A complete treatise on the electro-deposition of metals

Front matter

^ v y

X

A COMPLETE TREATISE

Preface To The Fourth American Edition

THE rapid sale of the third American edition of Dr. George Langbein's work, Vollstandiges Handbuch der Galvanischcn Metall-Niederschlage, and the continued demand for it, may be accepted as the best proofs of the value and usefulness of the book.

In the arrangement of the text in this, the fourth edition, now presented to the public, but few changes have been made. A number of new processes and improvements in older methods which have become known, and have been practically tested, since the publication of the previous editions, have been included, as well as the most recent machinery and apparatus, and special sections have been devoted to the quantitative determination of the contents of the baths most generally employed.

The editor is under obligations to the Hanson & Van Winkle Co., of Newark, N. J., the well-known manufacturers of, and dealers in, electro-platers' supplies, for valuable information and engravings.

The publishers have spared no expense in the proper illustration and the mechanical production of the work, and, like the previous editions, it has been provided with a copious table of contents and a very full index, so as to render reference to any subject prompt and easy.

W. T. B.

Philadelphia, February i, 1902.

(iii)

Preface To The First American Edition

The art of the electro-deposition of metals has during recent years attained such a high degree of development that it was felt that a comprehensive and complete treatise was needed to represent the present advanced state of this important industry. In furtherance of this object, a translation of Dr. George Langbein's work, Vollstandiges Handbuch der Galvanischen Metall- Niederschlage, is presented to the English-reading public with the full confidence that it will not only fill a useful place in technical literature, but will also prove a ready book of reference and a practical guide for the workshop. In fact, it is especially intended for the practical workman, wherein he can find advice and information regarding the treatment of the objects while in the bath, as well as before and after electro-plating. The author, Dr. George Langbein, is himself a master of the art, being the proprietor of an extensive electro-plating establishment combined with a manufactory of chemical products, machinery and apparatus used in the industry.

The results yielded by the modern dynamo-electric machines, to which the great advance in the electro-plating art is largely due, are in every respect satisfactory, and the more so since the need of accurate, and at the same time handy, measuring instruments has also been supplied. With the assistance of such measuring instruments, the establishment of fixed rules regarding the current-conditions for a galvanic bath has become possible, so that good results are guaranteed from the start. While formerly the electro-plater had to determine the proper current-strength for the depositions in an empirical manner, by time-consuming experiments, to-day, by duly observing the detervi PREFACE TO THE FIRST AMERICAN EDITION.

mined conditions and provided with well-working measuring instruments, he can at once produce beautiful and suitable deposits of the various metals.

The data referring to these current-conditions, according to measurements by Dr. Langbein, are given as completely as possible, while for the various baths, only formulae yielding entirely reliable results have been selected. To most of the baths a brief review of their mode of action and of their advantages for certain uses is added, thus enabling the operator to select the bath most suitable for his special purpose. To the few formulae which have not been tested, a note to that effect is in each case appended, and they are only given with due reserve.

To render the work as useful as possible, the most suitable formulae for plating by contact and immersion, as well as the best methods for coloring the metals, and the characteristic properties of the chemicals used in the industry, are given. However, the preparation of the chemicals has been omitted, since they can be procured at much less expense from chemical works than it would be possible for the electro-plater to make them in smali quantities, even if he possessed the necessary apparatus and the required knowledge of chemistry and skill in experimenting.

It is hoped that the additions made here and there by the translator, as well as the chapter on " Apparatus and Instruments," and that of " Useful Tables," added by him, may contribute to the usefulness of the treatise.

Finally, it remains only to be stated that the publishers have spared no expense in the proper illustration and the mechanical production of the book ; and, as is their universal practice, have caused it to be provided with a copious table of contents, and a very full index, which will add additional value by rendering any subject in it easy and prompt of reference.

W. T. B.

Phlladelphia, July i, 1891.

