TESTING 
 
 FOE THE 
 
 FLOTATION PROCESS 
 
 BY 
 
 A. W. FAHRENWALD, MET.E., E.M. 
 it 
 
 PROFESSOR OF MINING AND METALLURGICAL ENGINEERING, 
 NEW MEXICO STATE SCHOOL OF MINES 
 
 FIRST EDITION 
 
 NEW YORK 
 
 JOHN WILEY & SONS, INC. 
 
 LONDON: CHAPMAN & HALL, LIMITED 
 
 1917 
 
3 
 
 COPYRIGHT, 1917, 
 
 BY 
 A. W. FAHRENWALD 
 
To His WIFE 
 LOLA ELLSWORTH FAHKENWALD 
 
 THIS BOOK IS DEDICATED BY 
 
 THE AUTHOR 
 
 372710 
 
PREFACE 
 
 This work was undertaken with the object in 
 view of furnishing, as far as possible, the re- 
 quired information, to give students and any 
 one else testing for the flotation process, a suffi- 
 cient insight to conduct experiments in an in- 
 telligent manner. 
 
 The theory of flotation has been taken up in 
 a general way, no effort being made to advance 
 any special theory. Those which have been 
 most strongly emphasized have been discussed 
 quite fully and the reader is left to decide for 
 himself whether flotation cap be satisfactorily 
 explained by any one of them. 
 
 The knowlege of the effect of oil, acid, and 
 other reagents is absolutely essential to the 
 experimenter, and these have been taken up 
 with the object in view of throwing light on the 
 reason for their use. 
 
 To those who have contributed to the useful- 
 ness of this book, I express my extreme indebted- 
 ness. The work of 0. C. Ralston and Glen L. 
 Allen has been frequently referred to and the 
 material of Chapter VI is largely taken from 
 their invaluable article, " Testing Ores for the 
 Flotation Process." 
 
 I am especially indebted to my wife who has 
 made this compilation possible by her aid in 
 preparing the manuscript. 
 
 If this book aids those testing for the flotation 
 process its purpose will have been accomplished. 
 
 A. W. FAHRENWALD. 
 
CONTENTS 
 
 CHAPTER PAGE 
 
 I. CONCENTRATION BY FLOTATION 1 
 
 II. CLASSIFICATION OF THE FLOTATION PROCESS 4 
 
 III. THE THEORY OF FLOTATION 7 
 
 IV. THE FLOTATION OF OXIDIZED ORES 79 
 
 V. OIL AND OTHER REAGENTS IN FLOTATION.. 86 
 
 VI. TESTS 110 
 
 VII. COST OF FLOTATION 151 
 
 VIII. FORMULAS AND TABLES 155 
 
 INDEX. . 169 
 
TESTING FOR THE 
 FLOTATION PROCESS 
 
 CHAPTER I 
 CONCENTRATION BY FLOTATION 
 
 Due to the lack of a definite and formulated 
 state of the art of flotation a great deal of testing 
 is necessary before an .ore can be treated on a 
 large-scale practice. 
 
 The process of reducing the bulk of an ore 
 by decreasing the percentage of gangue in it, 
 and thus increasing the percentage of mineral 
 content, or what is usually known as the con- 
 centration of the ore, is both an important and 
 interesting part of metallurgy. Increasing the 
 percentage of valuable substances in the ore is 
 brought about by separating the mineral from 
 the gangue. Such a separation was effected, 
 until about the end of the nineteenth century, 
 by mechanical devices, such as jigs, tables, and 
 vanners, where the separation takes place in 
 virtue of the weight of the sulphide as compared 
 with that of the gangue. There are also other 
 methods of separation, the processes depending 
 upon one or more of the different physical 
 properties of the valuable and waste material. 
 The difference in the specific gravity of a mineral 
 and a rock, or of minerals, affords a very safe 
 1 
 
2 CONCENTRATION BY FLOTATION . 
 
 and sure way of separating them from each 
 other, the separating depending entirely on the 
 difference in the settling powers of the different 
 kinds of particles in air, water, or any other 
 medium. Other properties of minerals are also 
 taken advantage of, as electro-conductivity, 
 magnetic susceptibility, etc. 
 
 At the present, however, another method of 
 concentration, called " Flotation " (a definition 
 for which is, apparently, hard to supply), has 
 attracted the attention of the Mining World. 
 " Flotation, in its latest phase, is a process of 
 concentrating ores by frothing. When crushed 
 ore, previously mixed with water and a rela- 
 tively minute addition of oil, is agitated violently 
 in the presence of air, a froth is formed. This 
 froth, rising to the surface of the liquid mixture, 
 is laden with sulphides or other metallic par- 
 ticles, while the earthy material, or gangue, 
 subsides to the bottom. The froth is thick, 
 coherent, and persistent/' 1 
 
 " The flotation process for the concentration 
 of ores is a method by means of which one or 
 more of the minerals in the ore (usually the valu- 
 able ones) are picked up by means of a liquid 
 film and floated at the surface of a mass of fluid 
 pulp. Here they are separated from the other 
 minerals which remain immersed in the body 
 of the pulp. In general the minerals which 
 are floated are sulphides of metallic luster, but 
 
 1 Description given by the Minerals Separation Metal- 
 lurgists; it is a description denied by others, more par- 
 ticularly those using the Callow machine. 
 
CONCENTRATION BY FLOTATION 
 
 some other minerals of metallic luster, such as 
 graphite, and some sulphides with adamantine 
 luster, such as sphalerite and cinnabar, are 
 amenable to treat by this process." : 
 
 Some of the points to explain in the flotation 
 process are : 
 
 1. The flotation of solid particles in a liquid 
 the specific gravity of which is less than that of 
 the solid. 
 
 2. The preferential flotation of the sulphide 
 portion of the mass. 
 
 3. The functions of the reagents used. 
 
 1 "An Explanation of the Flotation Process/' by Arthur 
 F. Taggart and Frederick E. Beach, Bull. A.I.M.E., 
 August, 1916. 
 
CHAPTER II 
 
 CLASSIFICATION OF THE FLOTATION 
 PROCESSES 
 
 The apparatus used in flotation have been 
 classified a great many times, 1 so it has not been 
 deemed necessary to describe the various ap- 
 paratus used in the flotation process but only 
 a brief classification of the process will be given. 
 
 They are conveniently divided into three main 
 classes as follows: 2 
 
 1. Film-suspension, as in the Wood and Mac- 
 quisten methods. 
 
 2. Oil flotation, as in the Robson and Elmore 
 bulk-oil methods. 
 
 3. Bubble-leviation, as in the Elmore Vac- 
 uum, Delprat, Fromont, and Sullivan-Picard 
 methods. 
 
 The third class can be further subdivided ac- 
 cording as carbon dioxide or air is the principal 
 gas utilized for making bubbles. 
 
 Finally, the air-bubble methods can be classi- 
 fied according to the way in which the air is 
 introduced : 
 
 (a) From the bottom of the vessel, as in the 
 Callow and Owen cells. 
 
 (&) By being entrained or dragged into the 
 
 1 "The Flotation Process," by T. A. Rickard, Hoover, 
 Stander, and Megraw. 
 
 2 "The Flotation Process," by T. A. Rickard, p. 9. 
 
 4 
 
FLOTATION PROCESSES 5 
 
 pulp by the beating of paddles or some other 
 form of impeller, as in the Gabbett and Hoover 
 mixer. 
 
 (c) By escape from solution in water, as in 
 the Elmore vacuum machine and the Norris. 
 
 Another classification of the flotation proc- 
 esses is that given by H. J. Stander: 1 
 
 1. The process in which mechanical agitation 
 and oil are used to form a froth. 
 
 2. The purely surface tension process. 
 
 3. The process known as bulk-oil flotation. 
 
 4. Acid used to generate gas from the ore 
 which helps in the formation of the froth. 
 
 5. A process in which the dissolved air in the 
 water, with or without the help of oil, is used to 
 form a froth. 
 
 6. Pneumatic flotation, a process in which air 
 is forced into the mixture of ore, water, and oiL 
 
 Another classification is that given by A. F. 
 Taggart and F. E. Beach, and is as follows: 2 
 
 1. Film flotation, exemplified by the Wood 
 and Macquisten processes. When finely-ground 
 ore containing sulphides mixed with a siliceous 
 or earthy gangue is brought gently onto the sur- 
 face of a body of water in a direction forming an 
 acute angle with the surface of the water, a 
 considerable portion of the sulphide constit- 
 uent of the ore floats on the surface of the 
 liquid while the gangue sinks. 
 
 1 "The Flotation Process," by H. J. Stander. 
 
 2 "An Explanation of the Flotation Process," by Arthur 
 F. Taggart and Frederick E. Beach, Bull. A.I.M.E., 
 August, 1916. 
 
6 FLOTATION PROCESSES 
 
 2. Froth flotation, exemplified by the Min- 
 erals Separation apparatus and the Callow 
 pneumatic machine. When gas bubbles are 
 introduced into a fluid pulp composed of finely- 
 ground ore and water, to which has been added 
 (1) a small amount of certain oils, or (2) a small 
 amount of certain acids or acid salts, or (3) a 
 small amount of certain alkalis or alkaline salts, 
 or (4) a small amount of a mixture of oil with 
 acid or alkalis or alkaline salts, the sulphide 
 particles in the ore are brought to the surface 
 on the gas bubbles. These collect in a froth 
 heavily laden with sulphide particles. The 
 gangue particles are not brought up by the 
 bubbles but remain in the mass of the pulp. 
 
 This classification, it will be seen, is very 
 similar to the first, leaving out " bulk-oil " flo- 
 tation, which, of course, is only of historical 
 interest. 
 
CHAPTER III 
 THE THEORY OF FLOTATION 
 
 The great unsolved problem in flotation is 
 the identity of the forces that do the floating. 
 Some say that it is surface tension, some elec- 
 tricity, and some molecular attraction between 
 the air bubbles and the metallic particles; and 
 there is always the mystery as to exactly the 
 part played by oil. In fact, there has been, 
 little agreement among writers as to " why is 
 flotation." 
 
 It has been found that in order to grasp the 
 ideas connected with the flotation process, and 
 to be able to conduct experiments on any given 
 ore with any degree of intelligence, some knowl- 
 edge of colloidal chemistry, physical chemistry, 
 and electrical principles is absolutely essential. 
 Those who have been dealing with the laws of 
 gravity in connection with concentration will 
 find it to their advantage to review the theory 
 of colloids, and their general physico-chemical 
 properties, and the principles of elementary 
 physics. 
 
 In the many articles which have come out 
 in the Technical Press within the last two 
 years, the following terms have been used fre- 
 quently by the different writers: 
 
 (a) Colloids, (6) Surface Tension, (c) Con- 
 tact Angle, (d) Capillary Attraction, (e) Osmosis, 
 7 
 
8 THE THEORY OF FLOTATION 
 
 (/) Viscosity, (</) Adsorption, (h) Emulsification, 
 (i) Electrical Phenomena, and (j) Preferential 
 Flotation. 
 
 Colloids 
 
 Since the size of many of the particles of min- 
 erals treated by flotation is of the same magni- 
 tude as that of many colloids we cannot escape 
 from calling ore-slime " coarse suspension col- 
 loid " and must apply all the laws of colloid 
 chemistry to our problem. Physical chemistry 
 has been a recognized tool of metallurgists for 
 some time, although little used by most of them, 
 and now a particular branch of physical chem- 
 istry colloid chemistry is beckoning to us 
 alluringly. All questions in the treatment of 
 ore-slime should be studied in this new light. 1 
 
 Colloid Terminology. 2 Colloid chemistry has 
 developed a system of terminology of its own,' 
 and while it is not at all necessary to use this 
 terminology in discussing the subject matter of 
 the science, many of the terms are convenient 
 and are now thoroughly engrafted into the 
 literature. Most useful is the concept that 
 regards the size of particle as due to the " degree 
 of dispersion " of the particulate substance. A 
 decreased size of particle is spoken of as a 
 greater " dispersion " or the substance as more 
 highly " dispersed.' 7 By extension all suspen- 
 
 1 "Why Do Minerals Float?" by Oliver C. Ralston, 
 Min. & Sci. Pr., October 23, 1916. 
 
 2 "Colloid and Colloidal Slimes," by Edward E. Free, 
 Eng. & Min. Jr., February 5, 1916. 
 
COLLOID TERMINOLOGY 9 
 
 \ 
 
 sions and colloids are " disperse " (or " dis- 
 persed ") systems of " dispersoids;" the par- 
 ticles compose the " disperse " phase and the 
 medium is the " dispersion medium." A true 
 solution possesses a molecular or ionic degree of 
 dispersion and is a " mol- " or " ion-dispersoid." 
 These terms include all colloidal systems, re- 
 gardless of the solid, liquid, or gaseous state of 
 particle or medium. Colloidal solutions with 
 a liquid medium are frequently referred to as 
 " sols " (the oppositive term of " gel " will be 
 discussed in a moment). If the medium is 
 water, the colloid is a "hydrosol;" if alcohol, 
 an " alcoholsol " or " alcosol," etc. By analogy 
 with the systems of coarser particles the solid- 
 particle sols are frequently called " suspen- 
 soids;" those of liquid particles, " emulsoids." 
 The terms " sol," " suspensoid," and " emul- 
 soid," with their compounds, are properly ap- 
 plied only to systems within the assigned col- 
 loidal range of particle size. The adjectives 
 " hydrophile " and " hydrophobe " are remnants 
 of a terminology that is disappearing. They 
 were supposed to refer to the affinity or lack of 
 affinity of the substance for water. Roughly, 
 they are equivalent to " emulsoid " and " sus- 
 pensoid " respectively. 
 
 Much confusion has arisen from a loose use 
 of the terms " sol " and " gel " in metallurgical 
 literature. As noted, a sol is a colloidal solution 
 having a liquid medium and possessing the 
 essential properties of liquids. It happens that 
 some emulsoid colloids, of which gelatine is a 
 
10 THE THEORY OF FLOTATION 
 
 good type, have the property of setting under 
 certain conditions to form a more or less stiff 
 jelly-like table gelatine. These jellies are known 
 as " gels." They have much importance in 
 biology and some, perhaps, in the study of ore 
 genesis, but it does not appear that they are 
 important in metallurgy. They are produced 
 only by the special colloids of the type men- 
 tioned, and gelatinization is not a general 
 property of the colloidal state. The resemblance 
 between a jelly-like thickened slime and a real 
 gel is superficial only, and any consideration 
 of this resemblance in metallurgical investi- 
 gations is productive merely of confusion. A 
 similar confusion has arisen through the use in 
 the connection of the concepts of amorphous and 
 crystalline and from the definition of colloidal 
 substances as those which are not crystalline. 
 It is open to question whether real amorphity 
 exists except in fluids, but this discussion would 
 lead us too far into the minutiae of modern theo- 
 ries of matter. For present purposes it is enough 
 to recall that the particulate theory of colloids, 
 as we have developed it, includes no assumption 
 as to the amorphous or crystalline nature of 
 the particles, and it may safely be asserted that 
 none is necessary. " Gel " and " sol " and 
 " amorphous " in these senses could be well 
 spared from metallurgical terminology. 
 
 The Concept of Colloid Chenystry. 1 Colloid 
 chemistry is not the study of colloid materials 
 
 1 "Handbook of Colloid Chemistry," by Ostwald 
 Fischer. 
 
. 
 THE CONCEPT OF COLLOID CHEMISTRY 11 
 
 but that of the colloid state of materials. " Col- 
 loid " is not a chemical entity like salt, acid, or 
 base, oxidizing like mechanical heterogeneity. 
 The concept " colloid " does not even corre- 
 spond to that of " precipitate " since only special 
 forms of precipitates may be termed " colloid." 
 Nor may " colloid " substances be discussed as 
 we discuss " radio-active " substances, for radio- 
 active properties are more closely associated with 
 certain chemical compounds showing definite 
 properties (high atomic weight, etc.) than are 
 the colloid. Like considerations hold when we 
 try to parallel the colloid condition with the 
 " liquid crystalline," though as our knowledge 
 has increased we have found the latter state 
 less and less directly connected with definite 
 chemical compounds. In the same sense "col- 
 loid phenomena " are not to be regarded as due 
 to the properties of colloid materials but rather 
 as characteristic of any material observed in 
 the colloid state. The difference between these 
 two definitions will perhaps be clearer if we 
 compare colloid chemistry with thermo-chem- 
 istry. Just as the latter is not a study of 
 " warm " and " cold " materials, but a study 
 of the thermal condition of the material and its 
 changes, so colloid chemistry is not a descrip- 
 tion of individual colloid materials but treats 
 of the properties of which colloid systems are 
 but examples. Colloid chemistry deals with 
 the relations of the surface energies io other 
 kinds of energy as shown in an especially charac- 
 teristic way in dispersed heterogeneous systems. 
 
12 THE THEORY OF FLOTATION 
 
 Thus viewed, colloid chemistry appears as a 
 branch of physical chemistry coordinated with 
 electro-, thermo-, photo-, radio-chemistry, etc., 
 in other words, with sciences which also treat 
 of the relations of one kind of energy to others. 
 
CLASSIFICATION OF COLLOIDS 
 
 13 
 
 II 
 
 *-ll 
 
 8 S3 
 <*=* 
 |0| 
 
 ||1 
 
 _ O 
 
 o "3 ^ 
 
 8 ^ 
 
 I 
 
 ' ra o 
 O fc 
 
 1 
 
 
 -g 
 
 MM 
 
 
 
 1 
 
 
 ^ 
 
 
 
 r2 
 
 
 
 
 S 
 
 "o 
 
 "o 
 
 
 ^ 
 
 
 +3 
 
 
 
 O 
 
 
 
 VM 
 
 1 
 
 CQ 
 
 i 
 
 CO 
 
 s 
 
 d 
 
 s 
 
 d 
 
 ~ n* 
 
 0) 
 
 1 
 
 
 c3 
 
 
 g 
 
 
 
 *a 
 
 Classification c 
 
 ^3 
 
 ! 
 
 ^3 
 
 Ordinary suspensi 
 
 loidal solutions 
 
 tides. 
 Slimes, thickened 
 
 Wet plastic clays, 
 Turbidity in wate 
 Deflocculated gra] 
 
 Emulsions. 
 
 Oil in condenser 
 
 .a 
 
 "c3 
 
 S 
 
 "o 
 
 2 
 o 
 
 
 CD 
 
 r^ 
 | 
 
 TD 
 
 <X> 
 
 
 
 c3 d 
 
 ^ ^ o^ T3 "S 
 2 o J ^ ^ 
 
 l|l||| 
 
 EfJil 
 
 b o > ^ a? 
 
 S.^3 S 
 S3 
 
 KO 
 
 
 
 !> 
 
 I * 
 
 i 
 
 CO "" 
 
 II 
 
 13 73 
 
 .s 
 1-s 
 
 cr J3 
 
 as 
 
 d T 
 
 J S 
 
 c3 ^ 
 
 N c3 
 
 E?a 
 
 l 
 
 CC 
 
 oa is a 
 
14 THE THEORY OF FLOTATION 
 
 Properties of Colloids. How do we know 
 when we are dealing with a colloid? This 
 question can best be answered by presenting the 
 elementary properties and the experimentally 
 observed behavior of colloid substances. 
 
 1. Colloid properties are in no way connected 
 with substances of definite chemical composition, 
 in other words, " the colloid state is independent 
 of the chemical composition " and we can speak 
 of colloids only as we speak of crystal, amorphous 
 substances, soluble and insoluble substances, 
 or better still of gaseous, liquid, and solid sub- 
 stances. 
 
 2. All substances can appear as colloids under 
 appropriate conditions. 1 
 
 3. Only one law has thus far been deduced 
 governing the relation between chemical con- 
 stituents and colloid state: the more complex 
 chemically the compound, the greater the proba- 
 bility that it is in a colloid state. 
 
 4. Typical " mechanical suspensions " of sub- 
 stances but slightly soluble in liquids, as sus- 
 pension of quartz, kaolin, or oil in water, are 
 turbid in transmitted light, and their individual 
 particles can be recognized under the micro- 
 scope. 2 
 
 If no microscope is available, filtration is the 
 next simplest method by which a suspension 
 can be recognized. Ordinary filter paper holds 
 
 1 Depending upon experimental conditions one and 
 the same chemical compound can appear either as a col- 
 loid or a non-colloid. 
 
 2 Though sometimes only with high magnifications and 
 special optical means. 
 
PROPERTIES OF COLLOIDS 
 
 15 
 
 back particles having a diameter greater than 
 about 5ju; a hardened filter (Schleicher and 
 Schull, No. 602, e.h.) those about 2 p in diameter. 
 
 TABLE I. SIZE OF PORES AND FILTERS 
 
 (According to H. Bechhold.) 
 
 Filter. 
 
 Average size of 
 pores (permea- 
 bility to 
 water). 
 
 Size of largest 
 pores (permea- 
 bility to air). 
 
 Ordinary thick filter paper. . . 
 
 3.3/i 
 
 
 Filter paper No. 556 (Schleich- 
 er and Schull) 
 
 1 7 ju 
 
 
 Filter paper No. 602 (extra 
 hard, Schleicher and Schull) 
 Chamberland filter 
 
 0.8a-1.3 M 
 
 1-1. 5 M 
 
 0.23-0. 41 fji 
 
 Reichel filter 
 
 
 0.16-0. 175 M 
 
 
 
 
 Clay cylinders or so-called Pukall filters which 
 are frequently employed bacteriologically will 
 even hold back particles 0.4 to 0.2 /z in diameter. 1 
 When applied to emulsions, that is, suspensions 
 of droplets in a liquid, filtration is successful 
 only when the suspended droplets are not molec- 
 ularly deformed during filtration. 
 
 5. True solutions may be distinguished from 
 colloid solutions by their optical differences. 
 A liquid which is not chemically homogeneous 
 and which is not in coarse suspension is seen to 
 be turbid; we may suspect that it is a colloid 
 solution. The existence of a slight turbidity 
 may be recognized on inspection of a rather thick 
 
 1 For details regarding permeability and size of pores 
 in various filters, see H. Bechhold, Zeitschr. f. physik. 
 Chem., 64, 328 (198). 
 
16 THE THEORY OF FLOTATION 
 
 layer of the liquid in a thin-walled glass vessel 
 against an opaquely black background. 
 
 A far more delicate method of demonstrating 
 the presence of a very fine turbidity lies in the 
 use of the so-called Tyndall phenomena. 1 Ex- 
 traordinarily fine turbidities can be rendered 
 visible by such means; in fact this holds true to 
 such an extent that special measures become 
 necessary if we would obtain, for example, an 
 absolutely " optically empty " distilled water; 
 ordinary distilled water regularly shows in- 
 dividual dust particles. 
 
 Liquids which show no definite Tyndall light- 
 cone or show it only in high concentrations are 
 " molecular disperse " (true solution) solutions. 
 Practically all colloid solutions give a positive 
 Tyndall effect. 
 
 6. Substances in the colloid state practically 
 do not diffuse at all; at the best they diffuse 
 with extreme slowness when compared with the 
 behavior of substances in molecular solution. 
 
 7. Dialysis, a process closely related to dif- 
 fusion, depends upon the fact that animal, 
 plant, and artificial membranes hold back sub- 
 stances in colloid solution while they allow sub- 
 stances in molecular solution to pass through 
 whenever such a membrane separates the liquid 
 under examination from the pure dispersion 
 means. The dialyzer distinguishes colloid from 
 
 1 It is well known that when, for example, the air of 
 a room is intensely illuminated, say by sunlight, from 
 one side only, dust particles are rendered visible which 
 cannot be seen when illumination is equal on all sides. 
 
SUSPENSOIDS AND EMULSOIDS 17 
 
 true solutions in that it does not allow the former 
 to pass through the membrane into the outer 
 liquid. 
 
 Suspensoids and Emulsoids. These two 
 classes of colloid solution, namely, " suspension 
 colloids " (suspensoid) and the " emulsion col- 
 loids " (emulsoids) have interesting peculiarities. 
 Some of importance are: 
 
 1. The viscosity of a suspension colloid, 
 particularly in low concentration, is imper- 
 ceptibly greater than that of the pure dispersion 
 means. In contradistinction, the viscosity of 
 an emulsion colloid even in low concentration 
 is much greater than that of its dispersion 
 means. 
 
 2. The viscosity of an emulsion colloid generally 
 increased rapidly with decrease in temperature 
 which is not the case with the suspension colloid. 
 
 3. It is characteristic of colloid solutions 
 that the substance in colloid solution may be 
 easily precipitated or " coagulated " through 
 various agencies. Electrolytes, such as neutral 
 salts, are particularly effective. The suspension 
 colloids are easily coagulated when minute 
 quantities of salts, especially those having poly- 
 valent ions, are added to them, while the emul- 
 sion colloids are precipitated only after the 
 addition of much larger quantities of salt. This 
 is particularly true of hydrosols (that is, of 
 colloids having water as the dispersion means). 
 If, for example, aluminum sulphate is selected 
 as the coagulant, it is found that almost all 
 suspension colloids are precipitated by this as 
 
18 THE THEORY OF FLOTATION 
 
 soon as it is present in a 1 per cent concentra- 
 tion. 
 
 4. Colloid solutions have a characteristic 
 electric behavior which explains many of their 
 peculiar properties. Most substances in col- 
 loid solution assume an electric charge toward 
 their dispersion means, though the magnitude 
 of this charge varies greatly. Colloids can be 
 separated from their dispersion means by capil- 
 lary analysis. If the lower end of a strip of 
 filter paper is immersed in colloid solution one 
 of two things may happen, depending upon the 
 character of the electric charge of the colloid; 
 if the colloid carries a negative charge it wanders 
 up the strip of paper along with its dispersion 
 means. If the colloid carries a positive charge the 
 dispersion means continues to rise to the normal 
 height, but the " colloid phase does not." Oppo- 
 sitely charged colloids precipitate each other. 1 
 
 The character of the charge of the colloid 
 phase may be determined by noting the direction 
 in which it moves when subjected to the action 
 of an electric current. 2 To do this the colloid 
 is poured into a U-tube closed with corks and 
 provided with platinum electrodes which dip 
 into the solution; a few storage cells may suffice. 
 I: the colloid wanders toward the anode it is 
 
 1 If two typical test solutions are kept in stock, for 
 example, a positive colloid such as ferric hydroxide and a 
 negative colloid such as sulphur or arsenious sulphide, 
 the charge of an unknown colloid may frequently be de- 
 termined by ascertaining with which of the two solutions 
 it yields a precipitate. 
 
