GIFT OF [PROF. w.B. RISING QUALITATIVE ANALYSIS FOR SECONDARY SCHOOLS BY CYRUS W. IRISH, A.B. (HARVARD) HEAD MASTER OF LOWELL HIGH SCHOOL, LOWELL, MASS. NEW YORK : CINCINNATI : CHICAGO AMERICAN BOOK COMPANY COPYRIGHT, 1899, BY CYRUS W. IRISH. QUALITATIVE ANALYSIS. W. P. I PREFACE MANY teachers of chemistry in attempting to furnish a satis- factory course in Qualitative Analysis for secondary schools have been confronted by the lack of a text-book sufficiently simple, and at the same time sufficiently complete for their purpose. The many excellent text-books on Qualitative Analy- sis already published have been specially adapted to the needs of the more mature college student. This work, therefore, has been made as simple as possible, while providing a course of study adequate for secondary schools. Methods of basic analysis in the presence of phos- phates and oxalates have been omitted. The separation of the members of the iron group has been greatly shortened and simplified by the introduction of hydrogen peroxide to oxidize the chromium to the acid state. Obscure and complicated reactions have been omitted. The first half of a one year's course in chemistry should be devoted to a general introduction to the theory of the science, and to a close study of the most common nonmetallic radicals. The second half year should deal with the basic radicals and should be combined with the study of Qualitative Analysis. If descriptive chemistry of the basic radicals is studied by laboratory methods, the metals must be submitted to their more important reactions. These reactions, well studied, equip the student for intelligent work in qualitative separation of the metals. The subject presented in this way always holds the interest of the student to the end, and the stimulus for the work is always found in the fascination of the subject. Such a course as here outlined gives the best possible training in inductive reasoning, and adds as much to the general information of the student as any science taught in secondary schools. The large number of suggestive questions are divided into two classes, one to bring out the conclusions drawn from the experiments, the other to call attention to the metals dealt with, and to their more important compounds. 3 237577 ^4.\ i : PREFACE Wheu the student has performed a l< preliminary experi- ment," he should be directed to write the name of the chief product formed by the reaction and to describe its general appearance, in his notebook. After performing a series of pre- liminary experiments the student should complete and balance the equations representing the reactions. Descriptive Chemistry of the metals to be separated should be studied hand in hand with the Qualitative Analysis. A careful statement of each step of the analysis, and infer- ences drawn in the laboratory at the time of the experiments, should be recorded in the notebook. In the case of the known solutions, the teacher should mark the notebooks for neatness, order, and accuracy. In the case of the unknown solutions, credit should be given for neatness, order, accuracy of record, and results of analysis. It is highly desirable that the teacher should question each individual at his work at least once during each laboratory period, and give the student credit for his knowledge of the work. This method, carefully followed, will prevent a mechanical application of directions on the part of the student. If the student is precipitating Gr. I with the general re- agent, for instance, the line of questions should be like the following : Name and give the symbols of the substances that may be in the precipitate. What is contained in the filtrate ? How will you treat the filtrate ? What is the solubility of the chlorides of this group in H 2 ? Did the HC1 precipitate all the Pb? If not, where will the rest of the Pb be found? What kind of a reagent do you call the HC1, " general " or " special " ? What is your next step with this precipitate ? Why? The author wishes to acknowledge his great indebtedness to the teaching and works of his former instructors, Professor C. L. Jackson and Professor H. B. Hill of Harvard College. The author also wishes to acknowledge many valuable sug- gestions from Miss Helen M. Lambert of the Lowell High School. CONTENTS PART PAGE I. INTRODUCTION DEFINITIONS, METHODS OF NAMING . 7 Laboratory Directions . . . -. ... 12 Abbreviations used in the Book . . . . . 16 II. GROUPING THE BASES ... . 17 III. BASIC ANALYSIS 24 Group I 24 Group II, Division A 31 Group II, Division B . 41 Group III .... .... 48 Group IV 57 Group V . 64 Group VI 71 IV. SYSTEMATIC EXAMINATION OF SOLIDS .... 80 V. ACID ANALYSIS .88 Group I, Division A ....... 88 Group I, Division B . 89 Group II ...... . .91 Group III 93 VI. APPENDIX PREPARATION OF SOLUTIONS . . 95 Table of Solubilities .100 5 PART I INTRODUCTION Definitions and Methods of Naming A Radical * is an atom, or group of atoms that behaves like a single atom. Examples : H, K, Na, Cu, Pb, simple radicals ; NH 4 , SO 2 , NO 2 , compound radicals. A Basic Radical is a metal, or any radical behaving like a metal. Examples : Ag, Cu, Ca, Na, and NH 4 the last so classified because it behaves like such simple radicals as Na, K, and Li. An Acid Radical is a nonmetal, or any radical behaving like a nonmetal. Examples : Cl, Br, I, SO 2 , NO 2 . An Acid is a substance containing H that may be re- placed by a basic radical. When a nonmetal is combined with H only, as in HC1, HBr, H 2 S, the compound is said to be a binary (i.e. composed of two elements) acid, or an hydracid. When the nonmetal is combined with H and O, the compound is called a ternary (i.e. composed of three or more elements) acid, or an oxyacid ; and the char- acteristic name of the acid is formed by adding the termi- nation -ic to the name of the nonmetal to denote more oxygen, or the termination -ous to denote less. Exam- ples : H 2 SO 4 sulphuric, and H 2 SO 3 sulphurous acid. * The definitions of acids, bases, and salts, here given, are based on the definitions given by Professor C. L. Jackson in his course in Descrip- tive Chemistry at Harvard College. 7 8 METHODS OF NAMING A Salt is formed from an acid by the replacement of all or part of its H by a basic radical. Examples : from HC1, CaCl 2 , NaCl, NH 4 C1 ; from H 2 SO 4 , Na 2 SO 4 , CaSO 4 , (NH 4 ) 2 SO 4 . The specific name of the salt is the name of the basic radical changed to an adjective. If the salt is formed from an hydracid, its class name has the termi- nation -ide ; as, calcic chloride, sodic chloride, and am- monic chloride from hydrochloric acid. If the salt is formed from an oxyacid, the class name of the salt is formed by changing the -ic termination of the acid to -ate, and the -ous to -ite. Examples : from H 2 SO 4 sulphuric acid, we have sodic sulphate, calcic sulphate, ammonic sulphate ; from H 2 SO 3 sulphurous acid, we have sodic sulphite, calcic sulphite, ammonic sulphite. Organic acids frequently have other H atoms besides those that are replaceable, such as HC 2 H 3 O 2 acetic acid, in which only one of the H atoms is replaceable by a basic radical. An Acid Salt is a salt containing H that may be re- placed by a basic radical. Thus, from H 2 SO 4 , HNaSO 4 an acid salt, and Na 2 SO 4 a normal salt. An Hydroxide is formed from water by the replacement of one half its H by a radical. Examples : from HOH water, NaOH sodic hydroxide, KOH potassic hydroxide. When an acid radical combines with H, or H and O, an acid is formed ; and the ternary acids may be regarded as hydroxides. Examples : from HOH water, H O (NO 2 ) nitric acid; from 2 HOH, * ~ Q~ (SO 2 ) sulphuric acid. A Base or Basic Hydroxide is formed from water by the replacement of one half its H by a basic radical. DEFINITIONS 9 Examples: from HOH water, KOH potassic hydroxide, CaO 2 H 2 calcic hydroxide, NH 4 OH ammonic hydroxide. The term- " base " is frequently used in a general way to include all the basic radicals. When a basic radical combines with H and O, a base or basic hydroxide is formed. A base will neutralize an acid and an acid a base to form a salt. When a base and an acid are brought together, a salt is formed with loss of one or more molecules of water. HNO, + NaOH = NaNO, + HOH. NaOH + HC1 = NaCl + HOH. s, .> QUERY. To produce exact neutralization in such a case, is it necessary to consider the weights of the con- stituents used ? State the law involved in your answer. An Alkali is a base soluble in water. Examples : NaOH, KOH, NH 4 OH. The Quantivalence or Valence of a radical is the num- ber of H atoms that it can combine with or replace. One atom of H combines with one of Cl in HC1, therefore Cl is univalent( r ). Two atoms of H combine with one of O in H 2 O, therefore O is bivalent ( n ). Three atoms of H combine with one of N in NH 3 , therefore N is trivalent ( m ). A Cu atom will not combine with H, but will replace two atoms of H in H 2 SO 4 to form CuSO 4 , therefore Cu is bivalent. The terminations -ous and -io are used in certain cases with the first or specific name of a salt to distinguish between two salts composed of the same elements in different proportions. Examples : Hg 2 Cl 2 mercurous chlo- ride, HgCl 2 mercuric chloride, FeSO 4 ferrous sulphate, 10 DEFINITIONS Fe 2 (SO 4 ) 3 ferric sulphate. In such cases as these, the termination -ic denotes more of the acid radical, and -ous less. Qualitative Analysis is the method of detecting the chemical elements and their compounds by studying their properties. Quantitative Analysis is the method of determining the quantity of such elements or compounds. QUESTIONS 1. What is valence or quantivalence? 2. What is qualitative analysis V 3. What is quantitative analysis? 4. Show by examples the difference between a basic and an acid radical. 5. What is a base or basic hydroxide ? Give four examples. 6. What is an alkali ? Give four examples. 7. Give examples of at least two substances that are not alkalies in constitution, but show an alkaline reaction with litmus paper. Can you suggest a reason for this ? 8.- Name a salt that gives an acid reaction with litmus paper. 9. What is the difference between an acid salt and a normal salt? 10. Relying on the rules for naming already learned, give the correct chemical names for the following acids: HC1, IIBr, III, HF, H 2 S, HN0 3 , HC 2 H 3 2 , II 2 CO 3 , ILPO 4 , II 3 AsO 4 , HC1O 3 , II 2 S(> 4 , HNO 2 , H 2 SO 3 , HC1O 2 . 11. What is meant by basicity of an acid? 12. Give the basicity of each of the above acids. 13. Replace the H in the above acids by the following basic vi li- cals, and give the names and symbols of the salts formed : i i ii in Ag, NII 4 , Ca, Bi. 14. What is an hydroxide ? 15. What is meant by neutralization ? 16. In determining the chemical names from the symbols, classify the compound; that is, determine whether it is an acid, a base, or a salt, etc. If the substance contains both a metal and a nonmetal SOLUTION 11 (leaving the radical OH, which always indicates an hydroxide, out of consideration), it is a salt. Notice whether it is a binary or a ter- nary compound. If binary, suffix the termination -ide to the name of the acid radical. This .name is now preceded by the name of the basic radical changed to the adjective form. If the substance is a ternary compound, replace the metal by the correct number of H atoms, to show the acid from which the salt is theoretically formed. Give the correct chemical names for the following compounds: FeSO 4 , Fe 2 (SO 4 ) 3 , HNa 2 PO 4 , HNaSO 4 , NaOH, KOH, Ba(C 9 H 3 O 2 ) 2 , Bi(N0 3 ) 3 , As 2 S 3 , Sb 2 S 3 , Na 2 C0 3 , HNaCO 3 , CaO 2 H 2 ,. (NH 4 ) 2 S0 3 , FeCl 2 , Fe 2 Cl 6 , Hg 2 Cl 2 , HgCl 2 . Solution and Precipitation By far the largest portion of the work in qualitative analysis is carried on in what is known as the wet way ; that is, the substance to be examined and the reagents used are in solution, usually in water, or if in any other medium, with water always present. As a rule, water must not be taken into consideration in writing equations, as it does not undergo a chemical change. When, however, the water is decomposed and its atoms take part in the general rearrangement, it must, of course, be considered in writing the equation. Solutions. Of greater importance than any other one thing in qualitative analysis, is a knowledge of whether a substance is soluble, partly soluble, or insoluble in water; and, in the preliminary tests prescribed in this book, the question of solution must be thoroughly ex- amined by the student. A solution is called a physical solution when the sub- stance undergoes no chemical change, but is so finely diffused through the solvent that it cannot be seen or separated by nitration, though it can be recovered by evaporation. Example : salt or sugar in water. 