE. Neutralise acetic acid with sodium carbonate, filter and evaporate to crystallisation. Dissolve the salt in ten parts of water. SODIUM HYPOSULPHITE. The salt employed by photographers may be dissolved in six or eight parts of water ; and the solution is preferable as a test to the fluosilicic acid, which is troublesome to prepare. 24 SPECIAL TESTS. It will bo advisable for the student, in the first place, to learn the epeciiil reactions by which the various metals and their oxides are distinguished, and in the following pages only the most important tests are mentioned, the dlflferent metals being divided into groups by what are termed Group Tests. The application of these will become more comprehensible by inspection of the tables hereafter introduced BASES. IsT GROUP. Metals which form oxides and carbonates soluble in water. Tho oxides are the alkalies. The hydrates and some salts exhibit an alkaline action on litmus or turmeric paper, which, however, in tho case of ammonium varnishes on exposure or wanning. Tho salts, with very ^qyi exceptions, are soluble in water and of course give no precipitate with carbonates. POTASSIUM. 1. The hydrate or salt, if in rather strong solution, gives a crys- talline precipitate when mixed with excess of tartaric acid and well shaken. When tho hydrate or carbonate is used, it is necessary to fully supersaturate with the acid. 2. Hydric sodium tartrate (bitartrate of soda) may with advantage be substituted for the acid, but in that case the solutions must not be alkaline. 3. Tho hydrate or salt, when in not too dilute solution and acidu- lated with h^ ''-^chloric acid, gives a yellow precipitate with plati- num tetrachl e, which is difficultly soluble in water, insoluble in alcohol. 4. Salts of potassium communicate a faint violet colour to tho flame of alcohol or tho blowpipe. This test is best made by heating some of the salt on a piece of clean platinum wire, or by placing tho .salt in a small capsule, moistening with water, adding alcohol, gently warming and inflaming. ■;•.,:<•■• I'Sif'itUwbo.*';:! t' % iV'i ,■■■/';•-' ikw.'t,".«} hi ^L.iii V,',;, , i.-.; .■-:"", -i - -.iii -.u. ■ • ■ ' ' • -* . . ■'*, ■:[',:. ' .\'^tI ^•''•''r f'.''l^tc<; ■' ■..!,;.■. .;, „;. . ■ "^-r- ■ " ;:■.;.;•.-, ■■;•■ ,^ tW^T' *)Vt ;;-.' ■' ;*j "-•'.' ■ ' " '" ''■ ,. ..-..^'-i* Vs'.^lrt't't: , |:i-akii.:.5) ii^trfi^vfi^'.^iwd+i j.'V i, nu^zku ,;- ^^ :-'V}:,U-«^«' "•:i:i=:;:li^i'::»'^ ^- li'^io. ■ ■ F,' 25 SODIUM. 1. The hydrate or salt gives no prccipitato with tartaric aciil. 2. The hydrate or salt gives no precipitate with platinum totra chloride. 3. Salts of sodium give a prccipitato with potassium antimonatc, but this test is not very applicable. 4. Salts of sodium communicate a bright yellow colour to tho flame of alcohol or the blowpipe. The most minute trace of sodium can be detected in this way, indeed it is the only good test for this metal. AMMONIUM. 1. Tartaric acid only forms a prccipitato when the solutions em- ployed are very concentrated, as for instance, strongest solution of ammonia, and they are violently shaljen. Excess of acid must of course bo added. 2. Ilydric sodium tartrate produces a precipitate in not too dilute solutions. 3. riatinum tetrachloride produces a yellow prccipitato in the acidulated solution. 4. Salts of ammonium are entirely volatilised by heat, and if the experiment bo made in a tube, an amorphous sublimate will be found. 5. Salts of ammonium when treated with potassium or calcium hydrate evolve pungent vapours of ammonia, which form dense fumes if a rod moistened with hydrochloric acid be brought near. 2nd group. Metals which form oxides soluble or difficultly soluble in water, and carbonates quite insoluble. They, therefore form precipitates with alkaline carbonates especially after heating. The oxides are called alkaline earths. The hydrates exhibit more or less of a permanent alkaline reaction. BARIUM. 1 . The salts are precipitated immediately by a solution of calcium Bulphate or dilute sulphuric acid. The precipitate is insoluble in all i 20 (lilulo ncidn, but Hlighlly solublo in boiling nilrio and h^Jrooliloric acids. 2. Tho Raits givo a precipitate with etrong solution of soJiuni byposulphito if violently sluikon, n. Tlicy coniniunicatc ii faint RrccniHh yellow colour to tlio lliuno of alcohol. Tho salt best adapted for the experiment is tho chloride, which .'should bo well moistened and warmed. STUONTIUM. "*. Tho salts pivo a precipitate after a time with calcium eulphate, or, in V(!rj/ dilute solutions with sulphuric acid, in strong solutions the last rc-!igcnt produces an immediate precipitate. 2. They givo no precipitate with sodium hyposulphite. 3. They communicate a beautiful crimson colour to tho flamo of alcohol. This is a very characteristic tost. CALCiUM. 1. Calcium sulj)hato r''oduccs no precipitate in salts of calcium, however concentrated tl lion may be. Sulphuric acid pro- duces no precipitate if the oulution be vcr^ dilute, but the addition of an equal bulk of alcohol produces the precipitate. In strong solutions an immediate precipitate is formed. Tho above re-actions depend on tho partial solubility of calcium sulphate in water and its insolubility in even weak alcohol. 2. Sodium hyposulphite produces no precipitate. 8. Oxalic acid and ammonium oxalate produce a precipitate immediately in moderately dilute, but only after a time in very dilute solutions. This precipitate is soluble in hydrochloric acid, without cffcrvosccnco, and insoluble in acetic acid. If dried and heated before the blowpipe flame, it dissolves in both acids w 'h effervescence. 4. Salts of calcium communicate a yellowish-red colour to tho flame of alcohol, somewhat resembling that produced by salts of strontium. MAGNESIUM. 1. Calcium sulphate produces no precipitate. 2. Sodium hyposulphite produces no precipitate. 3. Ammonium oxalate produces a precipitate only in very con- centrated solutions, or after a time if somewhat dilute. M 5. rio^s^o it." 5' 4 J_^ , --^>^>.^ ^^^ ^^\^, ^J$^ \^f^ A ^rij, v^ '• '-'"r . --:aJ\ 1;. ^I '•' ?* I*' %.<} A/^^ fiO;^ "M^ A/H^^ >v •- M KH-o t-*^ n*^ i /(It a * */i^^i*-- HU. i- V^^M^ >*^ ^ *^^^i ' fl 27 4. Neutral salts arc partly decomposed by ammonia giving a pre- cipitate which is easily dissolved by ammonium chloride, or other salt of ammonia, Ilencc in a solution containing any ammonium^ salt or free acid, ammonia will produce no precipitate. 5. Sodium phosphate produces a precipitate from strong, none from very dilute solutions. The addition of ammonium chl ride and ammonia causes however a precipitate either immediate^ or after a time. In the latter case it is crystalline, easily soluble acetic acid, whether crystalline or not. 3rd group, first division. Metals which form oxides insoluble in water under ordinary circumstances. Ammonium sulphide produces in solutions of their salts a precipitate which is an oxide and not a sulphide. The oxides have some tendency to unite with strong bases, such as potassa. ALUMINUM. • \, \ 1. Ammonia produces in solutions of salts of aluminum (exdbpx when certain organic bodies are present) a white precipitate, scaitely soluble in any excess of the precipitant, especially when any amount of ammonium salt is present. The precipitate is often so transparent as to be scarcely visible until allowed to settle. 2. Potassium hydrate produces a similar precipitate, readily soluble in excess of the precipitant. The solution, even if dilute, is not altered by boiling. 3. This solution in potassium hydrate is decomposed by a solu- tion of ammonium chloride in large quantity, givinga white preci- pitate, but is not altered by ammoninm sulphide added in small quantity. 4. The dry oxide itself, or aluminum salts, t»hen moistened with solution of cobalt nitrate and heated, exhibits a fine blue colour. This test may be well made by adding to the solution a drop or two of cobalt qitrate, precipitating with sodium carbonate, collecting and washing the precipitate, which can then be dried and heated. ^ 28 CHROMIUM. The ouly salts of tliis metal likely to be met witli are those of the sesqui or chromic oxide. Ammonia produces a greenish or greyish precipitate slightly fible in excess of the precipitant, especially after standing for le time. A pink solution is formed, from which a precipitate is jduced by boiling. 2. Potassium hydrate produces a similar precipitate, easily soluble excess, with green colour. The solution, if not very strongly alka- Sne, yields a precipitate on boiling. 3. This solution in potassium hydrate gives a greenish precipi- |te with ammonium chloride, but none with ammonium sulphide. The former re-agent should bo added in excess, the latter in small quantity. 4. Salts of chromium fused with nitre in a platinum or porcelain capsule yield a yellow mass which dissolves completely in water. ^ The solution should be divided into two parts, one yields with lead acetate a bright yellow precipitate, the other boiled with alcohol and hydrochloric acid yields a bright green solution. ^ 5..'Saltsof chromium , 'boiled with potassium hydrate and a little lead dinoxide (binoxide of lead) yield a yellow solution, which may be tost^ as in 4. 6. The oxide communicates to a head of borax, a yellowish green colour to the inner, and an emerald green tint in the outer flame. The higher chromium oxide will be considered under the head of chromic acid. f SECOND DIVISION. Metals which form oxides insoluble in water under ordinary circumstances, and which are precipitated from their solutions as sulphides by ammonium sulphide. They are not precipitated from acid solutions by hydrosulphuric acid, as the sulphides are soluble in all moderately strong acids. Acetic acid will not prevent the precipitation. ZINC. 1. Ammonia produces a white precipitate, readily soluble it. excess of the precipitant. . - ^XX-o J^-«i-.^i^'. ^^-^^^^-^-^N "11*^^'. <»■■ .^ x»i «'• < -;' ^'' „!:'»1;' /. -Z^zH-d *3S *^ J ..'^ '. t^ I'v , .'"■■■r.» ^'^^^v :^ y,^/^ V. :^ X ::. .js,^^ -^^ ^-^.^ |i fc -r > '' "^ \ Jw U-J f .V A . ?%k,^. '. 'i3^-~>'- •*■•■, Wt. r u, ?.' « y 29 2. Potassium hydrate produces a white precipitate, readily soluble in excess of the precipitant. •3. This solution gives a \7hit0 precipitate with ammonium sul- phide, but none with ammonium chloride. ' 4. The dry oxide or salt moistened with cobalt nitrate and heated, i exhibits a fine green colour. The experiment may be better madtf as described under aluminum. ' 5. The salts heated on charcoal with sodium carbonate give rise to metallic zinc, which volatilises, and by combining with oxygen forms zinc oxide, which produces on the charcoal au incrustation, yellow while hot, but white when cold. a MANGANESE. The salts likely to occur are those of the protoxide, all the higher oxides are converted by boiling with hydrochloric acid into proto- chlorido under evolution of chlorine, which may be recognised by its odour, or by its bleaching action on moistened litmus paper. 1. Ammonia produces a white precipitate, insoluble in excess, which rapidly becomes brown and even brownish-black by oxidation. If much ammonium chloride is present in the solution no precipitate will be formed at first, but a brown oxide will separate on standing. 2. Potassium hydrate acts in the same way, except that the pre- sence of ammonium chloride does not so completely prevent preci- pitation. 3. Hydrosulphuric acid produces no precipitate in acid solutions, and has very little action even on neutral solutions. 4. Ammonium sulphide produces a very characteristic precipitate (manganese sulphide) of a buff or salmon colour. The tint is very easily altered by slight impurities, and the true colour obtained only from perfectly pure salts. The precipitate oxidises in the air, turn- ing brown, and is easily soluble in acids.* 5. Compounds of manganese free from chloride when boiled with red lead and nitric acid, also free from chlorine, communicate to the solution a fine purple colour, which becomes apparent on allowing the lead oxide to settle. • In trying the action of acids on precipitated sulpliideri, tUo precipitate sliould bo allowed to settle, the liquid poured off, water added, and tlus : 'pcated several times ; or perhaps it might be better to collect on a filter and wash witli distilled -water. 30 G. Compounds of manganese fused with sodium carbonate on platinum foil in tho outer flame of the blowpipe, produce a green colour owing to the formation of sodium manganate. Tho addition of a little nitro assists tho action, as is also tho case with borax. In making this experiment a very small quantity of tho manganese compound should bo used, as otherwise the colour appears almost black. 7. Beads of borax and miorocosmic salt dissolve manganese com- pounds, producing a violet coloured glass in tho outer flame, which becomes colourless in the inner. Tho addition of a particle of tin foil assists the action of the reducing flame. IRON. SALTS 01" Tllli PUOTOXIDE. » f FEia;OL*S HALTS, 1. Ammonia or potassium hydrate produces a precipitate which is nearly white in pure salts, but generally greenish, dirty green, or dark green ; turning to black, and lastly to reddish brown by expo- sure to the air. Salts of ammonia prevent the precipitation by potassa partly, and by ammonia entirely. 2. Ilydrosulphuric acid produces no precipitate in acid or neutral solutions. 3. Ammonium sulphide produces a black precipitate, or a green colouration if the solution be excessively dilute. The precipitate is easily soluble in acids. 4. Potassium ferrocyanide produces a pale blue precipitate which becomes rapidly dark blue. 5. Potassium ferricyanide produces a dark blue precipitate. G. Potassium suJphocyanate produces no alteration if both salts be pure, the least trace of peroxide causes a reddish colour. 7. Tannic acid or infusion of gall nuts produces little or no colour in perfectly pure solutions, generally a blue tinge. 8. A bead of borax is coloured dark -red by compounds of iron in the oxidising flame, the colour becoming bottle green in the reducing flame. The colours disappear almost entirely on cooling. For making the above experiments a solution of ferrous sulphate should be mixed with a solution of sulphurous acid and boiled till inodorous and colourless. #•' •iT ■ ''»•-;■■■ -J "'■«•< I.: Jl.J A2, ^.-S/T^^ %, .< Vv^-^*^ f !\; vUfh ■ niwU !•»• V^l Vf;i ,;! '.i" r\ V * .,.■» ' «■■•' '■— ' >>^ * v^.*- ^..t. ,;u.>V,j»"^ • -i«*«4> ^ - o ^■ ^ j^5. f" n 81 SALTS OF THE PEROXIDE. FEnmC SALTS. 1. Ammonia produces a reddish brown precipitate, unless when organic substances, such as tartaric acid, arc present. The precipi- tate is insoluble in excess. 2. Potassium hydrate acts in the same manner. 3. Ilydrosulphuric acid in excess produces only a milky precipi- tate or opalescence, owing to separation of sulphur. 4. Ammonium sulphide produces a black precipitate, or, if the solution be exceedingly dilute, a green colouration ; the precipitate is soluble in hydrochloric acid. 5. Potassium ferrocyauide produces a dark blue precipitate. G. Potassium ferricyanide produces a brown colouration. 7. Potassium sulphocyanato produces a blood red colour, des- troyed by mercuric chloride (corrosive sublimate). In order to show the action of the meiourio salt, the colour should not bo too deep. The red colour is not changed by boiling, 8. The blow-pipe tests are similar to those described for the ferrous compounds. COBALT. The salts of this metal are of rare occurrence, and of little impor- tance except as pigments. 1. Ammonia (very dilute) produces a blue precipitate soluble in excess, forming a brownish solution. The presence of ammoniacal salts prevents the precipitation. 2. Potassium hydrate produces a blue precipitate, which turns dirty green on exposure and reddish on boiling. 3. Ilydrosulphuric acid produces no precipitate in acid solutions. 4. Ammonium sulphide produces a black precipitate difficultly soluble in hydrochloric acid, easily soluble in nitric acid. 5. Potassium cyanide produces a brownish-white precipitate easily soluble in excess of the precipitant, especially on heating and in presence of free hydrocyanic acid. From this solution, containing potassium cobalticyanide, acids produce no precipitate, by which test cobalt is distinguished from nickel. G. Compounds of cobalt used with borax or microcosmic salt produce, both in the inner and outer flames, beads of a splendid blue colour. 32 NICKEL. This metal is of somo importance, as it is largely used in the manufacture of so-called German Silver, and some of its salts have lately been introduced as medicinal agents. 1. Ammonia (very dilute) produces a green precipitate, easily Bolublo in excess, forming a light blue solution. Ammonlacal salts prevent the action. 2. Potassium hydrate produces a pale green precipitate insoluble in excess. o. llydrosulphuric acid produces no precipitate in acid solutions and only a brown colouration in neutral solutions. 4. Ammonium sulphide produces a black prooipitate, difficultly soluble in hydrochloric acid, and not altogether insoluble in water containing ammonium sulphide. Ilenco the supernatant liquid is usually of a brown colour. 5. I'otassiura ferrocyanido produces a pale green precipitate. 6. Potassium cyanide produces a yellowish green precipitate, easily soluble in excess. The brown solution is decomposed by acids, giving a precipitate of nickel cyanide, herein dilTering from cobalt. 7. A bead of borax is coloured reddish yellow by oxide of nickel fn the outer flame of the blowpipe. An addition of nitre changes the colour to purple. 4Tn GROUP. FIRkT DIVISION. Metals which are precipitated, as sulphides from acid solutions by hydrosulphurio acid and the sulphides of which are insoluble in alkalic sulphides (to any great extent). FIRST S U B- D I V I S I O N . Metals which are precipitated from their solutions by hydrochloric acid under certain conditions. LEAD. 1. Potassium hydrate produces a white precipitate, which is slightly soluble in excess of the precipitant. A very small quantity of tho precipitate should be used for this experiment. ^v'ive>,V\^^^'.i^^^. -.^tv. t^,^ ^ ^^^^^ 2, /KZ^O /^H^ ^^ w /. /^^;//^ ^^ip 2,p^'*^<. ,^r J. p^s 4- 3. ^5.S m. .^■>* f 88 2. Ammonia produces a similar procipitato, except io the case of the aootttto, when no procipitato in formed unless a largo amount of ammonia bo used. The preoipitato is (^uito insoluble ia ezooss of ammonia. 8. llydrosulphurio acid produces a black precipitate, insoluble ia dilute acids and alkalic sulphides. The dry or elutriated procipitato is converted into white lead sulphate by boiling with nitrio acid. Heated on charcoal it gives a bead of lead and an incrustation. 4. Hydrochloric acid produces a white precipitate in not too diluto solutions, which dissolves in a largo excess of water especially on boiling. The solution on cooling deposits crystals. Lead chlorido is therefore not entirely insoluble in water, and tho metal must bo looked for in dilute solutions even after the addition of hydroohlorio acid. 5. Potassium iodide produces a bright yellow precipitate, soluble in a large excess of boiling water, from which it separates out on cooling in brilliant golden scales. 6. Potassium chromato produces a bright yellow precipitate, soluble in largo excess of potassium hydrate. The experiment suc- ceeds better with the nitrato than with the O'^etate, and also if the lead bo wholly precipitated and the hydrate added rapidly. 7. Sulphuric acid produces a white precipitate almost insoluble in water and dilute acids, soluble in large excess of potassium hydrate and in ammonium acetate, also in hot hydrochloric acid. 8. Salts of lead heated on charcoal with sodium carbonate yield soft malleable globules of metallic lead, and the charcoal is covered with a yellow incrustation. . ' SILVER, 1. Potassium hydrate produces a brown precipitate insoluble in excess, but readily soluble in ammonia. ■•' - ' '■■ ■ . i ', ; 2. Ammonia if veri/ dilute or added to an excess of the silver salt produces the same precipitate, soluble in excess of the precipitant. 3. Hydrosulphuric acid produces a black precipitate insoluble in dilute acids or alkalic sulphides, but soluble in strong hot nitrio acid. The precipitate should be either dried or freed from tho liquid before applying this test. ; • 'v 8 84 4. Hydrochloric acid produces a white curdy precipitate insoluble ia acids, soluble in ammonia, potassium cyanide and sodium hypo- sulphite. In using the latter salt, the chloride should be precipi- tated by sodium chlorde and not by hydrochloric acid, as, in pre- sence of free acid, sulphur would be set free and render the solution milky. "5. Salts of silver heated on charcoal with sodium carbonate yield brilliant hard globules of metallio silver, not very malleable. MERCURY. MERCUROUS SALTS. 1. Potassium hydrate produces a greenish-black precipitate, inso- luble in excess. 2. Ammonia produces a black precipitate, which is not the oxide but an ammoniacal compound. 8. Hydrosulphurio acid produces a black precipitate insoluble in strong nitric acid, but soluble in nitrohydrochlorio acid. This sulphide is also soluble in a hot solution of potassium sulphide, metallic mercury being separated. 4. Hydrochloric acid produces a white precipitate, blaokened by ammonia. This mercurous chloride, if well washed and boiled with strong hydrochloric acid, turns grey from separation of metallic mercury. The solution contains mercuric chloride. If any nitric acid be present, the whole will dissolve as mercuric chloride. 5. Potassium iodide produces a green precipitate. 