 2 Migration in an electric field. 
 
CONTROL OF COLLOID CONDITION 19 
 
 negatively charged; if it wanders toward the 
 cathode it is positively charged. 1 
 
 Control of Colloid Condition. 2 Colloidality 
 will be increased by: 
 
 1. The presence of small amounts of free 
 alkali (except lime). 
 
 2. Prolonged grinding or long exposure to 
 water or the atmosphere. 
 
 3. Grinding or storage at high temperatures. 
 
 4. The presence of organic material such as 
 would be supplied by decaying animal or vege- 
 table matter. 
 
 Colloidality will be decreased by the avoidance 
 of the four conditions just cited and also by: 
 
 1. The presence in solution of acids or of 
 neutral salts or of certain alkalis in certain con- 
 centrations. 
 
 2. Rapid grinding and handling. 
 
 The relative quantitative importance of the 
 various factors mentioned and the decision as 
 to which should be selected as a means of prac- 
 tical improvement will depend upon local con- 
 ditions different in each case. In general the 
 presence of organic matter has the most effect, 
 but is rarely encountered. Next in quantitative 
 importance is the presence of dissolved acids, 
 salts or alkalis. Of much less effect is the 
 time of grinding or storage, unless it runs into 
 years and of still less effect are changes of 
 temperature between usual limits. 
 
 1 Above remarks largely taken from "Handbook of 
 Colloid Chemistry," by Ostwald Fischer. 
 
 2 " Properties of Slime Cakes, II," by Edward E. Free, 
 Eng. & Min. Jr., June 24, 1916. 
 
20 
 
 THE THEORY OF FLOTATION 
 
 Surface Tension 
 
 Definition. Every liquid surface in contact 
 with a gas or its vapor behaves as if it were 
 under tension. The value of this contractile 
 force per unit width can be measured. 
 
 The basic factor in the making of bubbles is 
 surface tension. This is the force that causes 
 the surface to resist rupture. The particles at 
 the surface have a greater coherence than the 
 similar particles within the body of the liquid, 
 or the tendency of a liquid to reduce its exposed 
 surface to a minimum, that is, the tendency of 
 any liquid surface to act like a stretched mem- 
 brane is called " surface tension." l 
 
 Effects of Added Substances. Surface ten- 
 sion has been thrashed out pretty thoroughly 
 by articles appearing in the Journals of the 
 American Chemical Society beginning in 1908. 
 
 Jour. Am. Chem. Soc., Vol. XXX, No. 3, Mar., 1908. 
 
 XXX, 
 XXXIII, 
 XXXIII, 
 XXXIII, 
 XXXV, 
 XXXV, 
 XXXV, 
 
 7, July, 1908. 
 3, Mar., 1911. 
 5, May, 1911. 
 7, July, 1911. 
 
 10, Oct., 1913. 
 
 11, Nov., 1913. 
 
 12, Dec., 1913. 
 
 Some of their conclusions are that: 
 
 (a) The drop-weight of any liquid is pro- 
 portional to the diameter of the dropping-tube. 
 These tubes are uniform in diameter, thus dif- 
 fering from the ordinary burettes. 
 
 (&) The weight of a drop, other things being 
 
 1 "First Course in Physics," by Millikan and Gale, p. 
 107. 
 
EFFECTS OF ADDED SUBSTANCES 21 
 
 the same, is proportional to the surface tension 
 of the liquid. 
 
 (c) It is possible to calculate the temperature 
 at which the drop-weight would become zero, 
 namely, the critical temperature of the liquid, 
 for at that point the drop would disappear, 
 there being no distinction between the gas and 
 the liquid. 
 
 In the course of these experiments the sur- 
 face tension of a number of organic liquids in 
 aqueous solution was determined by drop- 
 weight and found to range from 21 up to that 
 of water. The tabulated results cover several 
 pages in the Journal: 
 
 AQUEOUS SOLUTIONS AT 30 C. 
 
 Ethyl 
 alcohol. 
 
 Methyl 
 alcohol. 
 
 Amyl 
 alcohol. 
 
 Acetic 
 acid. 
 
 Formic 
 acid. 
 
 Per 
 cent. 
 
 Sur. 
 ten. 
 
 Per 
 cent. 
 
 Sur. 
 ten. 
 
 Per 
 cent. 
 
 Sur. 
 ten. 
 
 Per 
 cent. 
 
 Sur. 
 ten. 
 
 Per 
 cent. 
 
 Sur. 
 ten. 
 
 0.000 
 
 71.030 
 
 0.000 
 
 71.030 
 
 0.000 
 
 71.030 
 
 0.000 
 
 71.030 
 
 0.000 
 
 71.030 
 
 0.979 
 
 65.600 
 
 1.011 
 
 68.120 
 
 0.250 
 
 53.712 
 
 1.000 
 
 67.756 
 
 1.000 
 
 69.816 
 
 2.143 
 
 60.847 
 
 2.500 
 
 64.845 
 
 0.500 
 
 46.157 
 
 2.475 
 
 63.995 
 
 2.500 
 
 68.024 
 
 4.994 
 
 53.137 
 
 4.097 
 
 60.294 
 
 0.750 
 
 41.247 
 
 5.001 
 
 59.435 
 
 5.000 
 
 65.706 
 
 10.385 
 
 44.668 
 
 9.994 
 
 53.661 
 
 1.000 
 
 37.631 
 
 10.010 
 
 53.500 
 
 10.000 
 
 62.061 
 
 17.979 
 
 37.311 
 
 10.000 
 
 48.817 
 
 1.500 
 
 32.504 
 
 14.980 
 
 49.451 
 
 15.000 
 
 59.197 
 
 25.000 
 
 32.941 
 
 25.000 
 
 41.809 
 
 2.000 
 
 28.667 
 
 20.090 
 
 46.455 
 
 25.000 
 
 55.190 
 
 50.000 
 75.000 
 100.000 
 
 26.521 
 23.850 
 20.756 
 
 50.000 
 75.000 
 100.000 
 
 31.843 
 26.173 
 21.073 
 
 2.498 
 
 25.726 
 
 49.960 
 79.880 
 100.000 
 
 37.109 
 31.026 
 25.725 
 
 50.000 
 75.000 
 100.000 
 
 48.112 
 41.990 
 35.281 
 
 100.000 
 
 22.296 
 
 It is to be noted that in all cases the very 
 first addition causes a very considerable lowering 
 of surface tension. The decrease in the surface 
 tension of water caused by the addition of a 
 
22 
 
 THE THEORY OF FLOTATION 
 
 small amount of amyl alcohol is especially 
 striking. Thus the presence in solution of 
 even so small an amount as 0.25 per cent changes 
 the surface tension of water from 71.030 to 
 53.7, or nearly 25 per cent at 30 C. 
 
 Morgan and Schramm studied many concen- 
 trations of a few salts. They selected the 
 molten hydrated salts for this purpose, those 
 salts which melt below 50 degrees in their own 
 water of crystallization being especially satis- 
 factory for this purpose, for the reason that 
 concentration in some of these cases could 
 have been carried to supersaturation. 
 
 10 15 20 25 30 35 40 
 Gm. salt per 100 gm. solution 
 
 FlG. 1. 
 
 45 50 
 
 In the case of salts which they studied it is 
 plain that surface tension is increased by the 
 salts introduced. Where calcium chloride was 
 used, the surface tension was increased from 
 
SURFACE TENSION PHENOMENA 23 
 
 71.03 to 102.57, approximately 50 per cent. 
 Taking a few specific cases it is noted that to in- 
 crease the surface tension 10 per cent it would 
 take 20 per cent CaCl 2 at 30 degrees; 43 per cent 
 Zn (N0 8 ) at 45 degrees; 29 per cent NagCrC^ at 
 30 degrees; 34 per cent N 3-282 3 at 40 degrees. 
 
 The fact is that some salts elevate while 
 others depress surface tension, but the former 
 predominate. In addition to the salts just 
 mentioned the tartrates, carbonates, oxalates, 
 citrates, lactates, and a part of the acetates 
 raise surface tension; while all the salicylates, 
 the butyrates, part of the acetates, and all the 
 acids lower surface tension. 
 
 Surface Tension Phenomena. Many mani- 
 festations of surface tension on water can be 
 cited. Fill a tumbler a little more than full 
 and the water will have a convex surface, in- 
 dicating that there is some force at work to 
 prevent the water from spilling. Note the 
 cohesion between two plates that have been 
 wetted. Dip a camel's-hair brush into water 
 and the hairs cling together; immerse the wet 
 brush in the water and the hairs separate. 
 Watch the formation of a drop of water and note 
 that it behaves as if enveloped by a stretched 
 membrane. Water-spiders can be seen run- 
 ning over the surface of a pond in summer; the 
 spider makes a visible dimple without wetting 
 his feet. The surface is not ruptured. Clean 
 a piece of iron wire and place it gently on the 
 surface of distilled water; it floats. The ap- 
 parent attractions and repulsions exhibited by 
 
24 THE THEORY OF FLOTATION 
 
 small floating bodies on the surface of a liquid 
 are due to surface tension. 1 Thus two small 
 pieces of wood floating on the surface of water 
 rush together if they come within about a 
 centimeter of one another. This is due to the 
 fact that the angle of contact between water 
 and wood is less than 90 degrees, so the water is 
 slightly raised up between the floating bodies 
 as in a wide capillary tube (Fig. 2). The pres- 
 
 FIG. 2. FIG. 2a. 
 
 sure in the liquid between is less than in the 
 surrounding mass and the bodies come together. 
 In the case where the angle of contact is greater 
 than 90 degrees, as, for instance, with needles 
 floating on mercury (Fig. 2), the liquid between 
 the bodies is depressed, and the hydrostatic 
 pressure on the outside forces the bodies to- 
 gether. 
 
 The Force of Surface Tension. The force 
 of surface tension has been measured by as- 
 certaining the weight that can be suspended 
 from a film of water in air. 2 It has been stated 
 
 1 "A Textbook of Physics," by Watson, p. 185. 
 
 2 "A Textbook of Principles of Physics," by Alfred 
 Daniel, 1911. 
 
THE FORCE OF SURFACE TENSION 25 
 
 as 3J gr. per inch, 1 or 81 dynes per centimeter. 2 
 A later determination is given by Theodore W. 
 Richards and Leslie B. Combs 3 as 72.62 dynes 
 per centimeter at 20 C. Many interfering 
 factors enter into the determination of this force. 
 
 Surface tension varies as between various 
 liquids and fluids in contact, an example being 
 that of the tension separating mercury from 
 water amounting to 418 dynes per centimeter, 
 while that separating olive oil from air is only 
 36.9 dynes. The surface tension of an oil-water 
 surface is only 14 as compared with the 73 of an 
 air-water surface at a temperature of 18 C. 4 
 While the film of oil on water may be only one 
 molecule thick, or one twenty-five millionth of 
 an inch, it will suffice to reduce the effective pull 
 of the water from 73 to 43; this latter figure 
 repesents the effective surface tension of water 
 modified by oil as used in flotation. 
 
 If surface energy is freed in any way it is 
 changed into other forms of energy, especially 
 heat, the surface of the system decreasing at the 
 same time. Conversely, if heat is introduced into 
 a system capable of developing free surface energy 
 the surface tension is decreased. Roughly, the 
 decrease in surface tension is proportional to the 
 increase in temperature. Place powdered sulphur 
 
 1 " Soap Bubbles," by C. V. Boys. 
 
 2 Clerk Maxwell in Encyclopedia Britannica, under 
 Capillarity. 
 
 3 "The Surface Tension of Water, Alcohols, etc.," 
 Jr. of Am. Chem. Soc. y July, 1915. 
 
 4 " A Textbook of Physics," by J. H. Poynting and J. J. 
 Thomson, 1913. 
 
26 THE THEORY OF FLOTATION 
 
 on the surface of the water on a horizontal plate 
 of clean metal; apply heat locally; the sulphur is 
 pulled away by the cold liquid as against the 
 feebler tension of the warmer liquid. If an 
 electric surface is produced, in that two phases 
 having different electric charges which are not 
 permitted to neutralize each other are brought 
 in contact with each other, the surface tension 
 of the phase decreases. 1 Further, the value of a 
 surface tension varies with the chemical charac- 
 ter of the phases which are in contact with each 
 other. 
 
 The elastic force at the surface of a liquid tends 
 to draw it into the most compact form. That is 
 why drops assume the form of a sphere. Let 
 alcohol be added to water until a solution is 
 obtained in which a drop of common lubricating 
 oil will float at any depth. Then with a pipette 
 insert a large globule of oil beneath the surface. 
 The oil will be seen to float as a perfect sphere 
 within the body of the liquid 2 (Fig. 3). 
 
 FIG. 3. 
 
 The reason that liquids are not more com- 
 monly observed to take the spherical form is 
 that ordinarily the force of gravity is so great 
 
 1 "Handbook of Colloid Chemistry," by Ostwald 
 Fischer. 
 
 2 "A First Course in Physics," by Millikan and Gale. 
 
as to be more influential in determining their 
 shape than are the cohesive forces. 
 
 Water has the highest surface tension of any 
 common liquid except mercury, so that the ad- 
 dition of another liquid usually lowers its sur- 
 face tension. When the water is modified by 
 oil, the contractile force of surface tension is 
 diminished, the bubbles are less fragile, and 
 they survive long enough to perform their metal- 
 lurgical duty of buoying the metal particles to 
 the surface of the liquid pulp. 1 In practice the 
 modification of water is effected by minute sub- 
 divisions of an insoluble oil, or it may be done 
 by means of a soluble oil or derivative, such as 
 creosol and amyl acetate. The surface tension 
 of a colloid solution at its free surface may be 
 more, or less, or equal to that of the pure dis- 
 persion medium. The surface tension of water, 
 while generally decreased by a contaminant, is 
 increased by gum arabic, starch, and plum gum. 
 Both the increase and decrease in surface tension 
 , follows the concentration of the colloid. Traces 
 of fatty acids, soaps, resins, tannic acid, etc., 
 suffice to greatly lower the surface tension of 
 water. 2 
 
 The surface tension of colloid solutions, as of 
 liquids in general, decrease as the temperature 
 rises, but is more marked than in the case of 
 the pure dispersion medium alone. Coarse sus- 
 pensions and suspensoids hardly alter the sur- 
 
 "The Flotation Process," by T. A. Rickard. 
 "H 
 Fischer. 
 
 2 ''Handbook of Colloid Chemistry, " by Ostwald 
 
28 THE THEORY OF FLOTATION 
 
 face tension of the dispersion medium. 1 L. 
 Zlobicki found coarse aqueous suspensions of 
 emery, mastic, and gamboge and colloid sus- 
 pensions of silver and platinum to have the 
 same surface tension as the pure dispersion 
 medium. The temperature coefficient of the 
 surface tension of these systems was also the 
 same as that of the pure dispersion means. 
 These results seem to show that only emulsoids 
 (colloids in the phase liquid-liquid) decrease 
 the surface tension of their dispersion media. 
 
 Sodium hydroxide affects greatly the surface 
 tension of soap solution. 
 
 Oil serves as a contaminant that lowers the 
 surface tension of water, also it augments the 
 viscosity of the liquid. These two effects unite 
 in facilitating the formation of strong and per- 
 sistent froth. 
 
 The Contact Angle 
 
 Definition. It can easily be shown, as we 
 know from flotation practice, that films of vari- 
 ous kinds on particles either produce or prevent 
 flotation. A clean copper wire floats, if the sur- 
 face is oxidized it sinks promptly, while if the 
 oxide film is changed to one of sulphide, the wire 
 again floats. 
 
 The reason for the different behavior of these 
 three wires is that the different films result in 
 different " contact angles/' The contact angle 
 
 1 "Handbook of Colloid Chemistry," by Ostwald 
 Fischer. 
 
CONTACT ANGLE IN FLOTATION 
 
 29 
 
 is the measure of " wetness " or " non-wetness " 
 and is shown in Fig. 4. 
 
 FIG. 4. 
 
 Contact Angle in Flotation. Valentine has 
 proved theoretically and by practical tests that 
 one of the flotation factors is the contact angle, 
 which must be of a certain degree to make flo- 
 tation possible, and we can, therefore, say that 
 surface films either produce or prevent flo- 
 tation, according to the contact angle. 
 
 We have been talking of coatings that are 
 solid films, but we can show that a film may be 
 either a solid, a liquid, a gas, or an electric 
 charge. The use of oil in practice illustrates a 
 liquid film, and just as with the solid film (oxide, 
 sulphide, metal) these liquid films will either 
 produce or prevent flotation according to the 
 resulting contact angle. Malachite particles hav- 
 ing a film of sulphide produced by the action of 
 H 2 S floats very well; they do so by the contact 
 angle caused by the strongly adhering film of gas. 
 
 The following quoted from Taggart and Beach 
 is very interesting. 1 
 
 1 "An Explanation of the Flotation Process," Bull. 
 A.I.M.E., August, 1916. 
 
30 THE THEORY OF FLOTATION 
 
 When, as is the common case in the flotation 
 process, there are three substances in contact, 
 a system of forces, as shown in Fig. 5, is brought 
 
 FIG. 5. 
 
 into play. If does not move indefinitely to 
 the right or to the left, equilibrium will be 
 attained when 
 
 TSL = 
 or cos0 = 
 
 TGL 
 
 where T GSj T GL , and TSL are the interfacial ten- 
 sions or pressure at the gas-solid, gas-liquid, and 
 solid-liquid contact respectively. From this 
 equation is deduced the important conclusion 
 that as TSL increases with respect to T G s, the 
 angle of contact 6 becomes smaller (the gas and 
 liquid being the same), or, in other words, the 
 angle of contact is a measure of the tendency 
 of one fluid to replace another on the surface of 
 a colloid. We have examined the angles of 
 contact of the water-air, oil-air, and oil-water 
 surfaces against a number of the common 
 minerals. We have found, in general, that the 
 air-water contact angle is less for gangue minerals 
 than for sulphide minerals, that the air-oil con- 
 tact angle is less for sulphides than for gangues 
 and less for any given sulphides than the air- 
 water contact angle, and that the water-oil con- 
 tact with solids takes the form shown in Fig. 6. 
 
CONTACT ANGLE IN FLOTATION 
 
 31 
 
 We found further that the invariable effect 
 of oiling a solid surface is to reduce the air- 
 water contact angles. This latter phenomenon 
 
 FIG. 6. 
 
 is undoubtedly aided by the reduction of the 
 surface tension of the water due to contamina- 
 tion by the oil, The conclusions forced by ob- 
 servation of the above phenomena are: 
 
 1. That water has a smaller tendency to 
 displace air on the surface of sulphide minerals 
 than on the surface of gangue minerals. 
 
 2. That the tendency of oil to displace air is 
 greater on the surface of sulphide minerals than 
 at the surface of gangue minerals. 
 
 3. That oil tends to displace water on the 
 surface of sulphides and that water tends to 
 displace oil at the surface of gangue minerals. 
 
 4. That water displaces air more readily on 
 an oil-solid surface than on a clean surface of 
 ths same solid. 
 
 5. That these tendencies toward displace- 
 ment are due to the interfacial tensions or pres- 
 sures existing between the various substances, 
 and that the resulting action of these interfacial 
 forces is a manifestation of the tendency toward 
 reduction of the total potential energy of the 
 system. Wherever an increase in the solid-fluid 
 interface will decrease the potential energy, such 
 a change will occur. 
 
32 THE THEORY OF FLOTATION 
 
 It can also be shown experimentally that an 
 electric charge will so modify the contact angle 
 on a particle as to permit flotation that would 
 otherwise not take place. A change of potential 
 at the surface of separation of a solid and liquid 
 will produce a change of surface tension and 
 contact angle, and conversely a change in sur- 
 face tension by any other means will produce a 
 difference of potential. 1 
 
 A particle heavier than water may be made to 
 float provided it is small enough, of proper shape 
 with respect to size and weight, and provided 
 it has a surface film the resultant of which is 
 a contact angle that permits flotation. Such 
 films may be either solid, liquid, gaseous, or 
 electric or a combination of any of these. 
 
 This statement is very near that for the con- 
 ditions required to produce a colloid solution or 
 suspension and it is, therefore, reasonable to 
 look to the subject of colloids and of electro- 
 statics, with which this is closely connected, to 
 furnish the real reason for flotation. 
 
 An absolutely clean particle free from films of 
 any kind (which is practically impossible) will 
 not float; therefore, we can have no flotation 
 without a surface film. While it is a fact that 
 certain films produce flotation by reason of 
 their contact angle, how do we account for the 
 fact that these films produce the contact angle 
 they do?- If some mineral particles whose con- 
 tact with water renders them non-wet are put 
 
 1 "How Flotation Works," by G. D. Van Arsdale, 
 Eng. & Min. Jr., May 13, 1916. 
 
CONTACT ANGLE IN FLOTATION 33 
 
 into the bottom of a vessel containing pure water 
 and a bubble of air is brought into contact with 
 this particle, they will become attached and the 
 particle will be carried up to the surface with 
 the bubble. This goes to show that it is not 
 necessary to form the bubble in solution nor is 
 it necessary to have nascent bubbles. 1 The 
 mere attachment of the mineral to the bubble, 
 or the simple contact of gas and liquid surface, 
 is all that is necessary. In explaining why the 
 bubbles attach themselves to the mineral and 
 not to the gangue, the accompanying sketch 
 represents a large magnified diagram of a bubble 
 of air or gas in contact with the two particles, 
 one of the particles having assumed a contact 
 
 Partical with Film Resulting Partical -with Film Resulting 
 
 In "Wet" Contact Angle I /in "Non-Wet" Contact Angle 
 
 FIG. 7. 
 
 angle that would enable it to float on a watery 
 surface, the other particle having a contact 
 angle that would produce immediate sinking 
 on a water surface (Fig. 7). Considering this 
 diagram, it will be seen that the bubble is really 
 only the surface of water in contact with air or 
 gas, and that the particles float on the surface 
 for exactly the same reason as they do in the 
 Macquisten tube. 
 
 1 "Why is Flotation?" by Chas. T. Durell, Min. & 
 Sci. Press, September 18, 1915. 
 
34 
 
 THE THEORY OF FLOTATION 
 
 Capillary Attraction . 
 
 Capillary Phenomena. A study of capil- 
 larity is of great aid in gaining a conception of 
 the conduct of the molecular forces of cohesion 
 and adhesion that cause some substances to 
 float on the surface of a liquid while others sink. 1 
 We must keep in mind two familiar facts: 
 First that the surface of a body of water at rest, 
 for example a pond, is at right angles to the 
 resultant force, that is, gravity, which acts upon 
 it; second, that the force of gravity, acting upon 
 a minute amount of liquid, is negligible in com- 
 parison with its own cohe- 
 sive force. Consider, then, 
 a very small body of liquid 
 close to the point 0, Fig. 8, 
 where water is in contact 
 with the wall of the glass 
 tube. Let the quantity of 
 liquid considered be so mi- 
 nute that the force of grav- 
 ity acting upon it may be 
 disregarded. The force of cohesion of the wall will 
 pull the liquid particles at in the direction of E. 
 The force of cohesion of the liquid will pull this 
 same particle in the direction OF. The result- 
 ant of these two pulls on the liquid at will then 
 be represented by OR, Fig. 8. If, then, the 
 adhesive force OE exceeds the cohesive force 
 OF, the direction of OR of the resultant force will 
 lie to the left of the vertical OM , Fig. 9, in which 
 1 "Molecular Forces and Flotation," by Will H. Cog- 
 hill, Min. & Sci. Press, September 2, 1916. 
 
 FIG. 8 
 
CAPILLARY PHENOMENA 
 
 35 
 
 case, since the surface of the liquid always as- 
 sumes a position at right angles to the resultant 
 force, it must rise up against the wall as water 
 does against glass. If the cohesive force OF 
 (Fig. 10) is strong in comparison with the ad- 
 hesive force OE the resultant OR will fall to the 
 right of the vertical, in which case the liquid 
 must be depressed about 0. Whether, then, a 
 liquid will rise against a solid wall or be depressed 
 
 FIG. 9. 
 
 FIG. 10. 
 
 by it will depend only on the relative strength of 
 the adhesion of the wall for the liquid, and the 
 cohesion of the liquid for itself. Since mercury 
 does not wet glass 1 we know that cohesion is 
 here relatively strong, and we should expect, 
 therefore, that mercury would be depressed, as 
 indeed we find it to be. The fact that water will 
 wet glass indicates that in this case adhesion 
 is relatively strong, and hence we should ex- 
 pect water to rise against the wall of the con- 
 taining vessel, as in fact it does. As soon as the 
 
 1 It is a well-known fact that there is a slight force 
 between mercury and glass and that mercury exerts an 
 attractive force upon air, but the quotation suffices for 
 the present. 
 
36 
 
 THE THEORY OF FLOTATION 
 
 curvatures just mentioned are produced, the 
 concave surface aob (Fig. 11) tends, by virtue of 
 surface tension, to strengthen out into a flat sur- 
 face ao 1 ?), but it no sooner begins to straighten 
 than adhesion again elevates it at the edges. 
 It will be seen, therefore, that the liquid must 
 continue to rise in the tube until the weight of the 
 
 FIG. 11. 
 
 FIG. 12. 
 
 volume lifted balances the tendency of the sur- 
 face to flatten out. Similarly a convex surface 
 aob (Fig. 12) falls until the upward pressure at 
 (which is small) balances the tendency of the 
 surface aob to flatten out. If, in the case of 
 water against glass, the water is pulled upward 
 and in the case of mercury against glass the mer- 
 cury is pulled downward, the converse must also 
 be true, namely, that in the former the glass is 
 pulled down and in the latter the glass is pulled 
 up. 
 