CHAPTER I. Historical Review of Electro-Metallurgy

PAGE

The method of coating metals by simple immersion known to Zozimus and Paracelsus; Luigi Galvani's discovery, in 17^9, of the electric contact-current; Alexander Volta's discovery, in 1799, of the true causes of the electric-contact current; Galvani's experiments . . 1

Erroneous inference drawn by Galvani from his experiments; General ignorance in regard to the electric current; Discovery which led to the construction of the pile of Volta, or the voltaic pile; Cruikshank's trough battery 2

Decomposition of water by electrolysis by Nicholson and Carlisle, 1800; Wollaston's observations, 1801; Cruikshank's investigations, 1803; Brugnatelli's experiments in electro-gilding, 1805; Sir Humphrey Davy's discovery of the metals potassium and sodium, 1807; Prof. Oersted's discovery of the deflection of the magnetic needle, 1820 . 3

Construction of the galvanoscope or galvanometer; Ohm's discovery, in 1827, of the law named after him ; Faraday's discovery in 1831, of electric induction; First electro-magnetic induction machine constructed by Pixii; Faraday's electrolytic law laid down and proved in 1833; Production of iridescent colors, in 1826, by Nobili; Production of the amalgams of potassium and sodium, in 1853, by Bird . 4

Discovery of the actual galvanoplastic process, in 1838, by Prof. Jacoby; Claims of priority of invention by Mr. T. Spencer, and by C. J. Jordan; Labors of the Elkingtons, and of De Ruolz; Murray's discovery, in 1840, of black-leading; Introduction, in 1843, of gutta-percha by Dr. Montgomery; First employment, in 1840, of alkaline cyanides by Wright 5

Patent for the deposition of nickel, 1840; Origination of the term "electrometallurgy" by Mr. Alfred Smee, 1841; Prof. Boettger's

(vii)

Vlll CONTENTS.

PAGE

discovery, in 1842, of the deposition of nickel from its double salt; First deposition of metallic alloys by De Ruolz; First use of thermo-electricity, in 1843, by Moses Poole; Advances in the art of electro-deposition 6

The first magnetic machine that deposited silver on a practical scale constructed, in 1844, by Woolrych; Attempts, since 1854, by Christofle & Co. to replace their batteries by magneto-electrical machines; The Alliance machine 7

Objections to Wilde's machine; Dr. Antonio Pacinotti's invention, in i860, of the ring named after him; Siemens' dynamo machine, 1866; Wheatstone's dynamo machine, 1867; Introduction, in 187:, ofZenobe Gramme's machine; Siemens & Halske's machine, 1884; S. Schuckert's machine, 1884 8

Various European and American constructions of dynamo-electrical machines; Investigators and practitioners who have contributed to the improvement of the electro-chemical processes and the perfection of galvano-plasty . . 9

IT.

THEORETICAL PART.

CHAPTER II. Magnetism and Electricity

i. magnetism.

Loadstone or magnetic iron ore; Natural and artificial magnets; Definitions of the magnetic poles and of the neutral line or neutral zone . 10

Magnetic meridian; North and south poles; Phenomena of attraction and repulsion; Ampere's theory 11

The solenoid; Rejection of Ampere's theory by many scientific men; Definition of the magnetic field 12

2. ELECTRICITY.

Definition of idio-electrics and non-electrics; Gray's discovery; Good and bad conductors; The electroscope; Existence of two kinds of electricity, Vitreous, or positive, and resinous, or negative electricity. 13

Double fluid hypothesis of electricity; Single fluid hypothesis of electricity 14

CONTENTS. IX

PAGE

Investigations of Prof. Herz; Coulomb's law; Series of electro-motive force or tension ........... 15

The galvanic current or hydro-electric current; Galvanic element or

galvanic chain; Electrical potential; Electro-motive force; Resistance. 1(3 Conducting power of metals; Quantity of current — Ohm's law . . 17 Essential or internal resistance; Non-essential or external resistance . 18

Coupling of elements in various ways 19

Coupling of elements for electro-motive force or tension; Coupling for quantity of current; Mixed coupling; Proposition deduced from Ohm's

law 20

Effects of the eletric current 21

Electro- magnetism .