12 PRECIPITATION A Chemical Solution is one in which the substance undergoes a chemical change and the new substance formed is dissolved in the menstruum. A substance dis- solved in this way cannot be recovered by simply evapo- rating the solvent. If copper is dissolved in nitric acid, cupric nitrate is formed and is held in solution by the water present. Precipitation. Substances that are in solution can be separated by addition of such a reagent as will form a new substance that is insoluble in the fluid. This process is known as precipitation. The new insoluble substance is a solid which may be separated from soluble substances by nitration. Knowledge of the conditions for forming precipitates of the various elements is indispensable. Berthollet's Law When two substances can form a substance insoluble or volatile under the conditions of the reaction, that in- soluble or volatile substance will be formed till one of the factors is exhausted. LABORATORY DIRECTIONS To each student should be assigned a locker in which he can safely keep his apparatus, and he should be held strictly responsible for all breakage and loss. The reagents for each individual should include the following : Dilute H 2 S0 4 , HN0 3 , HC1. Concentrated H 2 SO 4 , HNO 3 , HC1. HC 2 H 3 2 , NH 4 OH, NH 4 C1, (NH 4 ) 2 C0 3 , (NH 4 ) 2 S, K 2 Cr0 4 . LABORATORY DIRECTIONS 13 NOTE. Yellow ammonic sulphide is a mixture of ammonic sul- phide (colorless) and the higher sulphides of varying composition, and is sometimes expressed by the symbol (NH 4 ) 2 Sx. For the sake of simplicity its symbol is given in this book as (NH 4 ) 2 S except in reac- tions (as on pages 33, 42) in which it evidently furnishes two atoms of S for the reaction. The symbol is then written (NH 4 ) 2 S 2 . The three acids H 2 SO 4 , HNO 3 , and HC1 are always to be used dilute unless otherwise stated. The other reagents may be conveniently placed on a side table, and should include the following : To be kept in Solid Form Black oxide manganese, Potassic cyanide, Calcic hydroxide, Potassic nitrate, Copper foil, Sodic borate, Ferrous sulphate, Sodic carbonate, Ferrous sulphide, Tartaric acid, Iron nails, Zinc strips. Potassic chlorate, To be kept in Solution Alcohol, Limewater, Ammonic molybdate, Magnesic sulphate, Ammonic oxalate, Mercuric chloride, Baric chloride, Mercurous nitrate, Baric hydroxide, Potassic ferricyanide, Bromine water, Potassic ferrocyanide, Calcic sulphate, Potassic sulphocyanide, Chlorine water, Silver nitrate, Cobaltous nitrate, Sodic chloride, Disodic phosphate, Sodic hydroxide, Hydrogen peroxide, Stannous chloride. Lead acetate, (For the preparation of solutions see the Appendix.) 14 LABORATORY DIRECTIONS Apparatus necessary for Each Student : Eight test tubes, 6 in, x ^ in. One test-tube rack, One filter stand, Two beakers, Two filter funnels, Two evaporating dishes, One piece of platinum foil, 1 in. x 2 in.. One platinum wire, 3 inches, One pair steel forceps, One test-tube holder, One Bunsen burner or alcohol lamp, One match safe, One blowpipe, One iron ring stand, One piece of iron wire gauze, 5 in. x o in., One asbestos sheet, 6 in. x in., One flask, with stopple, glass tubing, rubber tubing (3 inches) for making wash bottle, One rat-tail file, and one three-cornered file, One test-tube brush, Litmus paper, in small strips, One package of filter paper, One glass stirring rod, One bulb tube. It is suggested that the student make his own glass rod by closing both ends of a glass tube about 8 inches long ; and his bulb tube by closing one end of such a tube and blowing gently into the tube till the end is blown into a bulb. Also, that he make a glass spatula by closing one end of a glass tube, melting the other end in the flame, and quickly flattening the melted end by pressing it with the round end of the steel forceps. TO THE STUDENT 15 Laboratory Directions to the Student 1. You are responsible for the good order and neat- ness of your table and everything belonging thereto. All your apparatus must be put away clean, all the bottles put in their proper places on your shelf, and the table itself left clean and dry at the close of each period of laboratory work. 2. Provide yourself with a towel and also with a large apron, frock, or linen duster to protect your clothing from acids. 3. Under no circumstances make experiments inde- pendent of the instructor's directions. If you wish to perform an experiment not prescribed, obtain permission. If you do such work on your own responsibility, remember that the dangers, of which you may know nothing, are very great. 4. In case of accident, notify your instructor instantly, as, in the case of burns from alkalies and acids, remedies must be applied at once. For Alkali Burns, apply acetic acid diluted with water so that to the taste it is about one fourth as sour as vinegar. This solution may be safely applied to the eye. For Acid Burns, quickly apply dilute solution of sodic carbonate, then wrap in vaseline. For Ordinary Burns, apply sodic carbonate, vaseline, or hydrogen peroxide. 5. All solid material to be thrown away must be de- posited in jars. If such material is allowed to drop into the sink, the drainpipe will become clogged. The water should be running very freely into the sink, before throw- ing in strong acids. 6. When using reagent bottles, never lay the stopple on the table, but hold it between first and second fingers 16 ABBREVIATIONS while using, and then immediately replace the bottle on the shelf. 7. Never carry reagent bottles from the side table to your table, but use them at the side table and return bottles to proper place. 8. Never put matches or charcoal in drawers or lockers. Never put anything but your regularly assigned appara- tus in your locker. Abbreviations The following abbreviations and signs are used in this book, especially in the tables of analysis : Pp. = precipitate . . = therefore Fil. = filtrate Res. = residue Gr. = group Dil. = dilute Sol. = solution Cone. = concentrated Orig. = original Bx. = borax Pres. = present + = plus Abs. = absent x = unknown W. = white c.c. = cubic centimeter Pt. = part C.P. = chemically pure PART II GROUPING THE BASES METHOD OF GROUPING THE BASES In the course of the basic analysis, the student will learn to detect twenty-seven commonly occurring bases or basic radicals. These are classified in six different groups in accordance with certain properties which permit a group precipitation by a single reagent. A reagent used for precipitation of a whole group is called a general reagent. A reagent used as a test for a single substance is known as a special reagent. Experiments showing Method of Classification It seems hardly advisable for the student to spend the time required to discover for himself the best method of grouping, by an exhaustive study of all the elements. If he studies with care the characteristic properties of one or two members of each group, it should be sufficient. Use the following solutions : AgNO 3 , Cu(NO 3 ) 2 , AsCl 3 , Fe 2 Cl 6 , Co(N0 3 ) 2 , Ba(N0 3 ) 2 , NaCl. Take about 2 c.c. of each solution, and add HC1.* Points to be Observed Whether a precipitate is formed. Whether the precipitate is soluble in an excess of the reagent. * Always use dilute acids unless otherwise directed. IR. QUAL. ANAL. 2 17 18 GROUPING THE BASES The color of each precipitate. Whether there is change in color of the precipitate. Change in color of solutions. Chemical equations. Tabulate all results carefully in your notebook, accord- ing to the following scheme : HC1 was added to the seven solutions with the following results : Typical of Gr. I AgNO 3 + HC1 = AgCl w. pp. + I IN ( ) 8 . Typical of Gr. II A Cu(NO 3 ) 2 + II Cl = No change. Typical of Gr. II B AsCl 3 + HC1 = No change. Typical of Gr. Ill Fe 2 Cl 6 + HC1 = No change. Typical of Gr. IV Co(NO 3 ) 2 + IIC1 = No change. Typical of Gr. V Ba(NO 3 ) 2 + HC1 = No change. Typical of Gr. VI NaCl + HC1 = No change. 1. Name the basic radicals that are represented in these solutions. 2. Can HC1 be used to precipitate one of these bases ? 3. Under what conditions ? 4. What is the effect of HC1 on some of these solutions as far as can be determined by your senses ? 5. Two of the twenty-seven bases, Hg 2 and Pb, behave like Ag under the above conditions, and are classified with Ag as Gr. I, or the Silver Group. 6. This group is precipitated as what class of salts ? 7. Under what conditions ? 8. What is the general reagent for Gr. I ? EXPERIMENTS 19 Take 2 c.c. of each of the same .solutions as before. Make the AgNO 3 acid with HNO 3 . Make the others acid with a few drops of HC1. Heat all the solutions and pass bubbles of H 2 S through each solution. AgNO 3 + H 2 S = Cu(N0 3 ) 2 + H 2 S = AsCl 3 + H 2 S Fe 2 CJ 6 + H 2 S Co(N0 8 ) a + H 2 S = Ba(N0 3 ) 2 +H 2 S = NaCl + H 2 S Determine the solubility of the precipitates in (NH 4 ) 2 S (yellow). To do this, filter and punch hole in bottom of filter, wash the precipitate through into test tube with (NH 4 ) 2 S. Pour the solution in the test tube upon the filter and repeat until the precipitate is completely re- moved. Then heat gently. 1. Which of the bases are precipitated by H 2 S in acid solutions ? 2. What is the solubility of the Cu and As precipitates in (NH 4 ) 2 S ? 8. The following bases behave like Cu: Hg, Pb, Bi, Cd, and are classified with Cu as Gr. II, Div. A, or the Copper Group. 4. Sn and Sb behave like As, and this class is called Gr. II, Div. B, or the Arsenic Group. 5. What is the general reagent for Gr. II ? 6. How may Div. B be separated from Div. A ? 20 GROUPING THE BASES To the same solutions as before, add NH 4 OH. AgN0 3 +NH 4 OH = Cu(NO 3 ) 2 + NH 4 OH = AsCl 3 + NH 4 OH Fe 2 Cl 6 + NH 4 OH Co(N0 3 ) 2 + NH 4 OH = Ba(N0 3 ) 2 + NH 4 OII = NaCl + NH 4 OH To the same solutions, add NH 4 C1 and then NH 4 OH. 1. Which of the above bases are precipitated by NH 4 OH ? 2. When NH 4 C1 is previously added, is the effect of NH 4 OH modified in any way ? 3. The bases classified with Fe a are Fe, A1 2 , and Cr 2 . and these four bases form Gr. Ill, or the Iron Group. To the same solutions as before, add NH 4 OH and (NH 4 ) 2 S. AgN0 3 + NH 4 OH +(NH 4 ) 2 S - Cu(N0 3 ) 2 + NH 4 OH + (NH 4 ) 2 s = AsCl 3 + NH 4 OH+(NH 4 ) 2 S Fe a Cl 6 + NH 4 OH +(NH 4 ) 2 S Co(N0 3 ) 2 +NH 4 OH+(NH 4 ) 2 S = Ba(N0 3 ) 2 + NH 4 OH -h(NH 4 ) 2 S = NaCl + NH 4 OH +(NH 4 ) 2 S 1 . What bases not already precipitated by other methods shown in these experiments are precipitated by (NH 4 ) 2 S in the presence of NH 4 OH ? 2. Try to obtain the same precipitates by making the solutions acid and adding (NH 4 ) 2 S. EXPERIMENTS 21 3. Co, Ni, Mn, and Zn are known as Gr. IV, or the Cobalt Group. 4. What is the general reagent ? 5. Under what conditions must it be added ? 6. What class of salts is precipitated by it ? To the same solutions as before, add NH 4 OH and (NH 4 ) 2 C0 3 . AgN0 3 + NH 4 OH + (NH 4 ) 2 C0 3 = Cu(N0 3 ) 2 + NH 4 OH +(NH 4 ) 2 C0 3 = AsCl 3 + NH 4 OH + (NH 4 ) 2 CO 3 Fe 2 Cl 6 + NH 4 OH + (NH 4 ) 2 CO 3 Co(N0 3 ) 2 + NH 4 OH + (NH 4 ) 2 C0 3 = Ba(NOg) 2 + NH 4 OH + (NH 4 ) 2 CO 3 = NaCl + NH 4 OH +(NH 4 ) 2 CO 3 1. In separating the groups by use of the general re- agents, the first group must be removed before attempting to precipitate the next. Why ? 2. Which of the bases are precipitated by (NH 4 ) 2 CO 3 ? 3. Under what conditions ? 4. Make the solutions acid and attempt to obtain the same precipitates with (NH 4 ) 2 CO 3 . 5. Gr. V includes Ba, Sr, Ca, and Mg, and is called the Barium Group. Na has not been precipitated by any reagents used in these experiments. We should find it a difficult matter to accomplish with any reagent. The other members of Gr. VI, or the Sodium Group, K, Li, and NH 4 , possess the same peculiarity, and there is no reagent that will precipitate all the members of this group together. 22 GROUPING THE BASES Perform the following experiments in separations, making use of the knowledge gained in the foregoing experiments : 1. Mix 2 c.c. each of AgNO 3 and of Cu(NO 3 ) 2 solu- tions. Separate by precipitation and filtration. How may the base contained in the filtrate be precipitated ? 2. Mix Cu(NO 3 ) 2 and Ba(NO 3 ) 2 solutions. Separate by precipitation and filtration. Also, precipitate the base contained in the filtrate. 3. Mix Fe 2 Cl 6 and Co(NO 3 ) 2 . Separate as before. 4. Mix Cu(NO 3 ) 2 , Co(NO 3 ) 2 , and Ba(NO 3 ) 2 . Separate as before. 5. Mix AgNO 3 , Cu(NO 3 ) 2 , Fe 2 (NO 3 ) 6 , Co(NO 3 ) 2 , and Ha(NO 3 ) 2 . Separate. 6. Mix AsCl 3 and Ba(NO 8 ) 2 . Separate. In what form was the Ag precipitated ? Cu ? Fe ? Co ? Ba ? As ? The methods used in the separation of the above elements represent the methods of separation for the corresponding groups. Group I Silver Group Hg 2 (-ous), Ag, Pb. Precipitated by HC1 as chlorides in acid solution. Group II Copper and Arsenic Groups ii ii in ii n Div. A. Hg (-ic), (Pb), Bi, Cu, Cd (Copper Group). in in Div. B. Sn, Sn, Sb, As (Arsenic Group). Both divisions of this group are precipitated by H 2 S in acid solutions. THE GROUPS 23 Sulphides of Div. B are soluble in alkaline sulphides, as yellow (NH 4 ) 2 S, while the sulphides of Div. A are insoluble. Group III Iron Group II VI VI VI (Fe), Fe 2 , A1 2 , O 2 . Chlorides and sulphides are soluble in acid solutions. Members of this group are precipitated as hydroxides in alkaline solutions by NH 4 OH. Group IV Cobalt Group ii it ii ii Co, Ni, Mn, Zn. Chlorides and sulphides are soluble in acid solutions. Hydroxides are not precipitated in alkaline solutions in presence of NH 4 C1. Members of this group are separated as sulphides by (NH 4 ) 2 S in alkaline solutions. Group V Barium Group ii ii ii ii Ba, Sr, Ca, Mg. Precipitated as carbonates from alkaline solutions by (NH 4 ) 2 C0 3 . Group VI Sodium Group Na, K, L'I, NH 4 . This group is not precipitated by any general reagent. Its members are detected by special tests. PAET III BASIC ANALYSIS GROUP I SILVER GROUP Precipitated by HC1 as chlorides in acid solution. Preliminary Experiments Use about 2 c.c. of any given solution for each experi- ment. Keep a careful and systematic record of results, and whenever a change occurs on addition of reagent, ask yourself the question, " What is it ? " a Hg 2 Mercury. Mercurous Compounds To a solution of Hg 2 (NO 3 ) 2 add : 1. HC1 = white precipitate. What is it ? Filter, make hole in bottom of filter with glass rod, wash pp. into test tube by directing a fine stream of water from wash bottle upon the pp. Boil the precipitate with H 2 O. Is it soluble ? 2. NaCl or any other soluble chloride = Filter and test solubility in NH 4 OH. 3. H 2 S = 4. Strip of Cu foil, remove after a few minutes and rub dry = 5. NH 4 OH = 24 GROUP I 25 Complete and balance the following, underlining all precipitates : Hg 2 (N0 3 ) 2 Hg 2 (N0 3 ) 2 Hg 2 (N0 3 ) 2 +H 2 S Hg 2 Cl 2 + 2 NH 4 OH = Hg 2 NH 2 Cl + NH 4 C1 + 2 H 2 O QUESTIONS On experiments. 1. What is the solubility of IIg 2 Cl 2 in H 2 O? 2. In NH 4 OH ? 3. In dilute acids? To be answered by reference to works on descriptive chemistry. 