 Result of the Capillary Attraction. Now 
 assume that you had two minerals so that they 
 are partly submerged by a liquid and that with 
 one adhesion is very great (relatively) and that 
 with the other adhesion is very slight. It is 
 obvious that the surface of the liquid will turn 
 
OSMOSIS 37 
 
 up at the contact with the former and down 
 and around the other, and that if these particles 
 are so small that the force of gravity is negli- 
 gible it is impossible for the former to float 
 and just as impossible for the latter to sink. 
 One of them cannot ride on the surface and is 
 actually drawn down into the liquid like gold 
 into mercury, while the other cannot by any 
 means enter the liquid unless its mass is sufficient 
 to overcome the contractile force in the sur- 
 face of the depressed liquid. 1 
 
 Osmosis 
 
 Definition. When two liquids are separated 
 by a porous membrane, each may pass through 
 the membrane into the other with more or less 
 freedom; this process is called " osmose." 2 
 
 Osmotic phenomena connected with osmosis 
 is closely connected with the process of diffusion 
 and dialysis. In fact, during dialysis the in- 
 crease in volume in the dialyzing liquid in the 
 interior of the cell is a phenomenon of osmosis. 
 
 Osmotic phenomena takes place whenever a 
 dispersoid is brought in contact with the less 
 concentrated one or its pure dispersion means, 
 under conditions which do not allow of free 
 diffusion. This may be accomplished by placing 
 between them a so-called semipermeable or, 
 better expressed, a selectively permeable mem- 
 brane, in other words, a device which gives pas- 
 
 1 " Molecular Forces and Flotation, "by Will. H. Coghill, 
 Min. & Sci. Press, September 2, 1916. 
 
 2 " Essentials of Physics," by Hoadley, p. 127. 
 
38 THE THEORY OF FLOTATION 
 
 sage to the dispersion means, but not the dis- 
 persed phase. These devices are nothing more 
 than such as are used in the dialysis of colloid 
 systems. In fact, osmotic phenomena may al- 
 ways be expected to appear during dialysis (sub- 
 stances which do not dialyze, or pass through 
 parchment paper, Graham called colloids; those 
 which do, molecular dispersoids) . Osmosis, like 
 free diffusion, tends toward the establishment 
 of a uniform spatial distribution of dispersed 
 phase and dispersion means. 
 
 The intensity of the tendency to bring about 
 a uniform distribution of dispersed phase and 
 dispersion means may be measured by opposing 
 this osmotic leveling process by the hydrostatic 
 pressure of a water column. The pressure thus 
 made evident is called the " osmotic pressure " 
 of the dispersoid. 
 
 Colloids and Osmosis. Colloids tend to 
 concentrate electrolytes upon themselves and 
 thereby to increase the possibility of developing 
 and exhibiting a greater osmotic pressure than 
 is really due to colloids themselves. 1 This in- 
 creased osmotic pressure would tend to drive the 
 air from the metallic particles leaving them in 
 the same condition as those of the gangue. A 
 proper strength will sometimes " kill " the 
 float, probably due to the above reason. 
 However, colloidal impurities, like tannin, 
 saponin, etc., or volatile oils and the like, destroy 
 
 1 The difficulty of " washing out" the last traces of 
 electrolytes from precipitates is one fact leading to this 
 conclusion. 
 
VISCOSITY 39 
 
 bubbles by reducing the surface tension, so that 
 the gas pressure bursts them. This weakening 
 of the surface tension by a colloid is thus seen 
 to be entirely different from the strengthening of 
 osmotic pressure by a crystalloid (molecular 
 dispersoid) although the result is practically the 
 same no froth. 
 
 The osmotic pressure of molecular dispersoids 
 is governed by the important law of Pfeffer and 
 van't Hoff : the " osmotic pressure is directly 
 proportional to the concentration." The rela- 
 tions in colloid systems are not so simple. 
 Examples are known where the law holds ap- 
 proximately but there are also those in which 
 the " osmotic pressure increases faster than the 
 concentration; or more slowly than this." 
 
 The Influence of Added Substances upon 
 Osmotic Pressure. The influence of added 
 substances upon the osmotic pressure of a given 
 system, that is, molecularly dispersed solution, 
 is purely additive. 1 In other words, the pressure 
 exerted by added substances is added to that 
 of the original system. The effect of added 
 substances on the osmotic pressure of colloid 
 systems is more complicated. Concentration 
 and temperature functions are encountered. 
 
 Acids or alkalis may either increase or de- 
 crease the osmotic pressure of different colloids. 
 
 Viscosity 
 
 A marked increase in the viscosity of inter- 
 facial films is produced by the presence of finely- 
 1 There are exceptions to this rule. 
 
40 
 
 THE THEORY OF FLOTATION 
 
 divided solid matter. This increase can be 
 shown experimentally 2 by pouring any clear oil, 
 kerosene, liquid vaseline, etc., on to water and 
 then bubbling gas through the water (Fig. 13). 
 The interface has all the appearance of an elec- 
 tric film. .Bubbles rising through the water 
 and striking the underside of the interface 
 stretch the film H (Fig. 13) and rising further 
 drag away a mass of water surrounded by this 
 viscous layer. The system now appears as 
 shown at M and rises to the oil-air surface on 
 account of its lower specific gravity. Here the 
 film, together with the excess of water carried 
 up as shown at (7, breaks away and falls back 
 through the oil, not in spherical form, as would 
 
 FIG. 13. 
 
 be the case were the water drop not surrounded 
 by a viscous film, but in hemispherical form 
 (see P, Fig. 13) often trailing behind it a film 
 with ragged edges as it broke from the bubble. 
 The tadpole-shaped water drops H (Fig. 13) 
 
VISCOSITY 41 
 
 are further evidence of the high viscosity of the 
 oil-water interfacial film. 
 
 Also if finely-powdered sulphide is thrown in- 
 to the oil and allowed to settle to the interface, 
 it will become entangled in the film; this in- 
 creased viscosity is apparent. If now gas 
 bubbles are introduced, as before, the return 
 water drops, coated with a film containing the 
 solid particle, are much more irregular in shape 
 than previously, and their coalescence after 
 reaching the interface requires days or weeks. 1 
 An even more convincing proof of the increase 
 in viscosity of an interfacial film is given by the 
 following experiment. If a needle is floated at 
 the center of a surface of pure water in a beaker 
 4 inches in diameter and a chip of wood is 
 floated near the wall of the beaker, the needle 
 may be caused to revolve by means of a magnet 
 without disturbing the chip. If the surface of 
 the water is dusted over with fine ore, the whole 
 surface together with the chip moves as though 
 it were a rigid solid. 2 
 
 When gas bubbles are introduced into a liquid 
 pulp where oil is present there is formed about 
 each bubble a liquid film whose surface tension is 
 less and whose viscosity is greater than that of 
 the bulk of the liquid. Some of the solid par- 
 ticles of the pulp move into the film and are 
 raised to the surface with the bubble. Since 
 
 1 "An Explanation of the Flotation Process," by Tag- 
 gart and Beach, Bull. A.I.M.E., August, 1916. 
 
 2 "An Explanation of the Flotation Process," by 
 Taggart and Beach, Bull. A.I.M.E., August, 1916. 
 
42 THE THEORY OF FLOTATION 
 
 there is a concentration of oil in the film, and 
 since the diminution in potential energy at an 
 oil-sulphide contact is greater than at a water- 
 sulphide contact, the contaminated layer re- 
 places the water on the sulphide and the 
 sulphide moves into the bubble film, while the 
 gangue, on which water displaces oil, remains 
 in greater measure in the body of the pulp. 
 The bubbles, therefore, as they arrive at the 
 surface, carry an excess of the sulphide minerals. 
 Upon their arrival at the surface, the bubbles 
 of the contaminated liquid persist, owing: (1) 
 to their low surface tension; (2) to their ability 
 to adjust this tension to a state of stable equi- 
 librium; and (3) to their greater viscosity which 
 is markedly increased by the presence of the 
 solid particles. 
 
 The following are some of the characteristics 
 of molecular dispersoids: 
 
 1. When a solid goes into solution the vis- 
 cosity of the dispersing medium is usually in- 
 creased; dilute solutions of some salts, such as 
 lithium, chloride, and potassium chloride, form 
 exceptions to this rule. 
 
 2. In normal cases the viscosity increases pro- 
 gressively with concentration. 
 
 3. When gases are dissolved in a solvent 
 they do not seem to change its viscosity. 
 
 Manifold and complicated conditions arise 
 when two liquids are molecularly dissolved in 
 each other. Thus, the mixture of alcohol with 
 water shows a characteristic behavior in that 
 the maximum of viscosity is obtained in medium 
 
VISCOSITY 43 
 
 concentrations of the one in the other, the value 
 of which is considerably greater than that of 
 pure compounds. 
 
 It may be regarded as typical of suspensoids 
 that their viscosity is but slightly greater than 
 that of their pure dispersing mediums. 1 Tem- 
 perature affects the viscosity of the suspensoids 
 in the same way as it does that of normal li- 
 quids: the viscosity decreases with increasing 
 temperature. Also according to H. W. Waustra 
 the condition of electrolytes influences the vis- 
 cosity of a suspensoid silver hydrosol (and prob- 
 ably that of all others) in a very characteristic 
 manner. The addition of an electrolyte de- 
 creases the viscosity; this decrease takes time, 
 occurring in some instances only after days, and 
 it is associated with a change in the state of a 
 colloid, namely, with its coagulation. 
 
 The electric charge on suspended particles 
 allow another possible explanation of flotation 
 phenomena. Quartz particles when suspended 
 in water are negatively charged; pyrite particles 
 positively charged; oil drops are negatively 
 charged, and air bubbles negatively charged. 
 The charges are somewhat small compared with 
 the weight of the particles, so they are hardly 
 strong enough to cause negatively-charged 
 quartz to stick to positively-charged pyrite, as 
 they can have only a few points of contact, and 
 currents in water could easily pull them apart. 
 However, the negatively-charged droplet of oil, 
 
 1 It must be remembered, however, that this is true 
 only when such systems are dilute. 
 
44 THE THEORY OF FLOTATION 
 
 which is repelled from a negatively-charged 
 particle of quartz, can wrap itself around the 
 positively-charged pyrite particle so that they 
 will stick together, and the same applies to air 
 bubbles. The other sulphides known to be 
 flotative have positive charges when suspended 
 in water or can be made to assume positive 
 charges by use of the proper amount of proper 
 electrolyte. The large effect of a small amount 
 of sulphuric acid on the condition of flotation 
 does not seem at all strange in this light. 
 
 The above is O. C. Ralston's theory, the logic 
 of which is supported by Mr. Callow. 
 
 Adsorption 
 
 Explanation of the Term. The surface layer 
 between two physical phases is the seat of con- 
 ditions of density and viscosity, also of apparent 
 forces and energy manifestations, which are 
 notably different from those in the bulk of 
 either phase. On philosophical grounds it is 
 impossible to consider that a real physical dis- 
 continuity occurs at the boundary between two 
 media. In other words, there must be a very 
 thin layer of transition in which there is a rapid 
 but continuous change in the concentration of 
 the components. This change in the concentra- 
 tion of a component at the interface is called 
 adsorption, and may occur even between two 
 phases which are ordinarily regarded as im- 
 miscible. 1 
 
 1 "An Explanation of the Flotation Process," by Tag- 
 gart and Beach, Bull. A.I.M.E., August, 1916. 
 
ADSORPTION IN FLOTATION 45 
 
 . The terms adsorption and absorption have 
 been used interchangeably in some writings, 
 thus contributing to the already existing con- 
 fusion of ideas. 
 
 Adsorption in Flotation. The question of 
 adsorption undoubtedly plays an important part 
 in flotation, since it is so requisite to the pro- 
 duction of a variable surface tension. There 
 can be, of course, no surface tension without 
 adsorption, which produces, in the case of 
 positive adsorption, an increased surface con- 
 centration resulting from a lowering of the sur- 
 face tension by contaminating and dissolved 
 substances, whatever they may be. The equa- 
 tion of Gibbs u = -7^ ~r gives the relation- 
 jKt dc 
 
 ship between surface tension and the distribution 
 of the solute between the bulk of the liquid inter- 
 face. Here the notation is 
 
 u = excess of substance in the surface layer, 
 
 c = concentration in the main body of the 
 
 liquid, 
 R = the gas constant, 
 
 t = absolute temperature, 
 
 o = surface tension. 
 
 This shows that when the surface tension is re- 
 duced by the addition of a contaminant the 
 
 quantity -7- is negative and " -^ " is positive 
 dc kvv 
 
 (from algebraic considerations). The surface 
 film, then, contains more of the contaminant 
 than the main body of the solution. If the 
 surface film contains less of the contaminant 
 
46 THE THEORY OF FLOTATION 
 
 than the main body of the solutions it is a 
 case of " negative adsorption/ 7 
 
 Adsorption at a gas-liquid interface may be 
 demonstrated as follows: If a solid, which has 
 been heated in a vacuum, is introduced into a 
 measured volume of a gas over mercury in a 
 calibrated tube, an amount of the gas will be 
 absorbed, as is shown by the change in pressure 
 and volume compared to the space originally 
 occupied. The following additional facts are 
 stated by Taggart and Beach: 1 
 
 (a) The amount of gas adsorbed at constant 
 temperature increases with the pressure. 
 
 (6) It is different for different gases. 
 
 (c) It is different for different solids. 
 
 (d) It increases as the temperature decreases. 
 
 (e) There is an energy transformation which is 
 indicated by the heat development through ad- 
 sorption. 
 
 (/) Chemical reactions are assisted by the 
 adsorbed layer. 
 
 It follows that the gas layers must vary in 
 density, falling off rapidly with increasing dis- 
 tance from the solid. Quincke assumes that 
 the density of the gas next to the solid is equal 
 to that of the solid and concludes that the 
 amount adsorbed will increase with the density 
 of the solid. From these facts are concluded: 
 
 1. That gases and solids exhibit selective ad- 
 hesion and that, therefore, gas bubbles will 
 attach themselves more persistently to some 
 substances than to others. 
 
 1 "An Explanation of the Flotation Process," Bull. 
 A.I.M.E., August, 1916. 
 
ADSORPTION IN FLOTATION 47 
 
 2. That the selective adhesion is a manifes- 
 tation of a definite amount of energy possessed 
 by each unit area of a gas-solid contact, and 
 that this potential energy is capable of variation. 
 
 3. That chemical reactions which diminish 
 this potential energy are aided by adsorption. 
 
 Adsorption of the gas at a gas-liquid surface is 
 indicated : 
 
 1. By the effect on the surface tension. The 
 surface of a freshly-formed mercury surface 
 does not change in a vacuum, but falls off in 
 the presence of different gases for about an hour. 
 Certainly the density of a liquid cannot be con- 
 stant at the boundary but must go over con- 
 tinuously into that of the gas. 
 
 2. By the increase in the solvent power of the 
 surface. 
 
 3. In the case of contaminated liquids by 
 the concentration of one or more of the com- 
 ponents of the liquid at the gas-liquid surface. 
 Every unit area of such a boundary possesses 
 a definite potential energy which always tends 
 to a minimum. If, therefore, the surface tension 
 of a solution depends upon the presence of any 
 component, such a change of concentration of 
 that component will occur as will reduce the 
 potential energy, i.e., interfacial tension. In 
 other words, any component which reduces 
 surface tension will be found in excess at the 
 surface of a solution. 
 
48 THE THEORY OF FLOTATION 
 
 Emulsification 
 
 Effect upon Flotation. By some writers the 
 combination of pulp, oil, water, acid, or whatever 
 other chemical substance is added, is often re- 
 ferred to as an emulsion. Going back to the 
 definition of an emulsion, we find that it is a 
 colloid suspension of one liquid in another. It 
 is true, that oil may be so finely divided that it 
 simulates a true emulsion. If, as has been said, 
 the colloid condition is antagonistic to flotation 
 success, then the pulp-oil combination is not a 
 true emulsion since we clearly do get flotation 
 results from it. The latter statement is true; it 
 is not an emulsion. 1 
 
 In this connection G. D. Van Arsdale states: 2 
 
 From experiment I think it is safe to say that 
 if a particle meets emulsified oil, there will be 
 no attachment of oil to mineral unless some 
 factor is introduced that will break up or de- 
 stroy the emulsified condition, and that conse- 
 quently emulsification of an oil should be avoided 
 in flotation practice. If this is true, we would 
 expect that substances capable of producing 
 an emulsified condition of oils would be harmful 
 in practice, and conversely that substances 
 capable of preventing or breaking up emulsi- 
 fication would be beneficial. I believe that this 
 is the explanation for the puzzling deleterious 
 action of some organic substances, such as glue, 
 tannin, and saponin, since these all belong to the 
 class of compounds that are efficient and emulsi- 
 fying oils. Furthermore, it is easy to show 
 
 1 "The Flotation Process," by Megraw, p. 30. 
 
 2 "How Flotation Works," by G. D. Van Arsdale, 
 Eng. & Min. Jr., May 13, 1916. 
 
EMULSIFICATION 49 
 
 experimentally that sulphuric acid prevents or 
 breaks up emulsion of oils, and it seems reason- 
 able to suppose, therefore, that this is one of the 
 reasons, although it may not be the only one, 
 for the use of acid. The fact that acid is not 
 generally used at present is probably due to the 
 fact that the oils and mixtures now in use in 
 many places are not such as to emulsify readily. 
 
 There are- a number of other substances besides 
 sulphuric acid having the property of preventing 
 or destroying emulsions. Table II shows the 
 relative efficiency of some of these that have 
 been tested. 
 
 TABLE II. EMULSION MODIFYING AGENTS. 
 
 Sulphuric acid 0.244 per cent entirely prevents 
 
 emulsification. 
 
 Cresylic acid . 006 per cent entirely prevents 
 
 emulsification. 
 
 Acetic acid 0.014 per cent entirely prevents 
 
 emulsification. 
 
 Citric acid . 06 per cent entirely prevents 
 
 emulsification. 
 
 Aluminium sulphate ... . 06 per cent prevented emul- 
 sification. 
 
 Copper sulphate . 30 per cent prevented emul- 
 sification. 
 
 Ferrous sulphate no action. 
 
 Caustic soda . 30 per cent no action. 
 
 Sodium chloride stabilizes and increases 
 
 emulsification. 
 
 In a case where sulphuric acid is used for 
 preventing emulsification of oil, we would, 
 therefore, expect that the substances enumerated 
 could be substituted with equal effect in the 
 relative amounts indicated by the figures. 
 
50 THE THEORY OF FLOTATION 
 
 Wilder D. Bancroft has written a series of 
 articles on " The Theory of Emulsification " in 
 the Journal of Physical Chemistry, out of which 
 very useful data with regard to the character- 
 istics of an emulsifying agent can be obtained. 
 His article in the April number of 1915 is of 
 special interest as quite a number of very useful 
 experiments are cited. He says: 1 
 
 For a substance to be an emulsifying agent, it 
 must tend to pass into the surface separating the 
 two liquids and form a coherent film there. 
 If the emulsifying agent does not form a co- 
 herent film the emulsion will crack. 
 
 When two liquids, which are partially im- 
 miscible, come together, we have a surface that 
 separates these two liquid phases, and this sur- 
 face is called a dineric 2 interface. In order to 
 fully understand the water-air interface, it may 
 be of value to study a case where we have a 
 dineric interface. 
 
 The following extract from Wilson's 3 account 
 of an experiment which he carried out as early 
 as 1848 will serve the purpose as well as any. 
 
 When chloroform is placed in a test-tube, or 
 other vessel of glass, standing on a horizontal 
 surface, it exhibits, like other substances which 
 wet that solid, a curved surface with the con- 
 cavity upwards. If water, or an aqueous solu- 
 tion of nitric, sulphuric, or muriatic acid, be 
 poured upon the stratum of chloroform, the 
 surface of the latter immediately changes the 
 
 1 Bancroft, Jour. Phys. Chem., 19, 275 (1915). 
 
 2 Bell, Jour. Phys. Chem., 9, 531 (1905). 
 
 3 Jour. Chem. Soc.,'1, 174 (1848). 
 
EMULSIFICATION 51 
 
 direction of its curve, and becomes convex up- 
 wards, the convexity induced being much greater, 
 however, than the previous concavity. If, on 
 the other hand, an aqueous solution of potash, 
 soda, or ammonia be placed above the chloro- 
 form, the latter ceases at its upper limit to 
 present a sensible curvature upwards or down- 
 wards, and shows a surface which, to an un- 
 assisted eye, appears to be flat. It is to the 
 property of an acid to round, and of an alkali 
 to flatten, the surface of various liquids, of which 
 chloroform is one, that I seek specially to direct 
 attention. 
 
 The phenomena referred to cannot seem re- 
 markable when merely described but they have 
 appeared strikingly, and, I may say, startling 
 to most of those that have witnessed them. 
 They are best observed by dropping into a 
 perfectly clear, flat-bottomed glass vessel con- 
 taining pure water, a quantity of chloroform too 
 small in amount to touch the walls of the vessel 
 on every side. The heavier liquid then shows 
 itself as a brilliant, highly mobile globule. If 
 alkali be now added the chloroform in a moment 
 collapses, sinks as if exposed to a crushing force, 
 and flattens out on the bottom of the glass. On 
 slightly supersaturating the alkali with acid, 
 the flattened chloroform starts into its previous 
 globular shape with a momentum and rapidity 
 such as might be exhibited by a highly elastic 
 substance, like a ball of caoutchouc suddenly 
 relieved from enormous pressure. When the 
 acid in its turn is supersaturated with alkali, 
 and the flattening again occurs, by alternating 
 the addition of these reagents, the same globule 
 may be successively flattened and rounded for 
 any number of times. 
 
 Change in configuration, however, is not the 
 only alteration which the globule of chloroform 
 undergoes. Some of the other physical proper- 
 
52 THE THEORY OF FLOTATION 
 
 ties are markedly altered by its contact with 
 acids and alkalis. These changes are best seen 
 when a deep, white saucer, or flat-bottomed 
 porcelain basin, is made use of as the containing 
 vessel. When acidulated water is placed in this 
 and chloroform let fall into it, the denser fluid 
 is scarcely wetted, and, although nearly half as 
 heavy again as pure water, sinks reluctantly. 
 If the drops indeed be small, they never reach 
 the bottom, but on floating on the surface, evapo- 
 rate away. Those which descend form globules 
 very mobile and readily obeying the solicitation 
 of gravity. When separate globules melt, they 
 rapidly flow together, and scarcely one is seen 
 without a bubble of air attached to its upper 
 surface adhering tenaciously. When the water, 
 on the other hand, is an alkali, the chloroform is 
 quickly wetted and sinks swiftly. The drops, 
 if small, become circular discs with rounded 
 edges; if large they are oval, or spread out into 
 elongated, irregularly ovoidal, or flattened cylin- 
 drical forms. Their shape, however, is changed 
 by the slightest impulse, or inclination of the 
 containing vessel in a way which, perhaps, might 
 best be illustrated by comparing it to the ever- 
 varying elongation, contractions, and irregular 
 swellings, which alter the configuration of an 
 active living leech in a glass of water. The 
 flattened globule, moreover, is much less mo- 
 bile than the rounded one in acid. The former 
 moves sluggishly, even down an inclination, 
 clings to the vessel, and when compelled to move 
 rapidly leaves a tail behind it, like foul mercury. 
 No air-bells attach themselves to it and its 
 brilliancy is sensibly diminished, as if its re- 
 fractive index had altered. 
 
 From this experiment we can very clearly 
 see how the dineric interface changes in shape 
 when an acid or alkali is added to the system. 
 
ELECTRICAL PHENOMENA 53 
 
 The interfacial tension is markedly altered in 
 both cases. In the flotation process the emul- 
 sifying agent alters, in the same way, the inter- 
 facial tension existing between the surface of the 
 water and the air bubble. The result is that 
 the metallic sulphide particles find it more diffi- 
 cult to pierce the water-air interface than when 
 there is no emulsifying agent to make a more 
 coherent film. Thus the oil will make it possible 
 for a larger number of sulphides to adhere to 
 this usually spherical film. 1 
 
 Electrical Phenomena in Flotation 
 
 Such an authority as Thomas M. Baines, Jr., 
 states: 2 
 
 If one turns to " Elementary Lessons in Elec- 
 tricity and Magnetism," by Silvanus Thompson, 
 and studies the fundamental principles of 
 frictional electricity, as given in Chapter I, 
 a clearer idea of the causes of " flotation " may 
 be obtained. The electrical theory was taught 
 last year as possibly explaining flotation phe- 
 nomena to the class in ore-dressing, at the 
 Case School of Applied Science. 
 
 In his article Mr. Baines gives the following 
 summary of requirements for " flotation " from 
 the electrical standpoint: 
 
 1. Ores containing valuable minerals or metals 
 that are good conductors are the only ones 
 suitable for flotation. 
 
 2. To buoy these conductors, it is necessary 
 
 1 " The Flotation Process/' by Stander. 
 
 2 " The Electrical Theory of Flotation," by Thomas M. 
 Baines, Jr., Min. & Sci. Press, November 27, 1915. 
 
54 THE THEORY OF FLOTATION 
 
 to supply electrified bubbles from below to float 
 particles of the conductors that are attached; 
 hence the smaller the bubble, the better the 
 result, the gas being the same. 
 
 3. Some dielectric fluid is necessary to cover 
 the conductor of the bubbles to prevent the 
 dissipation of the electric charge. The thinner 
 the film of dielectric and the greater its dielec- 
 tric strength, the greater the effective attractive 
 force and the more permanent will be the froth. 
 
 4. Some material must be added to the water 
 to increase its conductivity to obtain a clean 
 concentrate; acids in small quantities are now 
 used. 
 