Rule for determining the direction which the magnetic needle will assume when placed in any particular position to the conducting wire. 21

Galvanoscope, galvanometers or multipliers ; The astatic galvanometer; The tangent galvanometer; The sine galvanometer . . . .22

Electro-magnets; The solenoid; Law of the action of two electrified wires on each other 23

Induction .

Definition of induction .......... 23

Primary or inductive current; Secondary, induced or induction-current. 24 Alternating currents; Extra currents . 25

Chemical Action of the Electrical Current — Electrolysis.

Reduction of the constituents of a fluid by the electric current; Pure

water a bad conductor . . .25

Faraday's discovery of the chemical actions of the electric current; Electrolysis; Electrolyte; Electrodes; Anode; Cathode; Ions; Anions; Rations; Atoms; Clausius' theory of the composition of matter . 26

Counter or polarizing current; Svante Arrhenius' theory of electrolytic dissociation; Electrolytes; Classification of the ions . . . .27

Table of most important ions; Formation of ions 28

Hittorfs's experiments; Osmotic pressure 29

Explanation of the formation of the polarizing current; Faraday's electrolytic laws 30

Local action; Electro-chemical equivalents; Joule's law . . .32

Consumption of power in electrolysis; Electric units adopted by the International Congress of 1881; Fundamental or C. G. S. (centimetre-gramme-second) units; Force or power — dyne; Work — erg; Quantity;

Potential or electro-motive force 33

Resistance; The ohm; The ampere; The volt; The farad; The coulomb; The watt; Definition of English and of French horse-power . . 34

CONTENTS.

Chapter III

Galvanic Elements— Thermopiles — Magneto- and Dynamo- Electric Machines.

a. galvanic elements.

PAGE

The voltaic pile; Trough battery 35

Reduction of local action by amalgamating the zinc; Various ways of

amalgamation . . 36

Bouant's recommendation; Definition and cause of polarization; Smee's

element , 37

Constant elements; Daniell's element ....... 38

Meidinger element 39

Grove element; Bunsen elements 40

Improved Bunsen cell 42

Electropoion and its composition; Best location of elements . . .43 Dupre's substitute for sulphuric and nitric acids for filling elements; A

soluble chromium combination which depolarizes with rapidity . . 44 Inspection and cleansing of the binding screws; Manipulation of Bunsen elements . . . . . . . . . . . .45

Advisability of having a duplicate set of porous clay cells; Renewal of

the acid; Foote's pinnacle gravity battery 46

Oppermann's element . . . . . . . . .47

Leclanche element; Lallande and Chaperon element . . . .51

The cupron element 53

Various elements; Dun's potash element 54

Element patented by Knaffe and Kiefer, of Vienna . . . .55

Plunge or bichromate batteries; The Bunsen plunge battery; Fein's

bichromate battery . . , 56

Keiser and Schmidt's bichromate battery ...... 57

Bichromate element for gilding or silvering small articles . . .58 Stoehrer's element; Plunge element manufactured by Dr. G. Langbein

B. THERMO-E1ECTRIC PILES.

Prof. Seebeck's discovery, in 1822, of a new source of electricity . . 60

CONTENTS. XI

PAGE

Definition of a thermoelectric couple and of thermo-electricity; Noe's thermo electric pile; Clamond's thermo-electric pile . . . .61

Hauck's thermo-electric pile 62

Giilcher's thermo electric pile . . . . . . . .63

C MAGNETO- AND DYNAMO-ELECTRIC MACHINES.