6. Stannous chloride produces a white precipitate, rapidly becom- ing greyish black if used in excess. 7. Solutions of mercurous salts produce a grey stain on copper or gold, which volatilises by heat. 8. Heated in a tube with sodium carbonate, a ring of metallic globules is obtained. These become more distinct by rubbing them with a glass rod or piece of wood.* SECOND SUB-DIVISION. 1 • "' Metals not precipitated by hydrochloric acid. * In making this experiment care should be taken that all moisture is excluded, as otherwiao the globules are not so apparent. The carbonate should be heated strongly before use. -i. ■"*> /cU4- ^«?\K N ^ nA > « ^3.^ ' . - '.--i . i ■ ■ ' .'- -: 4 ...... y f"*' itUjl^ i. u^s "^^kci^ "> \* ^i^AM «»*^ '"55c- ^,iv\ . ^. ^'t»i ^V> .Vi, V v^ V>^ '^A t^ -^ ->^ / d^.Z/^^ — ^-^ -I "'V ^•^t^''"*^^' * ^r'«*^i ^ -M y\ r ^ J .?•? I 35 MERCURIC SALTS. 1. Potassium hydrate added in small quantity produces a brown precipitate (oxychloride), in large quantity a bright yellow oxide. If ammonium salts be present a white precipitate is formed (mercur- ammonium chloride). ■ ' ,^, 2. Ammonia produces a white precipitate of a similar nature, varying according to the character of the mercuric salt. 8. Hydrosulphuric acid added in small and gradually increasing quantities produce a white precipitate, passing into yellow, orange, brown, and lastly black. This Bulphide is soluble in potassium sulphide and nitrohydrooulorio acid, insoluble in nitric acid, hydro- chloric acid, and ammonium sulphide. 4. Potassium iodide produces a precipitate o^ a yellow colour, which rapidly becomes of a brilliant scarlet, and dissolves in excess of the precipitant to a colourless solution. 5. Stannous chloride produces a white precipitate of mercurous chloride, changed by excess into grey metallic mercury. 6. Same as test 7 for mercurous salts. 7. Same as test 8 for mercurous salts. All salts of mercury are volatile, and produce sublimates generally amorphous. COPPER. The only salts of common occurrence are the cupric or salts of the black oxide. 1. Potassium hydrate produces a pale blue precipitate, if excess be added and heat applied it becomes black. 2. Ammonia when dilute produces a greenish blue precipitate, easily soluble ia excess forming a fine blue solution. 3. Ammonium carbonate acts in the same manner. 4. Hydrosulphuric acid produces a brownish black precipitate, soluble in hot nitric acid and not quite insoluble in ammonium sulphide. <, . ■ : . • ..^ 5. Potassium ferrocyanide produces a reddish brown precipitate, insoluble in dilute acids, decomposed by potassium hydrate with separation of blue cupric hydrate, or on heating of black, cqprio: oxide. -^ 36 6. Metallic iron, when introduced into a solution of copper, especially if slightly aciJulated, becomes coated with a film of red copper. 7. Any salt of copper fused on charcoal with sodium carbonate so thnt the melted mass sinks into the charcoal, yields brilliant red spangles of metallic copper when the fused mass is ground with a little water in an agate mortar and the liquid carefully poured off. More water can be added and the operation repeated until all the charcoal is removed. 8. Cupric oxide gives a fine green colour to a bead of borax; in the reducing flame (especially by the aid of a piece of tin foil) the bead becomes colourless while hot, but opaque red when cold. Micro- cosmic salt may also bo used instead of borax. CADMIUM. 1. Potassium hydrate produces a white precipitate, insoluble in excess. 2. Ammonia produces a white precipitate, soluble in excess. 3. Ammonium carbonate produces a white precipitate, insoluble in excess if the precipitant does not contain free ammonia. 4. Hydrosulphurio acid produces a bright yellow precipitate, in- soluble in dilute acids (in the cold), ammonia or alkalic sulphides. It is soluble, however, in boiling dilute sulphuric acid, and can thus be readily separated from cupric sulphide, and detected in the solu- tion by reprecipitation by hydrosulphurio acid. 5. Salts of cadmium reduced on charcoal by means of sodium carbonate produce a brownish yellow incrustation. BISMUTH. As all the salts of this metal, not containing an organic acid, are decomposed by water, it will be necessary to dissolve them by the aid ot a few drops of nitric or hydrochloric acid, heat being applied. As little acid should be employed as possible, and if" the original solution be diluted, a white precipitate will, in all probability, be formed, which must be re-dissolved by a little acid. 1. Potassium hydrate produces a white precipitate; insoluble in any excess. . • 2. Ammonia produces the sam«. .;, . fiisi^^tZi^ A; . 5:/y^. ?- ^<:tSj 4- jrii 3 A/ 03 ^s^-^ -fLJyo^ IV^^ * ^ ^-^"j ;,■•.■. f;'.K, ■i!..'., . ,;.VV:'!^; iVjiiO--!; ;.y-i-,v^ |,.,.,:i>v:atf \ .voit-^ _,• :^~^ . . ' ' 1. n .S^ \ 37 3. Ilydrosulphurio acid produces a black or nearly black precipi- tate, which, whcu dried or elutriated is soluble in nitric acid, but insoluble in alkalic sulphides. 4. Potassium chromato added in excess produces a yellow precipi- tate, insoluble in potassium hydrate. 5. The decomposition of salts of bismuth by water is one of the best tests. If much acid be present the solution must be evaporated to dryness and water added, a white salt will be forirled which is in- soluble in tartaric acid. Solutions containing a larp;e excess of acid are not decomposed by water in any ordinary quantity. G. Salts of bismuth treated in the usual way with sodium car- bonate on charcoal by the blow-pipe flame, yield a metallic bead which falls to powder on being i'auimored. The charcoal acquires a yellow incrustation. In examining the behaviour of the sulphides precipitated by hydrosulphurio acid, the precipitates must be allowed to subside, the supernatant liquid poured off, fresh water added and the opera- tion repeated a few times; by this excess of acid will bo got rid of, which in old ammonium sulphide will surely produce at least a milkiness. The metallic sulphide is tnen treated with ammonium sulphide (in preference to potassium sulphide which dissolves the mercurial compound). SECOND DIVISION. Metals which form sulphides soluble in alkalic sulphides. They may be divided into two classes. , riUST SUB-DIVISION. The sulphides are insoluble, and not altered by either hydro- chloric or nitric acids. GOLD. Metallic gold is insoluble in nitric, hydrochloric, or sulphuric acid ; but soluble in nitro-hydrochloric acid. 1. Salts of gold in concentrated solutions give with potassium hydrate and with ammonia a reddish yellow precipitate. 2. Stannous chloride, especially if partially oxidised, produces a purplish red precipitate or colouration. 3. Ferrous sulphate produces a brown precipitate of finely divided gold, which is blue by transmitted light if the gold solution is dilute. 38 4. Oxalic acid at a boiling tcmporaturo produces a precipitation of motallio gold, generally on the side of the test tube. In employing test 3, care must bo taken that no free nitric acid is present, as this of itself tuny produce a brown colouration with ferrous sulphate. NOTES ON GOLD. Articles made of tolerably pure gold are not acted on by nitric acid, while spurious or imitation gold is immediately attacked with evolution of red fumes and production of a greenish blue solution. An article may however be not pure gold, but only gilt ; in that case it will bo necessary to remove the outer coating before opplying the nitric acid. The specific gravity also gives a tolerably fair crite- rion of the purity. Pure gold has a specific gravity of 19.5, jewel- ler's gold considerably less, varying according to purity. Some substances are often mistaken for gold, more especially iron pyrites and golden mica. Iron pyrites in powder is attacked by hot nitric acid, with evolution of red fumes ; gold is not. The solution may be evaporated to dryness; dissolved in a little water and treated with a solution of ferrous sulphate. If gold be present in any considerable quantity a brown precipitate will bo formed, but if in only minute traces a blue solution will bo produced, which on standing will become colourless after a considerable time, yielding a brown precipitate. Iron pyrites heated in the blow-pipe flame gives oflF sulphur which burns with a blueish light, the residual ferrous sulphide fuses and after cooling is attracted by a magnet. Mica is quite insoluble in boiling acids. A description of the detection of gold and silver by fluxing with lead and cupellation of the resulting button, by which process alone the presence or absence of these metals can be absolutely proved, would be foreign to the scope of this small work, and of little use to the generality of students using it. PLATINUM. The metal itself behaves to acids like gold. 1. Potassium hydrate acidulated with hydrochloric acid produces, in not too dilute solutions, a yellow precipitate, diflBcultly soluble in water and insoluble in alcohol. .'i-> i,V" .■ '':''■' '.<" Bi" ■ *■:,;' ■ !■: y 1' ;ti'_:», S'y : , »i '.igftt, thtr 8» 2. Ammonia acts in tho same way. 3. Stannous ohlorido produces an intense brownish red colour. 4. PotasBium iodide produces an intense brown or nearly blaok colour. SECOND BUD-DIVISION. The sulphides are either dissolved or converted into insolublo oxides by hydroohlorio or nitric acid. TIN. STANNOUS HALTS. Jlany salts of tin are partly decomposed by water. 1. Potassium hydrate produces a white precipitate, soluble in excess. 2. Ammonia produces a white precipitate, insoluble in excess. 3. Ilydrosulphuric acid produces a brown precipitate, insoluble in fresh ammonium sulphide, but soluble in old sulphide or on the addition of sulphur. In this case the stannous sulphide is converted into stannic sulphide which is readily soluble. 4. Auric chloride produces a purplish red precipitate. 5. Mercuric chloride produces a grey precipitate of metallic mercury. 6. Salts of tin heated on charcoal with sodium carbonate give beads of metallic tin, intermediate in hardness between lead and silver, they are readily oxidised into white stannic oxide. The particles of tin may bo separated from the charcoal as described under copper. STANNIC SALTS. 1. Potassium hydrate produces a white precipitate, soluble in excess. 2. Ammonia produces a white precipitate, nearly insoluble ia excess. 3. Hydrosulphurio acid used in excess produces a pale yellow precipitate, insoluble in dilute acids, almost insoluble in ammonia,* but easily soluble in alkalio sulphides. If dried and treated with nitric acid it is converted into stannic oxide. * Before adding the nmrnonia nil excess of hydrosnlphnric neid must be removed, other- wise ammonium suliiliide will bo formed, and the prcciiiitate dissolved. 40 4. Stnnnio salts may bo reduced as in tent for stannous com- pounds 3Ictullic tin is converted into wliito stnnnio oxido (njotnRtannic ncid) by tbo action of hot nitric acid. AUSKNIC ARSENI0U3 ACID. This substance as well as tlio hif^her oxido is rnnl(od amon^ (ho mctnllio oxides, as it is readily detected by tlio usual tests for tuo metals. Arsenic in its characters, however, approximates much more clcsoly to nitrogen and phosphorus. 1. Potassium hydrate produces no precipitato. 2. Ammonia produces no precipitate. o. UydroBulphurio acid produces iu acidulated solution a bright yellow precipitate, insoluble in dilute acids. Easily soluble in am- monia, potassium hydrate, ammonium carbonate, and ammonium sulphide. Hereby easily distinguished from stannic sulphide and from cadmium sulphide. The solution in potnssium hydrate gives on boiling with bismuth hydrate, potassium arscnito in solution and bismuth sulphide as residue. The dried yellow precipitate fused with nitre gives potassium arsenate. 4. Cupric sulphate produces little or no precipitate in a solution of arscnious acidj the careful addition of ammonia produces a bright yellowish green precipitate, readily soluble both in acids and alkal'os. Ilonco excess of either must bo avoided, and a precipitato will bo at once formed if a neutral arsenito instead of the acid be used. 5. This green precipitate, if dissolved in potassium hydrate and heated, gives a fine red precipitate of cuprous oxide. G. Silver nitrate produces no precipitate or only a faint white one in solutions of arscnious acid, the resulting arsonite being held in solution by the acid set free (the same holds in lest 4). The careful addition of ammonia produces a bright yellow precipitate easily ./t^ soluble in excess and also very soluble in acids, even acetic. Neutral arsenites of course produce the yellow precipitate at once. 7. Arsenious acid or any of its compounds soluble in hydrochloric acid, when boiled with a moderate excess thereof, with a piece of bright copper foil or gauze, turns the metal of a steel grey colour '■ ;.v^ > ■ ■•■ ;■ .' • ' ■" ? 11 ' ! ' '^ ^.^ vv ..•'.,,:.- r ■ •■ I • ■■■»•' -•• ■-. ■ ■^:.:ti: ir-^::i-'v' 'rfjri' ''■•■*- **#, f' •i ■;'..' 'W . *■■ . _> .'■ . '..■>.' ' •. : "■/'.■ ''mV.v 41 from tho deposition of arsenic on it, forming an alloy. If the quantity of arsenious acid present be very small the boiling must be continued for flftcen minutes, if the quantity be large the alloy soon separates oflF in scales. These scales or the coated copper when ■washed, dried and heated in a small glass tube, yield a white subli- mate of arsenious acid, tho octahedral form of which may readily be recognised by a magnifying glass. The above, with the exception of the latter part of No. 7, may be called the liquid tests for arsenious acid; tho following may be distinguished as the dri/ tests, 8. Arsenious acid (dry) heated in a tube with dry sodium acetate, evolves the horrible odour of alkarsin, the addition of stannous chloride causes the production of tho still more oifcnsive alkarsin chloride. In makin,^ this experiment, as indeed in all with arsenic, care must be taken to avoid inhaling more of tho vapours than is possible. 9. Arsenious acid (dry) heated in a tube with charcoal gives rise to an easily volatile ring, of a bright metallic lustre when the arsenic is present in moderate quantity, but only brown when very minute traces are present. 10. If the tube be cut off by means of a file somewhat be' ring, and a gentle heat applied, a very characteristic gar' will be evolved. 11. If the tube be held in an oblique position, and a gentle heat , be applie'd to the ring, it will sublime and form a white sublimate some distance above. In this the octahedral crystals may readily be recognised, and if obtaiiicd in suflBcient quantity they may be dis- solved in dilute hydrochloric acid and examined I ^ the tests formerly described. ^ 12. If the ring be treated with hot nitric acid it will dissolve, and if the solution bo then evaporated to dryness so that all trace of nitric acid be expelled, and a drop of silver nitrate added, a brick red colour will be produced. 13. Arsenious acid or any of its salts introduced into a mixture of zinc and dilute sulphuric acid w '11 cause the hydrogen evolved to be mixed with arseniuretted hydrogen. The gas will burn with a blueish white flame and will form dark brown metallic spo. on pieces of glass or porcelain held in it. Other plans of obtaining 42 those deposits and methods of examining them will be detailed here- after under the head of Poisons. ARSENIC ACID. 1. Potassium hydrate produces no precipitate. 2. Ammonia produces no precipitate. 3. Ilydrosulphuric acid, when passed into an acidulated solution for a considerable time, produces a yellow precipitate similar in most of its properties to that formed by arsenious acid. The addition of a solution of the gas will seldom produce the precipitate unless after long standing. 4. Silver nitrate produces a slight precipitate of a reddish brown colour, which is greatly increased on the addition of an alkali to neutralise the acid set free. If an arsenate be used tho dense pre- cipitate is produced at once, soluble in moderate excess of ammonia, easily soluble in nitric acid, rather difficultly soluble in acetic acid. By this reaction an admixture of an arsenate with an arsenite may readily be detected ; the solution is wholly precipitated by silver nitrate, and acetic acid gradually added drop by drop. If arsenate be present a red colour will be produced. 5. Ammonia and a salt of magnesium, added to a solution of arsenic acid or an arsenate, produce a white precipitate which is crystalline when obtained from dilute solutions, easily soluble in acetic acid. In composition and prop I'ties it corresponds to the similar precipitate obtained with phosphoric acid. • 6. Arsenic acid and its salts act like arsenious acid as regards metallic copper when treated with hydrochloric acid. The acid used must however be generally stronger than in the former case. 7. Arsenic acid and its salts act in the same way as arsenious acid in presence of zinc and sulphuric acid. 8. Arsenic acid and its salts are reduced by heating with sodium carbonate and charcoal (or potassium cyanide), in the same way as arsenious acid and its salts. ANTIMONY. Salts of antimony not containing an organic acid are decomposed by water with formation of white basic salts soluble in acids, even tartaric. The salt commonly used for experiments is the antimonic • • ■■■'.'h. ?•■■,"(.;■•• • >,. i-aU'Vt iiV?,*., lv»»i*N '.: ■'> ft)j!ui ;■•.. ■!• - Jiv-.-, .*'- .-r 'i:'''-' '.:...':i,s ;i'-.r :i ;■■■•. -.j-i^' ■ ■i T»4>.f: ■r u'.-.' i^- »..! flH'. > i <-.-Ui ■:'■ ;<,' ••-K.' ; ■>•,'>: ■■irV, .»';-;■ )v.i;t -■" ■ J' ■.,"1 ' ;/ , ii^r'-.iii yi],iin»i-:<: *l)h ;■:» f>? wji"i 'i'* W;^ t! ■ifl^-. , :.'i!«siii«jil m-^ ■ : I : f'li" ' '■■:' ,..U ..H \ ..V ''■■■ i '> ■ 'It (;:»■.; fkf y Cf »;;'■;. -^r: '■;;: . '.-=. 47 the other with sodium nitroprusside when a fine purple colour will be produced. 3. The free acid, even when dilute, will char paper if gently warmed so as to drive off the water. SULPHUROUS ACID. 1. Sulphites give a white precipitate with barium chloride, easily soluble in hydrochloric acid. As those salts readily oxidise, they frequently contain some sulphate unless freshly prepared, in which case the precipitate is partly insoluble in hydrochloric acid. 2. Sulphites are decomposed by sulphuric acid with effervescence and evolution of gaseous sulphurous acid. 3. The gas evolved may be recognised by its smell or by its action on paper moistened with starch paste and iodic acid. Iodine is set free and produces a blue colour with the starch. 4. Sulphurous acid or sulphites mixed with hydrochloric acid and metallic zinc give rise to hydrosulphuric acid, recognisable by its smell or by its darkening action on lead paper. Stannous chloride may be used instead of zinc. PHOSPHORIC ACID. 1. Magnesium salts do not produce a precipitate with phosphates unless the solutions are very concentrated, but if ammonium chloride and ammonia be added a white powder is thrown down only slightly soluble in water, soluble in acetic acid and insoluble in ammonia. In dilute solutions the precipitate forms only after a time or after violent shaking. When slowly formed it is granular and crystalline. The formula is N H*. Mg. P 0*, the only modification of phos- phoric acid which need be considered being tribasic. 2. Lead acetate produces a white precipitate which, when well washed, dried and heated in the outer blow-pipe flame fuses and becomes highly crystalline on cooling. It is not reduced by the inner flame. 3. Silver nitrate gives a yellow precipitate, easily soluble both in nitric acid and ammonia. All salts of tribasic phosphoric acid, whether they contain one, two or three atoms of fixed base, yield the same precipitate having the formula Ag' P 0*. 48 4. If a solution of a phosphate, which must not bo strongly acid, bo mixed with a considerable quantity of sodium acetate and a drop of ferric chloride bo added, a yellowish white precipitate of ferric phosphate will bo formed. 5. Ammonium molybdate mixed with nitric or hydrochloric acid until the precipitate first formed is re-dissolved, produces in a dilute solution of a phosphate, especially by the aid of a gentle heat, a yellow colour and yellow precipitate. The quantity of phosphate used should be small as otherwise the precipitate is dissolved. BORACIC ACID (BORIC). 1. A concentrated solution of a borate when mixed with sulphuric acid to strongly acid reaction, deposits crystalline scales of boric acid on cooling. 2. If alcohol be added to a portion of this mixture and kindled, it will burn with a bright green flame. 3. Turmeric paper moistened with a solution of boric in hydro- chloric acid acquires a bright brownish red colour, especially distinct afler drying. CARBONIC ACID (CARBON DIOXIDE). 1. The gas itself is readily detected by giving a white precipitate when shaken with lime water, excess of gas re-dissolves the salt. 2. All carbonates are decomposed by acids, with eflFervescence. The escaping gas is inodorous. 3. Carbonates gives precipitates with calcium and barium chlo- rides, easily soluble with effervescence even in weak acids. CHROMIC ACID. 1. All the chromates are yellow, red or brown. 2. The solutions when strongly acidified are reduced by hydro- sulphuric acid if added in large excess. The solution becomes of a green colour and milky from separation of sulphur. The test will not succeed unless the liydrosulphuric acid is freshly prepared and used in great quantity. 3. Chromates are reduced by boiling with alcohol and hydro- chloric acid, a bright green solution being produced, in which the presence of chromic oxide may be detected (chromium). i^ ,•'.'