4. What is calomel? 5. How prepared? 6. For what used ? 7. Derivation of the name. , i Ag Silver To any solution of Ag, as AgNO 3 , add : 1. HC1 = a. Filter and expose a portion of the precipitate to sunlight. b. Reduce another portion on charcoal in blowpipe flame. 2. NaCl = Filter and test solubility in hot H 2 O. 26 BASIC ANALYSIS 3. NH 4 C1 = Filter and add NH 4 OH to pp., pouring the solution through two or three times until pp. is all dis- solved. Now add HNO 3 to solution. What is the precipitate? Filter and expose pp. to sunlight. 4. H 2 S = 5. Any soluble chloride = Complete and balance the following, underlining all precipitates : AgN0 3 + HC1 = AgCl + NH 4 OH = (NH 3 ) 3 (AgCl) 2 + (NH 8 ) 3 (AgCl) 2 + HN0 3 = AgN0 3 + H 2 S = QUESTIONS 1. In how many and what ways can you precipitate Ag as a chloride ? 2. What is the solubility of AgCl in H 2 O ? 3. InNH 4 OH? 4. In the latter case, how may AgCl be veprecipitated? 5. What is the effect of sunlight on AgCl? 6. What use is made of this fact in the arts? 7. Where is Ag found in nature? 8. In what forms ? 9. What is lunar caustic? 10. How is iron plated with silver ? 11. What is the basis of indelible ink? 12. Name any important uses of Ag and Ag compounds that you can. GROUP I 27 II Pb Lead To a solution of Pb(NO 3 ) 2 or Pb(C 2 H 3 O 2 ) 2 add: 1. HC1 = Filter and add hot H 2 O to pp. until it disappears. Allow to cool. Does all the substance crystallize out ? How can you determine this ? 2. NaCl or any other soluble chloride = Filter and reduce a portion on charcoal. To the remaining pp. add NH 4 OH. Is it soluble in NH 4 OH ? 3. H 2 S= 5. H 2 S0 4 = 4. (NH 4 ) a S= 6. K 2 Cr0 4 = Complete and balance the following, underlining all precipitates : Pb(N0 3 ) 2 + HC1 Pb(C 2 H 3 O 2 ) 2 + NaCl Pb(NO 3 ) 2 + NaCl Pb(N0 3 ) 2 + H 2 S Pb(C 2 H 3 2 ) 2 +(NH 4 ) 2 S = Pb(N0 3 ) 2 + H 2 80 4 Pb(NO 3 ) 2 + K 2 Cr0 4 QUESTIONS 1. What is the solubility of PbCl 2 in cold H 2 O? 2. In hot H 2 O ? 3. InHCl?" 4. InNH 4 OH? 5. Name and describe three compounds of Pb that may be pre- cipitated to prove the presence of Pb. 6. In what forms is Pb found in nature? 7. Give some of its physical properties. 28 BASIC ANALYSIS 8. Lead pipes are much used for water pipes. What is the danger of such use for drinking water? Air and water together dissolve Pb according to the following reaction : Pb + O + H 2 O = FbO 2 H 2 . The lead hydroxide thus formed is slightly soluble in water. From this source, in certain classes of water, there is danger of lead poison- ing. Waters containing chlorides, nitrates, and acid carbonates in solution are particularly dangerous, as the presence of these com- pounds aids the solution of the Pb. Waters containing phosphates, sulphates, and sulphides are not to be feared, as these substances form an insoluble film, and prevent further action. 9. How may the presence of Pb in drinking water be detected? For this purpose, select the most delicate of the tests for Pb that you have studied. 10. What is the antidote for Pb poisoning? 11. What is litharge? 12. Sugar of lead? 13. What is white lead, and for what used ? 14. What is chrome yellow, and for what used ? The class should now analyze two or three known solutions of this group, to be followed by two or three unknown solutions, according to the following directions for analysis. Analysis. Gr. I To the original solution add HC1. A white precipitate formed may contain Hg 2 Cl 2 , AgCl, PbCl 2 , SbOCl, and BiOCl. Add more HC1, and the last two substances will redissolve if present. The filtrate contains Grs. II-VI, and is marked and set aside. Wash the precipitate with hot H 2 O, and test the wash water with H 2 SO 4 . A white GROUP I 29 precipitate of PbSO 4 shows the presence of Pb. Con- tinue the washing with hot water until the wash water fails to give any further precipitate with H 2 SO 4 . NH 4 OH is now poured on the HC1 precipitate and the filtrate poured on two or three times to insure complete solution of the AgCl. A black residue is mercurous amido-chloride, Hg 2 NH 2 Ci, proving the presence of Hg 2 . To the NH 4 OH nitrate add HNO 3 . The formation of a white precipitate of AgCl shows the presence of Ag. TABULATION, GR I Solution contains Grs. I VI. Add HC1 to cold solution. Pp. Hg 2 Cl 2 AgCl PbOlj Wash with hot H 2 until Pb is all dissolved. Pp. Hg 2 Cl 2 AgCl Wash with NH 4 OH. Filtrate PbCl 2 Add H 2 S0 4 . Pp. Hg 2 NH 2 Cl, black, Hg , present. Fil. AgCl in sol. Add HN0 3 . Pp. white PbS0 4 , Pb present. Pp. white AgCl, Ag present. Fil. = Grs. II-VI. Notes and Suggestions Explanation of the tabulation. The reagent which pro- duces the precipitation, or separates part of the sub- stances in the form of solution and part as a solid, is always underlined thus: | . Now trace the long line underneath and in contact with [ to the left, and the symbols of all precipitates will be found. At the first 30 BASIC ANALYSIS vertical line to the -right of these symbols will be found the symbols for the contents of the filtrate, thus : Reagent Precipitate Filtrate Always add the reagent until there is no further precipi- tate. Determine this point by adding a drop of the re- agent to the filtrate. Avoid excess of the reagent, as it will finally make the solution too dilute for use in subsequent operations. The directions are given with the assumption that all the elements are present, but the student is warned to give special attention to all negative observations, and correct inferences therefrom. PbCl 2 is slightly soluble even in cold H 2 O. Therefore, Pb will be found in Gr. II, A, when it is present in Gr. I. A precipitate may be formed on addition of HC1, although no member of Gr. I is present, but will dissolve in an excess of the reagent. This would be due to the presence of Sb or Bi, which form the oxychlorides in water. H 2 S and (NH 4 ) 2 S give the most delicate reactions for Pb. A Specimen Page from Notebook When a solution was found to contain Ag and Pb. Orig. sol. was neutral to litmus paper. Orig. sol. + HC1 = w. pp., .-. Hg 2 , Ag, and Pb may be pres. Fil. = Grs. II-VI and is set aside. Pp. + hot H 2 O. Res. Hg 2 Cl 2 and AgCl. Fil. + H 2 SO 4 = w. pp. PbSO 4 , .*. Pb pres. Res. was washed with hot H 2 O until wash water gave no further pp. with H 2 8O 4 . Res. + NH 4 OH entirely dissolved, .-. Hg 2 abs. Fil. + HNO 3 = w. pp. AgCl, . . Ag pres. Found in solution, Ag, Pb. GROUP II DIVISION A 31 \ GROUP II, DIVISION A COPPER GROUP ii ii in ii ii Hg(-ic), (Pb), Bi, Cu, Cd. Precipitated by H 2 S, in acid solutions, as sulphides in- soluble in (NH 4 ) 2 S (yellow). Preliminary Experiments ii Hg Mercury. Mercuric Compounds To a solution of HgCl 2 add : y 1. H 2 S = a. Filter and test solubility of one portion in (NH 4 ) 2 S (yellow). b. Test solubility of second portion in HC1. 2. (NH 4 ) 2 S = Filter and test solubility in HNO 3 . 3. Cu foil = 4. SnCl 2 = Complete and balance the following, underlining all precipitates : HgCl 2 + H 2 S HgCl 2 + (NH 4 ) 2 S = HgCl 2 + SnCl 2 . = HgS + HN0 3 QUESTIONS 1. What is the solubility of HgS in HNO 3 ? 2. InHCl? 3. InH 2 0? 4. In (NH 4 ) 2 S? 5. Describe three tests for Hg. 32 BASIC ANALYSIS 6. Where and in what form is Hg found in nature ? 7. What are the physical properties of Hg ? 8. What are some of its uses ? 9. What is amalgam ? 10. What is vermilion ? 11. Corrosive sublimate ? 12. What was the celebrated experiment of Priestley in which he used HgO? 13. What is fulminating mercury? 14. What is the antidote for Hg poisoning? 15. Explain the use of the terminations -ous and -ic in naming Hg 2 Cl 2 and HgCl 2 . There are two classes of mercury compounds : one in which the double atom Hg 2 is bivalent, and another in which the single atom Hg is bivalent. In the first case, the two atoms are supposed to be united with each other. Hg - Cl - Cl I Hg Hg - Cl - Cl Mercurous chloride Mercuric chloride The termination -ous here denotes less of the acid radical (e.g. Cl above) and -ic more. 16. Name the following salts : Hg(N0 3 ) 2 , Hg 2 (N0 3 ) 2 , Hgl,, Kg,!, in Bi Bismuth To a solution of BiCl 3 or Bi(NO 3 ) 3 add : 1. NH 4 OH = Filter, dissolve pp. in a few drops of cone. HC1, and add the solution to a large quantity of H 2 O. The oxychloride of bismuth is formed. What is its symbol ? GROUP II DIVISION A 83 2. H 2 S = Filter and determine solubility of one portion of pp. in hot HNO 3 , and of a second portion in HC1. 3. (NH 4 ) 2 S in excess = To (NH 4 ) 2 S add HC1. What is deposited ? The BiCl 3 solution contains free acid. Can you explain what occurred at first in reaction No. 3 ? Can you see an objection to adding (NH 4 ) 2 S to an acid solution? Complete and balance the following, underlining all precipitates : BiCl 3 + NH 4 OH Bi(N0 3 ) 3 + NH 4 OH = BiO 3 H 3 + HC1 BiCl 3 + H 2 BiCl 3 + H 2 S Bi(N0 3 ) 3 + H 2 S (NH 4 ) 2 S 2 * + HC1 = QUESTIONS 1. What is the solubility of Bi 2 S 3 in HNO 3 ? 2. In (NH 4 ) 2 S? 3. In H 2 0? 4. What is the effect of H 2 O on BiCl 3 ? 5. What is a basic salt ? 6. What is the symbol for the basic nitrate or subnitrate of bis- muth? 7. For what is it used ? 8. How does Bi occur in nature? 9. What is fusible alloy and for what used ? * See page 13, note. IR. QUAL. ANAL. 3 34 BASIC ANALYSIS ii Cu Copper To a solution of either CuCl 2 , Cu(NO 3 ) 2 , or CuSO 4 add : 1. NH 4 OH = Salt of cupra-aniraonium 2. H 2 S = a. Filter and test solubility of one portion in HNO 3 . b. Test solubility of second portion in (NH 4 ) 2 S (yellow). 3. (NH 4 ) 2 S = a. Filter and test solubility of one portion in HC1. b. Test solubility of second portion in KCN.* 4. KCN in slight excess = 5. HC 2 H 3 2 + K 4 Fe(CN) 6 = Complete and oalance the following, underlining all precipitates : Cu(N0 8 ) 2 +NH 4 OH =Cu(NH 3 ) 2 (N0 3 ) 2 + CuCl 2 + H 2 S CuS0 4 +(NH 4 ) 2 S Cu(NO 3 ) 2 + KCN = Cu(CN) 2 + Cu(CN) 2 + 2 KCN = (KCN) 2 Cu(CN) 2 2 CuCl 2 + K 4 Fe(CN) 6 = Cu 2 Fe(CN) 6 + * Warning. KCN is a fatal poison, and care must be taken that it does not come in contact with abrasions of the skin. KCN must not be added to an acid solution, as cyanogen gas, which is a deadly poison, may be liberated. All KCN solutions must be poured into the sink after using. GROUP II DIVISION A 35 QUESTIONS 1. Describe three different tests for Cu. 2. What is the solubility of CuS in HC1 ? 3. InHNO 3 ? 4. In(NH 4 ) 2 S? 5. In KCN? 6. Where and in what forms is Cu found in nature ? 7. Give some of the uses of Cu. 8. What is an alloy ? 11. Aluminum bronze? 9. What is brass? 12. What is blue vitriol? 10. German silver ? 13. What is verdigris ? There are two classes of Cu compounds, cuprous and cupric, as in the case of mercury. The cupric compounds are the more important, and our study will be confined to them. Cd Cadmium To a solution CdCl 2 , CdSO 4 , or Cd(NO 3 ) 2 add : 1. H 2 S = Filter and pour on pp. HNO 3 . 2. (NH 4 ) 2 S = Filter and pour on pp. sol. of KCN. 3. KCN in slight excess = 4. NH 4 OH = 5. NH 4 OH in excess = Separation of Cd from Cu Mix a few drops of CuSO 4 and CdSO 4 . Add NH 4 OH in excess. What is formed? Add a solution of KCN with constant stirring until blue color just disappears. Any excess of KCN must be avoided. Now pass H 2 S through the solution. A yellow precipitate of CdS is formed. CuS is not precipitated in presence of KCN. 36 BASIC ANALYSIS Complete and balance the following, underlining all precipitates : CdCl 2 + H 2 S > 4 + (NH 4 ) 2 S = Cd(NO 3 ) 2 + NH 4 OH = CdCl 2 + KCN QUESTIONS 1. What is the solubility of CdS in H 2 O? 2. InHNO,? 3. In (NH 4 ) 2 S? 4. In KCN? 5. In what form is Cd found in nature ? 6. Give physical properties and some of the uses of the metal. 7. Give uses of any of the salts of Cd. Analysis. Gr. II, Div. A Heat the filtrate from the first group precipitate, or the solution found not to contain Gr. I, acidulate with HC1, and pass H 2 S through for some time. Filter and dilute the filtrate with two or three times its volume of H 2 O, heat, and pass H 2 S through. Add the pp. if any to the original pp. Repeat this operation until the precipitation is complete. The filtrate contains Grs. III-VI and is set aside. The precipitate is HgS, PbS, Bi 2 S 3 , CuS, CdS, SriS, SnS 2 , Sb 2 S 3 , Sb 2 S 6 , As 2 S 8 , and As 2 S 5 . Make hole in filter, wash precipitate into beaker, and heat with large volume of H 2 O. Decant. Repeat three or four times and filter. Reject the wash water. This process should wash out all free HC1. Make hole in filter and wash the precipitate into a test tube with as little (NH 4 ) 2 S (yellow) as pos- sible. Pour through the filter several times to remove all adhering precipitate. Warm gently and filter. GROUP II DIVISION A 37 The filtrate contains Gr. II, Div. B, Sn, Sb, and As in solution, and is set aside. The precipitate is HgS, PbS, Bi 2 S 3 , CuS, and CdS. Make a hole in the filter and wash pp. into beaker with HNO 3 . Heat to boiling. All but HgS will be dissolved. Frequently, a small mass of S with adherent particles forms in the beaker and should not be confounded with HgS. After filtering, dissolve the HgS by putting a pinch of KC1O 3 * on the precipitate and adding cone. HC1. Dilute the solution with H 2 O and add SnCl 2 . A white or gray precipitate of Hg 2 Cl 2 shows Hg present. An alternative method is the addition of Cu foil, which will be coated silver white with Hg. The HNO 3 solution is now partially evaporated with a few drops of H 2 SO 4 . A white pp. on filtration is PbSO 4 . If the filtrate now contains much free acid, it should be evaporated still further. Then add NH 4 OH in slight ex- cess. The precipitate is white BiO 3 H 3 . The filtrate contains Cu and Cd. Wash precipitate and add two or three drops of cone. HC1 and allow to drop into a large volume of H 2 O, when the formation of white BiOCl con- firms the presence of Bi. If the NH 4 OH filtrate is blue, it shows the presence of Cu. Make an additional test for Cu, if the solution is not blue, by acidifying a portion of it with HC 2 H 3 O 2 and adding K 4 Fe(CN) 6 , when a brown precipitate will show even a trace of Cu. If Cu is ab- sent, add H 2 S to remaining sol. A yellow precipitate of CdS shows Cd present. If Cu is present, cautiously add a solution of KCN until the last drop causes the blue color to disappear on stirring, and add H 2 S, when a yellow precipitate of CdS will indicate Cd. * Warning. KC10 3 , in the presence of H 2 S0 4 , is dangerously explosive. Take care that all solutions used with KC10 3 are free from H 2 SO 4 . 