Faraday's discover}', in 1831 65

Magnetic field or the region of the lines of force; What a magneto-electric or dynamo-electric machine actually is 66

Prof. S. P. Thompson's definition of a dynamo-electric machine . . 67 Pixii's electrical machine, 1832; Saxton and Clarke's improvements; Dr. W. Siemens' improvement, 1857; Pacinotti's ring armature, i860; Dr. W. Siemens' and Sir C. Wheatstone's simultaneous discovery . 68 Classes of electric generators; Continuous current and alternating current machines; The Gramme machine 69

The Gramme armature; Modern Gramme dynamo for galvanoplastic

purposes 70

Disadvantage of the Gramme machine -71

S. Schuckert's flat ring machine 72

Substitution of a dynamo of the drum-armature type for the flat ring

machine; Fein's dynamo machine 73

Siemens & Halske's dynamo-electric machines 74

Kroettlinger dynamo .......... 76

Lahmeyer dynamo . . . . . . . . . . .77

Shunt-wound dynamo constructed by Dr. G. Langbein &Co.; Armature

of this dynamo 79

Resume of the evolution of the dynamo for plating purposes in the

United States 80

The Weston dynamo; "Little Wonder" dynamo; The "Wonder"

dynamo 81

The new Hanson & Van Winkle dynamo 82

Direct connected motors to machines; Mode of connecting the generator

and motor 85

Various dynamo machines; Value of the dynamo, and its effect upon

the electro-plating industry 86

Data for the most suitable machine 87

D. SECONDARY ELEMENTS (ACCUMULATORS).

Planters practical application of accumulators, and his accumulator . 87

Faure's use of lead grids . . - 88

Storage capacity of accumulators; Chemical processes which take place

in the accumulator; J^lbs's theory 89

Liebenow and Loeb's theory .90

Common form of an accumulator; Charging the accumulator; Diagram showing the connection of a plant as installed by the Electro- Chemical Storage Co. of New York 91

Xll CONTENTS.

CHAPTER IV. Arrangement of Electro-Plating Establishments in General

PAGE

Necessity of sufficient light and thorough ventilation . . . .93 Location of Bunsen elements; Provision for heating . . . .94 Importance of a good supply of water; Best materials for floors . . 95 Size of the operating room ; Grinding and polishing rooms . . .96 Prevention of dust in the polishing room; Location of the transmission carrying the belt pulleys ......... 97

ELECTRO-PLATING ARRANGEMENTS IN PARTICULAR.

Parts constituting the actual electro-plating plant; Arrangement with

elements 97

Choice of coupling the elements; Proportion of the effective zinc surface

of the elements to that of the anodes and articles .... 98

Requisites as regards the result of the process of deposition . . .99 Coupling of elements for thick, solid, and thin deposits . . . . 100 Auxiliary apparatus; The rheostat, current-regulator, resistance-board

or switch board 101

Conditions upon which the action of the resistance-board is based . 102

Horizontal and vertical galvanometers 103

Location of the resistance-board and galvanometer; Improved H. and V. W. patent underwriter's switch-board ...... 104

Indications made by the galvanometer ....... 106

Positive or anode wire; Negative or object wire; Vats or tanks; Wooden

vats and their construction 109

Wooden vats lined with sheet lead for acid copper and nickel baths . 110 Objections to such vats; Enameled iron vats; Agate vessel for gold and

other solutions Ill

Conducting rods; Anodes and their arrangement 112

Binding posts and screws; Mode of suspending the anodes . . . 113 Mode of suspending the objects; Slinging wires; Protection of the conducting rods; Cleansing and rinsing apparatus 114

Dipping or pickling; Sawdust for drying the objects; Arrangement with dynamo-electric machines; Rules for setting up and running a

dynamo . 115

Insulation of the object- and anode- wires; Special wire carriers; Arrangement with one machine which has to feed several baths . .117

CONTENTS. Xlll

PAGE

Scheme of a dynamo, with the auxiliary apparatus, the main conducting wire and a few baths; Location of the dynamo rheostat: The amperemeter or ammeter, and the voltmeter; On what the character of a deposit obtained in a certain solution largely depends . . .118