 The following experiments were conducted 
 to illustrate electrical phenomena: 
 
 If powdered galena ore with a limestone 
 gangue be dropped into pure water, most of the 
 powder will immediately sink to the bottom. 
 As the air enclosed by the particles is expelled 
 gradually, one sees the formation of" armored " 
 bubbles, some of which may last for days. 
 Here is flotation without oil or acid. If nitric 
 acid is added, the gas bubbles, formed by the 
 action of the acid on the gangue, will carry up 
 particles of galena, some reaching the surface 
 and bursting, while others too heavily loaded 
 with galena particles will hover just below the 
 surface. These will form clusters, resembling 
 bunches of grapes, and when enough gas bubbles 
 join the clusters, they start upwards toward the 
 surface, but generally before reaching there 
 they are overloaded by particles falling from 
 the bubbles that are bursting at the surface. 
 The bubbles with their loads often resemble 
 balloons, with the galena hanging onto the 
 
ELECTRICAL PHENOMENA 55 
 
 bottoms, as do the baskets of actual balloons. 
 Some of the bubbles will be completely " ar- 
 mored " while others will be nearly free from 
 galena. Another experiment that may be suc- 
 cessfully used in the laboratory for flotation for 
 different sulphides, such as old rusty pyrite 
 concentrate, like sweeping from floors of old 
 mills, is as follows: Mix the ore with bleach- 
 ing powder, some carbonate (say, sodium car- 
 bonate), and water. Put the mixture into a glass 
 beaker and add concentrated nitric acid until 
 red nitrous fumes are given off. Chlorine also 
 will be evolved. The bubbles of gas are so 
 highly charged electrically that pyrite from the 
 Mother Lode between 10- and 20-mesh size was 
 floated, making a complete separation from the 
 quartz gangue. In this experiment nitrous 
 oxide was the active agent, for if the same ex- 
 periment is conducted with sulphuric acid, no 
 such separation takes place. 
 
 Mr. Baines accounts for the electrification of 
 bubbles as follows: 
 
 (a) Two different substances, whether gase- 
 ous, liquid, or solid, when brought intimately 
 into contact and moved one over the other, 
 always produce electrification. 
 
 (6) Difference of temperature of two similar 
 substances in frictional contact will cause elec- 
 trification, the warmer usually being negatively 
 charged. 
 
 (c) Something certainly happens when the 
 surface of two different substances are brought 
 into intimate contact, for the result is that 
 when they are drawn apart, they are oppositely 
 charged. The nature of the charge depends on 
 the substance. Fur rubbed on glass electrifies 
 
56 THE THEORY OF FLOTATION 
 
 the glass negatively; while if glass is rubbed 
 with celluloid it will become positively charged. 
 
 (d) A blow struck by one substance on an- 
 other produces opposite electrical states on the 
 two surfaces. 
 
 (e) The evaporation of liquids is accom- 
 panied by electrification, liquid and vapor as- 
 suming opposite charges, though this is only 
 apparent when the surface is in agitation. A 
 few drops of copper sulphate thrown on a hot 
 platinum plate produces violent electrification, 
 as the copper sulphide evaporates. 
 
 (/) Electrical charges are set up by various 
 other means, such as vibration disruption of 
 material, crystallization, combustion, pressure, 
 and chemical reactions. 
 
 He concludes: 
 
 It would seem easier, therefore, to electrify 
 a bubble than to keep it from being electrified. 
 I assume that the bubbles are electrified, whether 
 by means of air being forced through canvas, 
 by beating air into water with paddles, or by 
 other means. So air bubbles that are electri- 
 fied will attract conductors near them that are 
 free to move. Air, being a poor conductor of 
 electricity, the bubbles as a whole do not dis- 
 charge immediately upon contact with a con- 
 ductor. The only part of the surface discharged 
 is that in immediate contact with the conductor, 
 and this discharged film of air acts as a di- 
 electric and non-conductor to the rest of the 
 bubble, which remains charged. 
 
ELECTRICAL PHENOMENA 57 
 
 The above theory has been tolerated by 0. C. 
 Ralston l and supported by J. M. Callow. 2 
 Ralston states as follows: 
 
 The electric charges on suspended particles 
 allow another possible explanation of flotation 
 phenomena. We find in some of the colloid 
 chemical literature that quartz particles when 
 suspended in water are negatively charged, 
 pyrite particles positively charged, oil droplets 
 negatively charged, and air bubbles negatively 
 charged. The charges are somewhat small 
 compared with the weight of the particles, so 
 that they are hardly strong enough to cause 
 negatively-charged quartz to stick to positively- 
 charged pyrite, as they can have only a few 
 points of contact, and currents in water could 
 easily tear them apart. However, the nega- 
 tively-charged droplet of oil, which is repelled 
 from a negatively-charged particle of quartz, 
 can wrap itself around the positively-charged 
 pyrite particles so that they will stick together 
 and the same applies to air bubbles. The 
 other sulphides known to be flotative have posi- 
 tive charges when suspended in water or can 
 be made to assume positive charges by the use 
 of the proper amount of the proper electrolyte. 
 So it can be seen that the application of these 
 principles gives no difficulty in explaining flo- 
 tation from an entirely new standpoint. 
 
 Callow's theory is stated briefly as follows: 
 
 That oil flotation is an electrostatic process. 
 It is a scientific fact that when a solid particle is 
 suspended in water the water will form around 
 
 1 "Why Do Minerals Float?" by O. C. Ralston, Min. 
 & Sci. Press, October 23, 1915. 
 
 2 "Notes on Flotation," by J. M. Callow, Min. & Sci. 
 Press, December 4, 1915. 
 
58 THE THEORY OF FLOTATION 
 
 the particle a contact-film that generally pos- 
 sesses an electric charge, the amount and polarity 
 of which will depend upon the nature of the 
 surface of the particle and the electrolyte in 
 which it is suspended. The presence of these 
 charges can be demonstrated by the fact that 
 particles possessing them will migrate when 
 placed in an electric field. It has been dem- 
 onstrated that floatable particles have charges 
 of one polarity (positive), and that non-float- 
 able particles have charges of opposite polarity 
 (negative), and that this froth is charged 
 negatively and so attracts the positively-charged 
 or floatable minerals, and repels the negatively- 
 charged or non-floatable ones. It is this, it is 
 believed, that causes the floatable minerals, 
 such as galena or sphalerite, to adhere to the 
 froth and rise, while the gangue minerals, such 
 as silica and limestone, remain in the liquid where 
 they can be discharged as tailings. 
 
 C. T. Durell in his osmotic hypothesis states: 1 
 
 Electricity may manifest itself in various 
 ways, but flotation cannot take place without 
 nascent or occluded gas and that, all theories 
 of flotation, be they electrical or otherwise, must 
 come to osmosis for their solution. 
 
 F. A. Fahrenwald conducted a series of ex- 
 periments to investigate the phase of the process 
 that caused the bond between the flotative min- 
 eral and the bubble carrier. 
 
 Before proceeding to the discussion of the 
 electrical theory, he very wisely stated eight of 
 
 1 " Flotation Principles," by C. T. Durell, Min. & Sci. 
 Press, February 19, 1916. 
 
ELECTRICAL PHENOMENA 59 
 
 the most important fundamental facts of electro- 
 statics. They are : 1 
 
 A. The production of electricity by friction 
 is a common phenomenon; almost any two 
 bodies become electrified if they are rubbed to- 
 gether. In the case of several instances, con- 
 siderable force is then necessary in order to 
 separate them. Attraction or repulsion also 
 occurs when an electrified body is brought near 
 bodies that have been subjected to friction, and 
 if these are light enough (as -bits of pitch, feathers, 
 wood, paper, etc.) they may be lifted. Bodies 
 may also become electrified by coming in con- 
 tact with other bodies that already carry a 
 charge. In this case the first body receives 
 electricity of the same sign from the charged 
 body and is then repelled. 
 
 B. Bodies that when electrified at one point 
 are immediately electrified all over are called 
 good conductors; those over which the charge 
 diffuses slowly are poor conductors. All metals, 
 many metallic ores, graphite, ordinary distilled 
 water, and aqueous solutions of salts are good 
 conductors. 
 
 C. If a piece of metal, or other conducting 
 material held in the hand is rubbed against a 
 non-conductor say, a piece of dry flannel 
 only the non-conductor appears afterward to be 
 electrified. The reason is that the electri- 
 fication produced on the metal spreads over the 
 hand, arm, and body of the experimenter to the 
 floor and walls of the room. If, however, the 
 conductor is insulated, the degree of its electri- 
 fication cannot be increased or decreased. 
 
 D. By whatever process a body is electrified 
 there is always an equal amount of electricity 
 of the opposite sign, which may reside upon the 
 
 1 "The Electrostatics of Flotation," by F. A. Fahren- 
 wald, Min. & Sci. Press, March 11, 1916. 
 
60 THE THEORY OF FLOTATION 
 
 walls of the enclosing room or upon some other 
 surface insulated from the conductor. Bodies 
 carrying opposite charges, when brought in 
 contact or connected by a conductor, become 
 discharged. If the charges are equal they are 
 neutralized, but if one carries more than the 
 other the system takes on the sign of the excess 
 charge. 
 
 E. If these bodies are strongly electrified, 
 discharge can take place through an appreciable 
 thickness of non-conducting material, such as 
 air, oil, or glass. This discharge is facilitated 
 by the presence of sharp projections upon either 
 body. 
 
 F. (a) The space between two charged bodies 
 is filled with lines of force that tend to move a 
 contained body in the direction of the local lines 
 of force leading to the surface carrying the op- 
 posite sign. 
 
 (b) These lines of force do not penetrate the 
 surface of the conductors forming its boundaries 
 and a hollow conductor is electrified on its 
 outside or inside surface only, depending upon 
 whether the opposite charge resides upon one 
 contained without the sphere or upon one con- 
 tained within and insulated from the shell. In 
 the latter case the entire field is contained within 
 the inner surface of the sphere, and in the 
 former case there is no charge within the hollow 
 conductor. 
 
 G. The force .exerted between two small 
 charged bodies as given in the equation, 
 
 in which q and q' are the charges in electro- 
 static units carried by each of the two bodies 
 and d is the distance between their centers of 
 
ELECTRICAL PHENOMENA 61 
 
 charge. 1 If the bodies are separated by a 
 medium other than air a factor K y known as its 
 dielectric coefficient, must be used and the 
 equation becomes 
 
 jF^i.ffl! 
 
 fc" d*' 
 
 H. Matter itself is not acted upon by an elec- 
 tric force, which acts only between different 
 quantities of electricity. When a conductor is 
 introduced into an electric field it represents a 
 gap or an interruption of the lines of force, 
 resulting in an electrification of its surfaces only, 
 that part becoming positive which is presented 
 toward the negative boundary of the field and 
 the reverse. In other words, the original field 
 is divided into two. This same effect is produced 
 in the case of a poor conductor but to an ex- 
 ceedingly small degree. This explains the at- 
 traction of small bodies by another that has 
 been electrified by friction, in which case elec- 
 trification by influence precedes attraction, and 
 what is really observed is attraction between 
 opposite electric charges. 
 
 The following experiments were conducted by 
 Fahrenwald (see Fig. 14) which should serve 
 to check the various points, as outlined by Mr. 
 Baines, as requirements for the electrical theory. 
 
 1. Galena ore was ground in an agate mortar 
 and poured from an agate spoon (to prevent 
 discharge of positive electricity, if present, from 
 ore) between two plates of an electrostatic ma- 
 chine. The material was deflected as shown. 
 Plates were electrified almost to discharge 
 point. This shows that galena ground under 
 
 1 The force by a charged sphere acts as if originated at 
 the center. 
 
62 
 
 THE THEORY OF FLOTATION 
 
 ~ 
 
 x 
 
 
 rJ?n_ : 
 
 % 
 
 
 Eo: 
 
 Q 
 
 _u_u_ : 
 
 i! 
 
 
 rijc : 
 
 1 
 
 
 S&; 
 
 Fig. 1. 
 
 Fig, 4. 
 
 ''' V uv\ 
 
 
 
 *: ^ 
 
 o 
 
 :^p: 
 
 'V 1 ' 
 
 o 
 
 -^- 
 
 '.* 
 
 
 
 ' 
 
 
 
 fe 
 
 
 rY^'^^t. 
 
 : o-t-Q-. : 
 
 Fig. 2. 
 
 - 0- '_ - 
 
 Fig. 5. 
 
 Connecting Spheres, connected 
 by conductor (water) 
 
 FIG. 14. 
 
 Fig. 8. 
 
ELECTRICAL PHENOMENA 63 
 
 insulating conditions carries a charge and that 
 a particle of this nature, suspended in a non- 
 conductor in an electrostatic field, is attracted. 
 
 2. Ore was ground in conducting earthed 
 mortar and poured from earthed spoon. De- 
 flection of only a very few particles was shown. 
 Perhaps the deflected particles were insulated 
 with oil or did not come in contact with earthed 
 surface. 
 
 3. Ore treated as in No. 1 and poured between 
 glass sides of a cell. Glass was 1 mm. thick 
 and separated by two centimeters. Potential 
 between plates of machine was 8500 volts. 
 Deflection as shown. The interposition of 
 glass had very little effect. 
 
 4. As in No. 3, but the cell was full of water. 
 Used conductivity, tap, and acid water. No 
 deflection. This indicates that particles charged, 
 or otherwise, suspended in a conducting solu- 
 tion (i.e., enclosed within our hypothetical 
 conducting sphere) are not affected by electro- 
 static forces without. 
 
 5. Cell contained ore and nitric acid solution 
 to generate gas. Neither bubble rising nor ore 
 particles dropping showed deflection. Potential, 
 10,000 volts. The conditions here duplicate 
 those of No. 4. 
 
 6. Bubbles blown through canvas into water 
 or acid solution were not deflected. A charge 
 of bubbles flowing in one direction would pro- 
 duce an electric current, and even if they were 
 charged they could not be attracted, as here 
 again the charges are enclosed in a conducting 
 material. 
 
 7. Ore poured into cell containing gasoline. 
 There seemed to be a slight deflection. 10,000 
 volts between plates. Conditions here should 
 not differ greatly from those of No. 3. Solution 
 may not have been sufficiently non-conducting. 
 
 8. Solution placed in electrolytic cell, ar- 
 
64 THE THEORY OF FLOTATION 
 
 ranged as shown, gave no deflection of ore or 
 bubble with conducting or non-conducting solu- 
 tion. Both ions and charged colloids are sus- 
 ceptible to this treatment, and no doubt they 
 would move easier than the large body and so 
 lessen the potential on the larger masses. 
 
 9. The water itself was electrolyzed to furnish 
 gas. A two-way switch gave either hydrogen 
 or oxygen at the bottom pole, which was covered 
 with a layer of ore. Both gases carried ap- 
 parently equal amounts of ore with equal 
 readiness. Bubbles in either case, upon striking 
 the upper plate, did not discharge their burden 
 of ore, no matter what the sign of electrode. 
 
 10. Set up as in No. 9, except that gas was 
 furnished by action of nitric acid on ore. Chang- 
 ing of sign produced no discernible effect upon 
 bubble or ore or upon bubbles with load when 
 coming in contact with upper electrode plate. 
 
 Preferential Flotation 
 
 The term " Preferential Flotation " has. often 
 been confused with that of " Selective Flo- 
 tation. " " Preferential flotation " is the term 
 applied to that process by which one mineral is 
 separated from another, both being amenable 
 to the flotation treatment. " Selective flota- 
 tion," on the other hand, means the flotation 
 of a valuable mineral in the presence of waste 
 material. Making a froth concentrate of galena 
 and blende from a lead-zinc ore is a sample of 
 selective flotation, but if two separate con- 
 centrates, one containing a high percentage of 
 lead and the other a high percentage of zinc, 
 are made by means of two or more different 
 
ROASTING PROCESS 65 
 
 treatments, the process would be " preferen- 
 tial/' * 
 
 So far the chief methods of preferential flota- 
 tion can be classified into these three groups: 
 1. Roasting Methods. 2. The Use of a Chemical 
 Solution. 3. Controlling Flotation. 
 
 Roasting Process. The roasting process was 
 developed chiefly by Wentworth, Ramage, and 
 Horwood. This process really consists in the 
 deadening of certain sulphides by short and 
 slight roasts, while other sulphides, which may 
 be present, remain unaffected by the heat. 
 Ramage terms this " fractional roasting/' while 
 Horwood speaks of it as " preferential flotation." 
 The Horwood process of preferential flotation is 
 practically the same as the processes of Went- 
 worth and Ramage. 
 
 The Wentworth Process: 
 
 " The process consists in the preliminary 
 treatment of ore mixtures containing several 
 sulphides, which converts some of the sulphides, 
 superficially at least, into metallic compounds 
 which are differentiated in their behavior " with 
 respect to flotation processes as commonly prac- 
 ticed. To the words of a later patentee, the 
 surfaces of such minerals as galena, pyrite, and 
 chalcopyrite are " deadened " by a very short 
 and slight roast in a roasting furnace, while the 
 sphalerite is unaffected. Thus the sphalerite 
 can be removed by flotation from such an ore, 
 leaving the other sulphide minerals to be removed 
 by other means. A few minutes heating at a 
 dull-red heat has been found to be sufficient. 
 
 1 "Advancement and Present Status of Preferential 
 Flotation, " by H. J. Stander, Min. & Eng. World, Nov. 18, 
 1916. 
 
66 THE THEORY OF FLOTATION 
 
 The Ramage Process: 
 
 " This process has for its object the separation 
 of the valuable minerals from such ore as chal- 
 copyrite, bornite, or erubescite, and mixtures of 
 the same with pyrite, in which ores the copper 
 is in chemical combination with the iron; and 
 also from such ores containing zinc blende. The 
 method is also applicable to compound ores, 
 such as those of the Cobalt district and other 
 sulph-arsenides." " The principle of the process 
 is founded on the combination of fractional 
 roasting with chemical floating/ 7 Ramage's 
 introduction of the term " fractional roasting " 
 is particularly felicitous, as it more accurately 
 describes the method than does the term " pref- 
 erential flotation/ ' used by Horwood. 
 
 Ramage described the process by the use of 
 three examples, which are decidedly interesting. 
 The first example is of an ore containing iron 
 pyrite and chalcopyrite, with a content of about 
 5 per cent copper and 30 to 40 per cent sulphur. 
 The ore is roasted at about a red heat long 
 enough to decompose the pyrite slightly and 
 not affect the chalcopyrite. " The burnt ore is 
 then crushed to at least 15 mesh and passed 
 through a solution of acid sulphate of soda and 
 nitric acid (the solution being formed by adding 
 nitric acid to sulphate of soda), which solution 
 is kept near the boiling point. The copper 
 sulphide immediately rises to the top of the 
 bath and can be slammed off." The copper 
 dissolved in the bath can be recovered in known 
 ways. This method of flotation (hot acid bath) 
 is not new, having been patented by DeBavay, 
 Potter, Delprat, and others. The fractional 
 roasting had been previously patented by Went- 
 worth, and so the only thing that seems new is 
 the combination of methods. 
 
 A second example is that of an ore containing 
 
ROASTING PROCESS 67 
 
 pyrite, chalcopyrite, and zinc blende in quantity. 
 The ore is roasted at a temperature of not 
 over 600 C., so that only the iron pyrite is 
 deadened. The roasted ore is then subjected to 
 the acid sulphate of soda solution for flotation 
 of the unchanged sulphides of zinc and of copper. 
 This product is then roasted at about 700 C., 
 until all of the zinc sulphide is decomposed and 
 the copper sulphide unchanged. This mixture 
 is treated with a solution of dilute sulphuric acid 
 for the dissolution of the zinc, to be recovered 
 from solution by any familiar process, such as 
 electrolysis, the copper sulphides being sent to 
 the copper smelter. There are certainly most 
 interesting facts disclosed in this patent. The 
 great resistance of copper sulphides to the roast- 
 ing process, as compared with the sulphides of 
 zinc, is something new and will be a most valu- 
 able characteristic, if true. 
 
 The third example is that of the ores of the 
 Cobalt district, Canada, where cobaltite, nic- 
 colite, chalcopyrite, pyrite, and native silver 
 occur. All the sulphide and sulpharsenide 
 minerals are floated, leaving the silver in the 
 gangue. The sulphides are roasted at about 
 800 C. and everything is decomposed except 
 the copper sulphide, which can be floated from 
 the calcine. Again we have mention of the 
 almost incredible property of copper sulphides 
 to resist roasting. 
 
 The next patent was that of H. A. Wentworth, 
 amplifying on this former patent in claiming the 
 chemical change of minerals as a method of 
 separating them preferentially by flotation. He 
 had in mind particularly the treatment of the 
 ore with chlorine, which would sink when sub- 
 jected to a film-flotation process, while others 
 would have their flotative properties enhanced. 
 As an example, a mixture of zinc and iron sul- 
 phides, when treated with chlorine gas in a 
 
68 THE THEORY OF FLOTATION 
 
 slightly damp state, is so altered that the 
 blende will float on a film-flotation machine 
 much better than before treatment, while the 
 pyrite has a coating formed over its surface 
 which is much more easily wetted, so that it 
 will sink. Still a further example is the appli- 
 cation to the separation of pyrite and chal- 
 copyrite. The latter is attacked much slower 
 than pyrite; hence it can be floated when both 
 are present. A similar behavior of the minerals 
 is observed when they are suspended in water 
 containing dissolved chlorine in the proper con- 
 centration, but the best work seems to be done 
 with minerals fed onto one of the film-flotation 
 machines, such as that of H. E. Wood of Denver, 
 although Wentworth gives the design of one of 
 his own in the specification. It is easy to see 
 that with chlorine water and one of the me- 
 chanical frothing methods of flotation the soluble 
 coatings that are formed on the surfaces of the 
 minerals would be simply washed off and the 
 preferential part of the flotation lost. Tests in 
 our laboratory seem to show this. So far as is 
 known to me, this process is not being used. 
 
 The Horwood Process: 
 
 It depends upon the " deadening " of galena 
 and pyrite in a short roasting at 300 to 500 C., 
 whereby the galena is coated with lead sulphate 
 and the pyrite with iron oxide, while the sphal- 
 erite is unaltered. This allows a separation of 
 the undesirable zinc from the lead-iron-silver 
 product and allows their separate marketing. 
 This process has received more careful attention 
 than any other process, and reference to original 
 articles is best. 1 According to the data given in 
 
 1 T. J. Hoover, "Concentrating Ores by Flotation," 
 Min. & Eng. World, July 18, 1914; Eng. & Min. Jour. 
 (1914), 97, p. 1208; Min. & Sci. Press, April 18, 1914, 
 p. 657; Metal. & Chem. Eng. (1914), No. 12, pp. 350 and 
 592. 
 
ROASTING PROCESS 69 
 
 some of this literature, it appears that it is 
 possible to take a flotation concentrate contain- 
 ing 36 per cent Zn, 15 per cent Pb, and 22 oz. 
 Ag per ton, and divide it into a zinc product 
 running as high as 50 per cent Zn, 7 per cent Pb, 
 and 15 oz. Ag, and a lead product containing 
 38 per cent Pb, 8 per cent Zn, and 42 oz. Ag 
 per ton. This is of great interest to all pro- 
 ducers of " complex sulphide" ores, as the mill- 
 ing of coarsely crystalline material has presented 
 much difficulty in the past for the reason that 
 some finely-divided material (slime) is bound to 
 form in crushing, and while the combined lead 
 and zinc sulphides can be floated nowadays 
 without much difficulty, the mixture is of far 
 less value than the two minerals separated. 
 This is important enough, not to speak of the 
 possibility of treating the microcrystalline sul- 
 phide ores and those containing gangue of high 
 specific gravity, such as barite. While flo- 
 tation has been a boon to the concentration of 
 all sulphide slimes, preferential flotation is much 
 more important for the ores containing unde- 
 sirable combinations of sulphides. Hence Hor- 
 wood's work should receive the highest praise. 
 
 Another detail, as regards the process, is that 
 35 Ib. of sulphuric acid per ton of ore is neces- 
 sary and 2 to 3 Ib. of oleic acid for the flotation 
 of the unaltered zinc. All of this appeared in 
 Horwood's first patent, No. 1,020,353, of 1912, 
 and he later came out with improvements on 
 the process in patent No. 1,108,440, of 1914. 
 In this later patent he stated that he had found 
 there was a tendency for the silver to follow 
 the zinc, which is undesirable, but that this 
 could be prevented by simply washing away all 
 soluble salts on the concentrate before it was 
 subjected to the deadening roast. This re- 
 duces the amount of oxidized zinc formed and 
 lost by solution in the dilute acid in the mill- 
 
70 THE THEORY OF FLOTATION 
 
 water as well as allowing the silver to become 
 deadened to a greater extent. He also found 
 that the most successful flotation took place 
 with the pulp at a temperature of about 120 F. 
 
 It will be seen that the Horwood process has 
 been applied only to concentrates from previous 
 flotation or from other concentration processes. 
 This is the logical place to apply it, as there is 
 no object in leaving a non-flotative galena or 
 other sulphide mixed with gangue, by using the 
 process on crude ore. The same remark applies 
 to many of the other processes. To be sure, 
 there has been some success in the Australian 
 mills as well as in the United States in the treat- 
 ment of mixed galena-sphalerite concentrates 
 from flotation machines on concentrating tables. 
 As an example, the Timber Butte mill is treating 
 the flotation concentrate of a zinc ore containing 
 some zinc concentrate carrying 53 per cent Zn, 
 1.5 per cent Pb, and 4 per cent insoluble. How- 
 ever, this method has not always met with the 
 best results, and where the proportions of lead 
 and zinc in ordinary complex sulphide concen- 
 trates are about equal it is quite hard to get two 
 products that are sufficiently pure. Where it 
 can be done, it is certainly more desirable than 
 the more complex fractional roasting and prefer- 
 ential flotation processes of Horwood, Went- 
 worth, and Ramage. 
 
 The Use of Chemical Solution. In the 
 Lyster process the preferential action is brought 
 about by the use of a chemical solution. This 
 process has received some consideration by 
 
ROASTING PROCESS 71 
 
 the Zinc Corporation. The process is as 
 follows : 
 
 This process is carried on in neutral or alkaline 
 solutions (never acid) of the sulphates, chlorides, 
 or nitrates of calcium, magnesium, zinc, iron, 
 acid sodium, or sodium-potassium sulphates. 
 Using eucalyptus oil or a similar frothing agent, 
 the agitation of the pulp takes place in centrif- 
 ugal pumps, throttled to give further agitation, 
 and discharging into spitzkasten with constricted 
 tops. It is said that a galena froth can be 
 collected carrying 55 to 60 per cent lead and 
 that by sending the tailing to a second machine 
 with further addition of oil, the sphalerite can 
 be floated. 
 