38 BASIC ANALYSIS TABULATI Sol. contains Grs. II-VI. Pp. HgS PbS Bi 2 S 3 CuS CdS Wash several times by decantation. (SnS (NH 4 ),S ant Pp. HgS PbS Bi 2 S 3 CuS CdS Make hole in filter, wash into beaker with HNO ;i , and h Pp. HgS, black. Dissolve in cone. HC1 and KC10 3 and add SnCl 2 Fil. Pb(N0 3 ) 2 Bi(N0 3 ) 3 Partially evaporate with a fe^ Pp. white is PbS0 4 ; Pb pres. Fil. Bi(N0 3 ) 3 Add NH White or gray pp. of Hg 2 Cl 2 , Hg pres. Or, Add Cu foil. Silver-colored deposit on foil shows Hg pres. Pp. Bi0 3 H 3 , white, Bi pres. Confirm by dissolving in 2 or 3 drops of cone. HC1 and allowing solution to drop into large volume H 2 0. White cloud of BiOCl, Bi pres. GROUP II DIVISION' A 39 H. II, DIV. A boiling and add H.,S. Sb 2 S 3 Sb 2 S 5 As 2 S 3 (Div. B, Gr. II) 'ash through filter with As 2 S 5 ) Filtrate = Grs. Ill- VI. riling. i(N0 3 ) 2 of H 2 S0 4 . i(N0 8 ), ' light excess. Cd(N0 3 ) 2 Cd(N0 3 ), Fil. = Gr. II, Div. B. Sn, 'Sb, and As. , blue, u pres. doubt, test rtion of sol. HC,H 3 2 . K 4 Fe(CN) 6 ; n pp., u pres. If Cu is abs. add H 2 S to remainder of sol. Pp. yellow CdS, Cd pres. If Cu is present, add KCN solution until color just disappears, and then H 2 S. blue | Pp. . yellow CdS, Cd pres. 40 BASIC ANALYSIS Notes and Suggestions A known solution containing this group should be worked through twice, to be followed by unknown solu- tions containing some of the members of Gr. I and Gr. II, Div. A. Following is a specimen page of notebook record of a solution found to contain Pb and Cd, and limited to Grs. I and II, Div. A : Sol. was neutral to litmus paper. Sol. -f HC1 = w. pp., .-. Hg 2 , Ag, and Pb may be pres. Fil. = Gr. II, Div. A, and is set aside. Pp. + hot H 2 O entirely dissolves, .-. Hg 2 and Ag absent. This solution + H 2 SO 4 = w. pp. of PbSO 4 , .-. Pb pres. Fil. containing Gr. II, Div. A, heated and H 2 S added : yellow pp., .-. Gr. II, Div. A, pres., but probably limited to Cd and trace of Pb from Gr. I. Filtrate was rejected. Pp. was washed by decantation. Pp. -f HNO 3 dis- solved entirely, .-. Hg abs. Partially evaporated with a few drops H 2 SO 4 , w. pp. PbSO 4 , .-. Pb pres. Fil. -f NH 4 OH in excess, no pp., .-. Bi abs. No change in color, .-. Cu probably abs. Small portion of sol. acidified with HC 2 H 3 O 2 and K 4 Fe(CN) 6 added. No change, .-. Cu abs. Remainder of sol. + H 2 S gave yellow pp. ofCdS, .-. Cdpres. Solution contains Pb and Cd. It will be noticed that the directions for analysis as- sume the presence of all the elements and all the groups. The student must not conclude from this that he must search for all the groups when the solution is known to be limited to certain groups. When the addition of a reagent shows no change, a correct inference from this GROUP II DIVISION B 41 negative observation may greatly shorten the work of analysis. Of course it is useless to go through the analy- sis for substances already proved absent. QUESTIONS 1. What is the general reagent for Gr. II, Div. A? 2. Give the names, symbols, and colors of all precipitates pro- duced by the general reagent for this group. 3. What is the reaction of HNO 3 on PbS? 4. OnCdS? 5. On Bi 2 S 3 ? 6. Reaction of HgCl 2 on SnCl 2 ? 7. How would you separate Cu from Cd? 8. Hgfrom Cu? 9. Bifrom Cu? 10. Pbfrom Cu? GROUP II, DIVISION B ARSENIC GROUP II IV III III Sn, Sn, Sb, As Precipitated by H 2 S, in acid solutions, as sulphides soluble in (NH 4 ) 2 S (yellow). Preliminary Experiments II IV Sn, Sn Tin. Stannous and Stannic Compounds 1. To a solution of SnCl 2 , add H 2 S = Filter, make hole in filter paper, and wash pp. into test tube with a few c.c. (NH 4 ) 2 S (yellow), and warm gently. Does it dissolve ? Treat the solu- tion with HC1. What is the main precipitate? Anything else ? 42 BASIC ANALYSIS 2. Boil SnCl, 2 with cone. HNO 3 . This converts the stan- nous chloride into stannic chloride. To the SnCl 4 thus produced, add H 2 S = ? Filter and boil pp. with cone. HC1 till H 2 S is expelled. Solution now contains SnCl 4 . Dilute slightly, add iron nail, and warm for a short time. The SnCl 4 is reduced to SnCl 2 . Decant into another test tube and add HgCl 2 . The precipitate is Hg 2 Cl 2 . 3. Make a little SnS and test solubility of one portion in (NH 4 ) 2 CO 3 . Test solubility of second portion in (NH 4 ) 2 S (yellow). 4. Add a little HC1 to SnCl 2 in beaker and put in a small battery made by placing Ft foil and Zn in con- tact. When all action ceases, remove the Ft foil, and wash the foil in warm H 2 O and HC1. The Sn will dissolve from the Ft as SnCl 2 . Four off solution and add HgCl 2 . What is the precipitate ? 5. To SnCl 2 add HgCl 2 = 6. To SnCl 2 add HgCl 2 in slight excess = Complete and balance the following, underlining all precipitates : SnCl 2 + H 2 S = SnCl 4 + H 2 S = SnS + (NH 4 ) 2 S 2 * = (NH 4 ) 2 SnS 3 (NH 4 ) 2 SnS 3 + 2 HC1 = SnS 2 + 2 NH 4 Cl + H 2 S Sn + HC1 = SnCl 2 + HgCl 2 = Hg 2 Cl 2 + SnCl 2 + Hg 2 Cl 2 = 2Hg + * See page 13, note. GROUP II DIVISION B 43 QUESTIONS 1. What is the solubility of SnS in (NH 4 ) 2 S (yellow)? 2. How does the iron nail affect the SnCl 4 on boiling ? Explain fully. 3. What is reduction ? When an element has two degrees of quantivalence, reduction changes it to the lower degree, while oxidation changes it to the higher degree of quantivalence. 4. Describe two tests for Sn. 5. Where and in what form is Sn found in nature? 6. State some of its uses. 7. What is bronze ? 8. Britannia metal ? 9. Pewter? 10. Name one use for SnCl 2 . in Sb Antimony. Antimonious Compounds Use a solution of SbCl 3 , or SbOKC 4 H 4 O 6 tartar emetic. The latter can be used in cases where a dilute solution without free acid is desired, as it is the only soluble anti- monious salt that is not decomposed by H 2 O. 1. Add H 2 S to SbCl. = it O 2. Add H 2 S to tartar emetic = Filter and dissolve precipitate in (NH 4 ) 2 S (yellow). Treat the solution with HC1. What is the pre- cipitate ? Anything else ? Filter. Throw on precipitate a pinch of KC1O 3 and add cone. HC1. Dilute the solution with H 2 O and put in the Pt and Zn battery. A black stain, on the Pt foil indi- cates the presence of Sb. Dissolve this stain in tartaric acid and a few drops HNO 3 , and add H 2 S. 44 BASIC ANALYSIS 3. Add H 2 S to SbClg = Determine if careful dilution with H 2 O will aid the precipitation. Filter aoid test solubility of one portion in (NH 4 ) 2 CO 3 and second portion in (NH 4 ) 2 S (yellow). 4. Add H 2 O to SbClg = Complete and balance the following, underlining all precipitates : SbClg + H 2 S = SbClg + H 2 = Sb 2 S 3 + 3(NH 4 ) 2 S 2 = 2(NH 4 ) 3 SbS 4 + S 2(NH 4 ) 3 SbS 4 + 6 HC1 = Sb 2 S 6 + 6 NH 4 C1 + 3 H 2 S QUESTIONS 1. What is the solubility of Sb 2 S 3 in (NH 4 ) 2 S (yellow)? 2. In (NH 4 ) 2 C0 3 ? 3. Describe two tests for Sb. 4. How does Sb occur in nature ? 5. What are some of its uses? 6. Give uses of one of its compounds. As Arsenic. Arsenious Compounds As behaves both as a basic and as an acid radical, but is precipitated from acid solutions by H 2 S as a sulphide, whether it is present as an' arsenious or arsenic salt. (Special tests for arsenites and arsenates will be found on page 88.) 1. Add H 2 S to AsC] 3 = Filter and test solubility of one portion in (NH 4 ) 2 S (yellow), and of second portion in (NH 4 ) 2 CO 3 . 2. Add H 2 S to sol. of Na 3 AsO 3 = A 66 GROUP II DIVISION B 45 3. Acidify sol. of Na 3 AsO 3 with H 2 SO 4 and add H 2 S. Filter and dry pp. Now mix a minute quantity with Na 2 CO 3 and KCN, and heat cautiously in bulb tube. Black ring formed on tube is metallic As. Complete and balance the following, underlining all precipitates : AsCl 3 + H 2 S = + 3(NH 4 ) 2 C0 8 =(NH 4 ) 8 As0 8 + (NH 4 ) 2 S 2 =(NH 4 ) 2 As 2 S 5 + 3H0 H 2 S QUESTIONS 1. What is the solubility of As 2 S 3 in (NH 4 ) 2 S? 2. In (NH 4 ) 2 CO 3 ? 3. With a knowledge of the solubilities of the sulphides of As, Sn, and Sb, state how the sulphides of As may be separated from the other sulphides of this group. 4. Give a symbol for an arsenate. 5. For an arsenite. 6. On which side of a symbol is the acid radical, and on which side is the basic radical? 7. In what forms is arsenic found in nature? 8. What is the " arsenic " sold in drug stores ? 9. What is white arsenic? 10. What are some of its uses ? 11. What is Paris green ? 12. What is Scheele's green ? 13. What is the Marsh test for As? 14. What are some of the dangers of As in fabrics, wearing ap- parel, and wall paper? 15. What is the antidote for acute arsenical poisoning? 46 BASIC ANALYSIS Analysis. Gr. II, Div. B To the (NH 4 ) 2 S (yellow) solution formed by the sepa- ration of Gr. II, B, from Gr. II, A, add HC1. Reject filtrate. A yellow precipitate may show the presence of Sn, Sb, and As (besides Sz). Do not mistake the deposit of S for this group. Wash precipitate twice with cold H 2 O and add cold (NH 4 ) 2 CO 3 . The filtrate contains As 2 S 3 and As 2 S 5 in solution. The residue is SnS 2 and Sb 2 S 6 . Wash with H 2 O, and add a few particles of KC1O 3 and cone. HC1. Divide the solution (which contains SnCl 4 and SbCl 5 ) into A and B. To A add a small iron nail and warm gently for some time. Filter, and to the filtrate add HgCl 2 . A white precipitate of Hg 2 01 2 shows the pres- ence of Sn. Pour B into evaporating dish, dilute with H 2 O, and put in a small battery of strips of Pt foil and Zn in contact. Use enough Zn so that it will not be entirely dissolved, and allow the battery to remain until effervescence of H ceases. The Sb will give a black deposit on the Pt foil. If Sn was not found in A, the Pt foil may be washed in warm H 2 O and HC1, the wash water filtered, and HgCl 2 added to the filtrate. White precipitate of Hg 2 Cl 2 proves the presence of Sn. The black stain of Sb on the Pt foil may be dissolved in IINO 3 and H 2 C 4 H 4 O 6 , and H 2 S passed through the solution, when a precipitate of Sb 2 S 3 confirms the presence of Sb. To the (NH 4 ) 2 CO 3 solution of As 2 S 3 and As 2 S 5 add HC1. Yellow precipitate of As 2 S 3 and As 2 S 6 indicates As. To confirm its presence, dry the precipitate, mix with equal parts of Na 2 CO 3 and KCN, and heat cautiously in bulb tube, when the formation of metallic mirror or ring of As on upper part of tube proves the presence of As. GROUP II DIVISION B 47 TABULATION, GR. II, DIV. B Solution contains Sn, Sb, and As in (NH 4 ) 2 S (yellow) solution. Add HC1. Pp. (Sjc) SnS SnS a Sb 2 S 3 Sb 2 S 5 As 2 S 3 Wash twice with cold H 2 and add (NH 4 ) 2 C0 3 . Fil. reject Pp. SnS 2 , Sb 2 S 5 . Wash, add KC10 3 and cone. HC1. Divide the solution into A and B. To A add small iron nail and warm gently. Filter, and to the filtrate add HgCl 2 . Reject pp. W. pp. Hg 2 Cl 2 , Sn pres. Dilute B with H 2 0, and add battery of Pt foil and Zn. Black stain on Pt foil, Sb pres. Wash the Pt foil carefully with warm H 2 and HOI, filter, and add HgCl 2 to filtrate. W. pp. Hg 2 Cl 2 , Sn pres. Fil. = As 2 S 3 and As 2 S 5 in solution. Add HC1. Pp. yellow As 2 S 3 and As 2 S 5 (S#), As pres. Confirm by drying pp., mixing with Na 2 C0 3 and KCN, and heating in bulb tube. Arsenic mirror on upper part of tube, As pres. Notes and Suggestions The precipitation of S, on addition of HC1, must not be mistaken for this group. Sulphur will precipitate, white, when HC1 is added to (NH 4 ) 2 S. This difficulty can be overcome in part by using small quantities of (NH 4 ) 2 S. When heating solution A with an iron nail, a precipitate may be due to carbon from the iron, or metallic Sb from the reducing action of nascent H, or particles of undissolved iron. In the case of the battery 48 BASIC ANALYSIS action in solution B, if enough Zn is used to neutralize all acid and the action is carried to completion, most of the Sn will be deposited with Sb on the Pt foil. The Sn may be dissolved off with HC1 and warm H 2 O as SnCl 2 . Sb is undissolved. This test for Sn serves as a check on the preceding test. The (NH 4 ) 2 CO 3 should not contain much NH 4 OH, as its presence will dissolve traces of SnS and Sb 2 S 3 , and thus make necessary the confirmatory test for As, with Na 2 CO 8 and KCN. QUESTIONS 1. How is this group originally precipitated? 2. Give symbols and colors of the precipitates produced by the general reagent for this group. 3. How is this group separated from Div. A? 4. Why boil with an iron nail? 5. What is the confirmatory test for As? 6. What is the test for Sn ? 7. How do you separate As from Sn ? 8. SbfromCu? GROUP III -IRON GROUP II VI VI VI (Fe), Fe 2 , A1 2 , Cr 2 Precipitated as hydroxides by NH 4 OH in presence of NH 4 C1. Preliminary Experiments II VI Fe, Fe 2 Iron. Ferrous and Ferric Compounds 1. Dissolve a very small piece of FeSO 4 , free from white coating, in hot water. Divide the solution into A GROUP III 49 and B. Dilute A with hot H 2 O, divide into three por- tions, and quickly add : a. Potassic ferrocyanide = b. Potassic ferricyanide = c. Potassic sulphocyanide = Boil B with HNO 3 . Dilute with H 2 O, divide into three parts, and add : a. Potassic ferrocyanide = b. Potassic ferricyanide = c. Potassic sulphocyanide = Name a test for ferrous iron. Describe two tests for ferric iron. 2. Dissolve a piece of FeSO 4 in hot H 2 O and divide into A and B. Dilute A with H 2 O, divide into two parts, and add : a. NH 4 OH = b. NH 4 C1 + NH 4 OH = Oxidize B to the ferric state with HNO 3 , dilute with H 2 O, divide into two parts, and add : a. NH 4 OH = b. Filter and test solubility of precipitate in HC1. 