The Starrett improved voltmeter 120

The little H. & V. W. voltmeter; The Weston voltmeter . . .121

The Weston ammeter 122

Scheme showing the coupling of the main object wire and the main anode wire with the resistance-boards, the voltmeter, the switch, and

two baths 123

Ground-plan of an electro-plating establishment 125

Table for freeing the articles from grease 127

Plating-room arranged by the Hansen & Van Winkle Co., of Newark, N. J. ; Mode of calculating the thickness of the conducting wires for dynamos 129*

CHAPTER V. Treatment of Metaeuc Articles

a. mechanicae treatment.

Treatment before electro-plating; Scratch-brushing; Formation of the

deposit in correspondence with the surface of the basis-metal . . 132 Modes of scratch-brushing; Various forms of brushes .... 133 Treatment of scratch-brushes; Circular scratch-brushes .... 134 Circular scratch-brush for cleaning purposes, and its construction . 135

Brushes; Use of sand blast for cleaning . 13(>

The La Pierre patent sand blast; Other types of sand blasts . . . 137

Sand blast combined with a scouring drum 138

Cleaning metallic surfaces in the tumbling barrel or drum . . . 139

Adjustable oblique tumbling barrel 141

Grinding; Grinding wheels and their construction 142

Grinding wheels of pasteboard and of cork waste . ." . . 143

Roughing wheel, medium wheel, and fine wheel; Treatment of the

grinding wheels 144

Vienna lime; Grinding lathes 145

Execution of grinding; Fibres 146

Fibre brushes; Grinding iron and steel articles 147

Grinding brass and copper castings, sheets of brass, German silver and

copper, zinc castings, sheet zinc; Polishing 148

Foot-lathe for polishing; Cloth bobs; Union canvas wheel; Walrine

wheel 149

Foot-power grinding and polishing lathe ; Double polishing lathes;

Lathe manufactured by the Hanson & Van Winkle Co. . . . 150 Electrically driven grinding and polishing lathes 152 xiv CONTENTS.

{page Glue pot; Belt strapping attachment or endless belt machine . . 153

Flexible shafts for grinding, polishing and buffing 154

Polishing materials; Rouge composition 155

Burnishing; Mechanical treatmeut during and after the electro plating process; Scratch-brushing the deposits . ...... 156

Effect of scratch-brushing; Scralch-brushes used for different metals;

Decoctions used in scratch-brushing 157

Scratch-brushing by hand . 158

Lathe-brush; Treatment of the finished electro-plated objects; Sawdust for drying the objects; Method of freeing nickeled objects from

moisture . 159

Polishing deposits of nickel, copper, brass, tin, gold and silver and platinum; Operation of burnishing and forms of burnishers . . .160

B. CHEMICAI, TREATMENT.

Pickling and dipping; Mixture for pickling cast-iron and wrought-iron objects; Excellent pickle for iron; Pickling in the electrolytic way; Duration of pickling .......... 162

Pickling zinc objects; Cleansing and brightening copper and its alloys, brass, bronze, tombac and German silver; Preliminary pickle; Bright-dipping bath 163

Use of potassium cyanide for pickling; Handling of pickled objects;

Matting 164

Matting by chemical means; Mixture for the production of a matt-grained surface by pickling; Matting by mechanical means . ., 165 Matting by galvanoplasty; Main points in pickling . . . .166

Absorbing plant for escaping acid vapors ...... 167

Regaining of acid and metal from exhausted dipping baths . . . 168 Removal of grease and cleansing ........ 169

Preparation of lime mixture; Cleansing with benzine .... 170

Tying the objects to metallic wires; Removal of oxide from the metallic

objects 171

Steel spring carboy rocker 172

CHAPTER VI. Processes of Electro-Deposition

Importance of the constitution of the water used as a solvent; Spring and well water; Rain water 173