 It will be noticed that this, with the possible 
 exception of Wentworth's second patent, is one 
 of the first proposals to give a true " preferen- 
 tial " flotation to a mixture of sulphides, as the 
 roasting methods above mentioned involve an 
 actual conversion of some of the minerals, so 
 that sulphide surfaces are no longer presented 
 to the oils and air bubbles in the flotation opera- 
 tion. Lyster's process, however, involves the 
 actual flotation of one mineral in preference to 
 another, unless the chemicals used are chemically 
 altering certain of the sulphides so that they 
 cannot float. Anyone who has worked with 
 mixtures of sulphides has doubtless noticed that 
 greater care is necessary in the flotation of zinc 
 sulphide than in floating galena; in fact, galena 
 is one of the most easily floated minerals outside 
 of molybdenite, and zinc sulphide is considerably 
 
72 'THE THEORY OF FLOTATION 
 
 more difficult. The fact that a froth running so 
 high in lead, as the Lyster process is reported 
 to give, would also tend to make one suspi- 
 cious that rather poor flotation conditions are 
 maintained, so that only the most easily floated 
 material (galena), and only the purest of that, is 
 coming up in the first product. This takes 
 place even in the presence of considerable oil, 
 whenever flotation conditions are poor, on almost 
 any type of machine, and while the grade of 
 froth that is obtained is high, the extraction is 
 poor on account of the fact that only the best 
 mineral is floating. It is possible that some 
 such combination of results as this has caused 
 the process not to be considered unfavorably. 
 
 Controlling Flotation. It is a known fact 
 that the percentage of extraction by flotation 
 of a sulphide in an ore depends on such factors 
 as the degree of fineness of the gangue and of the 
 mineral particles and so also do some of the other 
 variables such as the amount and kind of oil 
 or acid used, the time and speed of agitation and 
 the temperature at which the experiment is con- 
 ducted. And furthermore, we know that one sul- 
 phide is more flotative than another, a very impor- 
 tant property in this particular phase of flotation. 
 
 In 1913 Nutter and Lavers made use of these 
 different behaviors of sulphides under different 
 conditions, and brought out their process for 
 preferential flotation of minerals. It is "a 
 process for concentrating ores which consists 
 in treating the crushed ore by a flotation process, 
 two or more times under different conditions, 
 
CONTROLLING FLOTATION 73 
 
 to obtain froths or scums, having the constitu- 
 ents of each in certain ratios of size, and there- 
 after subjecting the powdered mixture contained 
 in each froth to a classifying step to separate the 
 constituents." According to the description 
 of their process, the one sulphide can be sepa- 
 rated from the other by correctly controlling 
 certain conditions in the flotation plant. 
 
 The following is an example cited by the in- 
 ventors: 
 
 An ore, containing galena, chalcopyrite, and 
 sphalerite, is crushed and admitted to the ^flo- 
 tation machine. Using cresylie acid without 
 any mineral acid, it is possible to float most of 
 the chalcopyrite and a small quantity of galena. 
 So, from this first treatment, a chalcopyrite 
 concentrate is obtained, the residue being given 
 a second treatment, and with the help of sul- 
 phuric acid, a galena froth concentrate can be 
 produced, most of the sphalerite being left in the 
 tailings, from which it can then be recovered. 
 In case the ore contains only copper and zinc 
 sulphides, a preferential action can be produced 
 by the use of eucalyptus oil or creosol. No 
 mineral acid is necessary, and a concentrate, 
 containing most of the chalcopyrite and very 
 little sphalerite, can be obtained. 
 
 In a method where the separation of one 
 mineral from another depends largely on certain 
 conditions, the process becomes somewhat deli- 
 cate, especially in the case of flotation. Never- 
 theless it seems as if this is one of the chief ways 
 in which preferential flotation will be successfully 
 developed in the future. 
 
 /The phenomena in connection with preferen- 
 
74 THE THEORY OF FLOTATION 
 
 tial flotation, according to Thomas M. Baines, 
 Jr., furnish new evidence to strengthen the 
 electrical theory. The following interesting 
 material is taken from his article: 1 
 
 The simplest experiment, demonstrating pref- 
 erential flotation, may be performed as follows: 
 Upon a 4-in. watch-glass, place a little galena, 
 blende, and quartz of 20 to 30-mesh size. Add 
 dilute nitric acid and place the glass under a 
 microscope. The acid attacks the galena, form- 
 ing bubbles of H 2 S gas that adhere to the galena. 
 The particles of galena are electrified also, as can 
 be seen by the actions of the particles. The 
 blende and quartz are not attacked. If the ore 
 had been finely pulverized and dilute nitric acid 
 added, the bubbles of H 2 S would have been 
 sufficient to float the galena, leaving the blende 
 and quartz at the bottom. However, with fine 
 particles, some blende and quartz would have 
 been entrapped, brought to the surface, and 
 held there by surface tension. The bubbles are 
 not sufficient to float the coarse galena, but by a 
 vanning motion of the glass, the galena will 
 collect, being brought and held together by the 
 H 2 S bubbles, forming a mat which is lighter / 
 than quartz or blende and can, therefore, be 
 panned off, leaving the blende and quartz. 
 This experiment seems to show that the H 2 S is 
 charged oppositely to the galena. 
 
 If more concentrated nitric acid had been 
 added to the ore, the blende would have been 
 attacked and the process would have been re- 
 versed, the blende forming the mat while galena 
 and quartz were left behind. If dilute sulphuric 
 acid, one part of acid to four of water, had been 
 used, then both the blende and galena would 
 
 1 " The Electrical Theory of Flotation," Min. & Sci. 
 Press, December 11, 1915. s 
 
CONTROLLING FLOTATION 75 
 
 have been attacked and if the ore had been 
 finely pulverized, no " preferential " separation 
 would have resulted, both galena and blende 
 finding their way into the float concentrate. 
 However, with coarse material, the blende is 
 much more highly charged than the galena and 
 if the watch-glass be tapped and the contents 
 given a vanning motion, the blende will gather 
 most of the H 2 S bubbles and finally float, leaving 
 galena and quartz behind. This shows that 
 the electrification of minerals varies with differ- 
 ent acids and also with different strengths of the 
 same. This action of one mineral, " robbing " 
 the others of their bubbles, has not been utilized 
 in practice, as yet, but there is no reason why 
 " preferential " separations could not be made 
 on a large scale, utilizing this principle. Less 
 air or gas would be necessary than in the present 
 type of frothing cells and a clean concentrate 
 would be produced at once. A separation of 
 blende, galena, pyrite, and quartz may be made 
 as follows: 
 
 Add dilute sulphuric acid and pan off the 
 blende; then add dilute nitric acid and pan off 
 the galena; then add concentrated sulphuric 
 or nitric acid, which attacks the pyrite so that it 
 may be panned off. 
 
 Or the separation may be made with nitric acid 
 alone, varying the strengths; with sulphuric 
 acid, by use of the " robbing " action described 
 above or by use of hydrochloric and other re- 
 agents that attack one or another of the minerals 
 more strongly than the others. If galena or 
 blende and magnetite be treated with dilute sul- 
 phuric acid, the magnetite will not be acted upon 
 by the acid, but some of the H 2 S bubbles gener- 
 ated by the sulphide will attach themselves to 
 the magnetite, provided the bubble is formed 
 near the magnetite. This illustrates the fact 
 that electrical conductors in a conducting liquid 
 
76 THE THEORY OF FLOTATION 
 
 attract electrified bubbles. A slight jar, how- 
 ever, will displace these bubbles; or a piece of 
 sulphide in close proximity will rob the magne- 
 tite of the bubble, magnetite being a poor con- 
 ductor. 
 
 Referring to the article on page 668 of the 
 Mining and Scientific Press of October 30, 1915, 
 describing a patent for preferential flotation of 
 blende, galena, and pyrite, the second paragraph 
 read: " The new process consists of treating 
 ores in a medium (i.e., sulphuric acid and sodium 
 sulphide) that wets the zinc sulphide and which 
 does not wet the lead sulphide or pyrite. " This 
 phenomenon brings out nicely the part played 
 in flotation by the " dielectric film." When 
 thiosulphates, sulphites, or bisulphites are acted 
 upon by sulphuric acid, there is more to the 
 phenomenon than formation of SO 2 gas. The 
 following reactions take place when blende and 
 galena are treated with sulphuric acid and so- 
 dium sulphide : 
 
 ZnS+PbS+2 H 2 S0 4 = ZnS0 4 + PbS0 4 +2 H 2 S, 
 Na 2 S0 2 + H 2 S0 4 = Ns 2 S0 4 +H 2 0+S0 2 , 
 2 H 2 S+S0 2 = 2 H 2 0+3S. 
 
 This sulphur thus formed is in a very fine 
 state and acts as a dielectric film about the 
 galena, for which it had a great attraction. 
 Therefore, no frothing agent is needed in this 
 case, as the dielectric film about the bubbles is 
 formed by the sulphur similarly to the films 
 of oil formed in the ordinary flotation processes. 
 In the last paragraph of the above-mentioned 
 article on " Preferential Flotation," the statement . 
 is made that " the procuring of the effect aimed 
 at, is dependent upon the presence of a frothing 
 agent, only when a reducing gas is introduced 
 into the medium. It is not independent of the 
 presence of a frothing agent in the flotation 
 
CONTROLLING FLOTATION 77 
 
 medium, when a reducing gas is generated in the 
 flotation medium by a reaction of a substance 
 introduced into it." In other words, if sulphur 
 or any other " dielectric " is liberated in a very 
 fine state, by a " reaction of a substance in- 
 troduced/ 7 no frothing agent need be used. 
 
 This action may be nicely illustrated by 
 taking 20- to 30-mesh galena and blende and 
 treating them with dilute nitric acid on a watch- 
 glass and observing the result under a micro- 
 scope. The galena will gather all the H 2 S bub- 
 bles, when vanned. Now if the sulphuric acid 
 is added and the watch-glass be tapped and the 
 particles moved over one another, the H 2 S 
 bubbles on the galena will be robbed by the 
 blende. Sulphur may be seen surrounding the 
 bubbles, the reaction being as follows: 
 
 ZnS +PbS + 2 H 2 S0 4 = ZnS0 4 + PbS0 4 + 2 H 2 S, 
 
 HoS + H 2 S0 4 = S0 2 + 2 H 2 + S, (1) 
 
 2 H 2 S + S0 2 = 2 H 2 O + 3 S. (2) 
 
 In (1) the sulphur is formed from the decom- 
 position of H 2 S; and would be charged oppositely 
 to the sulphur formed by the decomposition of 
 S0 2 gas. In (2) we have both negatively and 
 positively charged sulphur particles. 
 
 In conclusion, Mr. Baines states: 
 
 It may be well to call attention to the fact that 
 for laboratory experiments in preferential flo- 
 tation, any one of the sulphides may be separated 
 from the other sulphides, (a) by the use of gome 
 reagent that attacks this particular sulphide 
 and not the others, (6) by the use of a reagent 
 that attacks one sulphide more vigorously than 
 the others (in this case, the vanning motion 
 allows the sulphide more highly charged to 
 gather up the bubbles from the sulphides less 
 highly charged, and if sufficient bubbles are col- 
 lected, the mass of bubbles and sulphides will 
 
78 THE THEORY OF FLOTATION 
 
 float). If not sufficiently buoyed, the mass 
 remains submerged, but it is lighter than the 
 other sulphides of gangue minerals and can be 
 panned off or separated by hydraulic classi- 
 fication. 
 
 The second point of interest is the formation 
 of a frothing agent within the pulp, when reac- 
 tions take place that liberate dielectric sub- 
 stances in a very fine state, electrically charged. 
 
 The third point is that laboratory experiments 
 may not work out in practice, due to failure to 
 understand the nature of the electrical charges 
 of the bubbles, dielectrics, and particles of ore. 
 A little stronger reagent or a different way of 
 frictionally electrifying the bubbles and pulp, or 
 too thick a film of dielectric or frothing agent, 
 causes the attraction to cease or change. It is 
 no wonder that great difficulty has been ex- 
 perienced' in the practical application of flotation 
 to ores, when such delicate electric forces have 
 to be considered. 
 
CHAPTER IV 
 THE FLOTATION OF OXIDIZED ORES 
 
 Concentration of natural sulphide ores by the 
 flotation process has met with such success that 
 attempts have recently been made to apply the 
 process to the flotation of ores other than natural 
 sulphides. 
 
 A recent article by 0. C. Ralston and Glen L. 
 Allen 1 covers quite thoroughly the work done 
 on the subject up to date, and what follows is 
 largely taken from their work. 
 
 Flotation of oxidized minerals depends upon 
 preliminary " sulphidizing " by any method 
 that will convert at least the surface of the 
 mineral particles to a sulphide of the metal. 
 This step is followed by flotation of the artificial 
 sulphide, which results in a concentration of the 
 valuable metals in the low-grade oxidized ore 
 being treated. 
 
 The methods of sulphidizing so far investigated 
 are as follows: 
 
 1. By the use of hydrogen sulphide on either 
 the dry or wet crushed ore. 
 
 2. By the use of solutions of the various 
 sulphides and sulpho-compounds of sodium. 
 
 3. By the use of solutions of the various 
 sulphides and sulpho-compounds of calcium. 
 
 1 "The Flotation of Oxidized Ores," by O. C. Ralston 
 & Glen L. Allen, Min. & Sci. Press, July 29, 1916. 
 79 
 
80 FLOTATION OF OXIDIZED ORES 
 
 4. By the use of a sulphur vapor. 
 
 5. By the use of a sulphuretted oil. 
 
 6. With colloidal sulphur. 
 
 It has been found that treatment by some of 
 these methods will form a film of sulphide over 
 the surface of the particles of such minerals as 
 lead carbonate or copper carbonate, whereas 
 in the other cases the mineral particles are 
 sulphidized to the core. Other methods failed. 
 
 By the Use of Hydrogen Sulphide. In sul- 
 phidizing with hydrogen sulphide gas, as applied 
 to lead-carbonate ores/ the best method of ap- 
 plying the hydrogen sulphide gas is in a tumbling 
 barrel with the gas inlet in the end. It is also 
 found that a low extraction and likewise a low- 
 grade concentrate of lead is obtained if an 
 attempt is made to float the blackened sulphide 
 (after treating with H 2 S) without previously 
 acidifying the pulp. The concentrate is cleaner 
 but the extraction still low. Only by prolonged 
 treatment by H 2 S gas can the extraction of lead 
 be raised to commercial grade. 
 
 Hydrogen sulphide can be generated quite 
 cheaply. With iron matte available at $5 to 
 $10 per ton, the cost of the H 2 S gas resulting, 
 including labor, etc., is between $30 and $50 
 per ton. A ton of H 2 S gas, if it were not for the 
 fact that the gas attacks the metallic particles 
 of the ore with such avidity that by the time 
 the latter are sulphidized sufficiently to permit 
 of good extraction by flotation, they have been 
 sulphidized to the core, could be made to film 
 many tons of ore. 
 
SODIUM AND CALCIUM 81 
 
 Owing to the fact that the value of lead con- 
 centrate obtained is very low as compared to the 
 amount of H 2 S necessary to sulphidize it, this 
 process is not regarded as commercially practi- 
 cable. 
 
 Joseph T. Terry, Jr., states: 
 
 That H 2 S gas is the most satisfactory reagent 
 and can be cheaply produced without the use 
 of acids by the destructive distillation of nu- 
 merous organic substances mixed with sulphur, 
 and that the sulphide filming of the carbonate 
 minerals is best accomplished by introducing the 
 gas into the ore pulp crushed to 80 mesh, with 
 a density *of 20 per cent solid, kept in motion 
 or agitation in an enclosed agitator, or other 
 suitable apparatus, this paralleling conditions 
 when using a solid sulphide. 
 
 By the Use of Solutions of Sulphides and Sul- 
 pho-compounds of Sodium and Calcium. 
 
 Good results on lead-carbonate ores have been 
 obtained when sulphides of sodium calcium were 
 used for sulphidizing agents; also sodium 
 polysulphides Na 2 S 4 , and Na 2 S 5 and the sulph- 
 hydrates of sodium, calcium, and ammonium. 
 Of these the sulph-hydrates seem to be very 
 effective. Different ores require 10 minutes to 
 24 hours of contact with the solutions of sodium 
 sulphide, depending upon the properties of the 
 ore and the strength of the solution, 10 to 20 Ib. 
 per ton of ore usually being sufficient, and should 
 be applied to pulp containing about one ton of 
 water per ton of ore. When a good black color 
 has developed, and the color has ceased to increase 
 in thickness, the pulp is diluted with water 
 
82 FLOTATION OF OXIDIZED ORES 
 
 to a 3 : 1 or 4 : 1 mixture and floated in either 
 mechanically agitated or pneumatic machines. 
 
 By the Use of Sulphur Vapor. Sulphidizing 
 with sulphur vapor has been tried with little 
 success, for the reason that it must be applied 
 at a temperature above the boiling point of 
 sulphur in order to prevent condensation of sul- 
 phur. This means that the ore must be brought 
 to a temperature above 445 C. Pyrite could 
 be used to furnish the necessary sulphur, for 
 when it is heated in a closed space, it gives up 
 half of its sulphur. Sulphur dioxide gas can 
 be reduced to elemental sulphur by passing it 
 through a heated zone in the presence of a re- 
 ducing agent. 
 
 This method has the disadvantages of having 
 to be applied to dried, heated, and finely divided 
 ores. Although it is stated that sulphur vapor 
 was tested at one of the large plants for flotation 
 of oxidized forms of copper, it gave better results 
 than any other method of sulphidizing. 
 
 On oxidized copper ores H 2 S seems to be by 
 far the best sulphidizing agent. It is best ap- 
 plied to wet pulp and seems to cause true filming. 
 As little as J Ib. of sulphur per ton of ore is 
 giving good results in the plant of the Magma 
 Copper Company, at Magma, Arizona. 
 
 For oxidized copper ores containing a fraction 
 of 1 per cent 1 ) 2 to 3 Ib. per ton of ore is giving 
 satisfactory results. 
 
 Calcium polysulphide has been used for some 
 time in a number of the large copper concen- 
 
 1 Sulphides are present, of course. 
 
THE MAUREX MAGNETIC PROCESS 83 
 
 trating mills with indifferent success, and seems 
 to be detrimental in some instances. 
 
 By the Use of Sulphuretted Oil. Much 
 secrecy is observed by a number of plants using 
 sulphuretted oils as to the technical details of 
 this work. 
 
 With Colloidal Sulphur. Oxidized forms of 
 copper, so far as is known, are not floated by 
 colloidal sulphur. Neither have the silicates 
 of copper been floated. 
 
 It is a peculiar fact, but repeated attempts to 
 float natural sulphides along with sulphidized 
 minerals ha^e failed, as the sulphidizing agents 
 cause trouble with the flotation of natural sul- 
 phides. By careful adjustment this difficulty has 
 been solved in one plant, though the details are 
 not available. 
 
 The treatment of zinc ores and carbonates, as 
 a whole, has been unsuccessful. The sulphide 
 film does not adhere very strongly and hence 
 comes off too soon. 
 
 So far as the writer is aware, in all of the sue-- 
 cessful work in floating oxides and carbonates, 
 there has been an alteration of the oxide to sul- 
 phide. A number of parties claim to be success- 
 ful in the flotation of copper carbonates without 
 sulphidizing, and others in the flotation of schu- 
 lite, fluorite, and magnetite. 
 
 The Maurex Magnetic Process. This proc- 
 ess was invented and patented by A. A. Lock- 
 wood. Various blendes of crude oils are used in 
 the proportion of 15 to 20 Ib. (or f to 1 per 
 cent) of oil per ton of ore, to which is added 
 
84 FLOTATION OF OXIDIZED ORES 
 
 an equal quantity of magnetite, ground to 100 
 mesh. This mixture of oil and magnetite forms 
 a permanent paint, which, no matter how finely 
 it may be divided or broken up, will always be 
 found to be composed of the two substances in 
 the same ratio. The selective affinity of the 
 oil in the magnetic mixture enables it to adhere 
 to any particle of valuable . mineral, either sul- 
 phide or oxide, contained in the ore, with which 
 it may come in contact, forming a rich mag- 
 netic-oil-mineral mixture containing little or 
 no worthless gangue. 
 
 In practice the crushed ore and water, to- 
 gether with a regulated quantity of oil mix- 
 ture, are fed through a horizontal tube revolving 
 slowly, which contains several hundred pounds of 
 J-inch rough iron shot. The shot becomes 
 oiled and collects the mineral particles, both 
 fine and coarse, in the form of a paste that ad- 
 heres. This paste is continuously broken away 
 from the shot by attrition and flows with the 
 pulp through a screen at the opposite end of 
 the agitator tube into a shaking tray which feeds 
 it under a powerful electromagnet. The coated 
 mineral particles are attracted by the magnet 
 from the flowing stream of pulp to the under- 
 side of an endless belt traveling under the mag- 
 net at right angles to the shaking tray, thereby 
 suspending them until they are carried out of the 
 magnetic field, when they are washed off by a 
 spray of water into the concentrate box provided. 
 
 The points of advantages claimed for this 
 process are the following: 
 
THE MAUREX MAGNETIC PROCESS 85 
 
 1. The ore need only be ground fine enough to 
 free the mineral particles from the gangue, in 
 some cases being only crushed to 5 mm. 
 
 2. Both sand and slime are treated together 
 in one operation, so that no classification is 
 necessary. 
 
 3. This process is suited to the treatment of 
 practically all the sulphide ore, and also suc- 
 cessfully treats lead, copper, and zinc car- 
 bonates and oxides, making extractions up to 
 93 per cent in some cases. 
 
CHAPTER V 
 
 OIL AND OTHER REAGENTS IN FLO- 
 TATION 
 
 Oils Used in Flotation. The question of 
 what oils to use in flotation has probably given 
 more trouble from a practical standpoint than 
 any other. In some cases the situation has been 
 something like this: The manufacturer or 
 producer of oils cannot get any definite ideas as 
 to what kinds or qualities of oils are needed, so 
 he sends to the plant superintendent products 
 or mixtures marked " 240B " or " 1000A," or 
 whatever he happens to call them, with little 
 information as to their chemical composition 
 or physical qualities. One of these oils is used 
 with good results, although he has no information 
 as to the real composition or the physical qualities 
 that have given him the results obtained. When 
 he needs more oil he naturally asks the pur- 
 chasing agent for a quantity of " 240B," or 
 whatever he has been using. The purchasing 
 agent then finds in the meantime either " 240B " 
 has trebled in price, or the producer's plant has 
 burned, or he is unable to deliver for some 
 unknown reasons, but that he can get from an- 
 other producer " 360X," which he is assured 
 is much better and may be cheaper. It is at 
 this point trouble begins. 
 86 
 
COAL-TAR PRODUCTS 
 
 87 
 
 The following are some of the oil's used in the 
 flotation process i 1 
 
 1. Coal-tar Products. 
 
 2. Coal-tar Cresols. 
 
 3. Fuel-oils. 
 
 4. Gas-oil (stove-oil). 
 
 5. Crude-oil Turpentine. 
 
 6. Pine-oils, Wood-tar Oils, Fir-oils, Wood- 
 creosotes, etc. 
 
 Coal-tar Products. Of the coal-tar products 
 cresylic and carbolic acids are the best known 
 reagents. Commercial cresylic acid is an *oily 
 refractive liquid, generally with a red or yellow 
 tinge, has a specific gravity of about 1.044 and 
 consists of approximately 40 per cent meta- 
 cresylic, 35 per cent orthocresylic, and 25 per 
 cent paracresylic acids, the properties of these 
 three isomers being, according to Lunge and 
 Keane: 2 
 
 Acid. 
 
 Boiling-point. 
 
 Solubility of 
 100 parts water 
 at ordinary 
 temperature. 
 
 Orthocresvlic 
 
 Decrees. 
 
 191 
 
 Volumes. 
 
 2 $0 
 
 Metacresylic 
 
 203 
 
 0.53 
 
 Paracresylic . 
 
 202 
 
 1.80 
 
 
 
 
 This acid is much less soluble in water than its 
 homologue, carbolic acid, and is still more easily 
 broken down by sulphuric, which probably ac- 
 
 1 "Oils Used in the Flotation Process, " by An Occa- 
 sional Contributor, Min. & Sci. Press, May 1, 1915. 
 
 2 "Technical Methods of Chemical Analysis," 1911. 
 
88 OIL AND OTHER REAGENTS 
 
 counts for the statement that sulphuric acid may 
 not be used along with either of these weaker 
 acids. 
 
 Coal-tar Cresols. Cresylic acid should be 
 handled carefully, as it gives rise to painful 
 skin wounds, and may easily flash into the 
 operator's eyes. It is well to keep a bottle of 
 olive oil handy as a remedy. 
 
 Cresylic acid is an expensive reagent, costing 
 at least $1.25 per gallon delivered at western 
 American mills in time of peace. It comes 
 principally from Germany and England. Crude 
 coal-tar creosote, which is a by-product of gas- 
 works, blast furnaces, and gas producers has 
 shown some promise as a substitute. 
 
 Carbolic acid (phenol) is a homologue of 
 cresylic acid. It is difficult to distinguish be- 
 tween them, the smell and color being so much 
 alike. Carbolic acid is easily broken down by 
 H 2 S0 4 , yielding oxalic acid. It appears to be 
 much less selective than cresylic acid in its 
 action on metallic sulphides, and a slight ex- 
 cess brings over a concentrate high in insoluble 
 matter. 
 
 Fuel-oils. Fuel-oils from various localities 
 have widely different action on any given ore. 
 They are not highly selective like cresylic acid, 
 pine-oils, etc., but are strongly emulsive; they 
 serve the purpose of giving body and mineral- 
 carrying power to the relatively weak but more 
 selective froths; they are cheap, quickly ob- 
 tainable, and when used in moderation bring 
 over a little gangue. 
 