3. To Fe 2 Cl 6 or any other soluble ferric salt add : (NH 4 ) 2 S = FeS + 50 BASIC ANALYSIS There are two sets of iron compounds, ferrous and ferric. In the ferrous compounds, the single atom Fe is bivalent, and in the ferric, the double atom Fe 2 is sextiva- lent. Cl /Cl Ferrous chloride. Fe-Cl n . Ferric chloride. /Cl Fe^-Cl \C1 Ferrous compounds are converted to ferric by oxida- tion, as with HNO 3 , acid reducing agents reverse the change. The simplest form of the reaction for converting a ferrous to a ferric salt would be 2 FeCl 2 + 2 HCl-f O = Fe 2 Cl 6 + H 2 O, or 2 FeSO 4 + H 2 SO 4 + O = Fe 2 (SO 4 ) 3 + H 2 O. The O may be supplied by HNO 3 or any other oxi- dizer. A ferric salt may be converted to a ferrous salt by the use of nascent hydrogen. Fe 2 Cl 6 + Zn + 2 HC1 = 2 FeCl 2 + ZnCl 2 + 2 HC1 ; or, a simpler form, Fe 2 Cl 6 + H 2 = 2 FeCl 2 4- 2 HC1. The HC1 dissolves the Zn, forming ZnCl 2 , and setting free hydrogen. This nascent H removes C1 2 from Fe a Cl 6 , forming HC1. GROUP III 51 Complete and balance the following, underlining all FeS0 4 +(NH 4 ) 2 S = 3 FeSO 4 + 2 K 8 Fe(CN) 6 = Fe 8 (Fe(CN) 6 ) 2 + 3 K 2 SO 4 Fe 2 (S0 4 ) 3 +(NH 4 ) 2 S = Fe 2 (SO 4 ) 3 + NH 4 OH = - Fe 2 (S0 4 ) 3 + 6 KCNS = Fe 2 (CNS) 6 + 3 K 2 SO 4 2 Fe 2 (S0 4 ) 8 +3 K 4 Fe(CN) 6 =(Fe 2 ) 2 (Fe(C,N) 6 ) 8 + 6 K 2 S0 4 QUESTIONS 1. What is the behavior of the iron solutions (both -ous and -ic) with NH 4 OH ? 2. With NH 4 OH in presence of NH 4 C1? 3. Do you see a reason why (since NH 4 C1 must be added to this group) Fe must first be oxidized to Fe 2 ? 4. What is green vitriol ? 5. What is water of crystallization ? 6. What is Turnbull's blue ? 7. What is Prussian blue ? 8. What is " writing fluid " ? 9. Why does " writing fluid " turn black on exposure to the air ? 10. What is cast iron ? 11. Pig iron? 12. Wrought iron ? 13. Steel? 14. Where and in what forms is iron found in nature ? 15. What are some of the physical properties of steel ? 16. Of wrought iron ? 17. Of cast iron? 52 BASIC ANALYSIS VI A1 2 Aluminum To a solution of A1 2 (SO 4 ) 3 , or a solution of alum, add : 1. NH 4 OH = Filter and test solubility of precipitate in HC1. 2. NH 4 C1 + NH 4 OH = 3. NaOH in excess = a. Upon addition of NaOH, A1 2 O 6 H 6 is formed, and, with an excess of NaOH, the hydroxide dissolves, forming sodic aluminate Na 6 O 6 Al 2 . In this case, the A1 2 O 6 H 6 acts as an acid, allowing its H to be replaced by the basic radical Na. b. Add NH 4 C1 to the solution in (3 a) and heat = 4. (NH 4 ) 2 S = A1 2 6 H 6 + Complete and balance the following, underlining all precipitates : A1 2 (S0 4 ) 3 +NH 4 OH = A1 2 (S0 4 ) 8 + NaOH = A1 2 6 H 6 + NaOH = Na 6 O 6 Al 2 + Na 6 6 Al 2 +NH 4 Cl = A1 2 (S0 4 ) 3 + 3(NH 4 ) 2 S + 6 H 2 = A1 2 O 6 H 6 + 3(NH 4 ) 2 SO 4 + 3H 2 S (Problem. Make a solution of A1 2 C1 6 from alum.) QUESTIONS 1. Does NH 4 C1 affect the precipitation of A1 2 O 6 H 6 by N H 4 OH ? 2. What form of A1 2 is precipitated by (NH 4 ) 2 S? 3. What is the effect of NH 4 C1 on Na 6 O 6 Al 2 ? 4. What is the solubility of A1 2 O 6 H 6 in NaOH ? GROUP III 53 5. In what forms does A1 2 occur in nature? 6. What are some of its uses and physical properties ? 7. What is alum? 8. For what is A1 2 O 6 H 6 extensively used in the arts? 9. How are porcelain and earthenware made ? VI Cr 2 Chromium To a solution of Cr 2 Cl 6 , Cr 2 (NO 3 ) 6 , or chrome alum, add : 1. NH 4 OH = Filter and test solubility of precipitate in HC1. 2. 3. 4. Pb(C 2 H 3 2 ) 2 = To solution of Na 2 CrO 4 add Pb(C 2 H 3 O 2 ) 2 = To solution of Cr 2 (NO 3 ) 6 add NH 4 OH = Filter, wash pp. Make hole in filter, and wash into beaker with NaOH. Add a few drops of H 2 O 2 , and boil. If sol. is not perfectly clear, filter, notice color of filtrate, which should be yellow from for- mation of Na 2 CrO 4 , and add Pb(C 2 H 3 O 2 ) 2 . To solution of Cr 2 (SO 4 ) 3 add (NH 4 ) 2 S=Cr 2 O 6 H 6 + (Problem. Starting with chrome alum, make a solu- tion of Cr 2 Cl 6 and Cr 2 (NO 3 ) 6 .) Complete and balance the following, underlining all precipitates : Cr 2 Cl 6 + NH 4 OH = Cr 2 Cl 6 + NH 4 C1 + NH 4 OH = Cr 2 Cl 6 + NaOH = Cr a (NO 8 ) 6 + Pb(C 2 H 3 O 2 ) 2 = no change. Why ? Pb(C 2 H 3 2 ) 2 + Na 2 Cr0 4 = Cr 2 (S0 4 ) 3 -}- 3(NH 4 ) 2 S + 6 H 2 O = Cr 2 O 6 H 6 + 3(NH 4 ) 2 SO 4 3H 2 S IR. QUAL. ANAL. 4 54 BASIC ANALYSIS PbCrO 4 "chrome yellow," is the most desirable form in which to precipitate chromium in order to detect it. Cr 2 acts both as an acid and as a basic radical. When H 2 S has been added in the preceding group, Cr 2 compounds, if present, are reduced to the basic form, and Cr 2 is pre- cipitated as a base in the course of analysis of Gr. III. In the presence of NaOH, Cr 2 is easily oxidized to the acid form by H 2 O 2 , when it is readily precipitated by Pb(C 2 H 3 O 2 ) 2 , as PbCrO 4 . QUESTIONS 1. What is the solubility of Cr 2 O 6 H 6 in HC1? 2. In NH 4 OH? 3. In NaOH? 4. In NaOH combined with H 2 O 2 ? 5. Does the presence of NH 4 C1 affect its precipitation as a hydrate? 6. How does Cr 2 occur in nature ? 7. What is chrome yellow, and for what used ? 8. What is chrome alum, and for what used? Analysis. Gr. Ill Test the original solution for Fe and Fe 2 , with potass ic ferricyanide and potassic sulphocyanide (pages 48, 49). If iron is present, and H 2 S has been added to remove Gr. II, the iron will be in the ferrous state, even if it was present only in the ferric state in the original solution. It must be oxidized to the ferric state by boiling with a very little HNO 3 . To the nitrate from Gr. II, or the solution found not to contain Grs. I, II, add consider- able NH 4 C1, and NH 4 OH in excess. The filtrate con- tains Grs. IV- VI, and is set aside. The precipitate is Fe 2 O 6 H 6 , Cr 2 O 6 H 6 , and A1 2 O 6 H 6 . Make hole in filter, GROUP III 55 and wash through with NaOH into beaker. (If neces- sary, transfer the precipitate from the filter to the beaker with spatula.) Boil and filter. The precipitate contains Fe 2 O 6 H 6 and Cr 2 O 6 H 6 . The filtrate is Na 6 O 6 Al 2 . Warm with NH 4 C1, and allow to stand some time, when a white flocculent precipitate of A1 2 O 6 H 6 indicates the presence of A1 2 . The precipitate of Fe 2 and Cr 2 is washed through the filter with NaOH as before, and boiled with a few c.c. of H 2 O 2 . The precipitate is Fe 2 O 6 H 6 , and may be dis- solved in cone. HC1 and submitted to the iron tests. If Cr 2 is present, the filtrate will be yellow. Acidify the filtrate with HC 2 H 3 O 2 , and add Pb(C 2 H 3 O 2 ) 2 , when a yellow precipitate of PbCrO 4 confirms the presence of Cr 2 . TABULATION, GR. Ill * Solution contains Grs. III-VI. Add NH 4 C1 and NH 4 OH in excess. i Pp. Fe 2 6 H 6 Cr 2 6 H 6 A1 2 6 H 6 Wash through paper with NaOH and boil. Fil. = Grs. IV, V, and VI 1 Pp. Fe 2 6 H 6 2 6 H 6 Wash through paper with NaOH, add a few c.c. of H 2 2 and boil. Fil. Na 6 6 Al 2 Warm with NH 4 C1. Allow to stand some time. White pp. A1 2 6 H 6 , AL pres. Pp. Fe 2 6 H 6 . Dissolve in cone. HC1 and apply the iron tests. Test original solution for Fe and Fe 2 (pages 48, 49). Fil. Na 2 Cr0 4 , yellow. Acidify with HC 2 H 3 2 and add Pb(C 2 H 3 2 ) 2 . 1 Yellow pp. PbO0 4 , Cr 2 pres. * If Fe is present, it must be oxidized by boiling with a very little HNO S . 56 BASIC ANALYSIS An Alternative Method of Analysis for Gr. Ill Precipitate as in first method. Wash, dry, and fuse on Pt foil with KNO 3 and Na 2 CO 3 . Boil fused mass in H 2 O and filter. The precipitate is Fe 2 O 3 , brown. The filtrate contains Na 6 O 6 Al 2 and Na 2 CrO 4 . Yellow solution indicates Cr 2 . Divide the solution into A and B. To A add NH 4 C1, warm, and allow to stand. White precipitate of A1 2 O 6 H 6 indicates A1 2 . Acidify B with HC 2 H 3 O 2 and add Pb(C 2 H 3 O 2 ) 2 . Yel- low precipitate of PbCrO 4 shows Cr 2 present. TABULATION, GR. Ill * Solution contains Grs. III-VI. Add NH 4 C1, NH 4 OH in excess. Pp. Wash Fe 2 ,dry, } H 6 and fuse on Pt A1 2 6 H 6 foil with KN0 3 Cr 2 6 H 6 and Na 2 C0 3 . Fil. Grs. IV-VI Pp. Fe 2 3 , brown. Test original solu- tion for Fe and Fe 2 (pages 48, 49). Fil. Na 6 6 Al 2 Na 2 Cr0 4 Divide solution into A and B. To A add NH 4 C1 and warm. White pp. of A1 2 6 H 6 , A1 2 pres. To B acidified with HC 2 H 3 2 add Pb(C 2 H 3 2 ) 2 Yellow pp. of PbCr0 4 , Cr 2 pres. Notes and Suggestions Addition of NH 4 C1 prevents the precipitation of mem- bers of Gr. IV and Mg of Gr. V as hydroxides and aids the precipitation of A1 2 O 6 H 6 and O 2 O 6 H 6 on addition of * If Fe is present, it must be oxidized to Fe 2 by boiling with a very little HNO 3 . GROUP IV 57 NH 4 OH. The original solution must be tested to deter- mine in what form the iron was present. If H 2 S was added to remove Gr. II, any Fe 2 present will have been reduced to Fe, therefore Fe alone will be found on begin- ning the analysis of Gr. III. FeO 2 H 2 is soluble in pres- ence of NH 4 C1 and Fe 2 O 6 H 6 is not, therefore Fe must be oxidized. Care must be taken not to carry the oxidation far enough to oxidize manganous to manganic compounds, as we should then precipitate Mn with Gr. III. H 2 O 2 in presence of an alkali is used to oxidize Cr 2 from the basic to the acid state. QUESTIONS 1. What is the general reagent for Gr. III? 2. Give the symbols and colors of the precipitates formed by the group reagent. 3. What is the use of H 2 O 2 ? NH 4 C1? Why boil with HNO 3 ? * 4. How separate A1 2 from Cr 2 ? 5. How separate Cr 2 from Fe 2 ? 6. Give symbols which illustrate Cr 2 behaving as an acid radical. 7. As a basic radical. GROUP IV COBALT GROUP ii ii ii ii Co, Ni, Mn, Zn Precipitated as sulphides in alkaline solution by (NH 4 ) 2 S. Preliminary Experiments ii Co Cobalt. Cobaltous Compounds To a solution of Co(NO 3 ) 2 add : 1. NH 4 OH = 2. NH 4 OH in excess = 3. NH 4 C1 and NH 4 OH = 58 BASIC ANALYSIS 4. (NH 4 ) 2 S = a. Filter. Make a colorless bead of Na 2 H 4 O 7 on Pt wire in blowpipe flame, dip in precipitate, and heat in the oxidizing flame. b. Test the solubility of the remaining pp. in HC1. 5. NaOH = Complete and balance the following, underlining all precipitates : Co(NO 3 ) 2 +NH 4 OH = Co(N0 3 ) 2 +(NH 4 ) 2 S = Co(NO 3 ) 2 + NaOH QUESTIONS 1. What is the solubility of the hydroxide of cobalt in NII 4 O1I V 2. Jn NH 4 ClandNH 4 OH? 3. What is the solubility of CoS in HC1? 4. How does Co occur in nature ? 5. What are some of its uses ? ii Ni Nickel. Nickelous Compounds To a solution of Ni(NO 8 ) 2 or NiSO 4 add : 1. NH 4 OH = 2. NH 4 OH in excess = 3. NH 4 C1 + NH 4 OH = 4. (NH 4 ) 2 S = a. Filter and test precipitate with borax bead as in the case of Co. b. Test the solubility of the remaining precipitate in HC1. 5. NaOH = GROUP IV 59 Complete and balance the following, underlining all precipitates : NiS0 4 + NH 4 OH 4 + (NH 4 ) 2 S Ni(N0 3 ) 2 + (NH 4 ) 2 S = NiS0 4 + NaOH QUESTIONS 1. What is the solubility of MO 2 H 2 in NH 4 OH ? 2. In NH 4 OH and NH 4 C1? 3. InNaOH? 4. What is the solubility of NiS in HC1? 5. Where and in what forms is Ni found in nature? 6. What are its physical properties ? 7. What are some of its uses ? it Mn Manganese. Manganous Compounds To a solution of MnSO 4 or MnCl 2 add : 1. NH 4 OH = 2. 3. (NH 4 ) 2 S = a. Filter, make bead, on Pt wire, of KNO 3 + Na 2 CO 3 , dip in the precipitate, and heat in the blowpipe flame. b. Test solubility of the remaining precipitate in HC1. 4. NaOH = a. Filter and test with bead of KNO 3 + Na 2 CO 3 . b. Test solubility of remaining precipitate in HC1. 60 BASIC ANALYSIS Complete and balance the following, underlining all precipitates : MnS0 4 + NH 4 OH = MnS0 4 + NaOH = Mn0 2 H 2 + HC1 = MnS + HC1 QUESTIONS 1. What is the solubility of MnO 2 H 2 in NH 4 OH? 2. InNH 4 ClandNH 4 OH? 3. In NaOH? 4. What is the solubility of MnS in HC1? 5. In what forms does Mn occur in nature? 6. What is black oxide of manganese ? 7. What is potassic permanganate and for what used? 8. Add a solution of potassic permanganate to a solution of FeSO 4 acidified with H 2 SO 4 . Explain fully what happens. Note that Mn, like Cr ? , acts both as an acid and as a basic radical. ii Zn Zinc To a solution of ZnSO 4 , ZnCl 2 or Zn(N0 3 ) 2 add : 1. NH 4 OH = 2. NH 4 C1 + NH 4 OH = 3. NaOH cautiously = 4. NaOH in slight excess = Na 2 O 2 Zn -f Compare with A1 2 . 5. (NH 4 ) 2 S = Filter and test solubility of precipitate in HC1. Make ZnS and test its solubility in HC 2 H 3 O 2 . To ZnSO 4 add H 2 S = GROUP IV 61 Complete and balance the following, underlining all precipitates : ZnS0 4 + NH 4 OH = ZnSO 4 + NaOH = ZnO 2 H 2 + NaOH = Na 2 O 2 Zn + ZnS0 4 + (NH 4 ) 2 S = ZnS0 4 + H 2 S QUESTIONS 1. What is the solubility of ZnO 2 H 2 in NH 4 OH? 2. InNH 4 ClandNH 4 OH? 3. InNaOH? 4. What is the solubility of ZnS in HC1? 5. InHC 2 H 3 O 2 ? 6. Where and in what forms does Zn occur in nature? 7. How is it obtained from its ore ? 8. Give some of the physical properties of Zn. 9. What are some of its uses? 10. What is zinc white and for what used? 11. What is white vitriol ? 12. Tell what you can of the use of Zn in battery cells. 13. When a strip of Zn is nailed with iron nails and exposed to the air, why does the Zn soon dissolve around the nails ? 