Importance of the purity of the chemicals used; Examples of difference in chemicals 174

Concentration of the baths; Non-reliability of measurement by hydrometer degrees 175

Effects of baths too poor in metal, and too concentrated; Stirring up the baths 176

CONTENTS. XV

Effect of heavier and more saturated fluid on the anodes; Constant agitation of the baths by mechanical means; Advantage of constant agitation in silvering and in galvano-plastic operations . . . .177

Bossard mechano-electroplating tanks . . . . . . .178

Electro-plating apparatus for mechanical electro-plating, patented by the Electrolytic Plating Apparatus Co., of Walsall and Birmingham, England; Temperature of the baths 180

Boiling of the baths; Kettles and boiling pans; Solution of nickel salts dissolving with difficulty 181

Eiltration of the boiled solutions; Means of securing lasting qualities to the bath; Choice of anodes 182

Alloying of the deposit with the basis-metal; Gore's experiments . . 183

Conditions for the good performance of an electrolytic bath; Reduction of metals without a battery (electro-deposition by contact) . .184

Reduction of metal by dipping one metal into one fluid . . . . 185

CHAPTER VII. Deposition of Nicked and Cobalt

i. nickeling.

■Growth and popularity of nickel-plating; Properties of nickel . . 186 Nickel baths; General rules for preparing nickel baths; The active constituent in many prepared nickeling salts .... . 187 Use of the chlorine combinations; Additions to the nickel bath recommended by various experts; Effects of the presence of small quautitities of free acid; Boric acid as an addition to nickeling and all other

Action of boric acid; Determination of the acidity, alkalinity and neutrality of nickel baths 189

Formulae, preparation, characteristics and treatment of nickel baths . 190 Burning or over nickeling . . . . . . . . . 191

Nickel baths containing boric acid; Weston's bath ..... 192

Xaselowsky's formula; Preparation of a nickel bath containing boric

acid 193

Nickel baths for special purposes . . . . . . . .194

Bath for nickeling of a dark tone ........ 195

Compositions of a few nickel baths which have been highly recommended; An English formula; Addition of bisulphide of carbon to nickel baths; Bath for nickeling small articles; Bath for the production of very thick deposits 196

Correct working of freshly-prepared nickel baths; Cause of the deposition of somewhat more brittle nickel by freshly -pre pared baths; Peeling off of the deposit 197

Nickel bath without nickel salt; Nickel anodes 198

XVI CONTENTS.

PAGE

Objections to insoluble anodes 199

Use of rolled and cast anodes together in one bath 200-

Size of an ode- surface; Cause of a reddish tinge on the anodes; Manner of suspending the anodes; Restoration of the neutrality, or of a slightly acid reaction of a nickel bath; Process of nickeling .... £02. Coppering or brassing articles previous to nickeling .... 203

Suspension of the objects in the bath 204

Suitable current-strength for nickeling; Burning or over-nickeling . 205. Criteria for judging whether the nickeling progresses with a correct current-strength; Density of current most suitable for nickeling . £06

Solid nickeling - . . 207

Test for sufficiently heavy nickeling; Arrangement of object-rods and

anode-rods; Most suitable distance of the anodes from the object . 208 Use of the hand-anode; Additional rules for nickeling and other electroplating processes; Rules for suspending the objects in the bath . . 209

Polarizing phenomena 210*

Nickeling en masse of small and cheap objects 211

Warren's solutions of nickel and of cobalt to be decomposed in a simple cell apparatus ; Contrivances for electro -plating small articles en

masse 213

Dr. Geo. Langbein & Co.'s apparatus for this purpose; Plating drum recommended by Pfanhauser ......... 214