THE PURPOSE OF OIL IN FLOTATION 89 
 
 Gas-oils. Gas-oil, or stove-oil, a distillation 
 product of crude oil, is a strong emulsifying 
 agent, which is at times most useful. It must 
 be used in very small quantities. 
 
 Crude-wood Turpentine. This is a dark 
 reddish-brown liquid with a pungent smell. 
 On gravity-flow machines it is of little use, as its 
 action in slight excess is to bring over gangue 
 freely. As an emulsifier fuel-oil or tar-oil are 
 preferable. On machines through which the 
 flow of pulp is maintained by mechanical means, 
 it has been found a valuable reagent for the 
 purpose of controlling the levels of pulp, through 
 its physical action on the froth. 
 
 Pine-oils, wood-tar oils, fir-oils, wood-creo- 
 sotes, etc., are the products resulting in a 
 destructive distillation of soft wood. 
 
 The Purpose of Oil in Flotation. The exact 
 function of oil in flotation is a point that has 
 not yet been settled, although- it seems ob- 
 vious enough that we want oil for two main 
 purposes: 1 1st, to furnish a film around the 
 particle, and, 2d, to act as a means ol making a 
 foam or froth. 
 
 Oils may be roughly divided into two classes: 
 1. Collectors or Oilers; 2. Frothers or Foamers. 
 
 Oils that are good " collectors " are practi- 
 cally insoluble in water and form a film not 
 easily evaporated, so make persistent bubbles. 2 
 
 1 "How Flotation Works," by G. D. Van Arsdale, 
 Eng. & Min. Jr., May 13, 1916. 
 
 2 " Universal Flotation Theory, " by C. T. Durell, Mex- 
 ican Min. Jr., July, 1916. 
 
90 OIL AND OTHER REAGENTS 
 
 Good " frothers " are oils more or less soluble 
 and, while they make quantities of bubbles and 
 much froth, evaporate quickly, so that the 
 bubbles burst more readily. 
 
 The Qualities of a Flotation Oil. G. D. Van 
 Arsdale states t 1 
 
 I think it is safe to say that we want, first, 
 an oil whose viscosity is such as to enable it to be 
 finely divided or extended; second, that it 
 should not emulsify readily; third, that its 
 physical qualities should be such that the 
 resultant of the interfacial tensions between 
 water, oil, and particle should be such as to 
 cause with certainty the entrance of a mineral 
 particle into it and the exclusion of a gangue 
 particle. " 
 
 The object in the addition of a minute amount 
 of, for example, pine-oil is to change the surface 
 tension and contact angle of the other oil or of 
 a particle coated by it so as to enable it now to 
 float, which it otherwise would not do. Heat 
 apparently acts in the same way, for if we drop 
 some oil on the surface of hot water, it does not 
 film out but assumes the globular form. 
 
 It would seem that when two oils are used, 
 one for its filming effect and the other as a 
 frother, they should be used separately in the 
 apparatus, first using the filming oil, thus ob- 
 taining a maximum filming-out condition, then 
 followed by the frother. 
 
 In general, pine-oil makes a brittle froth, which 
 immediately dies; creosotes make a more elastic 
 froth, the bubbles of which may expand to 3 
 1 "How Flotation Works," Mexican Min. Jr., July, 1916. 
 
THE QUALITIES OF A FLOTATION OIL 91 
 
 inches in diameter or more before rupture. 
 Coal-tar products are poor frothing agents and 
 if used must be aided by either creosote or pine- 
 oil to produce a good froth and insure a high 
 recovery. Oils of a lubricating nature seem to be 
 of little value in flotation, while such light oils 
 as gasoline and naphtha are of value only for 
 thinning the heavy coal and wood-tars. On 
 some ores crude pine-tar will in itself combine 
 both the properties of frothing and collecting. 
 On others, this may have to be enriched by the 
 addition of some one of its more volatile constit- 
 uents such as refined pine-oil, turpentine, or 
 wood-creosote. 
 
 The following examples will illustrate how 
 oils are mixed to give a good flotation oil. At 
 the Inspiration, for instance, the mixture is 80 
 per cent crude coal-tar, 20 per cent coal-tar 
 creosote; at another plant on similar oil 45 per 
 cent El Paso coal-tar, 40 per cent coal-tar 
 creosote, 10 per cent cresol, and 5 per cent pine- 
 oil; at the Daily- Judge mine 40 per cent crude 
 coal-tar, 40 per cent creosote, and 20 per cent 
 pine-oil; in the Coeur-d'Alene on zinc ore 
 straight wood-creosote was used; on the National 
 Copper ore plain turpentine will work but pine- 
 oil will work better. 
 
 In the above examples at the Inspiration, 1^ 
 to 2 Ib. of the mixture are used per ton of ore; 
 at the Daily- Judge, 1 to 1J Ib; and at the 
 National T 3 ^ Ib. oil is sufficient. " The proper 
 kind or kinds of oil and quantity required can 
 only be determined at present by tentative 
 
92 OIL AND OTHER REAGENTS 
 
 experiments; so far no scientific short-cut is 
 known. " 
 
 The trend of work to-day seems to be to study 
 flotation from the standpoint of the ore, its 
 electrostatic charge (so-called), etc., and from 
 the standpoint of colloidal chemistry it is be- 
 lieved that, in addition, a study of oils would 
 give a better understanding of the process and of 
 the variables concerned, while also aiding in 
 the solution of certain theories not yet advanced. 1 
 
 Froth and Bubbles. The idea has been 
 abandoned by most people that a low surface 
 tension is the essential requirement for froth 
 formation. As mentioned by Coghill in a 
 recent writing, 2 " contamination of the liquid 
 with an impurity that will cause a variable sur- 
 face tension is the real requirement." 
 
 A bubble of air is spherical in shape, and this 
 shape can only be maintained if the external 
 pressure exceeds the internal pressure. Since 
 a bubble does not expand per se, large bubbles 
 can only be accounted for by heat, coalescence, 
 or electrification. Viscosity is an important 
 factor in froth persistence, as it increases the 
 tendency of the liquid film and thus prevents 
 ready rupture. The rupture or bursting of 
 bubbles is explained thus: 3 
 
 1. Concussion upon a surface film deficient in 
 
 1 "Oils for Flotation," by Chas. Y. Clayton and C. E. 
 Peterson, Min. & Sci. Press, April 22, 1916. 
 
 2 " The Science of a Froth," Min. & Sci. Press, February 
 26, 1916. 
 
 3 "The Flotation of Minerals," by Robt. J. Anderson, 
 Min. & Sci. Press, July 8, 1916. 
 
FROTHS FORMED BY FLOTATION OILS 93 
 
 the requisite viscosity and variable surface 
 tension. 
 
 2. Relief of pressure here the gas of the 
 bubble in expanding exerts a pressure exceeding 
 that of the liquid film. 
 
 3. Adhesive force of the entrained gas for the 
 atmospheric air. 
 
 4. Evaporation of the liquid film. 
 Flotation bubbles will burst for any one or a 
 
 combination of these reasons. 
 
 Furthermore i 1 
 
 (a) Frothing never occurs in pure liquids and 
 is a definite proof that the solute or dispersed 
 phase lowers tne surface tension of the solvent. 
 
 (6) A froth which shows adsorption at the 
 interfacial boundary of solution and gas de- 
 pends for its persistence on the production of a 
 viscous film at that boundary. 
 
 (c) These viscous films are the direct result 
 of surface adsorption of the dispersed phase, 
 that is, dissolved contaminant, the amount of 
 which is small disappearingly so. 
 
 The work of Hall and Miss Benson shows that 
 in a foaming liquid the foam is richer in the 
 dissolved contaminant than in the bulk of the 
 liquid. 
 
 Froths Formed by Flotation Oils. 2 The froth 
 produced by various oils differs with the ma- 
 chine in which it is made. For instance, in the 
 
 1 "The Flotation of Minerals," by Robt. J. Anderson, 
 Min. & Sci. Press, July 8, 1916. 
 
 2 " Froths Formed by Flotation Oils," by William A. 
 Mueller, Eng. & Min. Jr., July 1, 1916. 
 
94 OIL AND OTHER REAGENTS 
 
 Minerals Separation type of machine, where the 
 froth rides in the spitzkasten for some time 
 before leaving it, there is plenty of time to col- 
 lect and mat together, and in this case the froth 
 always lies in a " dead " state, only coming off 
 as it is forced out by other froth from the rear. 
 In this case the froth loses its characteristics so 
 far as the bubble itself is concerned. 
 
 In the Callow type of machine the froth is 
 always in rapid motion and no dead froth ac- 
 cumulates. It is kept overflowing by the con- 
 stantly rising bubble column formed. In the 
 Cole-Bergmann and Flynn-Towne types of ma- 
 chines the froth acts as in the Callow type. In 
 these two, however, a deeper froth column is 
 carried and this makes a slight difference in 
 the froth, making the bubbles slightly smaller. 
 
 In adding oils for flotation it is of the utmost 
 importance that they be well mixed with the 
 pulp before flotation is attempted. This is 
 usually done by adding the oils in the mills 
 during grinding, and this is the most desirable 
 method. Sometimes where this cannot be done, 
 as is the case where primary slimes are treated by 
 flotation and the oils are not wanted in the rest 
 of the feed, a Pachuca tank is used for the 
 mixing. This works fairly well, although it is 
 not the most desirable way of mixing where the 
 entire pulp is to be treated. If not thoroughly 
 mixed, the oils kill froth rather than produce 
 any. When a machine is in good working order 
 and some raw oil suddenly gets into the pulp, 
 the froth immediately seems to dissolve, leaving 
 
FROTHS FORMED BY FLOTATION OILS 95 
 
 the pulp showing through the froth. In these 
 cases the froth rushes back and forth in the 
 machine; the bubbles become very brittle and 
 finally disappear. 
 
 Another important feature in adding the flo- 
 tation oils is that they be fed in some continu- 
 ous way and not spasmodically, since the latter , 
 would entail constant attention at the machine 
 and abnormal conditions at all times. There 
 are several devices for uniform oil addition. One 
 is by a pump in which the stroke of the piston 
 can be varied, thus giving any desired amount 
 of oil, from a drop at a time to a steady stream. 
 Another satisfactory device is a method whereby 
 the oil is taken from the rim of a wheel which 
 operates so that the rim passes through oil 
 contained in a reservoir. A piece of flat metal 
 is then fixed by a set screw and spring to rest 
 against the rim. By adjustment of the screw 
 the piece of metal can be shifted across the rim 
 so as to take in a greater or less area, thereby 
 increasing or diminishing the oil flow. Still a 
 third method consists of a small bucket or two 
 on an endless chain passing over a pulley, much 
 the same as a bucket pump, located above the 
 launder where the oils are to be added and an- 
 other pulley in a barrel or drum containing the 
 oil mixture below. The bucket carries its small 
 amount of oil up, discharges into the launder, and 
 is refilled again on passing through the barrel, 
 etc. 
 
 In making any changes in increasing or de- 
 creasing the amount of oil or adding different 
 
96 OIL AND OTHER REAGENTS 
 
 kinds of oil, make them very gradually. In 
 increasing or diminishing, especially, be careful 
 and only change the rate very slowly, allowing 
 enough time to give the change a chance to show 
 up in the machine. Especially is this important 
 when the oils are added in "the mills, as it takes 
 some time for a change in oil to make its ap- 
 pearance, since it is diluted to such an extent 
 and worked over such a comparatively large 
 volume. 
 
 The froth characteristics here described apply 
 to live froths such as are formed in the air types 
 of machines. The agitator type, with the ex- 
 ception of the agitator-and-air type com- 
 bined, usually has a spitzkasten or settling com- 
 partment in which the froth congeals and so 
 loses its bubble characteristics. In these ma- 
 chines the froth characteristics are not so 
 noticeable. 
 
 Characteristics of Pine-oil 
 
 Pine-oil, as a general rule, is a rather poor 
 mineral collector, but a good frothing agent. 
 For this reason it is generally used only as a 
 frother, although there are some cases where it 
 will take the place of a mineral collector as well 
 as the frothing agent. Its action is delicate, 
 and at plants where pine-oil is largely used the 
 machines will require much closer attention. 
 For instance, it is a good mineral collector on 
 ores carrying chalcocite and on some zinc ores. 
 A pine-oil froth, in addition to being brittle, is 
 also watery and at times, when there is too much 
 
CHARACTERISTICS OF PINE-OIL 97 
 
 of it present, it tends to make a dirty froth and 
 low-grade concentrate. When present in these 
 large amounts, the concentrate froth will often 
 carry large particles of silica and gangue ma- 
 terial; that is, some that will pass 28-mesh and 
 stay on a 60-mesh screen. The froth, however, 
 does not toughen up because of its excess oiling, 
 and in this way pine-oil differs from most others. 
 The froth will be dirty, as is the case with other 
 oils, and cannot be cleaned, but the latter is due 
 largely to excess froth rather than to the tough- 
 ness of the froth, as is the case with other oils. 
 By the addition of acid, or sometimes a caustic, 
 its action as a mineral collector can often be 
 increased, but it still retains the same charac- 
 teristics of brittleness and delicacy. 
 
 Next to pine-oil the most important flotation 
 agent is coal-tar. As a general rule the coal- 
 tars are too stiff and thick to be used by them- 
 selves and so must often be diluted with some 
 other oil, preferably one in its own class. The 
 oils commonly used for this purpose are coal- 
 tar creosote, cresol, and other coal-tar products. 
 Sometimes, however, wood-creosote, fuel-oil, or 
 others are used. 
 
 Coal-tar is a poor frothing agent, but a good 
 mineral collector, and it is seldom used without 
 mixing with some pine-oil or other frothing 
 agent. The bubbles from coal-tar itself are also 
 brittle, but in the presence of mineral it often 
 seems to become tougher, the mineral and oil 
 film apparently mating together. The froth 
 from this oil is always mineralized to a high 
 
98 OIL AND OTHER REAGENTS 
 
 degree when it is mineralized at all. Coal-tar, 
 with a suitable frothing agent, is adapted to 
 almost any ore. By this statement I mean 
 that it is not adapted to any one mineral, but 
 works as a rule with the minerals of copper, 
 zinc, and some others. The froth does not 
 acquire any great depth unless some other oil is 
 mixed with it. For this reason we seldom see a 
 straight coal-tar froth except in an experimental 
 machine. Coal-tar is hard to mix with the pulp, 
 and it cannot be done well except by grind- 
 ing. I have seen coal-tar, even when mixed 
 with pine-oil, separate when reaching the ma- 
 chine, although in this case it had been added in 
 a Pachuca tank at the head of the machine. 
 When coal-tar shows up in the machine as raw 
 oil, it hag not the strong froth-killing power of 
 the other oils, but lies on the froth in flakes, 
 sometimes deadening the froth in the immediate 
 vicinity and at other times seeming to mate 
 the small bubbles together, forming a sort of 
 hole in the froth, toward* which the bubbles in 
 the vicinity have a strong tendency to rush. Ar- 
 riving, they seem to be swallowed up much as 
 a cork will act when thrown into a whirlpool. 
 Raw coal-tar in the machine is not so detrimental 
 as the other oils, but, nevertheless, it should be 
 avoided. When in great excess, coal-tar has a 
 strong tendency to separate, as has been noted, 
 even when apparently well mixed. Even though 
 it has no strong frothing power, when too much 
 is used it will cause some excess frothing and 
 a dirty froth, though not so easily as other oils. 
 
COAL-TAR CREOSOTE 99 
 
 Coal-tar Creosote 
 
 Coal-tar creosote is used mostly as a dilutant 
 for the cheaper coal-tar oil, and for this purpose 
 it is very good. The creosote bubble has a 
 tendency to be rather large, ranging in size 
 from about an inch in diameter to as much as 
 12 in. and sometimes even more. The bubble 
 has a tendency to be tenacious. It is very 
 tough and in breaking, the bubbles tend to ex- 
 pand rather than be destroyed altogether. With 
 two bubbles side by side, the breaking seems to 
 take place in the film uniting them, so that 
 where there were two bubbles at first, there is 
 only one after ^bursting. This enlarging of the 
 bubble, of course, has its limit, and we seldom 
 see them much over 12 in. in diameter unless 
 there is a great excess of creosote, when they 
 may get to be of such size as to reach across the 
 machine. On bursting, the mineral burden is 
 drawn by the film to the film of the neighboring 
 bubbles with which they were in contact before 
 bursting. The bubble has good carrying capac- 
 ity for mineral. When too much oil is present, 
 however, there is the same tendency to carry 
 gangue, and this is usually at the expense of the 
 mineral. The oil mixes rather easily, the action 
 in the Pachuca tank being sufficient, although 
 mixing in the grinding mills is at all times to be 
 recommended. 
 
100 OIL AND OTHER REAGENTS 
 
 Wood-creosote Bubbles 
 
 Wood-creosote has some of the same charac- 
 teristics of the coal-tar creosote, but differs 
 widely in others. The toughness of its bubbles 
 is even more marked. The size of the bubble is 
 also somewhat different. The two oils are not 
 interchangeable that is,' the one cannot be used 
 as a substitute for the other, as coal-tar creosote 
 seems to work better on copper-bearing ores 
 than the wood-creosote and the latter seems to 
 work better on zinc ores. Wood-creosote is often 
 used as a dilutant for coal-tar in the flotation 
 of zinc ores. The size of bubbles varies greatly. 
 The characteristic froth shows small ones re- 
 sembling the pine-oil bubble, together with the 
 larger ones. The froth, like that of coal-tar 
 creosote, is tough, and a small excess of oil makes 
 a dirty and voluminous froth that is hard to 
 break up. The bubble varies from this type 
 when an excess of oil is used, tending to become 
 larger and more elastic. 
 
 Turpentine is not used so much at the present 
 time as when flotation first appeared in this 
 country. The turpentine froth is persistent 
 and elastic. It has a tendency to hold every- 
 thing that comes in contact with it, and for this 
 reason it was formerly used to bring up the mid- 
 dlings and was added after the concentrates were 
 taken off. For this purpose it was good, but 
 the froth is so tough that it is hard to break 
 down, so that cleaning it is difficult. Usually 
 the middling produced by means of the turpen- 
 
CRESOL, OR J CRESYLIC ACID, 101 
 
 tine could not be cleaned to any appreciable 
 extent. The turpentine bubble ranges in size 
 from J in. to 2 or 3 in. in diameter. 
 
 Cresol, or Cresylic Acid 
 
 Cresol, or cresylic acid, formerly was the 
 chief flotation agent used in the flotation of cop- 
 per minerals, but its use is now limited to small 
 proportions in the mixtures with coal-tar. The 
 cresol bubble is of medium size that is, from 
 ^ to 2 and 3 in. in diameter and as a rule the 
 bubble is not too brittle and not too tough, but 
 makes a good froth to handle. The nature of 
 the oil, however, made it disagreeable to handle 
 and also somewhat dangerous; this, together 
 with the bringing out of coal-tar and the ad- 
 vance in price of cresol, gradually brought it 
 to a point where only a comparatively small 
 amount is now used. 
 
 The oil was a good frothing agent as well as a 
 good mineral collector, and its use was almost 
 universal a short time ago. The froth is rather 
 easy to break down, and for this reason the con- 
 centrate produced is rather easily cleaned. The 
 oil is very slightly soluble in water and mixes 
 rather easily. Violent agitation, as in a Pa- 
 chuca tank or in the Minerals Separation type 
 of machine, is often enough to give good dis- 
 tribution and a good flotation froth. 
 
 The froth produced by fuel-oil is of the same 
 appearance as that of coal-tar creosote as far 
 as the bubbles are concerned, which are nearly 
 the same size, ranging from 2 to 4 and 6 in. in 
 
102 OIL AND OTHER REAGENTS 
 
 diameter. The froth, however, is very brittle 
 when the right amount of oil is used and is much 
 cleaner than the creosote. In fact, the froth is 
 almost too clean, so that a clean tailing is hard 
 to make with fuel-oil alone. Mixed with some 
 oil like creosote, however, it sometimes does 
 good work. The concentrates from the prelimi- 
 nary treatment often need no further treatment. 
 Where a final product is made as concentrate, 
 the tailings are usually retreated, and in this 
 case the creosote effects seem to carry through 
 to the other treatment, while the fuel often has 
 to be added in the second treatment. Various 
 ores differ slightly on this point. Again, a 
 little fuel-oil in a coal-tar-creosote mixture will 
 sometimes aid in cleaning the froth. 
 
 When the fuel-oil is in excess, the froth pro- 
 duced is stringy and the bubbles often get to be 
 of such size as to stretch across the machine. 
 I have seen them over 2 ft. in length. The 
 froth under these conditions is also dirty and 
 will pass through a cleaner with practically no 
 better grade being produced than before enter- 
 ing. Acid is sometimes an aid in the use of fuel- 
 oil, especially when the oil is in excess. The 
 froth from excess fuel-oil is hard to break down. 
 
 Pine-tar oil is coming into the limelight more 
 just now as a possible flotation agent for copper 
 carbonates, but I doubt whether it will be use- 
 ful alone. It is stiff and flows poorly, so that 
 it must be mixed with some other oils in order 
 to make it of such viscosity as to flow so that it 
 may be added steadily and slowly. 
 
DEALERS IN FLOTATION OILS 103 
 
 The froth resembles that from wood-creosote 
 and pine-oil in appearance of the bubbles, but in 
 texture it is very much more fine-grained than 
 the wood-creosote It is a powerful frothing 
 agent similar to pine-oil. It is easy to flood 
 the plant with froth from this oil. The froth 
 is characterized by being dirty, but, like pine- 
 oil, is capable of holding up considerable coarse 
 mineral as well as gangue. When a flood of this 
 froth reaches the cleaner, it is subjected to very 
 little cleaning, owing to its frothing character. 
 Often the addition of a small amount of fuel-oil 
 will tend to make a cleaner froth, but with the 
 pine-tar oil a very clean froth must not be ex- 
 pected except at the cost of high tailings. 
 
 Oleic acid is used at several plants in this 
 country and *is confined mostly to zinc ores. 
 The size of bubbles varies with the amount of 
 oil used, but ranging from several inches to a 
 foot in diameter. The froth is very persistent 
 and stringy, and the bubble film is often strong 
 enough to support light objects. 
 
 Eucalyptus-oil is used mostly in Australia, 
 although a small amount of it may be encoun- 
 tered in this country at times. Its cost, how- 
 ever, is very much against it here. 
 
 Dealers in Flotation Oils. 1 The following is 
 a list of dealers in different oils who have placed 
 on the market various products. A host of 
 these dealers are prepared to supply these prod- 
 ucts at any time, of fairly uniform quality. 
 
 1 "Flotation-oils," by O. C. Ralston, Min. & Sci. 
 Press, June 10, 1916. 
 
104 OIL AND OTHER REAGENTS 
 
 None of them has been able to exactly dupli- 
 cate their car-load shipments, so that the general 
 practice is to test each shipment of oil in a 
 laboratory testing device to determine the proper 
 method of using a given shipment of oil. This 
 non-uniformity of shipments will doubtless van- 
 ish when the market becomes steady. 
 
 Dealers in Flotation Oils 
 
 Wood-oils 
 
 Pine-oils, Resin-oils, Wood-creosotes, Tar-oils, 
 Turpentines, etc. 
 
 1. Pensacola Tar & Turpentine Co., Gull Point, Fla. 
 
 2. General Naval Stores Co., New York. 
 
 3. Georgia Pine & Turpentine Co., 158 Perry St., New 
 
 York. 
 
 4. Central Distilling Co., Helena, Ark. 
 
 5. United Naval Stores Co., New York. 
 
 6. American Tar & Turpentine Co., New Orleans, La. 
 
 7. Cleveland Cliffs Iron Co., Cleveland, Ohio. 
 
 8. Chesapeake Tar & Rosin Co., Baltimore, Md. 
 
 9. Custer City Chemical Co., Custer City, Pa. 
 
 10. Yaryan Naval Stores Co., Brunswick, Ga. 
 
 11. Hussay & O'Connel, Savannah, Ga. 
 
 12. Florida Wood Products Co., Jacksonville, Fla. 
 
 13. Oregon Wood Distilling Co., Portland, Ore. 
 
 14. National Wood Products Co., Wilmington, N. C. 
 
 15. Chapman Manufacturing Co., Savannah, Ga. 
 
 16. Spiritine Chemical Co., Wilmington, N. C. 
 
 Eucalyptus-oil 
 
 17. Atkins, Kroll & Co., San Francisco, Cal., and other 
 
 importers. 
 
DEALERS IN FLOTATION OILS 105 
 
 Coal-tar, Coal-creosotes, and Aromatic 
 Hydro-carbons. 
 
 1. The Barrett Co., New York. 
 
 2. F. J. Lewis Manufacturing Co., Chicago, 111. 
 
 3. American Creosoting Co., New Orleans, La. 
 
 4. American Tar Products Co., Chicago, 111., and St. 
 
 Louis, Mo. 
 
 5. Republic Creosoting Co., Indianapolis, Ind., and 
 
 Minneapolis, Minn. 
 
 6. American Coal Refining Co., Denver, Colo. 
 
 7. Numerous by-product coke-ovens, such as: 
 
 Pennsylvania Steel Co., Steelton, Pa. 
 
 National Tube Co., Penwood, W. Va. 
 
 Milwaukee Coke & Gas Co., Milwaukee, Wis. 
 
 Pennsylvania Steel Co., Lebanon, Pa. 
 
 Solvay Process Co., Syracuse, N. Y. 
 
 By-products Coke Corporation, South Chicago, 111. 
 
 Semet-Solvay Co., Detroit, Mich. 
 
 Central Irpn & Coal Co., Tuscaloosa, Ala. 
 
 New England Gas & Coke Co., Everett, Mass. 
 
 Illinois Steel Co., Joliet, 111. 
 
 Maryland Steel Co., Sparrows Point, Md. 
 
 8. Numerous municipal and similar coal-gas plants. 
 
 Vegetal Oils 
 
 1. Cottonseed-oil, etc., Southern Cottonseed Oil Co., 
 
 New York. 
 