14. What is galvanized iron ? Analysis. Gr. IV To the filtrate from the precipitate of Gr. Ill, or solu- tion found not to contain Grs. I-III, heated to boiling, add (NH 4 ) 2 S and keep warm for some time. The filtrate contains Grs, V, VI and is set aside. The precipitate is' CoS, NiS, MnS, and ZnS. Wash in hot H 2 O, allow to cool, and add HC1 on filter. Pass solution through 62 BASIC ANALYSIS two or three times. The filtrate contains MriCl 2 and ZnCl 2 . The residue is CoS and NiS. Test residue with borax bead in outer blowpipe flame. A blue bead shows Co, and a brown bead shows Ni. If both are present, the borax bead will be blue from the Co, and the Ni will be obscured. To identify Ni in presence of Co, dissolve precipitate in aqua regia, evaporate nearly to dryness to expel acid, add NaOH in excess, and filter. Dissolve the hydroxides in a little concentrated KCN solution, and to this add NaOH and bromine water. On boiling, Ni, if present, is precipitated as Ni 2 O 6 H 6 . Co remains in solution. (An Alternative Method. To identify Ni in presence of Co, dissolve the sulphides of Co and Ni in aqua regia, evaporate nearly to dryness to expel acid, add tartaric acid and then NaOH in excess. Boil and pass H 2 S. A black precipitate is CoS, which may be tested with borax bead. The filtrate will be a deep brown or black if Ni is present. Test the solution with borax bead, which will become brown if Ni is present.) To the HC1 filtrate containing MnCl 2 and ZnCl 2 add NaOH in excess. The precipitate is Mn() 2 lI 2 , white, turning brown on exposure to the air. Make a bead of KNO 3 and Na 2 CO 3 , dip in the precipitate and heat in blowpipe flame. The formation of a green bead of Na 2 MnO 4 confirms the presence of Mn. The filtrate containing Na 2 O 2 Zn is acidified with HC 2 H 3 O 2 , and H 2 S is added. A white precipitate of ZnS indicates the presence of Zn. To confirm the pres- ence of Zn add cone. HC1, when ZnS, if present, will be dissolved, but S in suspension will not dissolve. A partial solution, on addition of cone. HC1, also indicates ZnS. GROUP IV 63 TABULATION, GR. IV Sol. contains Grs. IV- VI. Heat and add (NH 4 ) 2 S. Pp. CoS NiS MnS ZnS Fil. = Grs. V, VI. Wash with hot H.,0 and add HC1 on cold filter. Pp. CoS MS Test with Bx. bead ; blue indi- cates Co pres.; brown indicates Ni. If Co is pres., dissolve pp. in aqua regia. Expel acid and add NaOH in excess. Fil. MnCl 2 ZnCl 2 Add NaOH in excess. Pp. Mn0 2 H 2 . Test with bead of KN0 3 and Na 2 C0 3 . Green Na. 2 Mn0 4 , Mn pres. Fil Na 2 2 Zn Acidify with HC 2 H 3 2 and add H 2 S. i Pp. Co0 2 H 2 Ni0 2 H 2 Dissolve in cone. KCN solution. Add NaOH and Br 2 +H 2 0. Boil. W. pp. ZnS, Zn pres. To distinguish from S, add cone. HC1 and see if it dissolves. Pp. Ni 2 6 H 6 , black, Ni pres. Fil. Na 6 Co 2 (CN) 12 Notes and Suggestions Use as little acid as will do the work, thus avoiding the use of large quantities of alkali for neutralization, with the result of making the solution too dilute. If the solu- tion has become too dilute, it should be concentrated by evaporation. NiS is somewhat soluble in excess of (NH 4 ) 2 S, there- fore the filtrate from this group may contain NiS, shown by black or brown color. But NiS may be precipitated from this filtrate by boiling with a few drops of HC1. 64 BASIC ANALYSIS QUESTIONS 1. What is the group reagent? 2. Give the symbols and colors of all precipitates produced by the group reagent. 3. If the precipitate with (NH 4 ) 2 S should not be black, what inference ? 4. How separate Co and Ni from Mn and Zn ? 5. Mn from Zn? 6. Co from A1 2 ? GROUP V BARIUM GROUP ii ii ii ii Ba, Sr, Ca, Mg With the exception of Mg, precipitated as carbonates from alkaline solutions by (NH 4 ) 2 CO 3 in presence of NH 4 C1. Preliminary Experiments ii Ba Barium To any soluble Ba salt add : 1. NH 4 OH = 2. (NH 4 ) 2 C0 3 = a. Filter and test solubility of portion of pp. in HC1. b. Test solubility of remainder in HC 2 H 3 O 2 . 3. NH 4 C1+(NH 4 ) 2 C0 3 = 4. CaS0 4 = 5. H 2 S0 4 = 6. K 2 Cr0 4 = 7. Na 2 HP0 4 = 8. (NH 4 ) 2 C 2 4 = GROUP V 65 Complete and balance the following, underlining all precipitates : BaCl 2 + NH 4 OH = BaCl 2 + (NH 4 ) 2 CO 3 = BaCl 2 + (NH 4 ) 2 C0 3 + NH 4 C1 = BaCl 2 + CaSO 4 = BaCl 2 + H 2 S0 4 = BaCl 2 + K 2 CrO 4 = BaCl 2 +(NH 4 ) 2 C 2 4 = BaCl 2 + Na 2 HP0 4 = BaCO 3 + HC 2 H 3 O 2 = Ba(C 2 H 3 2 ) 2 + CaS0 4 = ii Sr Strontium To any soluble Sr salt add : 1. NH 4 OH = 2. (NH 4 ) 2 C0 3 = a. Filter and test solubility of portion of pp. in HC1. b. Test solubility of remainder in HC 2 H 3 O 2 . 3. NH 4 C1+(NH 4 ) 2 C0 3 = 4. CaSO 4 heat and allow to stand = 5. H 2 S0 4 = 6. K 2 CrO 4 = 7. Na 2 HP0 4 = 8. 66 BASIC ANALYSIS Complete and balance the following, underlining all precipitates : Sr(N0 8 ) a + NH 4 OH = Sr(N0 3 ) 2 +(NH 4 ) 2 C0 3 = Sr(N0 3 ) 2 4- NH 4 C1 + (NH 4 ) 2 CO 3 = Sr(N0 3 ) 2 + CaS0 4 = Sr(NO 8 ) 2 + H 2 SO 4 = Sr(N0 3 ) 2 +K 2 Cr0 4 = Sr(N0 3 ) 2 +Na 2 HP0 4 == Sr(N0 3 ) 2 -f (NH 4 ) 2 C 2 4 = SrC0 3 + HC 2 H 3 2 = Sr(C 2 H 3 2 ) 2 + CaS0 4 = ii Ca Calcium To any soluble Ca salt add : 1. NH 4 OH = 2. NH 4 C1 + (NH 4 ) 2 CO 3 = 3. (NH 4 ) 2 C0 3 = a. Filter and test solubility of portion of pp. in HC1. b. Test solubilit}' of remainder in HC 2 H 3 O 2 . 4. CaSO 4 and heat = 5. H 2 S0 4 = 6. K 2 Cr0 4 = 7. Na 2 HPO 4 = 8. (NH 4 ) 2 C 2 4 = Filter and test solubility in HC1. GROUP V 67 Complete and balance the following, underlining all precipitates : CaCl 2 + NH 4 OH = CaCl a +(NH 4 ) 2 C0 8 = CaCl 2 + NH 4 C1 + ( NH 4 ) 2 CO 3 = CaCl 2 + CaSO 4 = CaCl 2 + H 2 SO 4 = CaCl 2 + K 2 CrO 4 = CaCl 2 + Na 2 HP0 4 = CaCl 2 +(NH 4 ) 2 C 2 4 = CaCOg + HC 2 H 3 2 = a Mg Magnesium To any soluble Mg salt add : 1. NH 4 OH = 2. NH 4 C1 + NH 4 OH = 3. (NH 4 ) 2 C0 3 = 4. NH 4 C1+(NH 4 ) 2 C0 3 = 5. CaSO 4 = 6. H 2 SO 4 = 7. K 2 CrO 4 = 8. NH 4 OH + Na 2 HPO 4 = 9. (NH 4 ) 2 C 2 4 = 10. BaO 2 H 2 = Complete and balance the following, underlining all precipitates : MgCl 2 + NH 4 OH = MgCl 2 +(NH 4 ) 2 C0 3 = MgCl 2 +NH 4 C1 +(NH 4 ) 2 CO 3 = Solution MgCl, +NH 4 OH + Na 2 HP0 4 = MgNH 4 PO 4 + MgCl 2 +(NH 4 ) 2 C 2 4 = MgCl 2 + BaO 2 H 2 = 68 BASIC ANALYSIS QUESTIONS 1. What is the effect of NH 4 OH on the members of this group? 2. What is the effect of NH 4 OH in presence of NH 4 C1 ? 3. What is the effect of (NH 4 ) 2 CO 3 on members of this group ? 4. What is the effect of (NH 4 ) 2 CO 3 in the presence of NH 4 C1? 5. What is the effect of CaSO 4 on each member ? 6. H 2 S0 4 ? 7. K 2 CrO 4 ? 8. (NH 4 ) 2 C 2 4 ? 9. Na 2 HPO 4 ? 10. What is the solubility of the carbonates of this group in HC1 V 11. InHC 2 H 3 2 ? 12. How may Mg be separated from the other members of this group ? 13. In what forms does Ba occur in nature ? 14. Give one use for Ba(NO 3 ) 2 . 15. OneforBaSO 4 . 16. In what forms does Sr occur in nature ? 17. Give one use for Sr(NO 3 ) 2 . 18. In what forms does Ca occur in nature ? 19. What is marble ? 20. Limestone? 21. Chalk? 22. Stalactite? 23. Stalagmite? 24. Quicklime? 25. Slaked lime? 26. Limewater? 27. Gypsum? 28. Plaster of Paris? 29. What is the reaction tor making quicklime from limestone ? 30. What is mortar ? 31. Can you point out the changes that take place when mortar hardens ? GROUP V 69 Analysis. Gr. V The filtrate from the Gr. IV precipitate may be concen- trated by evaporation. If the solution is not colorless, boil with a few drops of HC1 and filter. To the concentrated colorless solution heated to boiling, add NH 4 C1 if not already present, NH 4 OH until alkaline, and (NH 4 ) 2 CO 3 . The filtrate is Mg and Gr. VI, and is set aside. The pre- cipitate is BaCO 3 , SrCOg, and CaCO 3 . This precipitate is washed with hot H 2 O and dissolved by pouring a few c.c. HC 2 H 3 O 2 orrthe filter, and passing through two or three times. Divide the solution into two unequal parts. To the smaller portion of the solution add CaSO 4 . An immediate precipitate indicates the presence of Ba. Ca and Sr may be present. A tardy precipitate shows Ba absent, Sr present Ca may be. No precipitate, on boil- ing and standing, proves the absence of Ba and Sr and the presence of Ca. If Ba is present, it is precipitated by adding K 2 CrO 4 to the larger portion of the solution, and is filtered out. To the filtrate is added NH 4 OH until alkaline, and then (NH 4 ) 2 CO 3 . The precipitate may contain SrCO 3 and CaCO 3 . This precipitate is washed with hot H 2 O and dissolved in HC 2 H 3 O 2 . To a small portion of the solu- tion add CaSO 4 . A tardy precipitate, showing only after heating and standing, is SrSO 4 , and indicates the presence of Sr. Ca may be present. No precipitate shows Sr absent and that the precipitate with (NH 4 ) 2 CO 3 must have been CaCO 3 . If Sr is present, it must be precipi- tated in the remaining solution with H 2 SO 4 , and filtered out. The filtrate is made alkaline with NH 4 OH and (NH 4 ) 2 C 2 O 4 is added. A white precipitate of CaC 2 O 4 indicates the presence of Ca. IR. QUAL. ANAL. 5 70 BASIC ANALYSIS TABULATION, GR. Solution contains Grs. V, VI. Heat to boiling and add NH 4 C1, NH 4 OH, and (NH 4 ) 2 C0 3 . f Pp. BaC0 3 SrC0 3 CaC0 3 Fil. = Mg and Gr. VI. Wash, dissolve in HC 2 H 3 2 . Divide sol. into A and B. To A add CaS0 4 .* Immediate pp., Ba pres. (Sr, Ca?) Tardy pp., Baabs. Sr pres. (Ca?) No pp., Ba and Sr a Us. Ca pres. If Ba is present, to B add K,Cr0 4 . Pp. BaCr0 4 , yellow. Reject Fil. Sr(C 2 H 3 2 ), Ca(C 2 H 3 0,) 2 Warm, add NH 4 OH and (NH 4 ),CO ;! . Pp. SrC0 3 CaC0 3 Wash, dissolve in HC 2 H 3 2 . Divide sol. into A and B. To A add CaSO,.t Tardy pp., Sr pres. (Ca?) No pp., Sr abs. Ca pres. If Sr is present, to B add H 2 S0 4 . Pp. SrS0 4 , white. Reject. Fil. Ca(C 2 H 3 2 ) 2 . Add NH 4 OH and (NH 4 )XA Pp. white CaC 2 4 , Ca pres. Notes and Suggestions NH 4 C1 keeps Mg in solution so that it is found with Gr. VI. It is not necessary to add NH 4 OH and NH 4 C1, if the *t When Ba and Sr on the first addition of CaSO 4 (*), or Sr on the second addition of CaS0 4 (t), are proved absent, the presence of Ca should be confirmed by adding NH 4 OH and (NH 4 )oC 2 4 to HC 2 H 3 O, solution B. GROUP VI 71 solution is a filtrate from Grs. Ill and IV, as they are in that case already present. The solution must not be acid when adding (NH 4 ) 2 CO 3 . The carbonates are washed to free them from the alka- lies NH 4 OH and (NH 4 ) 2 CO 3 and to avoid the use of much HC 2 H 3 O 2 . To distinguish between Ba and Sr, use is made of the fact that Sr precipitates as the sulphate slowly or in dilute solutions only with heat and standing. Ba is removed by K 2 CrO 4 . Sr is removed as SrSO 4 by H 2 SO 4 . All the Ba, Sr, and Ca must be removed before testing for Mg (see pages 72, 73), as they are all precipitated by Na 2 HP0 4 . QUESTIONS 1. What is the general reagent for Gr. V? 2. Give names and colors of all precipitates formed by it. 3. Why must Ba be removed before testing for Sr? 4. Why remove Sr before testing for Ca? 5. Suppose that the group precipitate is formed and that, on the addition of CaSO 4 , no precipitate is shown ; why do you infer the presence of Ca? 6. How confirm the presence of Ca? GROUP VI -SODIUM GROUP Na, K, Li, NH 4 This group is not precipitated by any single reagent, and its members must be detected by special tests. Clean a Pt wire by dipping in cone. HOI and burning in Bunsen burner flame. Examine the colorless Bunsen burner flame with a spec- troscope. 72 BASIC ANALYSIS Moisten the Pt wire, dip in a salt of Na, ignite in flame, and notice the color. Ignite before the spectroscope and draw diagram of the spectrum, noting particularly the location of the yellow line. Dip the clean wire into a salt of K, ignite in colorless flame, and note the color. If Na is on the same wire, the color will be obscured, but may be observed through cobalt glass. Ignite before the spectroscope. Draw diagram of spectrum, noting particularly the position of the narrow red lines. Dip the clean Pt wire into a salt of Li. Note the color on ignition in colorless flame. Ignite before the spectro- scope, and draw diagram of the spectrum, noting position of red lines. Rub NH 4 C1 and CaO 2 H 2 together in palm of hand. Note odor. To a solution of an NH 4 salt add CaO 2 H 2 or NaOH. Heat gently. Note odor and action of gas on moist red litmus paper. Be careful not to bring the litmus paper in contact with the reagent used, as it is an alkali. Analysis of Mg and Gr. VI The filtrate from the precipitate of Gr. V will contain Mg as well as Gr. VI. Divide the solution into two parts. To the first portion add Na 2 HPO 4 ; a white pre- cipitate of MgNH 4 PO 4 indicates the presence of Mg. If Mg is absent, evaporate second portion to dryness, ignite to drive off NH 4 , and test in spectroscope for Na, K, and Li. If Mg is present, evaporate second portion to dry- ness, ignite to drive off NH 4 salts (as MgO 2 H 2 will not pre- cipitate in presence of NH 4 salts), redissolve in H 2 O, heat, and add BaO 2 H 2 . The precipitate is MgO 2 H 2 . Reject this precipitate, as the presence of Mg in the spectrum MG AND GROUP VI 73 interferes with the detection of Na, K, and Li. The nitrate contains BaCl 2 , which must be removed, as Ba lines in the spectrum interfere with the detection of Gr. VI. Therefore add H 2 SO 4 . The precipitate BaSO 4 is rejected. The nitrate is now evaporated to dryness, ignited, and tested before the spectroscope for Gr. VI. As N H 4 salts have been added in the course of the analy- sis, the original solution must be tested with CaO 2 H 2 or NaOH for NH 4 . TABULATION, MG AND GR, VI Solution contains Mg, Na, K, Li, and NH 4 . Divide the solution into A and B. To A add Na,HP0 4 . Pp. MgNH 4 P0 4 , white, Mg pres. If Mg is absent, evaporate B to dryness, ignite, and test in spectro- scope for Na, K, and Li. If Mg is present, evaporate B, ignite, and redissolve in H 2 0. Heat and add Pp. Mg0 2 H 2 . Reject. Fil. BaCl 2 and Gr. VI. Add H 2 S0 4 . 1 Pp. BaS0 4 Reject. Fil. evaporate to dryness, ignite, and test with spectroscope for Na, K, and Li. Test the original solution for NH 4 with CaOoHo. QUESTIONS 1. What is the chief source of Na in nature? 2. What is common salt, and where found? 74 BASIC ANALYSIS 3. What is Glauber's salt? 4. Washing soda ? 5. Cooking soda? 6. Sal soda? 7. Bicarbonate of soda ? 8. Caustic soda? 9. What is the Le Blanc process? 10. What is Chile saltpeter? 11. How is hard soap made ? 12. What is the chief source of K in nature ? 13. What is potash ? 14. Pearlash? 15. Caustic potash ? 16. Saltpeter or niter? 17. Prussiate of potash ? 18. Saleratus? 19. How is gunpowder made? 20. How is soft soap made? 21. What is lithia water? 22. What is salatnmoniac, and for what used? 23. What is the source of the ammonia compounds used in com- merce ? 