■. ■','■■• '■*■': '"f '■•">'■ , ' i ' ■' , ' . ■ ■ '."■.' I * '^,,:, pf:-.;..-.-..!},:*^ r.*. *...l,..-;'?.- ' ;>:''■, »;/''" ■ ' .1'' ^ , • • 49 4. Soluble cliromatcs give a yellow precipitate with soluble lead salts the precipitate is soluble in large excess of potassium hydrate (lead). 5. Chromates heated with dry or fused sodium chloride and stron"' sulphuric acid, evolve dark red fumes of chromium oxychlo- rido. The vapours if conducted into a solution of ammonia will form a yellow solution. SILICIC ACID. 1. Hydrochloric acid causes, in strong solutions of silicates, the separation of a gelatinous hydrate. In weak solutions the acid remai is dissolved, but becomes insoluble in water, and all acids (except hydrofluoric) on evaporating to dryness. 2. To detect the acid in insoluble silicates, the substance in fine powder must be fused with four parts of sodium carbonate, the fused mass dissolved in water, hydrochloric acid added, evaporated to dryness, moistened with acid and washed with water. A white residue indicates silicic acid. 3. The finely divided acid will dissolve in boiling potassium hydrate or sodium carbonate. 4. Fused with sodium carbonate it dissolves with evident efferves- cence forming a clear bead. ARSENIOUS ACID. ARSENIC ACID. ANTIMONIC ACID. See under Arsenic and Antimony. HYDROFLUORIC ACID. 1. All soluble fluorides give a precipitate with neutral calcium chloride, insoluble in acetic acid. 2. AH fluorides when fused with hydric potassium sulphate evolve the above acid which acts upon glass. 3. Most fluorides when treated with strong sulphuric acid evolve hydrofluoric acid which acts on glass. 4. Fluorides when mixed with silica and treated with strong sul- phuric acid evolve silicon tetrafluoride which, in contact with water, is decomposed, dep.ositing gelatinous silica and forming a solution of hydrofluosilicic acid. 4 60 IODIC ACID. 1. Salts of tLis acid givo a precipitate with barium chloride. 2. The salts are reduced by sulphurous acid with separation of iodine which may bo recognised by its action on starch. 3. lodates deflagrato when heated on charcoal, evolving viu^et fumes of iodine. Ilcnco this acid belongs partly to Group III. SECOND SUD-GUOUP. Neutral salts give no precipitate with barium chloride, but one with silver nitrate. IIYDROCIILOTIIC ACID. (CHLORINE.) 1. Silver nitrate produces a white curdy precipitate which sepa- rates readily on violent agitation, insoluble in nitric acid, soluble in ammonia, blackening by exposure to light. 2. Chlorides treated with moderately strong sulphuric acid evolve pungent fumes of hydrochloric acid, producing a dense smoke in presence of ammonia. The gas evolved docs not bleach. 3. Chlorides heated with manganese dioxide and moderately strong sulphuric acid evolve chlorine, recognisable by its odour and by its bleaching action on moist litmus paper. The acid used should be made of abc it equal parts strong acid and water. 4. Chlorides heated with potassium chromato and strong sul- phuric acid evolve dark red fumes (page 49), soluble in ammonia with a yellow colour. IIYDRIODIC ACID (IODINE). 1. Silver nitrate produces a pale yellow precipitate insoluble in nitric acid and in ammonia, by which latter re-agent the colour generally becomes lighter. In trying the action of nitric acid, it is necessary to be careful that the iodide has been fully decomposed by the silver salt, as in presence of free iodide a brown colour or precipitate will be caused from separation of iodine. 2. Fuming nitric acid or solution of chlorine will produce in strong solutions a brown precipitate if added in sufScient quantity. An excess of the latter re-agent will dissolve the precipitate, form- ing a colourless solution; hence the use of chlorine is objectionable where only traces of iodine are present. In such cases tests 5 and 6 may be employed. ^.Mi! 'V I I;, i", '. v,;.,,; I'' .■ai.:i:i.;;, \ ^.Hl^t A;,^>-(r■iir'• ' - '■■ ■■■ ■ -,-.::8 a {jfeMj, ,^' ■■ •■ ■■■ •■ ■'■'•' '■■■■■■ ■• •:■• > ^>.- ■.Cfckbride, which tii**y ft.>uj»«fhaL .i'-,v^;« < 'u'.uuci/. i; i ... ;< J- ^'isf^^n ■.,* ' *. • ^ ^ftiry Oi**^-.& p4.'.v ■^A ': ■ (f ' I 51 .'{. Ill very dilute solutions only a yellow colour will bo produced. Thut this ariaos from freo iodiiio nmy bo proved by t-Iiuking tlio solution with a few drops of chloroform or curbou disulphidc, which liquids aboorb tho iodine and sink to the bottom with a line pink colour or dark rod if much iodine is present. JJenzolino or light petroleum oil may bo used, but these of course float on tho tup. 4. A small quantity of starch paste added to tho yellow solution will produce a bluo colour. It is to bo romemborcd that tho iodine must be in a free state. 5. The best method of using the starch test h to add the past.*' and a few drops of hydrochloric acid to tho solution of iodide, and then one drop of solution of potassium chromate. A blue colour will bo produced immediately or after a time, even when the amount of iodine is exceedingly small. G. Instead of chlorine water for sotting free the iodino, a solu- tion of nitrous in sulphuric acid may be advantageously used. Tho solution is obtained by passing the vapours evolved from a heated mixture of starch and nitric acid through common sulphuric acid. Tliis rc-agenfc has the advantage that it decomposes iodides, but has no action on chlorides and bromides. 7. A dry iodide heated with strong sulphuric acid, with or with- out manganese dioxide, will evolve violet fumes of iodine. 8. Lead acetate produces a bright yellow precipitate (page 3C.) 0. Palladium chloride produces an intense brown or black colour and precipitate witi' very dilute solutions of iodides. HYDROBROMIC ACID (BROMINE). 1. Silver nitrate produces a pale yellow precipitate very little soluble in ammonia, unless used in largo excess and on application of heat. 2. Dry bromides heated with moderately strong sulphuric acid, with addition of manganese dioxide, evolve brownish yellow vapours of bromine, recognisable by their smell and bleaching action on moistened litmus paper. The vapours may be distinguished from those of chromium oxychloride, which they somewhat, resemble, by passing them into ammonia^ with which they form a colourleaa golution. 52 3. IJroiiiinc mny bo sot free from its compounds hy chlorine or by bydrocblorio iicid and potassium cbroinato, and if starch bo added a yellowish or slij^btly reddish colour is communicated to the starch. This test is often not very satisfactory, but succeeds much bettor if made in the manner recommended by Frcacnius. Tho bromide with manj^ancsc dioxide and sulphuric acid is placed in a very small beaker, covered by a plate or watch glass on which has been fastened a piece of paper smeared with starch paste with somo dry starch sprinkled over it. On warming gently and standing, a fine reddish yellow colour is produced, the dry starch being bright red if any qnantiiy of bromine bo present. HYDROCYANIC ACID (CYANOGEN). 1. Silver nitrate produces a white precipitate, soluble in ammonia, but insoluble in dilute nitric acid. The dried cyanide when heated in a tube is decomposed giving off cyanogen which may bo made to burn at tho mouth of the tube with a pink coloured flame, the resi- due is metullic silver, easily soluble in nitric acid. By very long boiling in nitric acid the cyanide is dissolved. 2. If thii precipitate bo collected on a Alter, washed, dried and then introduced into a narrow quill tube in which a small fragment of iodine has been previously placed, on gently heating the iodine, beautiful acicular crystals of cyanogen iodide will be formed some- what above the cyanide. Tho heat must be very moderate. 3. If to a solution of ferrous sulphate (or chloride) mixed with a few drops of ferric chloride, hydrocyanic acid or a cyanide be added, and then potassium hydrate, a dirty green or dark precipitate will be formed, which on the addition of hydrochloric acid forms a dark blue liquid, from which a precipitate of the same colour gradually subsides. If the amount of hydrocyanic acid is very small, the solution is rather green than blue, and deposits a blue precipitate only after long standing. 4. If hydrocyanic acid be mixed ^vyith a few drops of yellow ammonium sulphide, and boiled till jjcr/ec/^y inodorous, or evapo- rated to dryness, ammonium sulphocyanatc •will be produced, which gives with ferric chloride a blood rod colour, destroyed by excess of mercuric chloride. The experiment is best made in a porcelain capsule. ;, /.gr ' • • ■ (ji) -I !• •u >Orf. I' I M'l';, ' I '■ r I. ;i.-(i '. ■• . (' .■■I ■ ■' '•• !' i^-^ ■' -l !l' l:. I ^•••'^ / \ ■ )■• ^■'il''. 1/1' tiltl'i i .l.fV J;W '*'■ ^^>'..-'^l-;t; iH !u- 1 .' i ' ■ ' ■''•■ '^ "'.iv'.' ;.,*•> C'fl 7!, '!,iiii |>I'>ji> «rfif' 68 5. Hydrocyanic acid is readily evolved from most of its com- pounds by moderately stronj; sulphuric acid, and is easily recopjnised by its odour. It is scarcely necessary to mention that caution is here required, the acid being so exceedingly poisonous. Other methods of testing for this acid will be given under the chypter on Poisons. HYDROSULPIIURIC ACID (SULPHUR). 1. Soluble and many insoluble sulphides are doconiposed by dilute sulphuric acid with effervescence, the gas escaping is hydro- Bulphurio acid recognisable by its peculiar odour, poniewhat resem- bling that of rotten eggs, by its burning with a blue flame, and by its darlcening action on lead paper. 2. Soluble sulphides give a magnificent purple colour with sodium nitro-prusside and a black precipitate with lead salts. 3. Many metallic sulphides when heated in a tube, open at both ends, and held in an oblique position, give off fumes of sulphurous acid, recognisable by thoir odour, and their action on paper soaked in a mixture of iodic acid and starch paste (page 47.) 4. Sulphides when treated with strong nitric acid, cause red fumes to be evolved, a yellow substance (sulphur) is often separated, and the resulting solution is found to contain sulphuric acid; before the addition of the barium salt, the solution must bo largely diluted. HYDROFERROCYANIC. 1. Ferric chloride gives a dark blue precipitate. 2. Ferrous chloride or sulphate gives a pale blue precipitate. 3. The solutions of ferrocyanides are usually turned blue by the addition of strong acids. 4. Silver nitrate produces a whitish precipitate, insoluble in nitric acid. IIYDROFERRTCrANIC. 1. Ferric chloride gives a brown colour. 2. Ferrous chloride or sulphate gives a dark blue precipitate. 3. Silver nitrate produces a yellowish red precipitate, insoluble in nitric acid. SULPHOCYANIC. 1. Ferric chlorido produces a blood-red colour, not altered by boiling, but destroyed by mercuric chloride in excess. 5-1: 2. Ferrous chlori'Jo or sulphate, if pure, produces no change of colour with pure sulphocyanatc. 3. Silver nitrate produces a whitish precipitate, insoluble in nitric acid. GROUP HI. Acids the salts of which give no precipitate with either barium chloride or silver nitrate, do not blacken when heated on charcoal, but produce deflagration. CHLORIC ACID. 1. Cliloratcs give no precipitate with calcium or barium salts; they give no precipitate with silver nitrate if quite pure, unless pre- viously heated so strongly that efFervescence takes place. By this oxygen is evolved and a chloride remains. 2. Clilorates deflagrate violently when heated on charcoal. 0. Chlorates heated with strong sulphuric turn yellow and evolve a gas which explodes violently. This experiment must bo made with care. 4. In solutions acidulated with sulphuric acid, chlorates will destroy the blue colour of solution of indigo on ajiplication of heat- NITRIC ACID. 1. Nitrates if pure give noprecipitrate with dilute calcium barium or silver salts. 2. Nitrates deflagrate when heated on charcoal. 3. Heated with sulphuric acid anT3 a little metallic copper they evolve red fumes. 4. In solutions acidulated with sulphuric acid, all nitrates destroy the blue colour of solution of indigo on applicalion of heat. IODIC ACID Has been already treated of in Group II. ; it belongs p;inly to Group III. ^■'■•:\f[], ■':,■". >,■;« ■ ;;"" ■;-.,^rA f^:"' \:ii- v \. ,,..'■>.,.■.■'■'', •'^, ;■ : ... ■• ■■, "''•• '■' ^'■■.- 1 '■■;;. V ii ';, i■r''^■!J■ i.v--H^(? wi^a««; ■ ■■'■■' '■;;•■''■',, *'■' "-' ■ ■,,.' A/, ■,:";. J jV.jr.-^ a lU^i'.'i^by^^ ' ■-;'-'' > 'l:'-^^,■■■; ■'' ; ■: ■. ■ " IX. ;■; * i/tr-V*." - , _. ■■: ■1'''" '■'■ii-^^ .i-' •-.' '''i ' .-'• .. ' '''" ■Is;; IV',, a^);. ••'■ ■■.■■;!.;>*;,•■.. ,">.<:/ •'■v'vv'. ■,■■„■, ■■ ' •■ 'i ' ''^ ',v * ■ ■ v:,,-;.'i; tivM.'' ,"', ':('! v .yn-<,h', 55 PLAN FOR DETECTING THE METAL IN A SUBSTANCE SOLUBLE IN WATER, AND CONTAININQ NOT MORE THAN ONE BASE AND ONE ACID. A rather strong solution of the substance is made, care being taken tliat the whole is dissolved ; the test tube containing this orujinal solution should bo always placed in a certain part of the test tube stand, say in the left hole of the upper row. A portion of this being diluted with water is tested with II CI. If a precipitate is form-cd the acid is added until no further deposit results, and a slight excess added. If no resolution takes place, the base belongs to Group I ; if no precipitate is formed, or if it is re- dissolved, pass on to Group II, adding to the same solution a large quantity of hydrosulphuric acid. If no precipitate is formed, or only a milky opalescence, pass on to Group III, adding to the same solution a considerable quantity of ammonium chloride, ammonia till the liquid after being well shaken smells strongly, and then whether a precipitate has been formed or not, a small quantity of ammonium sulphide. If no precipitate is formed pass on to Group IV, adding to the iome solution sodium carbonate. If no precipitate is formed the base must come under Group V, or perhaps there may be no base present. Having thus brought the base into the proper group, proceed according to the several tables. Note. — In some rasps n. rloiir crj-stallino salt may ri'fuso to disBolve in water, licpominj; opa(Hie (bisimith, antimony, tin), (■liaiit,'ing colour (moriniry) and leaving a sediment ([uito insulublt! in liot water, in sucli eases nitric or liydrocldoric acid should be carefully added, with ninilieation of heat, until a clear solution is obtained. As littlo acid as possible should be used. 56 ^k L. *^ 2 «»» o 3 5 o £ 2 IH "S 13 "^ ^ k is «f en pi g EH O O 5 a ** ? .1 3 W O o " - . „ « CT el 3 J3 "ja S O ' «J » o to I C^U Zr5 N -!5 O I" u R -a «— « I* &* • 'a I .5 5, tn CI fe5 fe:2 O 43 Z: Oh I OQ ^ to - 0) !- OJ ^2 03 a la o o " fc ® m-fr PhOSPU •S o •^ fl m s ® -6 1.2 td cr •C 3 -Sta.i3 , CO 2- 2 " o a 05 S •r a .n t: o a « o CA O QJ CO « " £, tr. B ^ a; 5, *^ • ^ n n e: " "> ■w ••< 4> ^'^ "5 ^ a o a u u V a rt .1-1 TO ^ .i*^- i ' « ' *,;v ^ ' ■^'>U'-'. ■^■i'lVM ", MiKi''. ■w.jvv . ■ ,. -: ■ ^ ; « 67 GROUP I. Ammonia added to the white precipitftto formed by hydrochlovio ncid. Di. ..i>)vi'3 it. Tiini •, I'l, bl.ii'k. Leave ; it .ilinoKt uiicli:uige(l. Ag II g rb In these, as in all other casoH, the student should make several confirmatory tests to arrive at perfect certainty, and never depend on one tost alone. GROUP II. A The precipitate is soluble iu (N IP)*S, especially on addition of powdered sulphur. Eli'iU. OHTiii.il soluliiiii Oiiiiiinl solniion Avitli U CI. •"Ill uiili F.;SO< K CI ;^ivi's yellow yivcT Iiruwa )irurijii(,iU'. li'''^t'iiiliit". Bi'owii. Orange. Yellow. Sulublu in:.' H3 Insoluble lu N n» Pt Au Sn Sb (Stannous) As Sn (Stamiic) 13 The precipitate is insoluble in (N IP)' S. YcUov,'. Oii;,'iiml .Miluliou Ori;;iiu\l solution Oriyinnl sdlulion Oi'i','inal soliii ion Rives <,ive>< wliiio (,'ives yellow ))ieeiiiite1e with pre iiiit.iie with WHO* KIIO Cd Pb Hg (Mercuric) ^ives blue colour with NH» Cu yellow prec'ijiilato with Ka Cr 0<, iii;,olublQ in K II O. Siilt;i (leeoinposed by 112 Bl TiS 0) '5 I- . a. t', a a 04 & o o to "o GQ a ~ o 3 '^ m ^ o Tci5 1-3 i-i -i; a 2 -J .S cUJ-" c is - 3 ■fc »! ? 3 •-< f ■sa-r- ■ et .^ ■♦3 ^ 3 Js S3 b U o > p^ o fv O To 3 H eO .3 HH 3 =5 XI a ;:-< IS c * ' _5uJ. ^ 3 >—• ^ ^ no a fit t; 0) .- o a 1' ^ • •-> fa >:^ !- ^a 3 "S.-tit: ^ ^ s ^^ 3 .n •* ^ k4 3 so ,a 02 •s o O >>•« •Ta ■«rf P ^ V) 1 to •5 3 c; CU — ^ CJ 2 Ch .•3 13 « A T) rt C3 K la 8 Jo a rt 03 -M u. t-1 1) a -5 2 2 a « •tl, « a •£ " g *j f^ i-H o Q^ a o 0) o -a a J - 1^ ^ jS O o .A CO a a o "a 'C o I- a o a o .22 c; a rt bi ■73 o a 1-0 o o .^ o >-< Ph 03 -^ S j3 ai Ph.2 a •tJ o es -a •- ns a w ^ •-< ^ ° .5 jj V 'tr. cu • 3 -73 to '-H a « -^ i u a r3 to to " S "^ 'a « (1 .0 a a ^s ^' o s a I 9 a cj a o a 53 tn o a C3 !.,■■ ^i-V"'-- 't.- . vi',»v'..i ^: ^4:*^ 59 GROUP IV. Tho orif^innl solution mixed with nrnmonium cliloriJo nnd cavbo- nntc gives : A whitu |ir«clilia1('. A iiniipltattt A intitliiitiito No iiri'ili'it'it'.'. at (Mio. iiftrr II liiut;. I \U Sr Ca Nil ini'cliiltiili'. Motliiiiii pliiiHiiliiitc inuH«'ii a invv\ lillllo. Mg GROUP V. Original solution acidulated with hydrocliloric acid gives with platinum tetniclilorido : A yi'llow ]iiH'cliiit.it«. No i>iv(iiiitati'. Dry Halt trcattil wlUi Kill) Dry salt trisitfil witli KllO Siiltn ciiniiiinnicato a tvdlvi's no N IP t'Volvus N 11* yollnw cdlour to iiiiy tlamo. Salts aw not volatiK'. Salts iiic vulalilo. E NH« Na 60 PLAN FOR THE DETECTION OP THE ACID OR HALOGEN IN A SALT SOLUBLE IN WATER, AND CONTAINING NOT MORE THAN ONE BASE AND ONE ACID. It is not possible to draw out so simple a plan for the detection of the acids as for that of the bases, some of them coming under several groups. Two tables have been constructed, in the first arse- nious, arsenic, antimonious and chromic acids have been omitted, as they must have been detected during the previous examination for bases. In using the second table the student must remember that fcr each column afresh portion of the original solution must be employed, and the group tests applied in succession, whatever may have been the result obtained in the previous experiments, except- ing when sulphuric acid has been found in the first trial. Confirmatory tesfs must in every instance bo resorted to, and the determination of the base previously will render the search for certain acids in a soluble salt unnecessary. Thus heavy metallic oxides or earths would prevent the presence of carbonic and many other acids which form insoluble salts. Barium, strontium and cal- cium, in an easily soluble salt, would prevent the presence of sulphuric acid, silver and lead of chlorine, iodine and bromine, and 60 on. When an alkali has been found, all acids may be present. 1 ^ ''S* ;S' .j'" ..,. 5. h ■ *t. ;p » !,} ^ ?;- i i i i ^ )> ,<2. 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S>» 3 DO '3 "i GO WOQ Pk « CO W ii,Cl- m ,0 K 3 w nnn CQ J a 11 3 •«-* .2 ■4^ 3 '■w _3 "o CO .S 73 "a a 3 0) "3 3 V SI s b. .~ hi ^^ >» a " '" o :3 cS ga)t,i:.2aa^ 0<5H0P«H0 S"" *" ^n .a ^ OS 60 •s »« M § ^ t »® ;s o o CQ ^ U 62 o C5 60 u CO o •a a S 2-s bo « C I" s CO o '— o ^ — ' W) a cu bo — i< o to a 3 rM & I a i gs •S fe 'J O o .2§ o '3 » ee 99 -, o S §« 1 B s > £,J= HHO >% U -!l i" M P "'n » .2 = .5 s*.t: o tc .!= IE Kl a (► o i> o W > 03 O ;5 ::a.. ■i [ J" «. ■ 1 I r. f 1 »■<:. .: *< ,■'!* *-* 'i: • ^1'.. . ••^' i T (*,i'«. •'.'' i ;r'~T I:*/; l> 1^' 'It' »*^ 63 u o .a r3 a o «4 9 "3 o Ul *«H eti o a a «3 a P- oraci ilicic xalic ca C5 02BO n o K CC a. o O O o hH I— I a .2 « H . o "3 -a o 3 o a o a o o to "o > 'A n O B O 9 "3 S a t-1 tj a o ° z =» o . - ,3 ^3 •? O f. te — ■ ■= -t? e rs c -•3 « C3 o a> en ;. o ♦^ O u "J 15 '^ «';;'=' 00 p cu 00 OJ -^ I' ° ■?; S " I. -o a «3 S « t< -a P a J 04 I •a S ® 2 "3 o o 2 o tqS can 1 .2 o 4i 5 1 1 o'i 1' g. p4 J3 >» {J t4 O O ^« o o o di .« ^^ d s (». t*. r- '3 nm 1 ts kt o o n 'A o pi; o o o to n o ««3 b Ai . I •7 .2 o ° .2-0 tea K-l .5 .2-§ .2 I •a u .2 o I o •n £ a OS c "E o >. Cq n (4 .a t^ I- 1.1 m o ki >» ta ■■'■ ';. 1 .:^^ ■■■M X .:!! ^ 65 a 2^-2 * 5^.J5 I i^i 1> > ^7 Is •l^ TT'f' .. •«» t" ■^ a _^a «J T « •c • - "3 S t^ o .e-i >. is ja w « O ^- o >• _2 c be o g .t 2 >• tfcs tt> OQ .« B «tf (aM > *« e 5 C/i s •d S 3 u -i iff 'd y >* rt ^ ^ -^o o 1- 'u "5-3 i?i U) Cj C r-' ^ Ih tti B o a Q o a ? s 4J jO rt ^ >a w ;; ■? 'I' M o ^i o 5; u, £ 2 "5 .S-'E 3 »-< o o o <2 « t-l £3 -4^ 0/ eu" [o CJ •" > !a o ■fib 9 S »« o o 00 3 1 o 1 1|_ «; ? a .-s — « ^ o o 13 -B a M II T3 a. S o . o >- • -■^ O • in -3 -J S=3 O 0.2 S o (• k 'i >- J:: a o H « .t: UttOHu o ■E 5 -= .2 2 E S 1 ^ d % 5 " O % ■a J3 u M o «'-"^ a" o o o o 2 % aS.S X .2 .2 aj fc- O fc- U -/J en 3 "2 c3 ^ _r.' «— ' K -i-i '-' TO »- M oa -gop^pH-^oj I go r 5 ■g. o 1^ a. CQ o W .2 rt .2 o •c o „._-., ^ o o '■^ a -o " "O T ■'" «> o a.*t) .2 £ S o S go o o "S d I- ti S-"^ ♦-» fi « ^p" o ° -^ — V a O 2 aMHco * o to a nI. n III S « 2 S >• ^ li: ','< -■ tn ■ ;.. .i M I .'IJ Tk- --;;'.'■'•■;,.■.:•;«$;■, ^'t^'. '> '>•; v^ "J :.** 67 SUBSTANCES INSOLUBLE IN WATER. In the precedinn; pages those substances only have been considered which are soluble in water, except when as in the cases of bismuth Baits, &o., decomposition ensues. The examination of bodies inso- luble in water is somewhat more difficult, the substance should be treated successively with water, hydrochloric acid, nitric acid and a mixture of the last two, and the solution obtained in each case evaporated to see if any thing has been dissolved. In using the mixture of the two last named acids, the solution must not be evaporated in a platinum capsule, as that metal would be dissolved. In each case the liquid being poured ofip and the residue washed repeatedly with water, any insoluble matter that remains may be treated with the re-agents above mentioned. A The substance exhibits a metallic lustre or glance, especially on recent fractures. B The substance appears to be of an earthy character. A 1. The substance treated with hydrochloric acid dissolves readily with evolution of hydrogen. Magnesium, aluminum, and metals of the iron class, and also tin and cadmium. The solutions may be examined by the proper tests for these metals. 