 2. Corn-oil, Corn Products Co., New York. 
 
 3. Palm-oil, Peter van Schaack & Co., Chicago, 111. 
 
 Animal Oils (Fatty Acids) 
 
 1. Oleic acid, Peter van Schaack & Co., Chicago, 111. 
 
 2. Oil-flotation grease emulsion, Mohawk Refining Co., 
 
 Cleveland, Ohio. 
 
V 
 
 106 OIL AND OTHER REAGENTS 
 
 PETROLEUM PRODUCTS 
 
 Crude j Asphaltum Base 
 
 1. California crude: 
 
 Union Oil Co., Santa Paula, Cal. 
 Associated Oil Co., Los Angeles, Cal. 
 Standard Oil Co., Richmond, Cal. 
 
 2. Road oil No. 80, Harris Oil Co., Los Angeles, Cal. 
 
 Reconstructed Petroleum Oils 
 
 1. Special mineral separator, Continental Oil Co., Salt 
 
 Lake City, Utah. 
 
 2. Solulene and minolene, Star Lubricating Co., Salt 
 
 Lake City, Utah. 
 
 Refined Petroleum Products 
 
 1. Stove-oil, Standard Oil Co., San Francisco, Cal. 
 
 2. Stanolind, etc., Continental Oil Co., Salt Lake City, 
 
 Utah. 
 
 3. Flotation-oils, Utah Oil Refining Co., Salt Lake City, 
 
 Utah. 
 
 4. Heavy mineral flotation-oils, Geo. P. Jones & Co., 
 
 St. Louis, Mo; 
 
 . 5. Refinery acid sludge, any refinery. 
 6. Lubricating oils, any company. 
 
 Special Mixtures of Mineral and Wool Oils 
 
 1. Calol-oils, Standard Oil Co., Richmond, Cal. 
 
 2. Mine & Smelter Supply Co., Denver, Colo. 
 
 3. Hendrie & Bolthoff Manufacturing & Supply Co., 
 
 Denver, Colo. 
 
 The costs of flotation-oils have varied so much, 
 owing to the unsettled market, that it is almost 
 impossible to give an idea of what they should 
 cost. For a rough estimate it is possible to say 
 
PETROLEUM PRODUCTS 107 
 
 that crude petroleum will cost the same as for 
 other purposes. Many of the specialized prod- 
 ucts, such as coal-tar, listed above, will cost 
 about 5^ or less per gallon. The coal-creosotes 
 and the wood-creosotes cost 15 to 30f per gallon; 
 the pine-oils 45 to 60^, and eucalyptus-oil will 
 cost $1.50 or more per gallon. The effect of 
 the ending of the war as regards coal-tar and 
 creosote in the American market is uncertain, 
 but, so far as known, wood products will not 
 be affected, and petroleum products for flo- 
 tation will almost certainly be little affected. 
 Flotation men do not like to have their oil costs 
 go over 5j per ton of slime treated, and 
 many costs are nearer to 2^ or possibly even 
 less. 
 
 There can be no doubt that the higher-grade 
 pine-oils and ather wood-oils are the best adapted 
 to general flotation work, but the question of 
 what is commercially feasible is entirely different. 
 Thus the wood-creosotes are meeting with much 
 favor. Many of the special petroleum products, 
 especially those high in sulphur, are adaptable 
 for rough concentration of copper ores, but the 
 most favored materials for such ores at present 
 seem to be the coal-tar products in combination 
 with topped crude petroleum, oils from which the 
 lighter fractions have been removed by distil- 
 lation. Coal-tars and creosotes, with a small 
 addition of pine-oils, are being used a great deal 
 in zinc work, and the wood creosotes find favor 
 in the treatment of galena ores. Gold and 
 silver ores seem to require much pine-oil, al- 
 
108 OIL AND OTHER REAGENTS 
 
 though the pine-oil can be diluted with some of 
 the coal-creosote oils. 
 
 It will be found that there is a considerable 
 number of oils that will give good results on 
 any given ore, if the mechanical treatment is 
 adjusted to suit each given oil. 
 
 Following is a table showing the amount of 
 flotation-oils being consumed every month 
 throughout the United States. These figures 
 were collected at the beginning of 1916 by direct 
 communication with the companies. 
 
PETROLEUM PRODUCTS 
 
 109 
 
 1 
 
 a 
 
 d 
 
 31 
 
 1? 
 
 .2 a 
 
 1 I? 
 .2 8 
 
 o 
 
 d 
 & 
 
 lO CO *O 
 t^ CO !> 
 
 5 O CO O5 
 
 coco 
 
 58 
 
 
 
 g 
 
 S 
 
 05 
 
 ' oT 
 
 
 I 
 
 5 O 
 
 ;& 
 
 o 
 
 <M 
 
 l 
 
 1 
 
CHAPTER VI 
 TESTS 
 
 The Important Points to Test f or. The 
 
 amount of work required, in testing any given ore 
 for the flotation process, is considerable, since 
 the proper kind or kinds of oil and quantity and 
 amount of other reagents, acid or alkali, can 
 only be determined at present by tentative 
 experiment; so far no scientific short-cut is 
 known. 
 
 The most important points to be tested on a 
 given ore with any given flotation machine are: 
 
 1. Method of Grinding. 
 
 2. Fineness of Grinding. 
 
 3. Kind of Frothing Agent Used. 
 
 4. Amount of Frothing Agent. 
 
 5. Temperature. 
 
 6. Acidity or Alkalinity. 
 
 7. The Effect of Varying the Speed of Agi- 
 tation when Mechanical Agitation is Used. 
 
 8. Necessity of Preliminary Agitation. 
 
 9. Effect of Addition Agents in Flocculating 
 Gangue-slime. 
 
 Preliminary Considerations. It may be seen 
 that there may be a certain best combination of 
 the above variables; hence the desirability of 
 doing the tests in a small laboratory machine 
 where many trials can be made in a short time. 
 110 
 
PRELIMINARY CONSIDERATIONS 111 
 
 In attacking refractory ores there are a num- 
 ber of ingenious things that can be done to the 
 pulp both in and out of the machine. The 
 trouble may be due to deleterious substances, 
 which sometimes can be: 
 
 1. Washed out. 
 
 2. Rendered harmless by boiling. 
 
 3. Overcome by acidifying. 
 
 4. Met with by making alkaline with lime 
 before entering the machine. 
 
 5. Occasionally, the ore will not work well 
 under ordinary conditions, but will yield beauti- 
 fully after fine grinding. 
 
 6. Sometimes extra reagents are necessary, 
 such as powdered charcoal, modified oils, argol, 
 soap, calcium, sulphate, alum, etc. 
 
 One can see that a rational method of de- 
 vising the proper tests in such cases must be 
 based on some theory of flotation. Colloid 
 chemistry is -e branch of knowledge that will 
 aid in the intelligent control of such tests. 
 
 After the best conditions have seemingly been 
 established, they should be further tried in a 
 larger-sized machine before they are incorpo- 
 rated into the general practice of a mill for 
 laboratory results are somewhat pessimistic as 
 compared to large scale work. 
 
 Again when a good set of conditions has been 
 found for flotation treatment of an ore, it is 
 best to recover the water from each test to see 
 what effect a closed circuit of the mill water will 
 have. Some oil and chemicals are thus re- 
 covered, cutting down the amounts necessary 
 
112 TESTS 
 
 for operation. In fact, a carboy or two of the 
 water to be used in the large mill should be 
 used to make certain that no deleterious con- 
 tamination will issue from this source. 
 
 Oil samples for test purposes can be obtained 
 from the various wood-distilling companies now 
 advertising in the Technical Press, from gas 
 companies, and from petroleum-refining com- 
 panies. 
 
 Finally, it is well to be prodigal in the amount 
 of analytical work connected with flotation 
 testing in order to discover interesting differ- 
 ences in gangue constituents carried into the 
 concentrate, as well as to find the best conditions 
 for leaving out some gangue constituent that is 
 less desirable than the rest. If an experimenter 
 does his own analytical work he can be expected 
 to spend three-fourths of his time analyzing 
 what has been done the other fourth. 
 
 Method of Grinding. As a rule laboratory 
 machinery for the pulverization of an ore is of 
 the dry-grinding type, with the exception of 
 small ball-mills that can crush from 1- to 100- 
 Ib. charges in the wet. Consequently, most 
 people start with weighed charges of finely- 
 ground dry ore, a known quantity of water, of 
 oil, and of acid or alkali. Generally most dry- 
 ground ore must be treated in an acidified pulp 
 to get good flotation. Doubtless, the surfaces 
 of sulphide particles become somewhat oxidized 
 in, or shortly after, dry grinding, and the func- 
 tion of the acid would be to clean the slightly 
 oxidized surfaces. Wet grinding usually does 
 
METHOD OF GRINDING 113 
 
 not call for so much acid. In nearly all labora- 
 tory work finer grinding than is used in practice 
 seems to be necessary. This is probably due to 
 the smaller amounts of froth that are formed. 
 Such small quantities of froth cannot form layers 
 as deep as those made in the large machines. 
 60 mesh is about the maximum size that can be 
 floated with any chance of getting high recovery, 
 while ore crushed somewhat finer than this gives 
 much more ease and expedition in operation. 
 Wet grinding is more desirable, as it parallels 
 conditions in practice, where most of the fine 
 grinding of ore is in Chilian, tube, or other mills. 
 However, wet grinding is much harder to ma- 
 nipulate in a small laboratory and requires more 
 time. The dry weight of the feed to the flotation 
 machine must be known; hence a weighed charge 
 of dry ore crushed to 10 mesh can be introduced 
 into a porcelain or iron pebble-mill for fine 
 grinding and ground for a length of time found' 
 necessary to reduce the pulp to sufficient fineness 
 15 minutes to 24 hours. The charge can be 
 poured and washed through a coarse screen 
 (to retain the bubbles) into a bucket and thence 
 into a flotation machine. The oxidation of 
 sulphide surfaces is thus avoided, but separate 
 grinding of each charge, in order to know its 
 exact weight, is rather tedious and requires a 
 number of small mills if many tests are to be 
 run (Fig. 15) on account of slow speed in grind- 
 ing. A mill with iron balls rather than pebbles 
 is of greater service. It is possible to introduce 
 the flotation oil before grinding, to be sure that 
 
114 
 
 TESTS 
 
FINENESS OF GRINDING 
 
 115 
 
 it will be thoroughly mixed. For thick viscous 
 oils this is highly beneficial, as a ball mill gives 
 about the best conditions 'for agitation and 
 mixing. Usually 1- to 2-lb. charges are used 
 and a small laboratory mill of the Abb6 type 
 
 J4 in bolt 
 
 FIG. 16. 
 
 serves well, although a good mill can be made 
 with a 10-in.., length, 8-in. iron pipe, and two 
 heavy iron caps for same (Fig. 16). 
 
 Fineness of Grinding. This would depend to 
 some extent upon the character of the ore. The 
 valuable mineral may be completely liberated 
 at fairly coarse meshes, but it has been found 
 from experience that 60-mesh material is often 
 hard to float with any chance of getting a high 
 extraction, while the operation is performed 
 with much more ease and expedition when the 
 ore is crushed somewhat finer. Some experimen- 
 ters have claimed that they were able to float 
 even as large as 30-mesh material. 
 
116 TESTS 
 
 Kind of Frothing Agent Used. An oil may 
 give a very good percentage of extraction on one 
 ore, whereas it will be an absolute failure when 
 used on another, although both ores chosen are 
 very adaptable to the flotation process. 
 
 In some cases a single oil will have both the 
 properties of frothing and collecting, but usu- 
 ally a good frother is not a collecting oil, so 
 that in most cases a combination of two or more 
 oils is necessary to give good results in the re- 
 covery. 
 
 Amount of Frothing Agent. In testing for 
 the efficiency of a given oil, it is advisable to 
 tabulate the results obtained with varying per- 
 centages of this oil; and it is best to start with 
 about, 0.01 per cent of oil in the solution, then 
 increasing the oil in each successive experiment 
 by about 0.02 per cent. 
 
 The following forms are convenient for the 
 tabulation of results: 
 
AMOUNT OF FROTHING AGENT 117 
 
 H 
 CO 
 
 o 
 
 I 
 
 sg 
 
 of ai 
 ol. to c 
 weigh 
 
 31 
 
118 TESTS 
 
 To show the effect of variation in quantity. Pine-oil. 
 
 Charge. 
 
 Variable, 
 grams. 
 
 Derived data. 
 
 Froth. 
 
 Assay of con. 
 
 ** 0* 
 
 *! 
 
 Zn 
 
 Pb 
 
 Ore, grams 
 Water, grams . . . 
 Acid, H 2 SO 4 .... 
 Oil, H 2 SO 4 
 
 400 
 1200 
 2.0 
 Variable 
 65 
 2000 
 7 
 
 
 
 
 
 
 0.5 
 1.0 
 1.5 
 2.0 
 
 29.0 
 
 38.0 
 37.0 
 51.0 
 
 53.2 
 43.1 
 42.4 
 28.6 
 
 
 74.6 
 79.2 
 75.8 
 70,0 
 
 Temp, in C. . . . 
 Speed, r.p.m. . . . 
 Time, minutes . . 
 
 
 
 
 
 
 
 
 
 
 EFFICIENCY CURVE 
 
 Efficiency of pine-oil in terms of frothy assay and, ex- 
 traction. 
 
 Per cent _-?l in Irofli 
 
 
 
 
 
 
 
 
 
 
 1 1 
 
 
 
 
 
 
 
 
 
 -60 
 50 
 10 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \c 
 
 5 drani Oi 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 J 
 
 1.0 JGra 
 
 nO 
 
 11 
 
 
 
 
 
 
 
 
 nn 
 
 
 
 
 
 
 
 
 fl\ 
 
 >Gr 
 
 anu 
 
 Oil 
 
 
 
 
 
 
 
 
 
 Of) 
 
 
 
 
 
 
 
 y 
 
 2G 
 
 ran 
 
 sO 
 
 1 
 
 
 
 
 
 
 
 
 
 10 
 
 
 
 
 
 
 
 ' 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Q 10 20 80 40 50 60 70 80 
 
 Per cent extraction. Zinc . 
 
 Acidity or Alkalinity. The amount of acid 
 or alkali required requires the same manipulation 
 as with oils. The following are some of the 
 probable effects of acid: 
 
 1. Prevents emulsification. 
 
 2. Prevents deflocculation. 
 
 3. Diminishes surface tension of the liquid. 
 
SPEED OF AGITATION 119 
 
 4. Diminishes the gas-liquid contact angle. 
 
 5. Increases the viscosity of the gas-liquid 
 surface. 
 
 6. From the standpoint of the electrical 
 theory sulphuric acid (as electrolyte) would 
 play a prominent part. 
 
 7. Removes surface oxidation and may con- 
 tribute in the addition of bubbles. 
 
 The Effect of Temperature. In many cases 
 heat is required and in some cases to a high 
 degree. For laboratory work solutions are best 
 heated by introducing steam, generated in a 
 suitable vessel. 
 
 Speed of Agitation. Many reports of flo- 
 tation test-work with mechanical-agitation ma- 
 chines gives the speed of the rotation of the 
 agitating paddles. In most flotation labora- 
 tories it is possible to get much the same work 
 done with quite a variation of speeds, the only 
 effect being to lengthen or shorten the time of 
 treatment. It seems that the importance of 
 this matter is somewhat exaggerated. Some 
 means of speed control is necessary and the 
 speed can be adjusted in each case until the froth 
 presents the proper appearance as to depth, 
 size of bubbles, color, etc. Speeding toward 
 the end of the test is good practice, as it gives 
 a deeper froth with a faint line of concentrate 
 on the top. The speed is better adjusted, for 
 each test, to suit the conditions, rather than 
 running a series of tests with different speeds. 
 Only in the slide machine, where operation of 
 the impeller must be suspended in order to 
 
120 
 
 TESTS 
 
 allow froth to collect, is the speed of much im- 
 portance. 
 
 In connection with the electrical theory, 
 Thomas M. Bains, Jr., states: 1 
 
 The amount of electrification of the bubble 
 will depend on various conditions, such, for ex- 
 ample, as the amount of friction produced by 
 the blades of a Minerals Separation machine. 
 Increase the speed and the electrification is 
 greater and the attraction for conductors will 
 increase, reducing the proportion of conduc- 
 tivities in the tailing. Referring to D. G. 
 Campbell's article in the Mining & Engineering 
 World of January 17, 1914, the speed of agi- 
 tation and the percentage of extraction is given 
 as follows: 
 
 Speed of blades, r.p.m. 
 
 Extraction, 
 per cent. 
 
 Weight of prod- 
 uct, grams. 
 
 1800 
 
 68 
 
 39 
 
 1200 
 
 54 
 
 32 
 
 900 
 
 46 
 
 26 
 
 600 
 
 39 
 
 18 
 
 
 
 
 The extraction seems to vary directly as the 
 square root of the increase in speed. But it 
 will be observed that in the increased extraction, 
 the percentage of sulphide in the concentrate 
 decreases, due to the extraction of the small 
 particles of mixed gangue and sulphide. If the 
 bubbles are highly charged, the concentrate will 
 not be as clean in a particular case as if they 
 were less charged. 
 
 Effect of Addition Agents in Flocculating 
 Gangue-slime. The froth of a flotation ma- 
 
 1 Min. & Sti. Press, November 27, 1915. 
 
FLOCCULATING GANGUE-SLIME 121 
 
 chine, when viewed in a glass window in the 
 side of the machine, has the appearance of 
 coagules of sulphide, as though the oil or other 
 agent has flocculated the sulphides. The gangue, 
 to sink away from the froth quickly, should also 
 be flocculated. While acids, alkalis, and other 
 addition agents may have other functions, they 
 can easily have a coagulating effect on portions 
 of the ore. A clean flotation concentrate when 
 the gangue is very colloidal is hard to obtain 
 and some method of coagulating the slimes of 
 the gangue is necessary. 
 
 The following table, "Effect of Addition 
 Agents " as outlined by 0. C. Ralston is of 
 interest. 1 
 
 TABLE H. EFFECT OF ADDITION AGENTS 
 
 Inorganic Electrolytes: 
 
 Sodium chloride is rarely an effective addition agent 
 for either flocculation or deflocculation of various slimes, 
 and when added to water to any extent demanded by the 
 ore, is likely to increase the viscosity so that the particles 
 will settle slowly in any case. 
 
 Ferrous sulphate, the copperas of commerce, is a fairly 
 efficient flocculating agent for negatively-charged parti- 
 cles by virtue of the fact that the heavy bivalent ion of 
 iron is strongly absorbed by the colloid particles. It is 
 a deflocculator of positively-charged particles under some 
 conditions. 
 
 Zinc sulphate, copper sulphate, magnesium sulphate, 
 magnesium chloride, calcium chloride, etc., act in the same 
 way as iron sulphate. Magnesium and calcium chlorides 
 are being used for flocculating slimes in the overflow 
 water of many German ore-dressing plants. 
 
 Alum and other aluminum and ferric salts containing 
 1 Engineering & Mining Jr., June 3, 1916. 
 
122 TESTS 
 
 trivalent positive ions are often tremendously effective in 
 the flocculation of negative ore particles. 
 
 Sulphuric acid and hydrochloric acid are often effective 
 coagulants of negative colloids owing to the hydrogen 
 ions. 
 
 Sodium hydroxide is a most effective deflocculator of 
 negative colloid owing to the strong adsorption of the 
 hydroxyl ions. It will flocculate positive colloids, owing 
 to the same cause. 
 
 Sodium carbonate, owing to its alkaline reaction, will 
 generally react in the same way as sodium hydrate. 
 
 Sodium Silicate: 
 
 This salt hydrolyzes into sodium hydrate and colloidal 
 silicic acid, which carries a negative charge. Both of 
 these products will tend to disperse or deflocculate a nega- 
 tively-charged ore slime, and hence sodium silicate is one 
 of the most effective agents of this kind, although its full 
 effect is felt rather slowly. 
 
 Lime: 
 
 The bivalent calcium ion is more strongly adsorbed 
 than the hydroxyl ions and hence lime usually coagulates 
 colloids negatively. It is widely used for that purpose 
 in cyanide mills. Its effect is the opposite of that of 
 sodium hydrate, in which the hydroxyl ion is predomi- 
 nant. The adsorbed ions have been found to be carried 
 down with the precipitated colloids, as has been shown 
 by any number of experimenters. 
 
 Organic Electrolytes: 
 
 As mentioned in the body of the article, these sub- 
 stances react in many diverse ways. Citric acid and 
 oxalic acid and their sodium salts have been found to 
 deflocculate most ores. Acid tartrates are said to slowly 
 flocculate the negatively-charged slime particles. This 
 field has been almost untouched by metallurgists. 
 
 Organic Colloids and Semicolloids : 
 
 Tannin seems to deflocculate nearly all ore colloids and 
 is known to affect clays in the same way. Inorganic 
 
MISCELLANEOUS 123 
 
 electrolytes in sufficient amounts will reflocculate the 
 slimes so treated with tannin, but the colloids have 
 been protected by the tannin so that these electro- 
 lytes are less effective than on the untreated ore. 
 It produces its maximum effect after standing 
 several hours. It is very deleterious in flotation, 
 although its solutions foam well. 
 
 Saponin, the substance used to make beer foam, 
 has an effect similar to tannin. 
 
 Albumen, from the white of an egg, is more or 
 less indifferent, but tends to deflocculate most ore 
 slimes. 
 
 Ox blood, which contains albumin among other 
 things, is a strong deflocculator and its effects are 
 very hard to counteract. 
 
 Soap is an effective flocculating agent with many 
 negative slimes, giving large fast-settling flocks. 
 
 Glue tends to flocculate most ore slimes effi- 
 ciently, especially in the presence of electrolytes, 
 and is known to be bad for flotation. 
 
 Gelatin is also an excellent flocculator. 
 
 Starch has not been experimented with, but the 
 good effect of flour at Miami is probably due to 
 starch. 
 
 Any of the foregoing colloids can be salted out 
 by electrolytes and thereby cause flocculation of 
 the ore slimes in which the process takes place. 
 
 Miscellaneous. The measuring and 
 testing of flotation-oils in the laboratory 
 have been more or less exact. It is com- 
 mon practice to count the number of drops 
 of oil falling from a small piece of glass 
 tubing. A Mohr pipette 1 of 1 cc. total 
 capacity for measurement of the amount 
 
 1 " Testing Ores for the Flotation Process, II," 
 O. C. Ralston & Glen L. Allen, Min. & Sd. Press, 
 January 8, 1916. 
 
124 TESTS 
 
 of oil used in each test is very convenient. 
 Such a pipette is shown in Fig. 17. It will 
 be seen that this pipette allows measurement 
 of the oil to the nearest 0.01 cc., which is close 
 enough for all purposes. If the density of the 
 oil is known, the volume as measured by this 
 method is quickly converted into the weight of 
 oil used. 
 
 In the article " Testing Ores for Flotation, 
 Process, II " it is stated: 1 
 
 The testing of oil samples for flotative power is 
 a matter that needs standardizing. It is desirable 
 to classify oils according to flotative power, but 
 just how to do this is not exactly clear. A unit 
 of " flotativeness" might be established and each 
 oil referred to that unit in terms of percentage. 
 But it has to be remembered that the best oil 
 for one ore may not prove to be the best oil for 
 another, although two such series of oils might 
 roughly parallel each other. For any given ore, 
 it would be permissible to make such a measure- 
 ment on a series of oils and group them according 
 to some definite standard. A standard oil might 
 be chosen, and the value of a second oil expressed 
 in percentages of the flotative power of the first, 
 as determined by using equal quantities of the 
 two oils in tests on an ore under identical con- 
 ditions. This test could not be fair for the 
 reason that different amounts of two different 
 oils are necessary to accomplish the same results. 
 Further, the conditions of acidity or alkalinity 
 might favor one oil and handicap another. If 
 we measured the amount of oil necessary to give 
 a fixed percentage of extraction, the first of the 
 
 1 "Testing Ores for the Flotation Process, II, " O. C. Ral- 
 ston & Glen L. Allen, Min. & Sci. Press, January 8, 1916. 
 
DISPOSAL OF THE FROTH 125 
 
 above objections would be satisfied, but condi- 
 tions of acidity or alkalinity could make the test 
 unfair for some oils. Hence the dilemma as to a 
 standardized test of a flotation-oil. 
 
 No single test could definitely place an oil in 
 any scheme of classification, and nothing can be 
 done but run a series of tests, using varying 
 amounts of the oil to be tested with varying 
 acidity or alkalinity. The temperature of the 
 pulp must be kept constant, although it has a 
 minor effect. 
 
 Considerable work has been done along this 
 line at the Missouri School of Mines and Metal- 
 lurgy. 1 Their work has been for the purpose of 
 investigating the properties or combination of 
 properties that make oils valuable as flotation 
 agents. They have suggested many points 
 worthy of investigation. 
 
 Disposal of the Froth. The handling of the 
 flotation froth in the laboratory finds diffi- 
 culties which are reflected in practice. It is 
 often very slow to settle and filters with diffi- 
 culty. A vacuum filter, connected with a 
 laboratory aspirating pump, is a very convenient 
 method of getting the concentrate out of the 
 froth. A large porcelain Biichner funnel fitted 
 into a filtering flask, as is shown in Fig. 23, is 
 found to be very convenient. A copper vacuum 
 filter is of much the same type, provided with 
 a porous false bottom of acid-proof wire-cloth, 
 resting on a punch plate, as shown in Fig. 32, 
 of the Callow test set. Such a filter can be 
 
 1 "Oils for Flotation," by Chas. Y. Clayton and C.E. 
 Peterson, Min. & Sci. Press, April 22, 1916. 
 
126 TESTS 
 
 placed under the froth discharge of a flotation 
 machine so that a fairly dry cake of the con- 
 centrate is ready for further drying at the end of 
 the flotation test. By loosening the outer rim 
 of filter paper and then turning the funnel up- 
 side down over a pan, the filter-paper with the 
 concentrate can be dropped into the dry-pan 
 by gently blowing into the stem of the funnel. 
 This is set aside in a warm place to dry and later 
 weighed against a filter-paper tear. After 
 weighing a numbered tag is put in each pan 
 along with the cake. 
 