24. Referring to the table of solubilities shown on the last page of this, book, note the solubilities of all the common salts of Na, K, and NH 4 . Unknown solutions containing any of the bases may now be analyzed. If the solution is to be examined for all the bases, first test small portions of the original solu- tion for Fe, Fe 2 , and NH 4 . Then, with a small portion of the solution, make a preliminary test with the group reagents to determine what groups may be present (see page 75). Knowledge may be gained in this way which will greatly shorten the work of analysis. On the four pages next after 75 all the previous tables of analysis are repeated, for convenience, in the form of one complete table. ALL GROUPS 75 PQ O O RATION AGENTS m & O h >V J w o ^ A PH P_i II o d * i nd PQ OT 6 Q N q q q ^ Q <1 * i S h PQ OQ d, PH 76 BASIC ANALYSIS Solution contains Gi Pp. Hg,Cl 2 AgCl PbCl 2 Fil. = Grs. II-VL Heat tc Wash with hot H,0 until Pb is all dissolved. j Pp. HgS PbS Bi 2 S 3 Pp. Hg.,CI 2 Fil - f" Agoi A> lute or gray pp. Hg.Cl* white, j Hg pres. Or, Bi pres. Confirui by Add Cu foil. dissolving in Silver-colored 2 or \p drops ( deposit on foil of ccfoc. HC1 .shows and allowing Hg pres. to arori into lar$e volume of k 2 0. White cloud of'BiOCl,, Bi pres. ALL GROUPS 77 Add HC1 to Cold Solution. ind add H 2 S. ~r CdS (SnS. SnS 2 Sb 2 S 3 Sb 2 S 5 As 2 S 3 As 2 S 5 ) ish through filter with (NH 4 ) 2 S and warm. Fil. = Grs. III-VI (see page 78). CdS to boiling. Fil. = Gr. II, Div. B, Sn, Sb, and As. Add HC1. Cu(N0 3 ) 2 Cd(N0 3 ) 2 a few drops H 2 S0 4 . Pp. (S#) SnS SnS 2 ' Sb As 2 S 3 As 2 S 5 ,83 Sb 2 S 5 Filtrate, reject. | Wash twice with cold H 2 ( ) and add ) 8 ) 3 Cu(N0 3 ) 2 Cd(N0 3 ) 2 (NH 4 ) 2 C0 3 . ^H in slight excess 1 Pp. SnS 2 Sb 2 S 5 Fil. = As in solution. Cu pres. t te*t a portion of sol Wash, add KC10 3 and cone. HC1. Divide sol. Add HC1. ~r H 3 0, and K 4 Fe(CN) 6 ; t , Cu pres. into A and JS. To A add small iron nail and warm gently. Filter and to Pp. yellow As 2 S 3 and As 2 S 5 (S4 abs. add H 2 S to filtrate add HgCl 2 . Reject As pres. Confirm by mixing sol. | pp. 1 dry pp. with Na 2 C0 3 7 CdS, Cd pres. Pp. w. Hg 2 C] 2 , Sn pres. and KCN and present, add KCN ntil blue color just , and then H 2 S. B. Dilute with H 2 and add battery of Pt and Zn. Black stain on Pt, heating in bulb tube= As mirror on upper part of tube, A tares 1 Sb pres. f CdS, Cd pres. Wash Pt foil with warm H 2 and HC1, filter, and add HgCl 2 . W. pp. HgoCL,, Sn pres. - 78 BASIC ANALYSIS I I 02 ^ I 111 ^ 2 -M o Q ff a 5 a II 3 * - - ' ISL oJ5 1 -i te I O '3 ' + o O -1 -1 l ?,& Q ^a I ft -5 f: 8| eS K tJD .-*- 'i '5 2 c *3 .5 1 >FJ -^ ALL GROUPS 79 M I fcJO*^ 05 .^4 ""* CD Jf 5*1 -a.aBi o* . M - <2 B '^18-9 tz; H -43 O i" "i p w ,0 a :^ 3 co ^r " IS O 02 ^ (C " '.2 a- PH PART IV SOLIDS THE SYSTEMATIC EXAMINATION OF SOLIDS IN this analysis not only will the bases be identified, but also the acids combined with them, and, therefore, the composition of the salt. Thus, if the analysis shows the presence of Ba and HC1, the substance is identified as BaCl 2 . Preliminary Examination If the substance is neither a metal nor an alloy, it must be powdered in a porcelain mortar, and small portions used for each test. (For metals and alloys, see page 86.) Do not spend too much time on this preliminary exami- nation, nor rely too much on results obtained from it until your experience in this particular work has been somewhat extended. I Heat Small Portion of Substance in Bulb Tube. 1. Turns black, or carbonizes, has burnt odor, organic substance. 2. Gives H 2 O; determine whether alkaline or acid. May be H 2 O of crystallization, or water mechanically held. 80 PRELIMINARY EXAMINATION 81 3. Hot Yellow Red to black Yellowish red Orange yellow 4. Color Cold White Zn salts Brownish red Fe or Fe 2 salts Yellow -Pb salts Pale yellow - Bi salts Gases with Odor or Color Odor Color Burning matches Colorless S0 2 Pungent Colorless -NH 4 Suffocating Green -Cl Stifling Brownish red Br Acrid Violet -I Peach blossom Colorless -CN Rotten eggs Colorless -H 9 S Garlic Colorless -AsH Odorless Colorless C0 9 Sulphites NH 4 salts Chlorides Bromides Iodides Cyanides Sulphides AsH 3 As compounds Carbonates Drop of limewater on glass rod rendered turbid CO 2 . 5. Sublimates White may indicate compounds of NH 4 , As, Hg, or Sb. Yellow, when cold S Free S, or sulphides. Black I Iodides. II Heat on Charcoal in Blowpipe Flame. SO 2 given off S and sulphides Decrepitation - Water Deflagration - Nitrates or chlorates Melts and runs into charcoal Bases of Grs. V, VI 82 SOLIDS To any residue on the charcoal add Co(NO 3 ) 2 and heat again in oxidizing flame. Blue indicates A1 2 Green indicates Zn Rose color indicates Mg III Heat on Charcoal with Na 2 GO 8 in Reducing Flame. Metallic globules or beads indicate Cu. Metallic globules or beads, malleable, indicate Ag, Pb, or Sn. Metallic globules or beads, brittle, indicate Sb or Hi. Dark-colored powder, magnetic, indicates Fe, Fe 2< (V or Ni. IV Fuse into Borax Bead and Heat in Oxidizing Flame, then in Reducing Flame. Oxidizing flame Reducing flame Blue Blue -Co Brown Gray or colorless Ni Blue Red or colorless Cu Green (yellowish) Green Cr 2 Colorless or yellow Bottle green - Fe or Fe 2 Amethyst Colorless -Mn PRELIMINARY EXAMINATION 83 Flame Colorations Moisten Clean Pt Wire in HC1 and ignite in Bunsen Burner Flame. Violet indicates K Yellow indicates Na Carmine red indicates Li Yellowish red indicates Ca Bright red indicates Sr Green indicates Ba Blue to green indicates Cu VI Ignite before the Spectroscope and examine for Characteristic Lines. VII Treatment with Cone. H 2 SO 4 This is the most important single preliminary test, as it will show the presence of the volatile acids, and some of them may be positively identified by color and odor. Place a small portion of solid in test tube, cover with a few drops of cone. H 2 SO 4 , and heat cautiously (see page 84, 3). Observe color of any gases given off and note odor with care. To examine the odor safely, hold test tube at slight distance and fan fumes toward the nose so that they will be diluted with air, and gradually bring test tube nearer. If any particular acid is indicated at this point, that acid may be further identified by applying the appro- priate acid test,* provided the solid dissolves readily in H 2 0. * See Acid Analysis, Part V. 84 SOLIDS * 1. Turns black, gives odor of burnt sugar, H 2 C 4 H 4 O 6 - Tartrates 2. Odor of vinegar, HC 2 H 3 O 2 Acetates 3. Yellowish green vapor, suffocating and acrid, C1 2 O 3 Chlorates Must not be heated, as chlorates are highly explo- sive with H 2 SO 4 . 4. Effervescence, odor of HC1 Chlorides Bring near the test tube glass rod moistened with NH 4 OH. Heavy white clouds of NH 4 C1 con- firm presence of HC1. 5. Effervescence with odor of burnt matches, SO 2 . Bring paper moistened with Hg 2 (NO 3 ) 2 near test tube. Paper turning black confirms presence of SO 2 Sulphites 6. Effervescence, odor of rotten eggs, H 2 S Sulphides 7. Effervescence, odor acrid, corrodes test tube, HF Fluorides 8. Effervescence sudden, no odor, CO 2 Carbonates Decant CO 2 carefully into test tube one fourth full of limewater and shake the limewater. Tur- bidity due to the formation of CaCO 3 confirms the presence of CO 2 . 9. Violet vapor, acrid odor, HI and I -Iodides 10. Reddish brown vapor, suffocating odor, NO 2 - Nitrates 11. Brownish red vapor, stifling odor, HBr and Br - Bromides 12. Odor of peach blossoms, CN (deadly poison) Cyanides STUDY OF SOLUBILITY 85 The Solid must now be Dissolved I Water Solution a. Place a very small quantity in test tube and treat first with cold water and then with boiling water. If it is entirely soluble, dissolve a larger portion. Use a portion of the solution and perform the basic analysis (Part III, pages 28-73). Follow with the acid analysis (Part V, pages 88-94). b. The substance may be partially soluble in water. This can be determined by evaporating a few drops of nitrate on Pt foil, when a residue will show that a portion has dissolved. Make this partial solution of a considerable quantity, reserving the residue for treatment by II, and perform the basic and acid analyses with this solution. II Acid Solution The substance insoluble in H 2 O, or the residue from the substance partially dissolved in H 2 O, is treated with dil. HC1, then Avith cone. HC1, first cold, then boiling. Treat in the same way with dil. and then cone. HNO 3 , and finally with aqua regia. After each treatment, a few drops of the filtrate should be evaporated on Pt foil to see if any has dissolved. Any solution produced by any one of these methods must be separately analyzed for bases and acids. If the substance has not dissolved, or if a residue is left undissolved, it should be treated by III. Ill Solution by Means of Fusion The original substance or the residue from II, insoluble in water or acid, is fused on Pt foil, or in a Pt crucible with KNO 3 and Na 2 CO 3 . Boil the residue with water until it is disintegrated. 86 SOLIDS BOIL WITH H 2 I Pp. contains bases as carbonates. Treat with cone. HC1 to dissolve. Evaporate part of acid and analyze in the usual way for bases. Fil. contains acid radicals. Treat a small portion with cone. HC1. W. pp. washed with hot H 2 and dried feels "gritty," Si0 2 , showing silicates. If Si0 2 is pres., this filtrate is analyzed for acids. If Si0 2 is abs., the remaining H 2 fil. is analyzed for acids. If the Substance is a Metal or Alloy Boil with one part cone. HNO 3 in three parts of H 2 O. If the substance dissolves with no residue, dilute with II 2 O, and proceed with the basic analysis. A few particles of carbon deposited from iron and a few other metals may be disregarded. If a white residue forms, dilute with con- siderable H 2 O and boil, as certain nitrates like Pb(NO 3 ) 2 are insoluble in cone. HNO 3 , but soluble in dil. HNO 3 . If a white residue still remains, it may contain the oxides of Sn and Sb. Filter and analyze the filtrate for bases. Dissolve the pp. in cone. HC1, dilute with H 2 O, and pro- ceed according to the basic analysis, Gr. II, Div. B. Order of Examination of Any Solid : I. Preliminary examination. II. A study of the solubility of the substance. III. If any acids have been identified, an elimination from consideration of any bases that must evidently be absent from the conditions of solution. For example, CO 2 is found in the preliminary examination, and the sub- stance is soluble in H 2 O. Under these conditions, no bases can be present except those of Gr. VI, as carbonates of Grs. SYSTEMATIC EXAMINATION 87 I-V are insoluble in H 2 O. (See table of solubilities on page 100.) Again, HC1 is found in the preliminary examination and the substance is easily soluble in H 2 O. Gr. I cannot be present, as the chlorides of this group are not readily soluble in H 2 O. (See page 100.) IV. Systematic basic analysis, preceded by a prelimi- nary examination of a small portion of the solution for the groups by use of group reagents. (See page 75.) This may greatly shorten the work of analysis, as certain groups may be found absent. V. An elimination from consideration of H 3 As0 3 , H 3 AsO 4 , and H 2 CrO 4 , as As and Cr 2 (including Cr), if present, will have been found in the basi'c analysis (As, page 46, and Cr 2 , page 55). It is now only necessary to determine whether the As is present in the -ous or -ic form, and whether the Cr 2 is* present as an acid or as a basic radical (page 88). VI. An elimination from consideration of any acids that are positively identified by H 2 SO 4 in the preliminary examination (page 83, VII); and of any acids that cannot exist, under the conditions of solution, with the bases pres- ent. The student will need to consider at this point prob- lems like these. In the basic analysis, Ag or Hg 2 has been found, and the substance is soluble in H 2 O : it is useless to test for HC1, as AgCl and Hg 2 Cl 2 are insoluble in H 2 O (page 100). Suppose that we have found Ag, Sr, and Cu in a water solution : AgCl, AgBr, Agl, SrSO 4 , and CuS are insoluble in H 2 O (page 100), therefore HC1, HBr, HI, H 2 SO 4 , and H 2 S must be absent. Or, if Ba has been found in a water solution, none of the acids of Gr. I (pages 88-90) can be present, as the Ba salts of those acids are insoluble in II 2 O (page 100). VII. Acid analysis (pages 88-94). PART V ACID ANALYSIS GROUP I -DIVISION A * H 2 CrO 4 , H 3 As0 3 , H 3 AsO 4 , H 2 SO 3 , H 4 Si() 4 , II 2 C0 3 The first three of these acids will have been found in the basic analysis (pages 47 and 55), as they are reduced by H 2 S in the presence of H'Cl. The presence or absence of the last three acids will have been proved in the preliminary examination (pages 83, VII, and 86). Special tests must now be applied to determine whether Cr 2 is present in the acid or basic form, and whether the As is in the -ous or -ic form. H 2 CrO 4 . Acidify with HC 2 H 3 O 2 and add Pb(G 2 H 8 O 2 ) 2 . Yellow precipitate of PbCrO 4 indicates Chromates. H 3 AsO 3 and H 3 AsO 4 . H 2 S precipitates As as As 2 S 3 from acid solutions in both cases. As in the -ous form is precipitated quickly, but in the -ic form very slowly. This will serve to distinguish Arsenites from Arsenates. H 2 SO 3 . Treat with H 2 SO 4 or HC1. SO 2 is given off and may be recognized by the characteristic odor of burn- * Although some of these acids never occur except in their salts, the full symbol of the hypothetical acid is here given. 