2. The substance treated with nitric acid dissolves readily with evolution of red fumes and without the formation of sulphuric acid; copper, bismuth, mercury, &c. 3. The substance is converted by nitric acid into a white powder; tin and antimony. 4. The substance is not acted on by either hydrochloric or nitric acid, but is dissolved by a mixture of the two : gold, platinum. 68 5. The substance is dissolved by hydrochloric acid under evolu- tion of hydrosulphuric acid ; ferrous, aritinionious or bismuth sulphide. Some other sulphides such as those of zinc and manga- nese would be acted on in a similar manner. 6. The substance is acted on by nitric acid with evolution of red fumes, and the solution obtained is found to contain sulphuric acid. The solution must be very much diluted before applying the barium nitrate for the detection of the above-named acid. Almost all metallic sulphides. Of natural ores cinnabar may be mentioned as an exception. 7. The substance, by boiling with nitric acid, is converted into a white powder, soluble in strong hydrochloric acid ; lead sulphide. In this case a portion of the metal will generally, unless very strong acid be used, remain in solution in the nitric acid| while in the case of tin and antimony no trace is dissolved. Stannic oxide (3) and antimouious oxide (3) may also be soluble in hydrochloric acid. 8. The metals will mostly melt before the blowpipe flame and form incrustations on the charcoal (see the several metals). Gold and platinum are infusible. Many sulphides will give oiF fumes of sulphurous acid, burning with a blue flame, and lead and bismuth sulphides will give easily a metallic bead. 9. The presence of copper in sulphides may be detected by roast- ing a particle in the blowpipe flame, moistening with hydrochloric acid and again exposing to the flame, a bluish colour will be seen if copper is present. The ore may also, when in fine powder, be digested in nitric acid, the solution supersaturated with ammonia, when a blue solution will indicate copper, a brownish red precipitate will show the presence of iron. 10. The addition of hydrochloric acid to the nitric solution and the production of a white precipitate soluble in ammonia will indi- cate silver, but when very small quantities of this metal are present recourse must be had to cupellation. B. The subsiance does not exhibit a metallic lustre or glance, and is insoluble or nearly so in hot hydrochloric acid. The dry substance is treated with ammonium sulphide. ..rjry,,; >l-; '-'T i't- ,. .-l.i,. .4ini<,-'5Ui-«>f-i-i:''::^"ft;>>Mik'*'d J ■ i:;\ ,;;rM\-N w. .v..-,\>,- -...;:■ -....l., ■ ■- . ■". .^ . :,;..''■,.' ■;'^ ;.;',;'' ..Jf,!,;! < :Ui fig's-. K;. '^'i,, •■.-:':•■;...;:., - .'."rl , ■: '' -i;.'^ r;'',, ;■■;■:• i! • iiH: 'f V^.i >< l< N.. ■■■..■ f ,'•>'■*'' Vl;. ^v;,^ ., ;.v_--'. ■;i-',r,KV -V .., -viu; tt:..:-' I • .1,; 'I', )i>. ill',' ' j; '--'■•. ,:,j. ,■; . •T ' • ,- ■ ' ■". V ' '^ .'' 7* '■' ;■ y.ni.n '•■.■■ Li' ■ .' i'.-r ',"/ ■ ^ '.',', '■!.■'. \t: ':■-■'■ ' ■ '''i; •J,.,, ,.. .', ^ . ■•4 'iJ-'^Vf ; ' ■*, .*. G9 TUBN8 BLACK. Some salts of silver, load, or mercury. Calomel (Ilg CI) may be recog- nised at once by being blackened by N 11', by giving a sublimate of metallic mercury when heated with sodium carbonate, and by being dis- solved by hot nitrohydrochloric aoiJ, the solution giving the re-actions of mercuric oxide. Lead in the sulphate (iodide and chloride) may best bo recognised by fusing with sodium carbonate on charcoal, when a malleable bead will be produced, which may be further examined. The acid may be detected by boiling or fusing (in a porcelain crucible) with sodium carbonate, and testing the solution obtained.* Silver may be detected in the same manner; the metallic bead ob- tained may be dissolved in nitric acid and the proper tests applied. NOT OHAMQED. Sulphates of the alkaline earths, alumina and aluminates, silica and silicates, The Sulphates may be decom- posed by fusing or long boiling with sodium carbonate, filtering ond wash- ing. In the filtrate the acid may be detected after supersatunition with pure nitric acid. The base may be detected in the residue remaining on the filter after dissolving it in dilute hydrochloric acid.f Alumina in its insoluble form and aluminates are best recognised by fusing with sodium carbonate, dis- solving the fused mass in hydro- chloric acid, and precipitating with ammonia. If the precipitate is red- dish, it may bo digested with potas- sium hydrate which dissolves the alumina, and filtered. This solution can be precipitated by ammonium chloride, and the deposit tested for alumina. Silica and silicates (see next paragraph). SILICA AND SILICATES. Pure silicic acid may, when in fine powder, be dissolved by strong boiling solution of sodium carbonate, or by fusion with the same when a clear liquid is formed under eflfervescence, which can T)e dissolved in water. The solution in either case is decomposed by hydrochloric acid, either with separation of gelatinous silica at once, or as an insoluble powder after evaporation of the acid solution to dryness, and treatment with water. Some silicates when in fine powder are decomposed by hydro- chloric acid even in the cold, with separation of more or less gelati- nous silica; the whole is evaporated to dryness, moistened again * Lead sulphate is .soluHe in boiling hydrodiloric acid, and tlie iodide and chloride in a large excess of boiling water. t Tlie sulphates of the e;irths may be readily decomposed by deflagrating with 2 parts fine clmrooal and 12 parts potassium nitrate ; on boiliug with water and washing, tue car- bouatos will remain umlisiiolved. 70 with hydroclilorio acid, filtered and the bases detected by appro- priate tests in tlie filtrate; the residue is pure silica. Others must be fused with sodium carbonate, or a mixture of equal parts of sodium and potassium carbonate ; the fused mass treated with hydrochloric acid to strong acid rc-action, evaporated to dry- ness and treated as above. Some silicates resist even this method of decomposition. When they contain alkalies they must be decomposed by hydrofluoric acid, or by fusing with calcium carbonate (4 parts) and ammonium chlo- ride (1 part). If the alkalies have to be detected the fused mass may be boiled with water which dissolves out tlie alkalic chlorides. The latter process is preferable to that with hydrofluoric acid. It is scarcely necessary to mention that a platinum crucible must be used for such experiments. The crucible should be imbedded ia magnesia con- tained in a hessian or common earthenware crucible, and heated strongly for at least half an hour. ADDENDA. CHROMIC IRON ORE. This dark coloured mineral is scarcely acted on at all by acids, it maybe recogni.scd by fusing it in extremly fine powder with hydric- potassium sulphate (bisulphate of potassa). The fused mass is dis- solved in water, filtered, precipitated by ammonia, rapidly filtered and washed, the precipitate dried and fused with nitre. The fused mass treated with water gives a yellow solution in which chromic acid may be detected. The chromic oxide may also be detected by the appropriate blowpipe test. For other methods of decomposing chromic iron ore see Fresenius. TITANIC IRON ORE. This rather common Canadian mineral is often mistaken for mag- netic iron ore, it occurs in large quantities in the neighbourhood of Gananoque. It is also found in some of our Canadian black sands. It may be recognised by its insolubility in hydrochloric acid, and is best detected by fusion, in very fine powder, with hydric potassium sul- phate. The fused mass is digested with a large quantity of water, , ,; !■ ■.,'.; »f}*i i'-'- ■■ '.,i',i(V ['::;<,': ■'■ .■ "-.I'll rn;^' atvi Jt «]iiin> M^I;,^•^ !■ " il ; ;. :;i!;fM9., I ■<■ 4 ■ -•..,■. I'', I'.i D'.jWU •l-;'U. W ■..^ ' ' ■ ' , *,' 1' ••'i;:' ;j:'; '■••iv ■• «l». . t ' •:. 1.',' ,.,'.. .'^■. itt :ij>*« . ■-- ,i ■ 1,.,. '. ■'• .::■■( ■;.♦ ;■ ■^;*,i . ; -, :T.i.=;»i '.,)<)ji V ■'<'!V!4<, ■-■ ''• V-?*"''* r;.;--;- -J--^-}- 71 and tlio solution boiled for Bomo time, when from tlio colourless Bolulion a precipitate of titanic acid is formed, generally of a yel- lowish or brownish colour from the presence of ferric oxide. IJoil- ing nitric acid will sonietimos extract the ferric oxide from this precipitate and leave pure white titanic acid. WOLFRAM. A compound of tungstic acid or oxide with ferric or ferrous oxide. The mineral is of a dark colour, when finely powdered and digested for a long time with hydrochloric acid, a yellow powder is produced which dissolves in ammonia or potassium hydrate. The solution gives with nitric aeid a white precipitate, which on boiling with excess of acid becomes yellow. The precipitate is insoluble in acids, herein differing from molybdic acid. A tungstate heated with stan- nous chloride and a little hydrochloric acid gives rise to a fine blue colour. For further tests see Frcsenius. MOLYBDENITE. MOLYBDENUM SULPHIDE. This mineral which greatly resembles plumbago is found in con- siderable quantities about Lake Superior. The ore may be ground fine and roasted for a considerable time at a low red heat. Yellow molybdic acid is formed which can be dissolved out by ammonia, the solution when mixed with nitric acid gives a white precipitate soluble in excess. Hydrochloric acid acts in the same way, and if zinc or tin be placed in this solution it becomes blue, green and finally black. For further tests see Frcsenius. PITCHBLENDE. This mineral which is of a pitchy black colour is found in some parts of Canada. lor detecting the uranium contained in it, the mineral should be finely pulverised, digested in nitric acid until all action ceases even on addition of more acid, the solution diluted with water and treated with hydrosulphuric acid until no more pre'jipitate is formed; the filtrate from the precipitate may be evapo- rated to dryness and the residue treated with ether, which on evapo- ration will yield the yellow uranium nitrate. Salts of uranium give a yellow precipitate with potassium hydrate, a red brown precipitate with potassium ferrocyanide and none with hydrosulphuric acid in acid solutions. 72 COMPLEX MIXTURE. It is not within tho scope of this work to give methods for tho analysis of all possible luixtures : the reader is referred to " Fres- enius' Qualitative Analysis," or other largo works. A few exam- pies only of more eoinmonly occurring mixtures will bo given, and tho student is reminded that by tho use of tho tables for the bases and acids they may bo divided into groups. Tho t ')lo for tho grouping of bases leaves nothing to be desired, but for tho acids tho arrangement is not so perfect. In examining for bases, if hydrochloric acid bo added in slight excess and the precipitate separated by filtration, no metals of tho first group can be present in the filtrate except a trace of lead. If excess of hydrosulphuric acid be added to this filtrate and the preci- pitate filtered oflF, no metals of tho second group can bo contained in tho filtrate, and so on; bearing in mind that for detecting tho metals of tho last group tho original salt or solution must bo used. GROUP I. SILVER. LEAD. MERCURY (as MEKcnRous salt). The precipitated chlorides may bo boiled with water as long as anything is dissolved^ and the lead detected in tho solution by hydrosulphuric acid, sulphuric acid or other appropriate tests. The residue may be treated with ammonia which will dissolve the silver chloride and leave a black residue of mercurous chlor- aniide. Tho solution will give a precipitate on addition of nitric acid, and from this metallic silver may be obtained by fusing with sodium carbonate. The black residue may bo examined for mercury by heating in a small tube with sodium carbonate. GROUP II. If the precipitate formed by hydrosulphuric acid is yellow or orange all those metals which form dark coloured sulphides are excluded, if the precipitate is dark coloured all may be present. ...j',,«v U::tA '■■".''■ ]' t .^:'^' <,»..; »! :■/!■ , ■■■>■ ••, ■■. ,,• w;.," - '■■■■ .-I '-.: * 73 TIio waitlicd prooipituto is digustod with excess of ammoDium sulpliido and filtorod. No rosiduo ih left — absonco of inotaU of division H. 1' 1 U M T DIVISION, A . The flolution of tho Bulphidos in aiiiuioniiitn sulphide is trontod with hydrochloric ucid. A precipitate which, after drying, docfl not burn owiiy completely on tho applicution of a moderate heat, indicates gold, pliitiiiuui, tin, or antimony. As tho first two metuls are very rare, and occurring in u metallic state are easily recognisa- ble, wo may confine ouiselves to tin, antimony and arsenic. The mixed sulphides are fused with sodium nitrate and a little carbonate, the fused mass treated with water yields up arsenic acid rccognisiiblo by proper tests; the residue consiHts of stannic and antimonious oxides which may bo fu<;ed with potassium cyanide. The resulting bead of metal, when pulverised and boiled with hydro- chloric acid, yields a solution of stannous chloride recognisable by proper tests (see page 39), and tho residue, if any, may be tested for antimony by the action of tho blowpipe, nitric acid, &,o., &o. .SECOND DIVISION, D. A yellow residue is left — absence of all metals in division B ex- cept cadmium. This yellow substance may be tested for cadmium. A dark coloured residue is loft — possible presence of all metals included in division 13. The residue is digested after washing, with dilute sulphuric acid which will dissolve out tho cadmium, precipitable again from the solution by hydrosulphuric acid. The washed residue when treated with nitric acid will dissolve entirely if mercuric sulphide is absent, if a black residue remains it must be dissolved in nitrohydrochloric acid and tho solution tested for mercuric oxide. The solution in nitric acid should be evaporated to dryness and treated with water, an insoluble residue indicates bismuth which may be further recog- nised by appropriate tests, the filtered solution will give a blue colour with ammonia if copper is present, and a white precipitate with sulphuric acid if lead is contained in the solution. When very strong nitric acid is used the lead sulphide is entirely con- verted into sulphate and remains undissolved. It may be extracted 74 by boiling with strong hydrocblorio acid or solution of ammonium tartrate or acetate. GROUP III. IRON. COBALT. NICKEL. MANGANESE. CHROMIUM. ZINC. ALUMINUM. It is not likely that all these metals should occur together, but to detect them the precipitate may be examined as to its colour, if not black it caunot contain any of the first three. If black it may contain them all. If white or nearly white it cannot contain any but the last two. Supposing that the precipitate is black and may therefore contain all the above metals, dilute hydrochloric should be added to the well washed precipitate — if a black residue remains it must consist of nickel or cobalt sulphide or both. For the separation of these use the cyanide test. Iron and aluminum may be separated by boiling the nearly neutralised solution with excess of sodium acetate, the precipitate consists of ferric oxide and alumina, the latter easily extracted by potassium hydrate and precipitated by ammonium chloride. Sodium carbonate will precipitate the other metals from the filtrate. In this precipitate the manganese may be detected by fusion with sodium carbonate, the chromium by fusion with potassium nitratC; wiiahing with water and testing the yellow liquid for chromic acid, and the zinc by fusion of the residue with a reducing agent on charcoal, when an incrustation will be formed, yellow when hot but white when cold. GROUP IV. BARIUM. STRONTIUM. CALCIUM. MAGNESIUM. The first three may be separated from the fourth by dissolving the precipitate of mixed carbonates in dilute hydrochloric acid, adding excess of ammonium chloride and then ammonium carbo- nate, the magnesium will remain in solution and may be detected by sodium phosphate. The separated precipitate may be dissolved in hydrochloric acid and evaporated to dryness to drive off excess *(»^*,«i^!jliw; 'rov'- t^i\4 '<>'' -^tVlulvn <;f '♦'•,r . "r' ,■ •' ."'•I %K>-l, '■'Ifvl''!''}*'V| J^ '''■•', .^'r .>r(U w -rf liV-'Vi^v '/r'- Tr i ' ,' 1 -••.•., -^• I'' •; ■ >'h^.^Pu bi^ Si,Ui<"l ?" the ■■■'■■ 'r -■ ,**;'V^:, • ■■■'.i^y^i^.ur 75 of acid. Potassium chromate added to the solution of this residue will precipitate all the barium, and the strontium may be detected in the filtrate by very dilute sulphuric acid or calcium sulphate. Another portion of the soludon of the residue may be precipitated by potassium sulphate, allowed to stand some hours, filtered, and the filtrate tested for calcium by ammonium oxalate. Of course only a small quantity of calcium will be found in this solutioa owing to the difficult solubility of the sulphate. GROUP V. POTASSIUM. SODIUM. AMMOxXIUM. The evolution of ammonia on heating a portion of the dry sub- stance with potassium hydrate shows the presence of ammonium. The remainder is then heated until no more fumes are given off, moistened with water and burnt with alcohol. A yellow colour indicates sodium; the residue is dissolved in a small quantity of water and tested for potassium by platinic chlorida or tartaric acid. 76 COMPLEX MIXTURES OF ACIDS. The detection of acids when several occur together or when they exist in insoluble substances, is much more difficult than that cf the bases. If combined with an oxide of a heavy metal, the action of hydrosulphuric acid may bo employed to separate the acid, either on the solid body or on its solution in some acid ; digestion with ammonium sulphide may also be resorted to, or the substance may be boiled with sodium carbonate for some time. In the latter case the solution should be acidulated with pure nitric acid, supersatu- rated with ammonia and boiled till perfectly neutral to test paper. In all cases of testing for acids the above neutralisation should be carefully observed. It is seldom that many acids occur together unless in samples given for practice, and the chemist has to rely principally upon special tests. ORGANIC ACIDS GIVING WHEN IN NEUTRAL SOLUTION A PRECIPITATE WITH BARIUM CHLORIDE. Gallic and tannic acid may be detected by their action on salts of iron, and separated from each other by a solution of gelatine which precipitates the latter. Benzoic acid by being precipitated from solutions by an acid and by special tests applied to the precipitated crystals. Uric acid by the action of nitric acid and of potassium hydrate. Tartaric and citric by giving precipitates with perfectly neutral calcium chloride, the former in the cold, the latter after boiling, separation of the two may in this way be effected. Acetic acid does not give a precipitate with barium on calcium chloride, but may be referred to here as being an organic acid. It may be detected by giving a red colour with ferric chloride and by yielding sweet smelling ethyl acetate when distilled with alcohol and sulphuric acid. inorganic acids giving a precipitate with barium .:;hloride. Sulphuric acid may at once be separated from a mixture by the insolubility of the precipitated sulphate ia hydrochloric acid, the 1 . v^:. .ii''C ,"> S.'t'vVy Mil m '•- ,' ^■:?^ .'• ■ , ■ ;, , - • '? , '" ' !'■ ■"■ ' ' ' «'•:.'- ,,. , . • ;.-•'■ ;>:• riiv. lit !■. . ■-■■■■ )?.■■ ■^v-.rK'j: ,\ ■■- '- ' ' ■ .-...^Vl?' 77 solution may bo neutralised with ammonia and the precipitate de- composed by sodium carbonate as above described. If the precipitate dissolves with eflfcrvesccncc carbonic acid may be present, and sulphurous acid may be detected by heating the salt with moderately strong sulphuric acid and allowing the vapours evolved to act on starch and iodic acid. A ncrlral solution having again been obtained it may bo treated with calcium chloride and the precipitate digested with acetic acid, fluoride and oxalate will remain undissolved and may be recognised by appropriate tests, the solution may also be tested specially for phosphoric and boracic acid, &c. ACIDS NOT GIVINQ A PRRCIPITATE WITH SO.MEWIIAT DILUTK SOLUTIONS OF BARIUM CIILOIIIDE, BUT WITH SILVER NITRATE. * Great difficulty wou'id occur in separating the acids of this group if many occurred together, but students are not likely to meet with very complicated mixtures. Hydrosulphuric acid may always be recognised by its action oa salts of lead, and may bo expelled by boiling with acid. Hydrochloric acid by the pungent vapours evolved when its salts arc treated with strong sulphuric acid, and by giving a white preci- pitate with silver nitrate easily soluble in ammonia, which is fused into a horny mass by strong heat. Hydrocyanic acid by evolving a well known smell when treated as above. If masked by the preceding acid it may be detected by forming the silver precipitate, which is easily soluble in ammonia. This solution may be again precipitated by the addition of nitric acid, the precipitate dried and heated, when cyanogen will be evolved (burning with t violet coloured flame), and the residue will contain metallic silver, which can be extracted by nitric acid, and its pre. eenoe detected ; the bromide and chloride are not decomposed by heat. The silver precipittae, insoluble or nearly so in weak ammonia, may contain bromide and iodide. By digesting with strong ammonia at a moderate heat all the bromide may be dissolved and the iodide left. The bromide may be reprecipitated by nitric acid, and it as well as the iodide decomposed by zinc and sulphuric acid, or better by sodium amalgam, and the resulting solutions examined. 