Rocking apparatus patented by Dr. Geo. Langbein & Co. for plating rods, bicycle spokes, chains, etc.; Arrangement for suspending

bicycle spokes in the bath . . . - 216-

Stripping nickeled articles; Stripping acid . . . . . .217

Stripping by brushing; Stripping by means of the battery or the dynamo; Remedy against a yellowish tone of nickeling; Resume of the principal phenomena which may occur in nickeling, and their

avoidance 218

Refreshing nickel baths 220

Treatment of articles after nickeling; Polishing nickel deposits; Treatment of articles which are to remain matt; Nickeling sheet zinc . 221 Preliminary grinding and polishing; Construction of cloth bobs . . 222

Mode of polishing or grinding the sheets 223

Self-acting sheet polishing machines; F. Rauber's sheet-grinding and

polishing machine 224

Automatic sheet-polishing machine constructed by F. W. Koffler, of

Vienna 228

Automatic sheet-polishing machine constructed by Friedr. Krupp, Grusonwerk, Magdeburg- Buckau, Germany ..... 230

Cleansing zinc sheets; Nickeling the sheets ...... 232

Advantages of previous coppering or brassing; Prevention of the peel-

ing-off of the nickel deposit 233

Coppering the sheets; Dimensions of vats for nickeling the sheets . 234

CONTENTS. xvil

PAGE

Anodes used for nickeling sheet-zinc, and proportion of anode-surface

to zinc-surface; Cause of black streaks and stains .... 235

Augmentation of the metallic content of the bath; Polishing the nickeled

sheets; Nickeling tin-plate, Nickeling copper and brass sheets . . 236 Nickeling sheet-iron and sheet-steel ....... 237

Nickeling wire and apparatus for that purpose 238

Nickeling wire-gauze; Nickeling knife-blades, sharp surgical instruments, etc 240

Nickeling skates ........... 241

Nickeling printing plates (electrotypes, cliches, etc.); Hard nickeling

and baths for that purpose 242

Recovery of nickel from old baths; Urquhart's plan for recovering nickel

from old solutions; To improve defective nickeling .... 244 Arrangement of the "doctor;" Nickeling by contact and boiling . 245 Deposition of an alloy containing nickel according to R. Kaiser; Deposits of nickel alloys; Nickel-bronze 247

French process for the deposition of German silver; Watt's method . 248 Examination of nickel baths; Method for the determination of the content of acid , . . 249

Methods for the examination of baths; Gravimetric analysis . . 251

Volumetric analysis 252

Electrolytic method of analysis 253

Apparatus for electrolytic analysis; Washing contrivance . . . 254 Examination of a nickel bath by electrolytic analysis .... 256

2. DEPOSITION OF COBADT.

Properties of cobalt; Baths for plating with cobalt .... 256

Cobalting of copper plates for printing; Determination of the quantity of copper dissolved in stripping the cobalt deposit from cobalted copper plates 257

Warren's cobalt solution; Cobalt solution recommended by G. W. Beardslee, of Brooklyn, N. Y.; Daub's bath for cobalting small fancy articles 258

Cobalting by contact 259/

Chapter VIII

Deposition of Copper, Brass and Bronze, 2. deposition of copper.

Properties of copper; Copper baths, their composition, preparation,

properties, and treatment . 261

Hassauer's copper bath; Copper baths for iron and steel articles . .262

Baths for coppering zinc articles . 263

Baths prepared with cupron and copper sulphite 265

Copper baths without potassium cyanide ; Weil's copper bath and method of coppering; Copper bath recommended by Walenn . . 266

XVlll CONTENTS.