88 GROUP I 89 ing matches and also by blackening of paper moistened with Hg 2 (NO 3 ) 2 . Zn and HC1 liberate H mixed with H 2 S from solutions of Sulphites. H 4 SiO 4 . Addition of HC1 separates H 4 SiO 4 in the form of a gelatinous precipitate. Filter, wash, and dry, when it is converted into SiO 2 and may be recognized by its gritty feel. Silicates. H 2 CO 3 . Add cone. HC1. Quick and energetic effer- vescence of CO 2 . Pass gas into limewater; a white pre- cipitate of CaCOg confirms the presence of Carbonates. Give the names of products formed in the following cases : Potassic chromate and lead acetate = ? Sodic arsenite and hydrogen sulphide = ? Sodic arsenate and hydrogen sulphide = ? Sodic sulphite and sulphuric acid = ? Sodic carbonate and sulphuric acid = ? Sodic silicate and hydrochloric acid = ? Silicic acid plus heat = ? GROUP I DIVISION B H 3 P0 4 , H 2 SO 4 , HF, H 2 C 4 H 4 6 , H 8 BO 8 * Group T, Div. A, of the acids, and certain bases, must be removed before testing for these acids. To do this, add HC1, and heat. This removes H 2 CO 3 and H 2 SO 3 , and precipitates Gr. I of the bases, and H 4 SiO 4 . Filter (if a precipitate occurs), and add H 2 S to the filtrate. This treatment precipitates Gr. II of the bases, including * For methods of removing the bases more completely than here indi- cated, the student is referred to Wm. A. Noyes's " Qualitative Analysis," pages 62, 63. IR. QUAL. ANAL. 6 90 ACID ANALYSIS H 3 AsO 3 and H 3 AsO 4 . To the filtrate add NH 4 OH in just sufficient quantity to' render the solution only slightly alkaline. This removes H 8 CrO 4 as well as Fe 2 and A1 2 . Use small portions of the filtrate for the fol- lowing tests, unless directed to use the original solid: Add BaCl 2 to the slightly alkaline solution, free from acids of Gr. I, A, and bases of Grs. I III. If no precipi- tate is formed, all the members of Gr. I, Div. B of acids are absent. If BaCl 2 produces a precipitate insoluble in HC1, it is BaSO 4 , and H 2 SO 4 is proved present. If the precipitate is soluble in HC1, H 2 SO 4 is absent. In either case, special tests must be applied for other members of the group. H 3 PO 4 . Phosphates may be detected in water solu- tions by addition of NH 4 OH, NH 4 C1, and MgSO 4 , when a white crystalline precipitate of MgNH 4 PO 4 will be formed on standing. In acid solutions (preferably HNO 3 solu- tions) phosphates may be detected by the addition of a few drops of (NH 4 ) 2 MoO 4 dissolved in HNO 3 . A yel- low precipitate immediately formed on warming slightly shows Phosphates. H 2 SO 4 . Add BaCl 2 to a neutral or slightly alkaline solution; a precipitate insoluble in HC1 is BaSO 4 , showing Sulphates. HF. Treat the original solid with cone. H 2 8O 4 in Pb dish. A gas evolved that will etch glass shows Fluorides. H 2 C 4 H 4 O 6 . Treat the original solid with cone. H 2 SO 4 . Carbonization with odor of burnt sugar shows the pres- ence of Tartrates. H 3 BO 3 . Stir cone. H 2 SO 4 into the original solid in porcelain dish. Add alcohol and kindle. An apple- green flame shows the presence of Borates. GROUP II 91 Give names of products formed in the following cases : Calcic phosphate and ammonic molybdate = ? Ammonic hydrate, ammonic chloride, and magnesic sul- phate = ? Sodic sulphate and baric chloride = ? Calcic fluoride and baric chloride =? Calcic fluoride and sulphuric acid = ? Potassic tartrate and baric chloride = ? Sodic borate and sulphuric acid = ? GROUP II Precipitated by AgNO 8 in HNO 3 solution. HC1, HBr, HI, H 2 S, HCN, H 4 Fe(CN) 6 , H 3 Fe(CN) 6 H 2 S and HCN will have been proved present or absent with certainty in the preliminary analysis (page 83, VII). Some indication as to the presence of HC1, HBr, and HI will also have been afforded. A solution of the original solid without removal of bases will, in most cases, be suitable for the analysis of this group. If the solid was originally dissolved in HC1, it is obvious that some other means of solution, such as the use of HNO 3 , must be found before proceeding to the analysis of this group. H 2 S, if present, 'must be removed. If it is present in the free state, it may be removed by boiling ; if in combination, by precipitation with some salt which will not affect the other acids of this group. Acidify a portion of the original solution of the solid, or a portion from which H 2 S has been removed, with HNO 3 , and add AgNO 3 . The precipitate may be AgCl (white), AgBr (light yellow), Agl (yellow), AgCN (white), Ag 4 Fe(CN) 6 (white), Ag 3 Fe(CN) 6 (brownish red). 92 ACID ANALYSIS If there is no precipitate with AgNO 3 , proceed to Gr. III. If a precipitate is formed, add NH 4 OH. If the precipitate dissolves, HI and H 4 Fe(CN) 6 are absent. Further investigation must be carried on by means of special tests. HC1, HBr, HI. If any one of these acids alone is pres- ent, the following is a simple method of recognizing it : To a portion of the 'solution add MnO 2 and cone. H 2 SO 4 . Apply heat very gently. Evolution of a yellowish green gas which bleaches calico shows Chlorides. Evolution of brownish red gas with suffocating odor, only partially bleaching calico, shows Bromides. Evolution of violet vapor which sublimes on the test tube shows Iodides. Also add starch paste and chlorine water to a solution of the solid. Blue shows Iodides. For methods of detecting chlorides, bromides, and iodides in presence of one another the student is referred to more advanced works on Qualitative Analysis. HCN. On treating the original solid with cone. H 2 SO 4 , CN with odor of peach blossoms is freed. (It is a deadly poison when breathed undiluted with air.) Cyanides. H 4 Fe(CN) 6 . To a portion of the solution add Fe 2 Cl G . A dark blue precipitate of Prussian blue shows Ferrocyanides. H 3 Fe(CN) 6 . To a portion of the solution add freshly made FeSO 4 . A dark blue precipitate of Turnbull's blue shows Ferricyanides. (AgNOg gives a brownish red precipitate with hydro- ferricyanic acid; consequently if the group precipitate with AgNOg was white, it need not be tested for.) GROUP III 93 H 2 S. Add cone. HC1 to original solid and heat. Odor of rotten eggs shows sulphides. Add aqua regia, and those sulphides which are not decomposed by HC1 throw down S and also form a small quantity of H 2 SO 4 . Sulphides. Give names of products formed in the following cases : Hydrochloric acid and silver nitrate = ? Hydrobromic acid and silver nitrate = ? Hydriodic acid and silver nitrate = ? Sodic chloride, black oxide manganese, and sulphuric acid = ? Sodic bromide, black oxide manganese, and sulphuric acid = ? Sodic iodide, black oxide manganese, and sulphuric acid = ? Potassic cyanide and silver nitrate = ? Potassic cyanide and sulphuric acid = ? Hydroferrocyanic acid and silver nitrate = ? Hydroferricyanic acid and silver nitrate = ? Sodic sulphide and silver nitrate = ? GROUP III HN0 3 , HC10 3 , HC 2 H 3 2 As the salts of this group are all soluble, there is no general group reagent. (See solubilities, page 100.) HNO 3 . To a solution of the original solid add con- centrated solution of FeSO 4 and cone. H 2 SO 4 , allowing a few drops to run down the side of the inclined test tube. Brown or black ring of NO 2 shows Nitrates. A Second Test. Add Cu filings to a solution of the original solid, and then cone. H 2 SO 4 . Brownish red fumes of NO show Nitrates. 94 ACID ANALYSIS HClOg. Treat portion of the original solid with cone. HC1. A yellowish green gas similar in odor to Cl shows Chlorates. This gas is observed when Sb and Sn are dissolved with KC1O 3 and cone. HC1. (See page 46.) Also, chlorates def- lagrate on charcoal. (See preliminary test, page 81, II.) HC 2 H 3 O 2 . Treat portion of the original solid with cone. H 2 SO 4 . Odor of vinegar shows Acetates. Second Test. Put a little of the solid in test tube, add a little alcohol and an equal volume of coric. H 2 SO 4 . The formation of ethyl acetate with a fragrant and fruity odor shows Acetates. Give the names of products formed in the following cases : Sodic nitrate, ferrous sulphate, and sulphuric acid = ? Sodic nitrate, copper filings, and sulphuric acid = ? Potassic chlorate and hydrochloric acid = ? Sodic acetate and sulphuric acid = ? QUESTIONS 1. How do you prove the presence of a chromate ? 2. A sulphite? 10. A chloride? 3. An arsenite? 11. A bromide? 4. A carbonate ? 12. An iodide ? 5. A silicate? 13. A cyanide? 6. A borate ? 14. A sulphide ? 7. A fluoride? 15. A chlorate? 8. Atartrate? 16. A nitrate? 9. A sulphate ? 17. An acetate ? 18. How prove the presence of H 2 S0 4 in the presence of silver, lead, or mercurous mercury? 19. A chloride in the presence of a sulphide? 20. A nitrate in the presence of an iodide ? PART VI APPENDIX . PREPARATION OF SOLUTIONS Acids Acetic Acid. A high grade of commercial acid may be used. Hydrochloric, concentrated. Use commercial acid. Hydrochloric, dilute, made by adding one part of cone, acid to four parts of H 2 O. Nitric, concentrated. Use commercial acid. Nitric, dilute, made by adding 1 pt. of cone, acid to 4 pts. of H 2 O. Sulphuric, concentrated. Use commercial acid. Sulphuric, dilute, made by adding 1 pt. of cone, acid to 4 pts. of H 2 O. Other Reagents Ammonic Carbonate. Dissolve 1 pt. of the salt in 4 pts. of H 2 O and add 1 pt. of strong ammonic hydroxide. Ammonic Chloride. Dissolve 1 pt. of the salt (free from sulphuric acid) in 10 pts. of H 2 O. Ammonic Hydroxide. Add 1 pt. of commercial am- monic hydroxide to 3 pts. of H 2 O. 95 96 APPENDIX Ammonic Molybdate. Dissolve 60 grams of the dry salt in 400 c.c. of NH 4 OH; add 400 c.c. of H 2 O ; then cau- tiously add 500 c.c. of HNO 3 (specific gravity 1.4). Ammonic Oxalate. Dissolve 1 pt. of the salt in 24 pts. of H 2 0. Ammonic Sulphide. Pass H 2 S through NH 4 OH until it will give no precipitate on heating gently with MgSO 4 . The yellow variety will soon form on exposure to the air. Baric Hydroxide. Make a saturated solution of BaO. Bromine Water. Made by adding a few drops of liquid bromine to water in a flask and shaking vigorously. Calcic Sulphate. Make a saturated solution. Chlorine Water. Made by adding cone. HC1 to KC1O 3 in bottle, then adding water ; keep stoppled and covered with opaque paper. Disodic Phosphate. Dissolve 1 pt. of the salt in 10 pts. of H 2 0. Hydrogen Peroxide. Use as bought. Keep in a cool place. Lead Acetate. Dissolve 1 pt. of the salt in 10 pts. of H 2 0. Limewater. Make'a saturated solution of CaO 2 H 2 . Potassic Chromate. Dissolve 1 pt. of the salt in 10 pts. of H 2 0. Potassic Ferricyanide. Dissolve 1 pt. of the salt in 10 pts. of H 2 O. Potassic Ferrocyanide. Dissolve 1 pt. of the salt in 10 pts. of H 2 O. Potassic Sulphocyanide. Dissolve 1 pt. of the salt in 25 pts. of H 2 O. PREPARATION OF SOLUTIONS 97 Silver Nitrate. Dissolve 1 pt. of the salt in 50 pts. of H 2 0. Sodic Chromate. Dissolve 1 pt. of the salt in 10 pts. of H 2 O. Sodic Hydroxide. Dissolve 1 pt. of the salt in 8 pts. of H 2 0. Solutions to be kept for the Purpose of making Known and Unknown Mixtures In nearly all cases, commercial salts will be of a suffi- cient degree of purity, but it is well to have on hand a supply of chemically pure nitrates of the metals, as by making use of the nitrates a large number of bases may be mixed in one solution. Alum. 1 pt. salt in 10 pts. of H 2 O. Aluminic Chloride. Precipitate A1 2 O 6 H 6 by adding NH 4 OH to a solution of alum. Wash the precipitate free from H 2 SO 4 and dissolve in HC1. Aluminic Nitrate. Same as A1 2 C1 6 except that the A1 2 O 6 H 6 is dissolved in HNO 3 . Aluminic Sulphate. A solution of alum will serve the purpose as well. Antimonious Chloride. May be bought in the form of solution. This should be diluted with an equal volume of water and cone. HC1 added to dissolve the basic salt formed. Arsenious Acid. Made by dissolving " white arsenic " in cone. HC1. Baric Chloride. 1 pt. salt in 5 pts. H 2 O. Baric Nitrate. 1 pt, C. P. salt in 10 pts. H 2 O. 98 APPENDIX Bismuth Chloride. Dissolve the subnitrate of bismuth in cone. HC1. Dilute with twice its vol. of H 2 O and add cone. HC1 to dissolve the oxychloride precipitate. Cadmic Chloride. 1 pt. salt in 10 pts. H 2 O. Cadmic Nitrate. 1 pt. C. P. salt in 10 pts. H 2 O. Calcic Chloride. 1 pt, salt in 5 pts. H 2 O. Calcic Nitrate. 1 pt. C. P. salt in 10 pts. H 2 O. Chrome Alum. 1 pt. salt in 10 pts. H 2 O. Chromic Chloride. Precipitate Cr 2 O 6 H 6 from chrome alum, wash free from H 2 SO 4 , and dissolve in HC1. Chromic Nitrate. Made like Cr 2 Cl 6 except that the hydroxide is dissolved in HNO 3 . Chromic Sulphate. Use chrome alum solution. Cobaltous Nitrate. 1 pt. salt in 10 pts. H 2 O. Cupric Chloride. 1 pt. salt in 10 pts. H 2 O. Cupric Nitrate. 1 pt. salt in 10 pts. H 2 O. Cupric Sulphate. 1 pt. salt in 10 pts. H 2 O. Ferric Chloride. 1 pt. salt in 20 pts. H 2 O. Ferric Nitrate. 1 pt. salt in 20 pts. H 2 O. Lead Acetate. 1 pt. salt in 10 pts. H 2 O. Lead Nitrate. 1 pt. C. P. salt in 5 pts. H 2 O. Lithic Chloride. Dissolve 10 grams LiCO 3 in HNO 3 and boil off CO 2 . Dilute with water to 500 c.c. Magnesic Chloride. 1 pt. salt in 10 pts. H 2 O. Magnetic Nitrate. 1 pt. C. P. salt in 10 pts. H 2 O. Magnesic Sulphate. 1 pt. salt in 10 pts. H 2 O. Manganous Chloride. 1 pt. salt in 10 pts. H 2 O. Manganous Sulphate. 1 pt. salt in 10 pts. H 2 O. Mercuric Chloride. 1 pt. salt in 20 pts. H 2 O. PREPARATION OF 'SOLtiTIO&S Mercurous Nitrate. Dissolve metallic mercury in cone. HNO 3 , using enough Hg so that a few globules will re- main undissolved. Mercurous nitrate will crystallize out. Make a saturated solution of this salt in H 2 O. Add a globule of mercury to the solution. Nickelous Nitrate. Dissolve 1 pt. C. P. salt in 10 pts. H 2 O. Nickelous Sulphate. 1 pt. salt in 10 pts. H 2 O. Potassic Nitrate. 1 pt. C. P. salt in 10 pts. H 2 O. Silver Nitrate. 1 pt. salt in 10 pts. H 2 O. Sodic Arsenate. 1 pt. salt in 10 pts. H 2 O. Sodic Chloride. Saturated solution. Stannous Chloride. May be purchased in form of solu- tion. Should be kept in the -ous form by adding some granulated tin. Strontic Chloride. 1 pt. salt in 10 pts. H 2 O. Strontic Nitrate. 1 pt. C. P. salt in 10 pts. H 2 O. Tartar Emetic. 1 pt. salt in 10 pts. H 2 O. Zinc Chloride. 1 pt. salt in 10 pts. H 2 O. Zinc Nitrate. 1 pt. C. P. salt in 10 pts. H 2 O. Zinc Sulphate. 1 pt. salt in 10 pts. H 2 O. 100 i ^ABLE OF SOLUBILITIES Li K X; Mg Ca. l-HO1O1OlrHOlrHrH^lrHrHrHCOT^rHrHTj