78 POISONS. Almost all substances when used in improper quantities may act as poisons, thus nitre and acetic acid have been known to produce injurious results. In the following p^RCS, only those substances wil* be considered which when administered in moderato amounts may produce fatal effects either by their physical or physiological action. SULPHURIC ACID. The free acid may be detected by the tests described at page 46 j if mixed with organic matter, as in the contents of the stomach, a clear solution should bo obtained and the appropriate tests applied, bearing in mind that traces of sulphate will always be found j but the strongly acid character of the mixture will indicate free acid. If lime or chalk has been administered as an antidote, the insoluble matter must be examined as described at page 46. If the acid has been thrown upon parts of the clothing, these maybe boiled in water and the proper tests applied to the filtered solution. NITRIC ACID. Is seldom used as a poison, but accidents may occur from its use. By neutralising with potassium carbonate and evaporating the solu- tion crystals of nitre may be obtained, which can be recognised by the proper tests, see page 54. OXALIC ACID. This substance has sometimes been used by mistake instead of mngnesium sulphate (Epsom salts), from which it may be readily distinguished by the striated and somewhat opaque crystals, its strongly acid taste, and its entire volatility when heated on platinum foil. Other tests will be found at page 44. Acid oxalates are sometimes sold .nder the name of salt of lemon j easily distinguished from citric acid by blackening but slightly when heated, giving off no very acid vapours, and leaving a residue which effervesces strongly with acids. Whon mixed with organic matter, the whole must be digested with water, filtered, precipitated with lead acetate, the lead oxalate .'*j ■,<:./-i.iii ^ '.■:v^-i'Y,( '' ■ , ■■ - . 'V' , ''':'i ■ ' ', ' . ?."'■ ' , .. 1... ' ' '' I ,. 1. ■ i'^ ' ['■■Li*' 'if I :• ::,rn:- ■' .',■,('''''■■.. 79 collected, washed, decomposed by hydrosulphuric acid, filtered, nnd tlio filtrate tested for oxulio ncid. The separation of the load sul- phide is often attended with difficulty ; sulpburio acid way be substituted for tho hydrosulphurio. Sorrel and some other vegetable substances contain oxalates ; tho non-employment of them as food must bo proved when only smull quantities of oxolio acid have been detected. If lime or magnesia has been administered as an antidote, tho insoluble matter must bo examined as described at page G8. ARSENIC. The chemist may bo called on to detect this substance in a solu- tion, such 08 Donovan's or Fowler's or in a solution of an arsenate; in a solid as in arsenic and arsonious acids, arsenates and arsenitcs, fly powder (metallic arsenic), sulphides and arsenides. It may also occur mixed with organic matter, as in food, the contents of tho Btoniach, vomited matter, fooces, urine, or in the liver or other organs of tho body. If a solution has to bo examined, tho ordinary tests for arsenio may be employed; if it be Donovan's solution, hydrosulphurio acid will produce a black precipitate from which ammonia or ammonium sulphide will extract the arsenious sulphide. Tho solution on evapo- ration will leave the arsenical compound, which may then be ex- amined by any of the tests previously described. If a solid has to be examined, it may be heated by itself in a reduction tube when a white crystalline sublimate will be formed if it be arsenious acid, the octohedral form of the crystals is very char- acteristic and can be readily observed by aid of a pocket lens. A metallic sublimate will be formed, mixed probably with more or less of white crystalline arsenious acid, if the substance be metallio arsenic or arsenical pyrites. Tho ring formed may be tested as described at page 41. The solid may be an arsenite such as Scheele's or Schweinfurth green, or it may be arsenious acid mixed with ferric oxide or other substances. In that case it should be heated in a reduction tube with sodium carbonate and potassium cyanide (or charcoal) when a metallic ring will be formed. Insoluble arsenites and arsenates may also be dissolved in acid and decomposed by hydrosulphurio acid* 80 tho prccipitatfid sulphide bcinp rooopnlsed by its solubility in nnimo- niii nnd by tho test mentioned below. It umy bo a sulphide such as orpiincnt when the samo mixture of carbonate nnd cyanide may be employed, but it will Kcnorally b« better to boil tho sulphide repeatedly with nitric acid, to evaporate to dryness and to test tho residue with tho above mixture of carbo- nate nnd cyanide. If the urine is suspected to contain arsenic, its pToscnco may be proved by paHsinjj; hydro.sulpliuri(5 acid through tho acidulated lifjuid, colloctin^ tho procipilatc, tiltoring, drying and te.sting by any of the previously described methods. Tho precipitated sulphide may readily bo converted into arsenious acid by dissolving it in potassium hydruto and boiling with bisinuthic hydrate, when bismuthio sulphide and potassium arscnitcaro formed. lu this filtered solution tho arsenious acid may bo readily detected. It arsenic sulphide baa been acted on, tho solution will contain arsenic and not arsenious acid. Coiilen/8 of the stomach. If the presence of arsenic is suspected, the contents should be mixed with water and well stirred in a beaker glass, allowed to settle for a few moments, the liquid poured off and the operation repealed several times with fresh portions of water so as to remove organic matters a.s far as po.ssiblo. If a white crystalline and sandy residue remains, a portion of it should be dried and tested for arsenious acid by the dry tests or if in sufficient quantity by the liquid tests for that substance. A white crystalline sublimate when heated in a tube is very characteristic of arsenious acid. If a black sandy residue remains, a portion may be heated in a tube when, if it be arsenic (fly powder), a brown or metallic ring will bo formed to which the usual tests may be applied. Another portion may be heated with nitric acid, the solution evaporated to dryness and tested with silver nitrate when a brick red colour will indicate arsenic. If no crystalline or black sediment is observed the whole of the itonts and washings should be evaporated over a water bath until reduced to a thick mass and treated as hereafter described. Stomach and other viscera. If no solid arsenic, either in the form of metal or arsenious acid has been found, it will be necessary 'V.ii.'.r '{■•■ ■)i d^sv''. iiiiif, litvi •■ • »ii '; *t/ii /^ .-■1 81 to test for tho poison in various parts of the body. The stomach and the evaporated contents and washings should be examined sepa- rately, and also the liver, kidneys and spleen, as the detection of arsenic in the liver, &o., is of especial importance, as showing that the poison had been administered during life. If the liver after death had been exposed to a solution of arsenious acid, ii "e will be found in the outer portions than in the inner, but such cases seldom occur, only after long interment in a soil which has been proved to contain arsenic. The whole of the intestines should be examined. The solid parts should be cut up into small pieces and these or the evaporated contents or urine mixed with about an equal weight of hydrochloric acid of about the specific gravity of l-ll. This is readily obtained by mixing strong acid with an equal bulk of water. The purity of the acid must have been previously ascer- tained, if not free from arsenic, hydrosulphuric acid must be passed through it for several hours, the precipitate filtered off from the dilute acid, and the filtrate gently warmed till the smell of hydro- sulphuric acid is lost. The operation of dissolving and destroying the organic matter is now conducted as follows : 1. The mixture contained in a perfectly clean porcelain dish is heated over a water bath (a common saucepan may be used) and powdered potassium chlorate added from time to time as soon as the effervescence caused by the previous addition has ceased. The stomach, intestines and contents will be very readily dissolved, but the liver and kidneys require long digestion. It has been recommended to conduct the operation in a retort connected with a receiver, 4;o avoid loss of arsenic as chloride, but this renders the operation much more troublesome, and if the temperature of the mass be kept below 100°, no volatilisation of arsenious chloride need be feared. Of course the operation must be conducted under a chimney to carry off the fumes arising; as soon as all solid particles are disintegrated and nothing but a yel- low flocculent matter remains in the liquid, an equal bulk of water is added and the heating continued till no smell of chlorine is observable. It may be necessary to add more hydrochloric acid if solid matter remains and no effervescence ensues on the addition of a fresh portion of chlorate. 6 82 2. The whole must then be filtered through white filtering paper which should have been previously tested for arsenic as some speci- mens have been found to contain it ; the residue well washed out with warm water and the filtrate, if too great in bulk, may be evapo- rated down to about a pint. 3. Washed hydrosulphuric acid is now passed in a moderate stream through the still hot solution, the precipitate formed thrown into a filter and well washed. The filtrate may deposit some more sulphide on standing or on evaporation. A pure yellow precipitate ;^ill indicate arsenic, an orange yellow antimony, and a brown or black mercury, lead, bismuth, &c. In these cases, however, arsenic may of course be present. A light coloured precipitate will often be formed even when no arsenic is present, from the action of a small quantity of chlorine still remaining in the solution. Such precipitate should be examined as if it were arscnious sulphide, that is by the following tests. 4. The precipitate while on the filter is drenched with ammonia by which the whole of the arsenic sulphide will be dissolved with only a trace of antimonious sulphide, the others will remain undis- solved. The filtrate is evaporated to dryness in a clean porcelain dish in a water bath. The solution of the sulphide in ammonia may bo aided by rubbing down with a feather. 5. The residue left after evaporation, which is generally of a brownish colour, is digested with fuming nitric acid ; by long con- tinued heating all the sulphur at first separated may be dissolved, but this is not absolutely necessary. The solution is neutralised with pure sodium carbonate and evaporated to perfect dryness- The carbonate must be free from chloride, the presence of sulphate is immaterid. By this process we have the arsenic converted into arsenic acid combined with soda, but organic matter may not be entirely absent; to remove this the next operation is adopted. 6. One or two drachms of pure sodium nitrate are fused in a porcelain crucible and the dry mass (5) thrown in gradually in small portions. A fresh portion should not be introduced until the blackening, which usually ensues, has entirely disappeared. I3y this process every trace of organic matter is destroyed and any free sulphur which may have been present converted into sulphuric acid. We have therefore in the fused mass sodium nitrate, sulphate and iiT'.' .1,;.,'. ^.ii'-i S?."'. ft^'-^ ' jV^'i^'t'-i't' 'i < - ^K,^ V:. ■ •;:; J': ■-'. ••'■ " '•-■>■. , * . f '.- xti V-f>); ^jr ' ;* ; vii ;;7'-/. ft. • • ;' '.':<:'i<:.i<;>i "if ;Y^>.: ■fv.; ;'^ ih .^ Ti •-,-•■;.(" i-jl -.•«,•» .« .''. :,;!■ "•,''.•"'■•11 '♦'"■ 'r'Jfr 'i') U-' ,5-1 y '!(. 83 arsenate, as hy tho fusion, if not by the previous action of nitric acid, all the arsenic will have been poroxidised. The nitric acid must now bo got rid of. 7. Add pure sulphuric acid and heat until all red fumes coaso to be evolved, and dense white vapours of sulphuric acid are formed. The operation should be conducted in a rather large crucible, and it may be necessary to add sulphuric acid from time to time. A modification of the process will lead to the detection of anti- mony if any is present, viz., dissolving the fused mass in water when sodium antimonate will remain undissolved. The solution filtered oflF from the insoluble antimonate may be mixed with sul- phuric acid, evaporated to dryness and treated as in the preceding paragraph. In this solution we have therefore arsenic and sul- phuric acids with sodium sulphate. 8. The solution should be introduced into a burette or alkali- meter and the volume noted, a portion may then be tested by Marsh's apparatus. A bottle with two necks, or a wide mouthed flask is fitted with a funnel reaching nearly to the bottom, and a delivery tube connected with a drying tube coi :aining calcium chloride or potassium hydrate. This again is connected with a tube about 17 inches long, bent perpendicularly about 3 inches from the end and drawn out into a rather fine point or jet. In 'ack of a long stemmed funnel, a wide tube may be inserted into the cork and a small funnel placed in this. Pure zinc and pure sulphuric acid diluted with 5 or 6 volumes of water are introduced into the bottle and the hydrogen allowed to pass off for a time, a portion of the tube near to the drying apparatus is then heated red hot by a spirit or gas-lamp, it may be prevented from bending by a covering of copper gauze, if no metallic ring is formed beyond the heated portion after a quarter of an hour, we may conclude that the materials used are free from arsenic. A small quantity of the solution (7) is then introduced while the tube is still heated, when a ring, more or less metallic, will be immedi- ately produced if arsenic is present. The gas both before and after the addition of the suspected solution may be kindled at the drawn out point, and will burn with the weh known pale flame if the hydrogen be pure, and with the characteristic bluish white colour if arsenic is present. If the stream of gas is slow all the arsenic S4 will be deposited in the tube, and only pure hydrogen will burn at the point, but if the stream is rapid, and the addition of arsenic causes the hydrogen to be evolved much more readily, a portion of the arseniuretted hydrogen may escape decomposition, and will give the above-named colour to the flame, which may be made to produce spots on porcelain plates held therein. The bent portion of the tube may be turned round and intro- duced into a solution of silver nitrate. If arsenic is present, metdlio silver will bo precipitated, and all the arsenic remain in solution as silver arsenite, which may be precipitated by the careful addition of ammonia. For delicate investigations the above apparatus is necessary, but for ordinary experiments a common 8 oz. phial may be used with a rather wide tube put through the cork, ground off obliquely below and drawn out into a not very fine point above. The hydrogen first evolved may be tested by its colour and by holding a porcelain plate or capsule in the flame about half way down. No spot will be pro- duced if the materials are pure, but immediately after the introduc- tion of the arsenical solution. Care should be taken not to hold the plate too long in the flame as the deposit of arsenic may be volatilised. If the antimony has not been eliminated by the process described in 4 and 7 the spots or rings produced may be owing to the presence of that metal. To distinguish them from spots or rings produced by arsenic, the following experiments may be made. The rings when gently heated volatilise completely — arsenic. The rings when gently heated volatilise only partially, and on appli- cation of a strong heat leave metallic globules — antimony. The ring when gently heated in a current of hydrosulphuric acid becomes yellow — arsenic. The ring similarly treated becomes orange — antimony. The coloured ring so produced, acted on by a current of hydrochlo- ric acid, remains unchanged — arsenic. Is dissolved and dissipated — antimony. The ring or spot treated with a solution of potassium iodate dissolves with an evanescent reddish colour — arsenic. The ring or spot is not dissolved by the same solution — antimony. The ring or spot is dissolved by so-called chloride of soda — arsenic- It is not so dissolved — antimony. . •, ,,; ,t -,■■■;'.••.;■■', I' .1 h ■ !-'.■■ ■■■-' .■■**'!;■>;.■. U ... •.-.■■:l[ Ul^'-I i .1'.' ," . ■.•..'I'->U . ' ■ l>' 1 1 I '. . 1. iW.-'T- r ■(' :;i ' ■•'!.;■. . i- .; ,;U.-rl'V 'I- ■i;"r{!,-' 'V j:ii'i.>it l/l'- •u\:rinL. ^':' .'m- y^ 1 f •■'■;, I ill ri UT, ■ t.u.;;iti'.i>.\t ',Mi. .u>.n!.c. :;■>'.'. -.i-n;. Ut;-;i ..-J ..,-, n.: ' •; '.: '■■'•■"^i 85 « The ring or spot treated with hot nitric acid and evaporated cure- fully to dryness until every trace of volatile acid is dissipated (thn temperature must not be much above that of boiling water), gives with silver nitrate a brick red colour — ursenio. Similarly treated the ring or spot gives no colour — antimony. The presence of arsenic having been proved by the above tests, it may be necessary to ascertain the quantity of the poison present, and it is desirable or advisable to do so in all oases requiring judi- cial investigation. The remainder of the liquid obtained in 7 may be treated in either of the following ways. It may be treated with sulphurous acid either in the form of gas or strong solution, boiled till all smell of sulphurous acid is lost, precipitated by a current of hydrosulphuric acid, the precipitate collected on a tared filter, washed, dried and weighed. Every 100 grains of the so-obtained arsenious sulphide correspond to or represent 80-4 of arsenious acid. The solution obtained in 7 may also be mixed with a solution of magnesium sulphate and ammonia, allowed to stand for 24 hours, the precipitate of ammonio-magnesian arsenate filtered, washed with dilute ammonia, dried and weighed (the weight of the filter must have been previously ascertained), every 100 grains of the salt so obtained correspond to or represent 521 of arsenious acid. From the quantity of sulphide or arsenate thus obtained from the portion of the solution remaining after detecting the arsenic, the whole quantity contained in the substance under examination may be easily calculated. The sulphide may also be dissolved in ammo- nia, the solution filtered, evaporated in a weighed capsule and the whole again weighed j by this process any precipitated sulphur is got rid of. In testing for arsenic, it may be remarked (Wohler), that the diflSculty lies not so much in the detection of the poison as in the proof of its absence from the re-agents and materials employed. It is difficult to obtain zinc perfectly free from arsenic, many speci- mens of sulphuric acid contain the same impurity and will of course give arseniuretted hydrogen when used in Marsh's test. Even the filtering paper as before mentioned may occasionally contain arsenic. 86 rUUIFICATION OF RE-AGENTS REQUIRED IN TESTING FOR ARSENIC. Ui/JmrliJoric acid, tlio commercial article, may bo diluted with an ccjual bulk of water and hydrosulphuric acid passed throujjh it for several hours, filtered from the precipitate formed and gently warmed until no smell of hydrosulphurio acid is perceptible. It may also be prepared by treating four parts of common salt with a cooled mixture of seven parts sulphuric acid with two of water, and conducting the gas evolved first through a small quantity of water contained in a two necked bottle, and thence into sir ounces of water kept cool. The operation is continued as long as any gas is evolved, and the acid obtained will bo sufficiently strong for the solution of organic matter as above described. Sulphuric acid often contains arsenic and may bo freed from it by diluting with twice its bulk of water and treating with hydrosul- phurio acid, the excess may be expelled by heat after filtration. Tills acid may bo concentrated by evaporation, but a pure strong acid may be obtained by heating strong sulphuric acid in a retort and passing hydrochloric acid gas into it for an hour or more ; the distillate is tested from time to time with hydrosulphurio acid until it gives no yellow precipitate. The residue in the retort may also be tested by IMarsh's apparatus, the greatest care being required to prove the absence of arsenic, and no reliance to be placed on the purity of commercial samples. Carbonate of soda. This must be perfectly free from chloride, as otherwise in operation 7 the arsenic may be volatilised as chloride and lost. To obtain pure carbonate, the common so-called bicarbo- nate may be placed on a filter and washed with water until the washings give no precipitate, or even opalescence with silver nitrate after supersaturation with 2>ure nitric acid. Nitric acid must be free from hydrochloric, and may be obtained sufficiently pure by distilling as long as the distillate gives a precipi- tate or opalescence with silver nitrate. The residue may then be distilled over, or in most cases may be used at once as pure acid containing usually only small traces of impurity, which produces no injurious effect in the operations above described. ^ <. 11' i ,,..1, •.'.'1 •,•■. (i,.ntVi'.v ;■'.,,>■ .-nn i rHf.Tw»i, ftiwi ( . t >.. -.1 *, { ',. ! :!