PAGE

Copper bath according to Pfanhauser; Gauduin's copper bath; Execution of copper-plating 267

Anodes used; Formation of slime on the anodes; Phenomena in baths containing cyanide 268

Necessity of carefully cleaning and pickling the articles before coppering; Scratch-brushing and treatment of defective places . . . 269

Prevention of the formation of stains; Schultz's patent to prevent the formation of stains; Polishing the deposit of copper . . . . 270

Treatment of coppered articles to be coated with another metal; Coppering sheet iron or sheet zinc which is to be nickeled . . . 271

Coppering small articles en masse ; Coppering by contact and dipping; To coat zinc plates with a very thin but hard layer of copper . . 272

Bacco's copper bath; Brush coppering; Application of a thin film of copper to iron and steel objects; Coppering steel pens, needles' eyes, etc 273

Inlaying of depressions of coppered art-castings; Examination of copper-baths containing potassium cyanide 274

Determination of potassium cyanide ....... 275

Determination of copper by electrolysis ....... 277

Volumetric determination of copper ........ 278

2. deposition of brass (Cuivre-poli Deposition).

Constitution and varieties of brass 280

Brass baths, their composition, preparation and treatment; Rules for baths containing more than one metal in solution; Brass bath according to Roseleur 281

Irregular working of fresh baths; Effect of an addition of arsenious acid to brass baths 282

Bath for brassing iron; Baths with cuprous sulphide .... 283

Bath for brassing zinc; Bath for brassing cast-iron, wrought-iron and steel 284

Norris and Johnson's brass bath; Solution for transferring any copper-zinc alloy which serves as anode; Bath for brassing all kinds of metal. 285

Execution of brassing; On what the color of the deposit depends . . 286

Anodes used and anode-surface required; Formation of slime on the anodes, and what it indicates; Remedies for the slow formation of the deposit 287

Importance of the distance of the objects to be plated from the anodes; Brassing of unground iron castings; Brassing by contact and dipping. 289

Examination of brass baths; Determination of free potassium cyanide and the content of copper; Determination of zinc by electrolysis . 2£0

Volumetric determination of zinc 291

3. DEPOSITION OF BRONZE.

Gountier's solution for coating wrought- and cast-iron with bronze; Other bronze baths, their composition, preparation and treatment . 292

CONTENTS. XIX

PAGE

Hess's bath for deposits of tombac; Execution of bronzing . . . 293

CHAPTER IX. Deposition of Silver

Properties of silver; Statistics of the amount of silver used in electroplating 294

Silver baths, their composition, preparation and treatment; Silver bath for a heavy deposit of silver (plating by weight) 295

Preparation of baths with silver chloride 296

Preparation of baths with silver cyanide; Preparation of silver cyanide . 297

Silver bath for ordinary electro-silvering; Treatment of silver baths — Silver anodes 298

Most suitable current-strength for silver baths; Coupling of the elements; Indication of the presence of too much, or not enough potassium cyanide 299

The behavior and appearance of the anodes as criteria of the content of potassium cyanide in the bath; Keeping the bath constant by silver anodes 300

Proper treatment of baths made with silver chloride; Gradual thickening of the baths 301

Augmentation of the content of silver in baths; Determination of the content in proper proportions of silver and excess of potassium cyanide. 3( ! 2

Contrivances to keep the objects to be plated in constant agitation . 303

Singular phenomenon in regard to silver baths ; Preparations for "bright-plating" 304

Remedy against a yellow tone of the silver-plating; Areas silver-plating as introduced by the London Metallurgical Co. ..... 306

Experiments in areas silver-plating ....... 307

Execution of silver-plating; Silver-plating by weight; Mechanical and chemical preparation of the objects; Treatment of copper and its alloys 308

Freeing from grease; Pickling; Rubbing; Pickling in the preliminary pickle; Amalgamating (quicking); Slinging wires .... 309

Treatment of the objects while being being plated .... 310

Amount of silver deposited upon various grades of plated table-ware manufactured by the William Rogers Manufacturing Co.; Method of controlling the weight of the deposit 311

Roseleur's plating balance 312

Plating balance together with the resistance-board, voltmeter, and silver bath 314

Treatment of articles which are to retain the crystalline dead white, with which they come from the bath; Polishing the articles; Ordinary silver-plating 315

Gore's process of silver-plating Britannia ware and articles of tin; Australian patent for directly silver-plating iron and steel . . .316