■■',•> .'icivttTJ.j ■ \ I ,-• .H. - .1 "\ .' -^ij t' -.•■ ,-, .- ■ .r - " I'l' . ' ■ ■ ■ '. » ),.i. ■■ , ... • •• - - ,- .1 .-Ul- •;■ --I'vi.u' -^i.- •S'*' 87 Zine. Tho proparation of porfootly puro zino can soarcoly be efTootod unless in a well appointed laboratory, but commorcial gampluH may often bo mot with suffioiently puro for toxicologioal invoHtigations. The other re-oqonls required oro usually frco from arsenic, and the paper may bo tested by treating with nitric acid, saturating with sodium carbonn 3, evaporating to dryness, fusing tho residue, treat- ing with sulphuric acid, and testing the solution for arsenic as described at page 41. ANTIMONY. Tho presonco of this metal, if unaccompanied by others forming dark coloured sulphides, is generally recognised at once by the orongo red colour of tho precipitate formed by hydrosulphuric acid. If collected on a filter, washed with water and treated with ammo- nia, tho arsenious sulphido will dissolve, and almost tho whole of tho antimonious sulphido remain behind ; it may bo dissolved in hydrochloric acid and examined by tests described at page 43. Any antimony that may have been dissolved by tho ammonia will remain as antimonato after fusion with sodium nitrate and washing with water. Tho characters of antimoniuretted hydrogen, and of the spots pro- duced by its imperfect combustion, have been already described. TIN. Salts of this metal arc poisonous, but are not often employed for criminal purposes. If any salt, such as those used by dyers, has to be sought for in organic mixtures, tho process previously described may be adopted, tho precipitated sulphido which will be of a dirty yellow colour, it may bo fused with potassium cyanide, and the resulting metallic bead treated with hydrochloric acid and the solu- tion tested for tin as described at page 39. BISMUTH. The sulphido is soluble in nitric acid, also in strong hydrochloric acid, the solution evaporated to dryness yields a residue which ia decomposed on the addition of water with separation of a white Bubsalt insoluble in tartaric acid. The salts of bismuth can scarcely ^ 88 1)0 reckoned amoii{» the poisons. Several cosmetics consist of sub- salts of bismuth and some are composed entirely of lead carbonate ; the soluble salts of lead are not decomposed by water, and the lead chromale is soluble in potassium hydrate while the bismuth chro- mate is not. ZINC. Salts of zinc are not often employed as poisons for criminal pur- poses, but accidents have happened from the accidental use of the sulphate and chloride. In the preceding process for the extraction of arsenic and other metals, the zinc will be contained in the filtrate from the precipitated sulphides, from which it may be thrown down by ammonia. The precipitate will usually be of a greenish colour from presence of iron, it may be dissolved in hydrochloric acid, the solution heated wif'^ a little nitric acid, precipitated by excess of ammonia, filtered, and the filtrate tested for zinc as described at pages 28-29. MERCURY. The precipitated sulphide is black, insoluble in nitric acid if pre- viously well freed by washing from hydrochloric acid; soluble in nitro-hydrochloric acid, forming a solution in which mercuric oxide may be detected by the tests described at page 35. The precipitate when dried may also be heated with sodium carbonate in a reduction tube acd a sublimate of metallic mercury obtained. It must be remembered that calonjel (mercurous chloride) will be converted during the process into corrosive sublimate (mercuric chloride), which will of course give the reactions of mercuric oxide. The mercury may perhaps best be detected in a solution acidified by hydrochloric acid, by the introduction of a piece of gold wire, round which some strips of tin foil have been wound ; a grey deposit on the portions of the exposed gold wire will indicate mercury; the stains are removable on the applic ation of heat. In cases of poisoning by corrosive sublimate, small particles of the salt may often be found in the folds of the stomach, and these when heated with sodium carbonate in a reduction tube will yield a subli- mate of metallic mercury. .0 ',, •) ;»i'i^ WiC <;i'ni!iw\ ;.*j-tsi vir.^op* I 1 ;'..- V '■'■■.:■ •.f 89 COPPER. If precipitated as sulphide from the decomposed organic mixture, the black sulphide will remain undissolved when treated with ammo- nia, it may be dissolved in nitric acid and the ordinary tests for cop- per applied. Sheelo's green (copper arsenite) gives a red residue when heated with potassium hydrate and a solution in which arsenious acid may be detected. Heated in a reduction tube with dry sodium carbonate and char- coal or potassium cyanide, it gives a ring of metallic arsenic which may be recognised by the tests mentioned at page 41. All compounds of copper when moistened with hydrochloric acid and exposed to the outer flame of the blowpipe, produce a blue or green colour. LEAD. This metal will be precipitated as black sulphide by the continu- ous action of hydrosulphuric acid, insoluble in ammonia or ammo- nium sulphide, but soluble in hot nitric acid of moderate strength, leaving more or less of a white residue of lead sulphate. If very strong nitric acid be employed the sulphide is entirely converted into sulphate which remains undissolved. It may be recognised by its solubility in hot hydrochloric acid, and by being reduced when heated before the blowpipe if mixed with sodium carbonate and potassium cyanide. In solution it may be recognised by the tests described under Lead. 90 ORGANIC POISONS. HYDROCYANIC ACID. This acid and tho potassium cyanide often act as poisons wliOQ used either purposely or accidentally. Potassium cyanide has been employed instead of potassium carbonate in making an effervescing drink, and the cyanide used by photographers has given rise to . many fatal accidents. Oil of bitter almonds contains the acid when in its crude state and has often been used as a poison. Peach ker- nels, bay leave? "nd various other substances yield hydrocyanic acid when distilled, especially if allowed previously to partially ferment. The amygdaline contained in them does not seem of itself to bo poisonous, unless decomposition has set in. The root of the latro- pha Manihot from which tapioca is obtained seems to contain the acid or some substance yielding It, which is dissipated in the drying process adopted in preparing cassava and tapioca. Nitrobenzol now extensively used as a "■ jstituto for oil of bitter almonds has been found to be a virulent poii-v/n, but is entirely free from hydrocyanic acid. If the acid or salt is in a pure state the various tests described uc page 52 may be applied, but if mixed with organic matter, as in the contents of the stomach the acid must be distilled off; tartaric acid having been added if the potassium salt is suspected. With thick liquids this process is attended with some difficulty, the best method is to heat the mass in a retort connected with a receiver or condenser and to pass steam into tho retort by means of a bent tube reaching nearly to the bottom. The distillate may then be examined by the proper tests and tho most minute trace of acid detected. Usually hydrocyanic acid escapes very rapidly from the body, easily recog- nised by its peculiar odour, and hencb after a few days it may hap- pen that no trace of it can be detected. By tl -^ abovo process of separation the writer has detected its presence after thirteen days interr:ent. The acid may also be detected without having recourse to distilla- tion, by suspending over the suspected mass contained in a dish and 'xd tnth hi'A-iir.r s^o;^, 12 ; •.•:yni' <-' pv»"';')(>';ill. tl Ij: ):V.:il uit r«'>n«.. . 1. '■'• ■ •' 1 ;;: ■' •;■ .I,^'/ •».'».'>. 1 i'. • :i .. ■" ■ (/;'.' '.<1u<;;;' -^^ ' ! ■■■■ ' "■ ■•: .' ■'\usy--' \ '■ .*' \ .' ; ■ r '. > : ; (i - ■> (/ / .i "■.•■.!■ • • ',;■■ r'i^u.Ai;«, ' " ' ;,•■ ■ v ■- .^ ■'.'! •■'•'• "' it' ,.;■ . ' ',,,. ;■ .'. ;. m». . >-li i< .- ■■■'.>',.■ ' ^ ;. t\t, , •■,ii;m., v'.^ • . . : iv^ yi:'.> :i l::.- 1-^ ,4 . . ^(;;:iv >.. t.'-'-, i.;' - 1 !;•■■*,.. ^ir .. \.:7 ^r■:^ 01 acidulated with tartaric acid, a watch glass or capsule moistened with silver nitrate or amtnonium sulphide, covoring the whole with a bell-jar and allowing to stand for somo hours. The silver cyanide or ammonium sulphocyanato produced, if hydrocyauio acid is pre- sent, may then be examined by the proper tests. ESTIMATION OF TIIK STRENGTH OF IIYDROCTANIC ACID. As the officinal acid is very apt to deteriorate and diminish in strength, it is of much importance to be able to determine it, for which purpose two methods may be adopted. 1. The acid is fully precipitated by silver nitrate, the precipitate collected on a weighed filter, washed, dried and weighed. The excess of weight over that of the filter gives the quantity of silver cyanide, every five grains of which indicate one grain of hydrocyanic acid, the molecule of which may be represented by 27 while tbat of the cyanide is 1C4. The latter number divided by 5 gives 268 very nearly equal to 27. 2. A much more expeditious process is by means of a standard solution of silver nitrate, the use of which depends on the following facts : When potassium cyanide is added to a solution of silver nitrate a precipitate of silver cyanide is formed which dissolves ia excess of the precipitant forming the double cyanide K Cy, Ag Cy. This compound will always bo formed whatever other acids may be present. If reversing the experiment silver nitrate be added to potas.siura cyanide containing (say) some chloride, no precipitate will be formed until the whole of the cyanogen present has been used up in forming the above salt; after that any excess of the nitrate will produce a permanent precipitate of o}-' rido. As two atoms of cyanogen are piesent in the above sal' ' ar that two molecules of hydrocyanic acid neutralised witl. >ou. ,a would ex- actly react upon one molecule of silver nitrate; the numbers repre- senting these molecules being 54 and 170. The proc S3 then is conducted as follows : 54 grains of the acid under examination are mixed with excess of potassium hydrate with a little sodium chloride ; 170 grains of silver nitrate are dissolved ia water contained in a burette divided into 100 parts. The solution of silver salt is added gradually with diligent stirring until a perma- nent precipitate or opalescence is formed, and the number of degrees 92 used read oflF. If 100 moasuro, i. e., tho whole had been used, then the acid must have been absolutely pure containing 100 per cent, of H Cy, but aa in practice wo never meet with such acid, it is bettor to use 17 instead of 170 grains of silver nitrate, a permanent prt- cipitiito after tho use of 100 measures would then indicate 10 per cent., after 10 measures 1 per cent., and after 1 measure 01 per cent. Supposing 25 measures of such solution bud been used before a permanent opalescence had been produced, but on the addition of a drop more a milkiness were produced not removable on stirring, then wo should conclude that the acid contained 25 per cent, of pure hydrocyanic acid. This process is far preferable to the one above described, as it may bo completed in a few minutes, while the other requires many hours. OIL OF BITTER ALMONDS The poisonous property of this oil in its crude state is owing to the presence of hydrocyanic acid which may bo detected by the usual tests. NITROBENZOL. This substance is now extensively used as a substitute for tho above oil in perfumery, and several accidents have happened from its use by swallowing or inhalation, the results appearing after a con- siderable lapse of time. The substance suspected to contain it may be di.stillcd, the distillate shaken with ether which dissolves up tho nitrobcnzol, tho ethereal solution evaported till all ether is expelled and mixed with a little zino and sulphuric acid, by this aniliuo will be produced which of course combines with the acid. The solution is treated with excess of potassium hydrate, and the whole shaken with ether which dissolves the aniline. The addition of ferric chlo- ride to this solution will produce a fine purplish violet colour. OPIUM. This substance may be often detected by its smell, and by the chemical test for meconio acid rather than by those for morphine. Ferric chloride added to a solution of meconic acid or to a light coloured solution of opium, produces a red colour which is not des- troyed either by heating or by the addition of a solution of mercuric chloride. It is thus distinguished from acetic and sulphocyanic acids. V3 .1.1 I't'v'O . .:.,]. 'tV' .' •vi:!. (I'l • \ ''.\'. 1 , !'>.'' \ ., ,-'1 ' • !'■:' .•. ' ■ '"•■' !i \"\ y'it 1,- i . ) ^. ■ . , . • M.i •■ ,.i->>^K ,., • ' !■-(■ •U'i't ' ' ■ 1 . ' ,.,, , : ■ ' t'., ! ■•,(, l>i'<.V * « .,1 .■,.(-• .■- ' 1 ■ .•■;•;■- 'V .♦-., n r>tj Al... ' 'f ." * . ' ^ ■■*' • ; "V. ■• ■•■■ ' ■ •\, •' ■, . 1 , ' ■ ■ t ' '.li' '•-!'« 'hi^Vv^ (*.••>.' Af *i . I -V \> 'KiV S'S. '■'\fl .• V. . ji-. 'Vl 93 In organio mixtures, tho nioconio acid may bo precipitated hy lead acetate, and tlit; wuHhod procipitoto dccomposod by a little dilute huI- pliurio acid. The filtrate from thia may bo tested with ferric clilurido. VOLATILE ALKALOIDS. The volatile nlkaloidH, nicotine and coniine can bo distilled over from Hubstnnccs containing them by boiling with water, some Htrong alknli must be added if acids aro present. To separate the alkaloid in a pure state tho distilluto must bo neutralised with oxalic acid, cvoporated to dryness, digested with spirits of wine, which dissolves the salt of the alkaloid nnd leaves any ammonium oxalate that may bo present. Tho solution is evaporated, di.stilled with potassium hydrate, and tho distillate shaken with ether which dissolves the alkaloid, and leaves it afi an oily liquid on spontaneous evaporation. NICOTINE. Remains as a colourless or yellowish liquid, which on heating evolves white fumes smelling strongly of tobacco. I'latinic chloride produces a yellowish ilooculent precipitate in an aqueous solution of nicotine, chlorine water produces no change. The alkaloid is easily soluble in water. CONIINE. When heated it gives off a very strong pungent repulsive odour, and has a very acrid and disagreablo taste. It is exceedingly poisonous. Platinio chloride produces no precipitate in aqueous solutions. Chlorine water produces a strong white turbidity. The alkaloid is difficultly soluble in water. FIXED ALKALOIDS. These cannot be distilled over with water. MORPHINE. This alkaloid is distinguished from all the following by being precipitated from solutions of its salts by potassium hydrate, but re-dissolved by excess. Morphine and its salts give with nitric acid a red colour, destroyed by reducing||agents, such as stannous chloride, sulphurous acid, sul- phites, &c. 94 With ferric chloride a green or bluish green colour is produced. Iodic acid produces a yellow colouration caused by separation of iodine, which may be detected by the addition of starch paste. Various other bodies produce the same colouration j but while in theiu it is destroyed by ammonia, it remains unchanged when caused by morphine. Other tests are of comparatively little value. The alkaloid when freshly precipitated is somewhat soluble in ether, and hence may be extracted by shaking a solution supcr- Situratcd by some base with elbei. If allowed to stand and become crystalline it is quite insoluble in that liquid. This fact is of importance in testing for morphine in poison cases. NARCOTINE. . This alkaloid, with quinine and cinchonine, form a group which is distinguished by tho salts giving a precipitate with potassium hydrate insoluble in excess; the salts are also precipitated by hydrio sodium caibonate (bicarbonate of soda), even from acid solutions. The salts are decomposed by ammonia or alkalic carbonates, and the precipitate is easily dissolved by shaking with ether; the ethe- real solution on evaporation leaves the pure alkaloid. Nitric acid dissolves it, and produces a yellow colour on heating. Narcotine dissolves in sulphuric acid to a colourless or very feebly yellowish liquid ; the addition of a most minute trace of nitric acid produces a red colour. QUININE. Alkalies and alkalic carbonates produce a white precipitate ia salts of quinine which after a time becomes slightly crystalline, insoluble or nearly so in excess of the precipitate, but easily soluble on shaking with ether, when two distinct layers are formed, the upper being an ethereal solution of the alkaloid. Ilydric sodium carbonate produces an immediate precipitate if the quinine be present in not less than one part to the hundred of acid and water. Chlorine water and ammonia, added to a solution of quinine, produce a fine green colour. Chlorine water and a little potassium ferrocyanide, added to solu- tion of quinine with the subsequent additions of a few drops of 95 ammonia, produce a fine red colour passing into brown, destroyed by acid and reproducible by ammonia. Concentrated sulphuric acid dissolves quinine and its salts ; on heating a yellowish colour is produced, which after a time passes into brown. Quinine itself, as well as its salts, is intensely bitter to the taste. CINCHONINE. Alkalies and alkalic carbonates produce in dilute solutions a white highly crystalline precipitate of cinchonine, insoluble or nearly so in excess of the precipitant, and also insoluble in ether, by which test it is easily distinguished from quinine. The precipitate is easily soluble in boiling alcohol. Hydric sodium carbonate acts in the same way. Chlonne water and ammonia produce no green colour. Chlorine water with potassium ferrocyanide and ammonia produce no red colour. Concentrated sulphuric acid dissolves cinchonine and its salts; on heating a brown or even black colour is speedily produced, therein differing from quinine. The salts of cinchonine are soluble in water and bitter to the taste, but the alkaloid itself being almost insoluble in water is very nearly tasteless, hence its use in the so-called sweet (juhdne, which contains no quinine at all, but is only a mixture of cinchonine with some saccharine matter. SALiriNE. This substance though not an alkaloid may be hero mentioned, as it is sometimes used as an adulieration of quinine and its salts, pos- sessing a bitter taste and souk vhat similar though weaker febrifuge qualities. Its presence may be detected by the addition of sulph- uric acid, when a red colour is produced, especially after gentle heating. Also by distilling with a little dilute sulphuric acid and potassium chromate, when a distillate is obtained giving a blue-violet colour with ferric chloride. Also by giving a clear solution with dilute sulphuric acid, which becomes turbid on boiling from formation of insoluble saliretine ; 96 the solution contains the quinine and grape sugar, which latter may be detected by heating with cupric sulphate and potassium hydrate. (See Sugar) NOTE. Quinine and its salts can scarcely be considered as poisons, but their constant use as medicinal agents renders their introduction among the alkaloids necessary. The following remarks on possible adulterations of its salts may not be without value. Starch may be detected by boiling with water and adding tinc- ture of iodine, when a blue colour will be produced. Also by the blackening action of sulphuric acid. Also by the formation of sugar by boiling with dilute sulphuric acid. Sugar may be detected by boiling for a few minutes with dilute sulphuric acid, adding cupric sulphate and excess of potassium hydrate and again heating, when red cuprous oxide will bo formed. It can also be detected by precipitating the quinine by ammonia and observing the sweet taste of the filtrate. Quinine and its salts blacken when heated on platinum foil, the charcoal requiring long continued heat to cause it to burn away ; any permanent residue of a white or greyish colour will indicate an adulteration of gypsum or some earthy matter. The action of ether on quinine may be employed as a means of distinguishing it from cinchonine, together with the other tests above described. STRYCHNINE. This alkaloid as well as brucinciind veratrine is precipitated from its solutions by potassiura hydrate but is insoluble in excess, it is not precipitated by hydric sodium carbonate. By the latter test this group of alkaloids is distinguished from the preceding. Potassium hydrate and sodium carbonate produce a precipitate which under the microscope appears highly crystalline, insoluble in exceso of the precipitants. Ammonia produces a precipitate soluble in excess but separating again after a time in the form of needles. Hydrio sodium carbonate produces a precipitate in neutral solu- tions immefliately, in acid solutions only after a time. p 97 Potassiuin chromatc and sulpliocyanato produce precipitates in solutions of strychuino which arc more or less crystalline according to the state of dilution. Nitric acid added to dry strychnine produces no colour if the alkaloid is pure; but usually a red colour is observed owing to the presence of brucine. Sulphuric acid dissolves pure dry strychnine without colouration, if to this solution an oxidising agent bo added, such as a chromatc, manganese dioxide or lead dioxide, a beautiful but evanescent bluish purple colour will be produced, changing rapidly to red. The chro- uiate iiiay bo used in solution, only a small fjuantity being added, or in the solid form, the crystal being moved through the solution will produce purple streaks. The reaction is prevented by the presence of verj'^ small quantities of impurities, hence the vessels employed must be perfectly clean and the strychnine pure. The evanescent purple colour is characteristic. The action of a solution of strychnine salts upon small frogs may also bo employed as a test. In from a quarter to half an hour tetanic convulsions will bo produced ; the animal should be fully immersed in the solution. BRUCINE. Does not often come under notice as a poison, in its reactions it closely resembles strychnine, but gives a deep red colour with nitric acid, and no purple with chromic acid, only a pink changing to yel- low. The red colour produced by nitric acid is not changed by reducing agents. VERA.TRINE. Nitric acid forms resinous lumps which dissolve to a colourless solution. Sulphuric acid also forms resinous lumps which dissolve to a faint yellowish fluid, changing to reddish yellow, and finally to deep blood red. The colour disappears after some hours. This test seems characteristic. Veratrine and brucine when occurring in a pure state may be at once distinguished from all the other common alkoloids by the action of a few drops of pwre sulphuric acid. Veratrine gives a 7 08 yellow colour changing to blood rod. Brucino gives a rose colour changing after a time to yellow, the rose colour is very characteristic. ]\Iori)hinc and brucinc give a red colour with nitric acid, destroyed by reducing agents in the case of morphine but not in that of bru- cinc. It must bo remembered that commercial strychnine often contains brucinc. The action of sodium hydrosulphidc on bruriuc, lately recommended, has not proved satisfactory in the writer's hands. SEPARATION OF ALKALOIDS FROM ORGANIC MIXTURES, The suspected substance is mixed with twice its weight of alcohol and about twenty grains of oxalic or tartaric acid, and gently warmed for some time. The liver and other solid organs may be cut up, moistened with the warm solution, pressed out, and the operation repeated several times. The alcohulic extract is evaporated to dry- ness in a water bath, extracted with water, again evaporated, and the operation repeated with alcohol and water several times. The aqueous solution may then bo shaken with ether to remove colour- ing matter, as the salts of the alkaloids are not soluble in that men- struum. Some ammonia or sodium carbonate is added to alkaHnc re- action and the whole rapidly mixed with ether and well shaken. If morphine has once become crystalline it is quite insoluble in ether. Amylio alcohol may also be used as a solvent, and dissolves mor- phine more readily. The solution in ether may then be drawn off by means of a pipette, and evapornted to dryness. If the residue appears impure it may be re-dissolved in a little dilute sulphuric acid, and the same operation repeated. In order to obtain as much as possible of the alkaloid on one spot, the solution may be poured drop by drop on to a heated capsule, and the appropriate tests applied to the residue. Chloroform may also be used for extracting the alkaloid. It may be remarked that morphine is the most difficult to extract, its successful separation being the exception. 99 ALCOHOL. It may sometimes bo nccossnry to determine the prcsenco of this Dubataiicc in thn contents of a stomach. The whole mass should bo distilled either by itself or by means of the contrivanco described under the hei'.d of hydrocyanic acid. The distillate should then bo introduced into a small retort with some potassium bichromate and Bulphurio acid j on applying heat tho solution will become of a green colour owing to formation of chromic oxide, and tho distillate will acquire a yellow colour on addition of potassium hydrate. Other parts of the body besides tho contents of the stomach may be sub- mitted to tho same treatment. CHLOROFORM. ]May be separated by distillation and recognised by its smell. Chemical tests are scarcely applicable. niosnioRus. This substance is not often employed as a poLson, but accidents occasionally occur from its consumption either as rat poison or matches. In such cases the peculiar odour of phosphorus will be perceptible in the contents of the stomach, and tho mass will be slightly luminous in tho dark if gently wnrmcd. To prove tho presence of phosphorus tho suspected substance may be mixed with dilute sulphuric acid and distilled, the vapours evolved conducted into a tube cooled by water, whcii a faint light will be seen at tho mouth of the tube, and small particles of phosphorus will condense and may be received in a proper vessel and further tested by solu- tion in nitric acid, &c. 100 U E I X E . It is often of importance to determine the specific gravity of tliis secretion, for which purpose various instruments may ])o used. The simplest, and, at the same time, the most accurate plan is to attach a piece of glass, such as a moderate sized stopper to a piece of fine platinum wire or silk. After this has been weighed in air, its loss of weight in water must be ascertained, let this be called A. Then to ascertain the gravity of any sample of urine, determine the loss of W{>ight in the urine ==B. The specific gravity will be found by iiividingnj by A; the weight of the stopper in air and its loss in water may be scratched on the glass itself by means of a hardened file. lleakhy urine varies from 1003 to 1030 according as the experi- ment is made before or after the digestion of a meal, or after much water or other fluid has been taken. The average may be said to lie between 1015 and 1025. Its reaction is generally slightly acid, but if examined after meals it is sometimes neutral, on keeping for some time it becomes alkaline from formation of ammonia. JNIorbid urine is frequently strongly alkaline, and will sometimes cfTcrvesco on the addition of acid, the urea having been decomposed into ammonium carbonate. Healthy urine deposits no immediate precipitate on cooling, but a deposit is not un frequently observed in the night's secretion, which on the addition of the morning's urine either disappears or not. In the former case the deposit is probably ammonium urate, in the latter ammonio-magnesian phosphate, or some earthy salt. UREA. Healthy urine concentrated to about one-half or one-third and mixed when cold with an equal bulk of pure nitric acid, deposits plates of impure urea nitrate ; if an excess of urea be present, the concentration need not be carried so far. The proportion varies from about liJij in healthy, to j^off in unhealthy mine. Oxalic acid may be used instead of nitric. 101 URIC ACID. Exists in healthy urine to the extent of about 1 part in 1000, in unhcahhy urino there is sometimes twice as much, in which case it IS usually deposited as a reddish sediment, not dissolved on heating. It is seldom free from ammonium urate. The deposition is much assisted by the addition of a little hydrochloric acid. See fig. 3, plate 2. To recognise the presence of free uric acid, the sediment should be boiled with a small quantity of water to dissolve out the urate, the residue will then be found to be soluble in potassium hydrate, and ro-precipitated on addition of hydrochloric acid, yomc of the precipitate being collected on a filter and washed, is removed i:.to a white porcelain capsule and treated with a few drops of pure nitric acid. EfTorvescenco takes place, and on carefully evaporating to dryness, a red colour is produced, which on the addition of potas- sium hydrate (after cooling) yields a fine purple colour. Care must be taken to drive off all trace of nitric acid, but not to heat so strongly as to char; when time is no object the operation is best conducted over a water bath. IIIPPURIC ACID. This acid appears to bo present in all urines especially in that of vegetarians. In certain diseases, such as chorea, its quantity in- creases considerably. It can be detected by evaporating a pint of urino to a syrup, acidulating with hydrochloric acid, shaking with ether, evaporating the ethereal solution and boiling the residue with a little water. On cooling, hippuric acid separates in feathery crys- tals. Its physiological relations are not well understood, and as it is found in the urine of herbivorous animals to a large amount it can scarcely be called a morbid constituent unless present in abnor- mal quantity. SALTS. Fresh and healthy urine contains only slight traces of ammonium salts, in disease the quantity is often largely increased. On evapo- rating urino and carefully incinerating, a residue is left amounting to about 12 or 15 in 1000, whi'ih yields to water alkalic sulphates, chlorides and phosphates. The insoluble portion consists principally of calcium and Uiagnesium phosphates with slight traces of silicic 103 acid find aluininti. Those earthy salts nrc sometimes hirgcly in- creased in quantity. AMMONIUM URATE. Is often present in morbid urine and is deposited on coolinf^. On applying heat it re-dissolves and the urine becomes perfectly clear. The deposit, which is usually of a reddish colour, may bo collected, washed and gently warmed with potassium hydrate; it dissolves with evolution of ammonia forming a solution from which hydro- chloric acid precipitates uric acid which can be recognised by the proper test. The deposit itself may at once bo treated with nitric acid, and the abovo method of examination is applicable to calculi consisting of urate as well as to deposits. Occasionally sodium urate occurs. The deposit if examined under the microscope appears in roundod grains without crystalline structure, if treated with a little hydro- chloric acid small crystals of uric acid soon make their appearance. The sodium urate may be recognised by not giving off ammonia when treated as abovo and by tinging the blowpipe flame yellow. Its microscopic appearance is also characteristic. See fig. 8, plate 2. MUCUS. Is often found in morbid urine in largo quantities, it forms a viscid sediment which, when shaken up, does not mix uniformly with the urine, but forms ropy masses in which frequently enormous quantities of the prismatic crystals of ammonio-magnesium phosphate are entangled, which render the mucus more opaque and cause it to resemble pus. Such urine however will give no precipitate with nitric acid or on boiling, while urine containing pus gives a slight precipitate. Urine containing mucus is often alkaline when passed, owing to the action of this substance on the urea. See figs. 10 and 11, plate 2. COLOURING MATTER. The red colour of urine may bo owing to purpurine which readily attaches itself to ammonium urate, or to blood. The latter can be detected under tlie microscope, or by the usual tests for blood, and by the red colouring matter being insoluble in alcohol while pur- puri;;!c is easily soluble. Various other colouring matters arc occa- 103 sionally found in urine. It has been proved that all urino contains a substance allied to the glucosidcs, wbich when treated with dilute acids or by natural decomposition yields grape sugar and indigo blue; hence occasionally blue urino is met with. For figures of blood corpusculcs see plate 2, fig. 12. FAT AND CHYLE. Urino containing these substances exhibits under the microscope numerous small transparent globules. See fig. 9, plate 2. If shaken with ether, the globules will bo removed if consisting of fat, but will be unaltered if composed of chyle, they arc also in this way distin- guished from the fat globules in milk, which are very similar in appearance, the latter being covered apparently with a coating of Bomo protein compound, arc not dissolved by other unless previously shaken with potassium hydrate. The ethereal solution may also bo evaporated and the residue examined. The substance called kies- tcin observed after some days on the urine of pregnancy, seems to owe its peculiar appearance to the presence of crystals of the triple phoephato mixed with some organic matter. SUGAR. This substance has been proved to be present in small quantities in almost all urines, whether as a natural product or as a result of the decomposition of a glucosiJo. Occasionally it is present in abnormal quantity pvoduciug or characteristic of tbo disease called diabetes mcUitus. The amount of grape sugar in the urine is some- times enormous, and occasionally immediately previous to decease, vanishes altogether. Diabetic urino has usually a high specific gravity, sometimes as high as 1055, usually from 1030 to 1045. The smell of the urine is usually different from that of the healthy secretion and generally forms a white scum on the surface after standing. Trommer's test. The urine is mixed with a few (8-10) drops of solution of cupric sulphate, potassium hydrate is then added till the blue precipitate first formed is dissolved and a clear solution obtained. The whole is then gently heated, not boiled, when a yellow or red precipitate will be formed. Occasionally no precipitate is produced, but only a red colour. It is always well to make a corresponding experiment with healthy urine. C *v ^' lOi Tliis test, althoup;h not absolutely infallible, is probably tbo best for f^encral use, ns that of Mauiiicn6 dopcndinp; on the use of stan- nic chloride is not available unless in well-appoiiitccl laboratories. -^ If the urino be mixed with half its volume of potassium hydrate ^V nnd boiled for a short timo, it will bocomo deep yellow or brown, y/ wTiich is not the case with healthy urine. Q-^^ If the urine be mixed with a few drops of solution of bismuth nitrate, sodium carbonate added to alkaline reaction, and the whole boiled for a few minutes, the mixture assumes a drab colour. The absence of albumen must be previously demonstrated. The fermentation nnd torula tests may be omitted as not adapted for use by the readers of this small work ; they arc referred to Bloxam's edition of Howman's IMedical Chemistry, or Lehtnann's book on Physiological Chemistry. For experiments to illustrate the action of the above tests, a little honey may be added to urine, and comparative trials instituted with and without sugar. ALBUMEN. In Brijiht's disease and many others, the urino often contains albumen, but the physical characters of the secretion vary so much that no general rule for guidance can bo laid down. The albumen is coagulated by heating the urine to a temperature of 7G-77° c. and the precipitate is then perfectly insoluble in water, but readily dissolved by potassium hydrate. It is precipitated by nitric and hydrochloric acids, but not by acetic or tartaric. It is precipitated by mercuric chloride (corrosive sublimate), by potassium ferro and ferri-cyanido and by many other metallic tests The mercuric compound has 1 3en said to be soluble in excess of albumen, hence in using white of egg as an antidote in cases of poisoning by corrosive sublimate an excess thereof should be avoided. If a precipitate is formed on boiling, it will be better to add a few drops of nitric acid, as the same result may be produced by earthy precipitates; in presence of albumen the precipitate will remain undissolved. The formation of a very faint precipitate may arise from the presence of pus in the urine. 105 If tlio urino bo nlkalino no precipitate will bo formed on boiling, it should bo carefully neutralised before hcatin<;;. The formation of a precipitate both by nitric acid and by boilin'; is conclusivo us to the prcsonco of albumen. Ill urino containing blood, albumen will naturally be found, but the proscncc of blood corpu.sclos may f^nncrally bo detected under the microscope, if sudiciont power (100) bo used. (Sco plato 2, fig. 12.) BILE. Urino suspected to contain bile, which gives to it a more or less yellowish brown colour, should be boiled to separate any albumeu that may bo present and concentrated by evaporation. A strong solution of a few j^niius of cane sujj;;u' is then added, and sulphuric acid gradually, with constant shaking, until the mixture becomes hot. About two-thirds of the acid will bo recjuired to produce the characteristic jn/rplish red colour. Another method is to add a little sugar and sulphuric acid to tho boiled and liltercd urino and to evaporate over a wator-bath nearly to dryness. This is the only test that can bo safely relied on. IJiliary calculi or gall-stones arc usually composed of cholestcrin more or less coloured. JJoiling ether extracts tho cholestcrin from tho powdered stones and deposits it in white crystalline scales on cooling. FIGURES OF URINARY DEPOSITS. coi'iri) riioM dkix.m'.s iditiun w iiow.man'.s mkimcal cur.uisTuv. Fig. I. — A drop of tho urine allowed to stand some short time on a glass plate may exhibit under the microscope, with a power of 2U0 diameters, tho appearance represented in this figure, that is stellate crystals, which disappear very rapidly on the addition of a drop of acetic acid — Amraonium-magnesian phosphate. Fig. II. — These crystals are often observed in uiine, especially in that which is diseased, often inclosed in a precipitate of mucus — they arc easily soluble in acetic acid, and of tho same composi- tion as those depicted in No. I, although tho form is very diiTcrent. In cases of disease the latter form is more generally apparent. Tho composition appears to bo the same. Fig. III. — Uric acid exhibits a number of forms, some of which arc depicted in the accompanying plate. The acid may bo 100 rocofjnlsed l»y its HoluLilily in caustic potassa, l)y its roprccipita- tinn by liytlrochlorio acid, and )>y the red colour produced by tbo action of nitric acid on tho Hcparatod precipitate. Tlio addition of potassium hydrate to tho evaporated solution pro- duces a blue or purple colour. The uric ncid crystals aro insoluble in dilute acids. rig.s. IV. i^ y. — Oetohedral crystals with distinct crosses, or soiuc niodillcations of the dumb-bell form, will indicate calcium oxalate. Tho crystals are insoluble in ncctio but soluble in hydrochloric acid. Figs. VI. it VII. — If the crystals aro niultangular plates exhibiting the form shown in fij^uro (i, insoluble or nearly so in water and dilute acids, but readily soluble in ammonia, tho solution Icav- in-j; on evaporation hexagonal plates shown in 7, they nro probably cystine. (The writer has never had an opportunity of examining these crystals, while the correctness of all tho other figures has been repeatedly tested.) An amorphous sediment, insoluble when warmed, but easily soluble in acetic or hydrochloric acid may probably bo calcium phosphate. If dissolved on warming and reprccipitated on cooling it may be ammonium or sodium urate, the latter Fig. VIII. often has tho form exhibited in Fig. 8. Fig. IX. — Small round globules, easily removable by shaking with ether, will indicate fatty matter. Chylous matter will be indicated by similar globules, partly removable by ether, but leaving small amorphous albuminous particles. The albumen may bo further detected by proper tests. Fig. X. — Round particles apparently granulated and entangled in tenacious stringy masses, which do not break up and mix uniformly with tho liquid on agitation, will probably bo mucus 10 a. Epithelial scales arc represented at 10 b. Fig. XI. — If the particles are round and granular, not held together by any tenacious matter, but floating freely in the liquid, they are probably owing to the presence of pus. Fig. XII. — Blood globules, colour destroyed by chlorine water. Fig. XIII. — Spermatozoa showing tho presence of semen. 107 Fig. XIV. — Pus globules scon under a high power (-100 diameters) both before and after treatment with acetic acid, which renders them more transparent and exhibits the internal nuclei. Fig. XV. — Crystals of sodium chloride, easily soluble in water. Fig. XVI. — Crystals of sodium chloride resembling cystine. Fig. XVII. — Cry.stal3 of cystine from ammoniacal solution. Fig. XVIII. — Crystals of calcium oxalate seen when dry. NoTK.— Tlio nbovo flKUi-cs have been poiiicil after rc]i('atiil coiillrmatioii, cxcevt in tlio rase of lysliut', I'lum L)loxaiu".s cdiliou uf iiuwniaii'.s Jluilical Chtmlstiy. MILK. Medical men may often bo required to give an opinion as to tho healthy or di.seased condition of liunian milk, but it does not appear that there arc any chemical tests by which a diseased condition can bo detected unless very abnormal. Recourse must be had to tho tnicroscope, a deficiency of fat globules, and tho presence of largo colostrum or pus globules, especially if of a red colour, and of red fibrinous particles, will indicate an abnormal condition. The lacto- meter for measuring tho quantity of cream has been recommended as a means of determining the value of the milk, but the instrument does not always yield indications that can bo relied on, and the nutritive powers of the secretion do not depend entirely on tho amount of fatty matter present. UrJXAK. CALCULI. All calculi blacken more or less and evolve an odour on tho appli- cation of heat, the mulberry c'.lculus (calcium oxalate) least of all. "With cystine the smell is vcy peculiar. They may be divided into two classes. 1. Those which are perfectly destructible by heat, or leave only a minute trace of ash. Uric acid, ammonium urate, cystine, xanthine. 2. Those which are imperfectly destructible by heat, leaving an earthy or alkaline residue after the separated carbon has been burnt off. Calcium oxalate and urate, sodium urate, calcium phosphate, ammouiaco-magncsiau phosphate, fusible calculus. 108 The first two leave a residue of calcium carbonate or oxide ; the third sodium carbonate; the fourth calcium phosphate; tlie fifth magnesium phosphate ; and the sixth a mixture of these two latter salts. Urinary calculi are frequently composed of two at least, of the above substances, the kernel is often difl'erent from the external coating, and hence the various parts must be examined separately; they almost all contain traces of uric acid. The calculus in fine powder is boiled fo; some minutes with water, filtered and the solution evaporated to a small bulk, a portion is evaporated to dryness, and the residue, if any, may be ammonium sodium or calcium urate. The ammonium may bo detected in another portion by boiling with potassium hydrate, the calcium by acetic acid and ammonium oxalate, and the sodium by adding hydrochloric acid, evaporating to dryness and burning with alcohol. The cubical crystals may also be observed. The washed residue is boiled with dilute hydrochloric acid, the presence of the rare calcium carbonate will be indicated by efferves- cence. If any residue remains it must be thrown on to a filter, washed and tested for uric acid as described at page 101. The hydrochloric solutions may contain lime from the carbonate, oxalate, cystine and the phosphates. Excess of sodium acetate being added, a precipitate may be formed of oxalate and perhaps of cystine, which however occurs very rarely. The precipitate may be washed and dried, it then dissolves in hydrochloric acid without effervescence, but after being dried and rather strongly heated with effervescence ; calcium oxalate. To the solution separated from the oxalate, excess of ammonium oxalate is added, which throws down all the lime, the precipitate being filtered off and the filtrate tested with oxalate to prove that all lime has been got rid of, will give a white precipitate on the addition of ammonia, if ammoniaco-magnesian phosphate be present. A mixture of these two phosphates forms the fusible calculus, which melts easily before the blowpipe flame. The phosphoric acid can often be detected by moistening the burnt calculus with silver nitrate, when a yellow colour is produced, or by dissolving in a very little nitric acid, adding the nitrate and then the ammonia very carefully. Also by ammonium molybdate. \ 109 The ammonia in the last named phosphato can of course bo detected by heating with potassium hydrate. Cystine dissolves in ammonia, and tho solution yields on evaporation hexagonal tables (see fig. 7). A calculus of cystine may bo easily recognised by this test and by the peculiar smell evolved on heating, Urino containing cystine has an aromatic odour when fresh, but is very ofTonsivo when decomposition commences. Cystine when boiled with potassium hydrate and mixed with a lead salt, produces a black colour from presence of sulphur; tho formula is apparently C-* II" N 0'^ S. Xanthine or Xanthic oxide C 11^ N^* 0^ is very rare, it dissolves in potassium hydrate, and is reprccipitated by hydrochloric acid, but is distinguished from uric acid by giving a yellow colour with nitric acid. It has been found in healthy urine and in many parts of the body. Tho residue left on heating sodium urate will bo found to bo alkaline by its reaction on red litmus paper, and the same will be observed with calcium urate if very strongly heated. Both these salts occur usually in combination with other bodies and not inde- pendently. BLOOD AND BLOOD STAINS. The chemist may often bo called upon to examine blood in a liquid form, or dried in stains on clothes or weapons. Blood some- times occurs in urine in which it may be detected by its appearance under the microscope, see fig. 17, plate 2, and by the fact that the urine is coagulated or becomes turbid on tho application of heat or nitric acid, owing to the presence of albumen. If the blood, or what is supposed to be blood, forms a stain on any article of clothing or any other substance, such as a knife, axe, woodi'H handle, &c., &c., it should be allowed to soak in water for several hours, when if the stains were caused by blood, a reddish solution will be obtained. A blood stain on steel will generally peel off when gently warmed, while a stain produced by rust or acid will not do so. If a portion of the stain can thus be peeled or scraped 110 off by a knifo, it may bo heated in a small tube in the upper part of which a piece of moistened red litiuus paper is placed ; if tho colour is turned to blue the presence of some animal matter contain- ing nitrogen is probable ; most vegetable substances, such as fruit stains, would have no action on red litmus, but would redden tho blue paper. To a portion of the red liquor obtained ammonia is added, which will produce no alteration in the colour if it bo owing to blood, but will turn most vegetable colours blue or green. Another portion is boiled, when the solution will become nearly colourless, and a dirty brown precipitate bo formed ; vegetable infu- sions are scarcely altered. Nitric acid is added to another portion, when if blood is present a precipitate will bo formed owing to the albumen. Chlorine is passed through another portion when in presence of blood the liquid will acquire a faint greenish tint and a flocculent precipitate bo produced. With vegetable infusions the colour is simply destroyed. Tho solution is then boiled until all smell of chlorine is lost ; filtered and tho filtrate tested with potassium sulpho-cyanate, if blood were present a red or faint pink colour will bo produced owing to the presence of iron, the colour becomes more apparent on looking through the tube lengthwise. The stains may be softened with dilute glycerine, and tho red liquid ramincd under a j.oworful microscope, the blood corpuscules may be easily recognised, but it seems doubtful whether human blood (after being dried) can thus be distinguished from that of mammals. A few drops of the solution may be mixed with a very little sodium chloride on a slide and evaporated over sulphuric acid, tho addition of a drop of strong acetic acid and subsequent evaporation at 100° C will cause the formation of red crystals, visible on tho addition of a drop of water. If blood stains are very old or mixed with rust the basmatine is often insoluble, in that case they moy be digested with potassium hydrate, and the iron detected by the use of chlorine and sulpho- cyanatc as above described. Various other tests have been proposed, many very valuable but not easily available. Ill MINERAL WATERS. It may often bo necessary to make a rough qualitative analysis of water supposed to possess medicinal properties when the following simple experiments may bo made. A few ounces aro boiled for an hour in a fla.sk, addin{^ distilled water occasionally to prevent con- centration ; tho formation of a precipitate easily soluble in dilute hydrochloric acid will indicate the presence of carbonates hold in solution by carbonic acid. If the precipitate is of a reddish colour ferric carbonate must havo been present, the solution in acid may be mixed with ammonium chloride and ammonia added, tho ferrio hydrate will be precipitated, in tho filtrate ammonium oxalate will throw down calcium oxalate, and in tho filtrate from this sodium phosphato will after standing, produce a crystalline precipitate if any magnesium is present. Tho presence of free carbonic acid may be doteclcd by the pre- cipitate formed on the addition of lime water, Ilydrosulphuric acid by its smell and its giving a yellow precipitate with an acid solution of arscnious acid. Sulphates and chlorides by barium and silver nitrates. Calcium and magnci?ium as above described, and tho alka- lies when present principally as chlorides by evaporating to dryness with a slight excess of oxalic acid, heating to redness and extracting with water, tho lime and magnesia remain undissolved. For the detection of iodine and other rarer constituents the reader is referred to Frcscnius. ALKALIMETRY. The determination of tho real quantity of alkali in commercial Boda, soda ash, sal soda and various othor similar preparations of potassa is often of great importance, the process being called alkalimetry. For this purpose an alkalimeter or graduated burette is required capable of holding 1000 grains of water and marked off into 100 divisions. Mohr's burette in which tho drawn-out lower end is con- nected with a small dropping tube by means of a piece of vulcanised tubing, is the most convenient as it can be supported in a clamp attached to the retort stand and the flow of tho acid stopped or regulated by a nipper-tap placed over the India rubber tube. A simple apparatus may be constructed from a glass tube about 5 inch 112 in diameter nnJ 10 inches in length, one end is closed by fusion and the open end furnished with a lip. A portion of water weighing; 50 grains is carefully weighed, intro- ducod into the tube and its height marked by means of a file or dia- mond, the operation is repeated with fre.-h portions until 20 measures have been introduced. The process of weighing out so many quan- tities is rather tedious, and the operation not very accurate when water is employed owing to its adhering to the glass. "When mer- cury is available 078.4 grains may be wi'ighed out, introduced into a small tube and its height marked off, every trace of the metal can bo poured into the burette and another portion measured off. The divisions corresponding to 50 grains of water or G7S.4 grains of mercury may then bo divided into five smaller divisions by the eye, each of which will contain 10 grains of water. The larger divisions arc numbered 5, 10, 15, etc., from the top, by means of a writing diamond, or a common file boated to a dull redness, cooled by throwing into water and ground to a point. Any bubbles of air adhering to the tube during tho operatian should bo removed by a thin wire. A test acid must now be prepared, every division of which as measured by tho burette will exactly neutralise one grain of soda Four parts of sulphuric acid are mixed with twenty parts of water and allowed to cool. An ounce or more of pure sodium bicarbonato is heated strongly for half an hour, to convert it into carbonate, and 170. G grains of this salt (containing exactly 100 grains of soda) weighed out and dissolved in three or four ounces of water, with the addition of a few drops of solution of litmus sufficient to render tho solution distinctly blue; to this the dilute acid must be poured from the burette filled up to the top mark, as long as cfTorvesccnce takes place and until the blue colour changes to bright red. The addition may bo made rather rapidly at first, but as soon as a violet colour appears, with more caution heating between each addition. Tho violet colour is caused by carbonic acid, and changes to blue when tho acid is expelled by heat. Towards tho end tho acid must bo added by single drops, and as soon as the bright red colour is pro- duced, the number of divisions read off. If exactly 100 divisions have been used the acid is of precisely tlie proper strength, but this is seldom the case with tho above-mentioned preparations. Supposing 90 measures have been used, tho acid is too strong and 118 must bo (lilutcJ, whii-h is easily ilono by pouring tlio ni-iil into t]ii> burctto up to tlio 10 divihion iind lilliiij^ up to with wntcr. Wlirro only ft modorato quantity of tost acid is required this plan is nuf. licionfly appliciihle, for larger operations a special mixing cyliinlcr must 1)L' graduated. ir now a sample of soda or its carbonate bas to bo examined, lOO RTains are weighed out and treated as above described with the test ncid, supposing the crystallised soda salt wore used, lili measures would bo employed, lience the 100 grains contain 21 f) per cent, of Hoda. The amount of dry carbonate may bo ascertained by a simple calculation : Na' O : Nu- C 0' : : 21 5 : x; or (12 : 10(5 : : 2ir) : ;]t>-7. Sodium biborato may bo examined in the same manner, but when potassium salts aro examined 1510 grains must bo used instead of 100, or tbo divisions read off at the end of the operation incioascd in the proportion of G2 : 01. In some samples there are containcj both the carbonated and caustic alkali, in that case one experiment must bo mado as abovo to determine tho whole amount of alkali present, and a second portion of 100 grains dissolved in water, pre- cipitated with l)arium chloride, and the precipitate filtered off and washed as rapidly as possible, lu the filtrate the amount of caustic alkali is determined. AVhen a sample does not dissolve perfectly the insoluble portion should bo separated l)y filtration. Sulphides and hyposulphites, which are sometimes present, uu4y bo destroyed by warming with a little potas.sium chromatc. ACIDIMETRY. The normal solution, when only occasional experiments arc requir- ed, may be made by dissolving 170 grains of pure sodium carbonate in water and filling the burette up to 0. This solution when well mixed will contain one grain of soda in eacb division ; lOO grains of the acid aro weighed out, mixed with water and litmus, and the Boda solution added until a violet tint is produced, which becomes blue on boiling. A calculation must bo made for each acid, as G2 grains of soda neutralise respectively 98, G3 and 30-5 of bydratcd sulphuric, nitrio. and hydrochloric acids respectively. 8 lU iMISCELLANEOUS EXAMrLKS. rOTASSlUM IODIDE May contain potassium carbonate, which is easily detected by tho cflfcrvcscence produced by tho add' on of dilute nitric acid and by the prccinitato formed by calcium chloride. It may also bo adul- terated with potassium chloride, and perhaps at the present timo with bromide, owing to tho low price of this latter salt. To detect these a solution of the iodide should bo fully precipitated by silver nitrate, the precipitate washed and treated in tho cold with a mode- rate excess of ammonia, which will dissolve the chloride but leavo most of tho bromide, tho residuo may then be gently warmed with It largo excess of ammonia, which will dissolve the bromide. These solutions, if acidulated with nitric acid, will yield precipitates if chloride and bromide have been present. Potassium iodato is sometimes present, which often produces a yellowish colour in tho otherwise perfectly white salt. It may bo detected by the addition of tartaric acid, when a yellow or brown colouration will be produced, owing to tho Koparation of iodine, which may bo further recognised by the tests described under lly- driodic Acid. MERCURIC OXIDE. Is sometimes adulterated with red lead, which can be easily de- tected by heating strongly in a porcelain crucible, when the mercuric oxide will volatilise (as mercury and oxygen), while yellow lead oxide will remain, whicn may be dissolved in dilute nitric acid and detected by the proper tests for lead. It has been sometimes adul- terated (?) by an admixture of brickdust, which could bo detected by heating as above and digesting with dilute acid, when if tho above impurity be present, an insoluble residue will remain. ANNOTTO. This colouring matter is sometimes used for colouring cheese and buns, and an adulteration of it once led to very serious resulta Lead chromatc was added, which can be easily detected by boiling. Mi-C-'- - . )■ I"-'- 115 with alcohol and hydrodiloric acid, when a brij^ht groon fiolution will be obtained, in which chromic oxide can readily bo detected. Orpiincnt or arsenious sulphide was added to the lead chrouiato or used as a substitute, and this can be best detected by the proce-s described under the head of arsenic (Poisons). CAt-OMEL. Often contains corrosive subliniato, and every specimen used by drujrgists should be carefully examined for this poisonous body before being used in prescriptions. It miiy bo detected with the greatest case by boiling the calomo fur a few minutes with water, Dlteriiig off and testing the fdtrato with excess uf hydrosulphuric acid. A precipitate which is whito or orange until a large excess of the precipitant is used, indicates corrosive sublimate. Other tests described under mercury may also bo employed. The colour of tho sulphide produced by an excess of hydrosulphuric acid is black, and tho precipitate when well washed is insoluble both in hydrochlorio and uitric acid.s, but soluble in a mixture of the two. LEAD CARBONATE. This substance, which is so valuable as a pigment, is not unfre- qucntly adulterated with barium sulphate, a salt which unless artificially prepared, is uffially crystalline and possesses little or no covering property (body) when used as a paint. It may bo easily detected by boiling the whito lead with rather dilute nitric acid. If pure it should dissolve entirely. The solution might, however, con- tain lime if tho carbonate had been used as an adulterant, which owing to its low specific gravity is not likely. In that case the lead may bo precipitated by hydrosulphuric acid, tho operation repeated until no further black precipitate is formed, and the filtrate tested for limo as described at page 2G. CHLOROFORM Is sometimes impure from tho presence of alcohol, which may bo detected by warming with a little potassium chromatc and sulphuric acid, when a green colour will bo produced if alcohol bo present. Ether and alcohol may also be dotectod by shaking the chloroform 116 with water in a graduated burette, wlion ilio volume of tlio latter ■should remain the same if pure. Sumo acids may also bo present but arc not usually found : llypochlorous acid detected by its bleaching power; Sulphurous acid by its action on starch and iodic acid ; Ilydruchlorio acid by acid reaction and silver nitrate ; JTethyl compounds arc sometimes pre- sent, and may usually bo detected by shaking the chloruibrm with strong sulphuric acid, when a brown colour will be produced. The specilic gravity should be from 1'49 to 1-50. SANTONINE AND STRYCHNINE. Very serious accidents have happened from the accidental admiu- i.'^tration of strychnine by mistake for santonine. The latter i.s uijually in scales and of a .slightly yellow colour, occasionally colour- less, the former is sometimes in rhombic crystals, but moro usually in powder and perfectly white. Strychnine is easily soluble in dilute acids, santonine is not. Strychnine gives an evanescent purple colour with potassium chromate and sulphuric acid, santo- nine docs not. Strychnine and its salts are intensely bitter, santo- nine is not. The writer would advise all druggists to keep poisonous substances in three cornered bottles, the peculiar feel of the bottle will at once arrest attention. ALCOHOL. The strength of alcohol may be ascertained by taking its spcciQc gravity and referring to the tables appended to almost all works on chemistry. For ascertaining the quantity of pure alcohol contained in wiuc or beer 4000 grains should be distilled with good cooling apparatus until about 1200 have passed over. The specific gravity of this may then be ascertained cither by the specific gravity bottle or other means described at page 100. By reference to tables the amount of alcohol per cent in the 1200 grains can be easily calcu- lated, and from this the per centage in the wine or beer e.xperi- luented on. Suppose the S G is 0.9G38, representing 20 per cent. 20 multiplied by 12 will then give the total quantity of alcohol contained in 4000 grains, and from this the per centage can be calculated. 117 Many wines arc slightly acid to litmus paper, owing to the prc- senco of acid salts, of tartaric or other flxed acid, but if the distillate should also exhibit an acid reaction it will indicate the presence of acetic acid which is volatile. If in any quantity it will show that acetous foruicntation had set in and that the wine or beer is more or less spoiled. ETHER. Should bo perfectly neutral to litmus paper. It often contains alcohol, the amount of which can bo roughly estimated by niixinjj; in a graduated buretto 50 measures of tho ether with 50 measures of water, shaking up, allowing to .settle and observing how far the 50 measures of ether have been diminished. The slight solubility of ether in water (1 in 10) must be taken into account. lis RE-AflENTS. Tlie I'ullowiii;^ i\j-a;reiils have bi.'cii omittcil in their proper place : POTASSIUM r.KMIUOMATi;. The (■(luiiiicrcijil suit, puritieil by r('-eryt;illi-ntion inny bo dissolved iti ten p:iit-f ul" witer, t!ii- palt may bo u>?cd instead of the ehromate. li:au acetate. JJissolvc the cudiiiieieiul salt in 10 parts of water, and filter. SILVER NITRATE. Tiic coinniereial .salt sliouhl be ro-erystalli-ed and dissulved in 20 pavl3 of water. CALCIUM SULPHATE. • Pure gypsum or precipitated suljdiatc should be macerated with cold water fur .some Iiours and filtered, or it may be boiled with water, allowed to cool and filtered. POTASSIU.M IODIDE. Di.ssolve in 10 parts of water. The solution should bo colourlcs.s. SOLUTION OF INDIGO. Mix one part of powdered indi;^o with 5 or G parts of sulphuric acid ke|)t cool, allow to stand .snnie b.ours, dilute with 20 parts of water and filter. AMMONIUM SULPHIDE. Ilydrosuljilmric aeid gas is passed into moderately strong ammonia until fully saturated, that is until the licjuid ceases to give a preci- pitate with salts of mai^nc ia. lis true formula is N 11^ II. S hydro- sulphide of ammonium, if mixed with (he same quantity of ammonia as first employed it becomes true sulphide (N IP) '■'S. Either solu- tion may be used. After a time it is apt to become colourless, and is then of no use. ;;*v*'. r 111) LITMUS I'Al'EIl. A few lumps of tills sub.stiinco may bo boiled in one or two ounces of water, tho solution liltcred, and strips of filtering pnpcr soaked in it. I''i)r rod paper a very Mli^dit trnco of aeid must bo added TURMEIUC P aim: II. Tho .solution must be luado willi aleoliol. I'lUNTKl) U\ Cul'l', ( l.AUU k CO., KINO STIiUH' LAST, Tnui.NTO