 The products coming from the flotation ma- 
 chine should be watched closely and occasionally 
 panned or examined with the microscope to see 
 what kind of work is being done. This is fairly 
 easy to determine as the sulphides are most of 
 them distinguished easily from the gangue under 
 the microscope, and likewise gangue particles 
 in the froth concentrate can often be dis- 
 tinguished. A microscope is a most useful ad- 
 junct in a flotation laboratory. 
 
 Types of Machines and Their Operation 
 
 Flotation-test apparatus must necessarily be 
 classified in the same way as large-scale ma- 
 chines, namely: (a) film-flotation machines, 
 (6) acid-flotation machines and (c) froth ma- 
 chines of both pneumatic and mechanically 
 agitated types. 
 
 Film Flotation, as exemplified in the Mac- 
 quisten l and in the Wood machines, does not 
 i Min. & Sd. Press, Vol. XCVI, p. 414 (1908). 
 
FILM FLOTATION 
 
 127 
 
 seem to have the same wide application as does 
 froth flotation; hence little need be said about 
 them. 
 
 Macquisten tubes have such a small capacity 
 that a single tube is small enough for test-work 
 on a few pounds of ore at a time (Fig. 18). A 
 
 -Feed 
 
 Concentrate 
 
 Tailing 
 
 * FIG. 18. 
 
 small 4-ft. tube is known to give trustworthy 
 results, although a larger one is more desirable. 
 The Wood machine can be built in miniature 
 and for several years a small machine of the 
 type shown in Fig. 19 has been used in the 
 plant of the Wood Ore-testing Works at Denver. 1 
 This machine was about 2 ft. long and 1 ft. 
 
 1 H. E. Wood, Trans. A.I.M.E., Vol. XLIV, pp. 
 684-701 (1912). 
 
128 
 
 TESTS 
 
 wide. The method of operation is the same as 
 that of a full-sized machine. As neither of 
 these machines has been much used in practice, 
 
 FIG. 19. 
 
 they are merely mentioned for the sake of com- 
 pleteness. Hoover l has recommended a test 
 on a vanning plaque so that the sulphides will 
 1 " Concentrating Ores by Flotation." 
 
FILM FLOTATION 
 
 129 
 
 float off onto the surface of the water, but this 
 method is not practical and Hoover has given it 
 merely as a test to illustrate the film processes. 
 In testing ores for the Potter and the Delprat 
 processes Hoover gives an illustrative test-tube 
 experiment. (See Fig. 20.) Tubes containing 
 3 per cent H2S0 4 or acid salt-cake solutions and 
 
 FIG. 20. 
 
 a little sulphide ore are warmed nearly to the 
 boiling temperature. Bubbles of C0 2 attach 
 themselves to the sulphide, travel to the sur- 
 face of the solution, discharge into the air, and 
 drop the Sulphide into the pocket on the under- 
 side of the tube, as shown in the sketch. In 
 another test a 200-cc. beaker is used with 100 cc. 
 of 3 per cent H 2 S0 4 and brought to nearly 
 boiling temperature. The ore when intro- 
 duced into this yields a froth composed of 
 sulphides supported by bubbles of C0 2 . In case 
 the ore is deficient in carbonate, an addition of 
 as much as 3 per cent of calcite or siderite is 
 made. The froth is skimmed with a spoon as 
 soon as it forms. The results obtained with 
 
130 
 
 TESTS 
 
 these tubes are, however, not reliable as a great 
 deal of the mineral is often lifted partly but 
 never reaches the surface; consequently ex- 
 tractions are low. A better test machine is the 
 small unit shown in Fig. 21. 
 
 The acid should be allowed to run down 
 through a section of garden hose to within an inch 
 
 Garden Hose 
 
 Wooden Paddle 
 
 Froth 
 
 FIG. 21. 
 
 of the surface of the ore and the ore should be 
 kept stirred with a wooden paddle so that the 
 bubbles of C0 2 generated by the action of the 
 acid can lift the sulphides out of the body of the 
 pulp. The froth formed should be skimmed with 
 the paddle as fast as made, then filtered, dried, 
 weighed, and analyzed. Not many ores yield 
 gracefully to this treatment as slimes give poor 
 extractions. Fines and Wilfley-table middlings 
 are better adapted, and the presence of siderite 
 in the pulp is desirable, as it reacts slowly with 
 
MECHANICAL FROTHING 131 
 
 dilute acid. From 1 to 3 per cent of H 2 S0 4 is 
 best in testing and \ to \\ per cent solutions on 
 the large scale will give about the same results. 
 The temperature of the pulp should be main- 
 tained at 70 C. by use of a steam jet. The 
 extractions obtained are always lower than in 
 full-sized units. While it is not necessary in 
 this process, it will greatly assist in the flotation, 
 and the addition of a small amount is often of 
 much assistance in test-work. 
 
 Mechanical Frothing. This process, as de- 
 veloped by the Minerals Separation Co., in 
 England and Australia, and modified by others, 
 has been one of the most important methods of 
 flotation, therefore the laboratory machinery 
 that has been developed is at as high a state of 
 perfection as any such machinery now in use. 
 
 The Janney machine is probably the best de- 
 signed machine for getting reliable quantitative 
 results on a small quantity of ore. See photo- 
 graph and sketch, Figs. 22 and 23. It can be 
 seen that the agitation-compartment is cylin- 
 drical in shape and that its top is surrounded 
 by a froth-box, which slopes into a spitzkasten, 
 where the froth can be skimmed. The tailing 
 sinks to a return-hole at the bottom, passing 
 into the agitation-compartment again. To pro- 
 vide good agitation, four vertical baffles are 
 attached to the wall of the agitation-compart- 
 ment, against which the pulp is swirled by the 
 two impellers. Lining the walls with expanded 
 metal lathing or with a coarse-mesh iron screen 
 adds to the thorough mixing that the pulp must 
 
132 TESTS 
 
 receive. The two impellers are on a common 
 shafting, which enters the machine through a 
 stuffing-box in the bottom of the machine. The 
 lower impeller with four vertical' vans is sub- 
 merged; it agitates and emulsifies the pulp with 
 the upper impeller, likewise, with four vertical 
 vans, acts as a pump to lift the pulp and beat 
 air into ifc. A pulley and belt connect the shaft 
 with a variable-speed motor. 
 
 A dome-shaped lid is used on the machine. 
 A small hole in the top of the dome allows the 
 introduction of oil, acid, water, or other material 
 of the test. The lid is so constructed that it can 
 be turned upside-down with the dome extending 
 down into the froth-box, and in this position it 
 can act as a funnel. The dome rests then on the 
 top of the agitation-compartment and no froth 
 can escape into the froth-box. This allows 
 a period of agitation of the pulp before the 
 dome-top is turned right-side up to allow aeri- 
 ated pulp to overflow into the froth-box and 
 down into the spitzkasten, where the froth can 
 be removed. 
 
 A discharge-plug at the bottom of the ma- 
 chine allows the flushing out of tailing after 
 the test has been completed. So careful has 
 been the design of this test-machine that even 
 this discharge-plug is beveled to fit flush with 
 the bottom of the machine and thus affords no 
 dead space in which the solids might settle. 
 
 The spitzkasten is long and narrow, in order 
 to permit a deep froth to be formed and to 
 travel over as long a space as possible, before 
 
MECHANICAL FROTHING 133 
 
 reaching the discharge. This tends to allow 
 more of the entrained gangue to settle out of 
 a mineral froth. The sides of the spitzkasten 
 are of heavy plate-glass, each fastened to a 
 metal frame by means of screws. The wrought- 
 iron shaft projects through a brass stuffing-box 
 and is supported by a ball-bearing beneath. All 
 the other metal parts are of cast aluminum. 
 
 The small variable-speed motor may be of 
 either direct-current or alternating-current 
 type. F. G. Janney recommends the use of a 
 General Electric shunt-wound, direct-current 
 motor for 230 volts, with a rated speed of 1700 
 r.p.m. and \ h.p. The impeller shaft is to be 
 driven at 1900 r.p.m. maximum speed. For 
 speed-control he recommends a General Elec- 
 tric direct-current field rheostat, with an ampere 
 capacity of 1.25 to 0.063 at 250 volts. 
 
 The operation of the machine is as follows: 
 It is set up on a bench convenient to the sink 
 and to running water. The motor is set up 
 1 ft. to (Jie rear with the switch and rheostat 
 placed so that they can be easily reached while 
 standing in front of the machine. A IJ-in. 
 round-leather sewing-machine belt is used for 
 the drive. The bearings are well oiled, the 
 stuffing-box is properly packed, and some at- 
 tention should be given to it occasionally in 
 order to see that it is kept screwed tight enough 
 to avoid leakage. 
 
 Enough clear water is run into the machine 
 to barely show in the spitzkasten and the mo- 
 tor is started at its lowest speed. A 500-gm. 
 
134 
 
 TESTS 
 
 charge of ore ground to at least 48 mesh is added 
 and the cover placed on the machine in its 
 
 FIG. 22. 
 
 inverted position. (See Fig. 22.) This is done 
 to allow thorough mixing without circulation of 
 the pulp. All or part of the oil and other re- 
 
MECHANICAL FROTHING 
 
 135 
 
 agents are now added and the motor brought 
 up to full speed for 30 seconds. The speed is 
 again lowered to the minimum and the cover 
 is turned over into its upright position. (See 
 Fig. 23.) The speed is then raised and water is 
 added through the hole in the top of the lid 
 
 until the froth in the spitzkasten is nearly 
 at the overflow lip. The ultimate speed of the 
 agitator will depend somewhat upon the charac- 
 ter of this froth, as some oils will give a deep 
 persistent froth, while other froths are thin and 
 brittle and allow of more water being added to 
 the machine, as well as more violent agitation 
 in order to beat more air into the pulp. The 
 
136 TESTS 
 
 froth may either be allowed to flow out of the 
 spitzkasten of its own weight or skimmed with 
 a small wooden paddle. It is a good idea to wet 
 the glass sides of the " spitz " with water while 
 the froth is rising, so that none of the froth will 
 stick to the glass. 
 
 The duration of the test is about 5 minutes 
 with an ore that floats easily, while other ores 
 will require a considerably longer time to allow 
 the entrained gangue to settle out of the froth 
 before it is discharged from the machine. In 
 such cases it is best to hold back the froth until 
 its appearance shows it to be fairly clean. Be- 
 ginners are likely to dilute their froth with too 
 much gangue. In a large-sized machine the 
 froth can travel over from 4 to 8 ft. of spitzkasten 
 before it is discharged, while in this test ma- 
 chine it only has a travel of about 10 in. Con- 
 sequently, the small machine is liable to yield 
 concentrate of too low a tenor. The same ap- 
 plies to most other machines for making tests 
 on flotation. 
 
 The concentrate may be caught in a pan or 
 on a filter. After the test the machine is brought 
 back to low speed and the tailing plug removed, 
 so that the tailing can be caught in a pan or 
 bucket or run to waste. 
 
 If it is so desired, this rough concentrate can 
 be put back into the machine and treated in the 
 same way as the original sample, or the con- 
 centrates from several tests combined to give 
 enough material for retreatment. If this is done 
 three products are made, namely: 
 
MECHANICAL FROTHING 137 
 
 1. A " rougher " tailing to waste. 
 
 2. A clean concentrate for shipment. 
 
 3. A " cleaner " tailing or middling which in 
 actual practice is returned to the head ma- 
 chine. 
 
 When these conditions are observed results 
 only slightly lower than those possible with a 
 big machine can be obtained. A test can be 
 run in from 5 to 30 minutes in such a machine 
 with 500 gm. of ore in anything from a 3 : 1 to 
 a 5 : 1 pulp. The glass sides of the spitzkasten 
 allow close observation of the condition of the 
 froth, and this is a great advantage to the be- 
 ginner. The small amount of ore necessary for 
 a test is a matter of considerable convenience 
 as fine grinding of the ore in the laboratories 
 is often irksome. The aluminum casting is 
 little corroded by either acid or alkaline elec- 
 trolytes. The return of pulp from the " spitz " 
 to the agitating compartment allows the material 
 to be treated until all mineral has been removed 
 without ^topping the machine, so that a single 
 treatment yields a clean tailing. However, a 
 second treatment of this " rougher-froth " is 
 sometimes necessary in order to get a high- 
 grade concentrate. Clean tailings generally 
 mean only medium-grade concentrates due to 
 entrainment of gangue in the removal of all the 
 mineral. 
 
 The stuffing-box in the bottom will probably 
 leak if not watched. However, this driving of 
 the impeller from below, instead of from above, 
 leaves the top of the machine free for the op- 
 
138 
 
 TESTS 
 
 erator and is more convenient in every way. 
 This is of importance in a laboratory machine 
 and will excuse the use of a stuffing-box. In 
 large-scale machines a stuffing-box underneath 
 would not be tolerated and the drive should be 
 from above. 
 
 The Hoover Machine. The so-called Hoover 
 machine was designed after a testing machine 
 described in the second edition of Hoover's 
 book, being copied from one of Lyster's patents, 
 and has been much copied by people wishing to 
 make flotation tests. In general, the machine 
 
 Pulp i 
 
 Impeller 
 
 " Contracted Spitzkaten. 
 
 FIG. 24. 
 
 is not nearly so convenient for making tests as 
 the Janney machine and other recent testing 
 machines on the market. Its cost of construc- 
 tion has been the main point in its favor. The 
 
THE HOOVER MACHINE 
 
 139 
 
 Janney machine will cost about $100 while the 
 Hoover machine can be built for a small frac- 
 tion of this amount. In the agitation-compart- 
 ment the pulp is swirled into the corners (see 
 Fig. 24) where it is well mixed with air; hence 
 the baffles sketched in the Janney machine are 
 unnecessary. One objection, however, is that 
 unless the agitation-compartment is very tall 
 the pulp being swirled in the corners has a 
 tendency to splash out, and a lid similar to the 
 
 FIG. 25. 
 
 one on the Janney machine is desirable. How- 
 ever, it is difficult to attach one because the 
 sfirrer shafting is in the way. The operation 
 of this machine is practically the same as that 
 of the Janney, except that without glass sides 
 on the spitzkasten it is hard to get as clean a froth. 
 A charge of 1000 to 2000 gm. was necessary in 
 this machine. 
 
140 TESTS 
 
 Other modified forms of the Hoover machine 
 are shown in Figs. 25 and 26. 
 
 The Slide Machine. This machine as shown 
 in Fig. 27 was designed by Hoover and per- 
 fected by many others. In recent practice 
 it is motor driven. Many people favor this 
 apparatus for the reason that they have had 
 little opportunity to use any other design. In 
 this machine the agitator is driven from below 
 through a stuffing-box, as in the Janney, with the 
 consequent freedom of the top of the machine for 
 the convenience of the operator. The top half 
 of the machine is so constructed that it can be 
 slid to one side, cutting off the froth formed in 
 the agitation from the gangue, which is allowed 
 to settle. The operation consists in agitating 
 the oil and other reagents, then a period of quiet 
 during which the froth collects at the top while 
 the gangue sinks. Two windows in the side 
 enable the observer to see when the gangue has 
 subsided sufficiently to allow the top half to be 
 slid along the rubber gasket, cutting off the 
 froth from the remainder of the pulp. The 
 time necessary for the settling of the gangue is 
 sufficient for much of the gangue to separate 
 from the froth, leaving only clean sulphides 
 in the froth. This element of the machine has 
 made it of some value in testing flotation-oils, 
 but in a weak froth much of the sulphide mineral 
 also settles out and is lost, so that the test re- 
 sults with this machine often show unneces- 
 sarily low extractions and a high grade of 
 concentrate. On the other hand when con- 
 
1 T \ 
 
 X H.PJMotor \ 
 
 }4 diam. .hol 
 
 * 
 
 Lead or Copper Pipe y 
 i/insidediam. -^ 
 
 to 1 diam. hole for cleaning, 
 to be fitted with a plug 
 
 Impeller.peripherical speed 
 (1500 to 1800 
 
142 
 
 TESTS 
 
 ditions are adjusted to give a froth persistent 
 enough to hold all the sulphide mineral, con- 
 siderable gangue is entrained in the stiff froth. 
 
 FIG. 27. 
 
 Further, after skimming one froth we find it 
 necessary to add more water and start the ma- 
 chine again to make more froth. It is hard to 
 make the slide machines give a high extraction 
 with only one agitation. The intermittent char- 
 acter of such work and the time necessary to 
 wait while settling are disadvantages that make 
 the Janney or Hoover machines of greater utility. 
 The parts are of cast aluminum with a rubber 
 gasket between. A charge of 500 to 1000 gm. 
 of ore is used. 
 
 The Case Machine. This machine consists 
 of a single aluminum casting, comprising the 
 
THE SLIDE MACHINE 143 
 
 FIG. 29. 
 
144 TESTS 
 
 agitation cell and a spitzkasten from which the 
 froth is collected. 
 
 The agitation cell contains a shaft and im- 
 peller. The impeller is provided with four 
 blades set at angles of 90 degrees. The steel 
 shaft is coated with lead and the impeller 
 blades are made of aluminum to resist the 
 corrosive action of acids. 
 
 A piece of extra heavy pressure tubing pro- 
 vides for connection between the bottom of the 
 spitz box and the agitation cell. (See Fig. 29.) 
 With this tubing is supplied a strong pinch-cock 
 for the regulation of pulp circulation, the 
 pressure tubing being easily removed for cleaning 
 purposes. 
 
 The operation of this machine is practically 
 the same as that of the Janney and the Hoover 
 type. It is apparently a modified Hoover ma- 
 chine, made by the Denver Fire Clay Company, 
 Denver, Colo. 
 
 The Roy and Titcomb Machine. This ma- 
 chine invented and made by Roy and Titcomb, 
 Inc., Nogales, Ariz., is a machine which is 
 self-contained (Fig. 30). 
 
 The cells are cast in one piece. This is a 
 machine apparently well suited for laboratory 
 testing purposes, especially if power is not 
 available. They are also made for motor drive. 
 A hand-power machine costs $85. 
 
 Separatory Funnels. During the past year 
 an article on practice in Mexico l mentioned the 
 fact that much of the preliminary testing on the 
 1 Min. & Sci. Press, July 24, 1915. 
 
THE CASE MACHINE 
 
 145 
 
 FIG. 30. 
 
146 
 
 TESTS 
 
 ore is done in separatory funnels (Fig. 31) in 
 which the charges of pulp, oil, etc., were shaken, 
 after which the cock at the 
 bottom of the funnel was 
 opened and the tailing run 
 into a second separatory fun- 
 nel for further flotation tests, 
 the cock being closed in time 
 to catch the froth. The ver- 
 satility of experiment per- 
 missible with the use of such 
 apparatus is commendable. 
 Obviously, this arrangement 
 is open to the same objection 
 as is the slide machine except 
 that separatory funnels are 
 simple and inexpensive. 
 
 In comparison of the above 
 mechanical agitation type of 
 laboratory machine the Jan- 
 ney and Hoover machines are by far the most 
 useful. 
 
 Pneumatic Flotation. Among the different 
 pneumatic machines, the Callow test-machine is 
 the only one of laboratory size that has been 
 much developed. It is merely the commercial 
 Callow machine reduced in size. (See Figs. 32, 
 33.) Fig. 32 shows the whole plant in miniature 
 as developed in the laboratory of the General 
 Engineering Company in Salt Lake City. It 
 consists of a Pachuca mixer, a roughing cell, 
 cleaning cell, vacuum filter, and sand pump to 
 return middling to Pachuca mixer. 
 
 FIG. 31. 
 
PNEUMATIC FLOTATION 
 
 147 
 
 As seen in the drawing, the pulp is mixed with 
 a Pachuca tank of small size overflowing into 
 the rougher flotation-cell. The tailing from this 
 rougher goes to a sand-pump and is returned 
 to the Pachuca. The froth is treated in a second 
 
 Air Line, 4 Ibs. Pressure 
 Pressure Gauge 
 s from Rougher 
 nd Cleaner Cells. 
 
 FIG. 32. 
 
 and smaller pneumatic-flotation unit, giving a 
 concentrate that overflows into an ordinary 
 laboratory vacuum-filter actuated by a water 
 or aspirating pump. The tailing from the 
 " cleaner cell " consists of a middling that like- 
 wise flows to the sand-pump and back to the 
 Pachuca. 
 
 A novice will have no small difficulty in oper- 
 ating such an installation, as there are a number 
 of things to be kept in operation at the same time. 
 
 The mixture of ore, water, oil, and any 
 other reagent is fed either into the suction of the 
 sand-pump or into the top of Pachuca after air 
 
148 
 
 TESTS 
 
 has geen started into the various machines. 
 The overflow from the Pachuca into the rougher 
 cell accumulates until a nice froth is coming up 
 
 FIG. 33. 
 
 and nearly overflowing. Then the tailing-dis- 
 charge valve is gradually opened and froth 
 allowed to overflow from the cell into the 
 " cleaner cell." It is best to get most of the 
 
PNEUMATIC FLOTATION 149 
 
 charge circulating before much concentrate- 
 froth is allowed to overflow, the overflow of 
 froth being controlled by the main air valves 
 leading to each unit. After the valves into 
 the individual wind-boxes beneath the machine 
 have been once adjusted they should never be 
 disturbed, and all control of air supplied should 
 be at the valves in the main pipes. When 
 everything is going well, the air-pressure in the 
 cleaner can be increased until concentrate-froth 
 is overflowing into the vacuum filter. A wooden 
 paddle to stir any settled material in the flo- 
 tation-cell is of value, as well as a small jet of 
 water from a rubber hose for washing concentrate 
 along the froth-launders and for beating down 
 froth when occasional too-violent rushes of 
 froth from the cells take place. After a test is 
 complete the pulp should be drained completely 
 from all parts of the machine while the air is 
 still blowing, so that solids will not settle in 
 passages or clog the canvas blanket in the cells. 
 Only practice will allow any one to get reliable 
 results with this machine. A watch-glass for 
 catching and panning occasional samples of froth 
 is another necessary auxiliary to this equip- 
 ment. The cost of installing such a set of 
 apparatus is from $100 to $150. At least 1000 
 gr. of ore is required for a test and about 30 
 minutes to 1 hour is spent. It can be seen that 
 nothing but a finished concentrate and a tailing 
 are obtained or a middling product may be left 
 in the cleaner cell. This middling may be 
 assayed as such and calculated into the con- 
 
150 TESTS 
 
 centrate and tailing or its sulphides may be 
 panned out and added to the concentrate. The 
 -machine is said to give results closely paralleling 
 those obtained with larger-scale apparatus. A 
 source of supply of air at 3 to 5 Ib. per square 
 inch is necessary and the main valves on the 
 air-pipe leading to each machine should be some 
 type of needle valve in order to insure exact 
 control. 
 
 In connection with this apparatus a quali- 
 tative oil-tester should be used. A good tester 
 consists of a glass tube of about 
 2 in. in diameter and 2 ft. long 
 (Fig. 34). This can be set on 
 end and closed at the bottom 
 with a one-hole rubber stopper 
 through which passes a glass 
 tube into a small canvas bag. 
 The small bubbles of air coming 
 through the canvas are similar 
 to those used in large-scale ma- 
 chines and can be observed through the glass 
 walls of the tube. With some pulp in the tube, 
 oils, acids, salts, etc., may be added in very short 
 tests until the proper appearance is obtained. 
 An overflow lip is provided in case it is desired 
 to examine the mineral in the froth. A slight 
 adjustment of the air will provide an ample 
 overflow of froth. 
 
CHAPTER VII 
 THE COST OF FLOTATION 
 
 After having determined a satisfactory com- 
 bination of oils, etc., and in general the ore is 
 found to be amenable to the flotation process, 
 the next important question confronting the 
 flotation engineer is, " How much will a flo- 
 tation plant of a given required capacity cost?" 
 Or, "How does the cost of flotation compare with 
 that of other methods of concentration?" It is 
 hard to obtain any exact figures that will apply 
 in all cases, but a few average and approximate 
 figures for some of the flotation processes are 
 given below; from these the reader can be able 
 to figure out for himself approximately the cost 
 of any particular kind and size of flotation plant. 
 
 For the Callow or Pneumatic agitation proc- 
 ess, the following figures are those given by 
 John M. Callow. 1 
 
 Power. The National Copper Co., which 
 treats 500 tons per day, requires 35 h.p. This 
 means 12.53 tons per horse power, or 1.25 kw- 
 hr. per ton. 
 
 A company which treats 2400 tons per day 
 requires 210 h.p., which means 11.45 tons per 
 horse power, or 1.56 kw-hr. per ton. 
 
 1 Paper as presented by him at annual meeting of 
 Utah section of the A.I.M.E., Salt Lake City, October, 
 1915. 
 
 151 
 
152 THE COST OF FLOTATION 
 
 The former company uses 10 cells and the 
 latter 60, which gives 3.5 horse power per cell in 
 both cases. 
 
 He gives the maximum figure as 2.5-kw-hr. 
 per ton of feed, with an air pressure of from 5 
 to 5.5 lb., the air being generated by a Roots or 
 Connersville positive blower. 
 
 Oil, Labor, and Maintenance. The oil costs 
 from 1J to 3 per pound, and about 1.5 lb. of 
 oil to the ton of feed is used. This would give 
 an average of 2.5^ per ton of feed. The average 
 cost of labor and maintenance would be about 
 If i per ton of feed. 
 
 The following is also given by Mr. Callow, 
 as being an average figure for a 2000-ton plant : 
 
 Labor $0.0125 
 
 Oil -. 0.0250 
 
 Maintenance . 0050 
 
 Power 0.0250 
 
 Total, per ton of feed $0.0675 
 
 And for a 250-ton plant about lOji per ton of 
 feed. As the size of the plant increases, one can, 
 of course, see that the cost per ton of feed will 
 decrease, and in one case a figure as low as $0.061 
 is given. 
 
 The Denver Fire Clay Co., Denver, Colo., 
 gives the cost of a complete flotation plant of 
 100 tons capacity as ranging from $1500 to 
 $5000. The cost of oil, 7 to 15 i per ton, cost 
 of acid 10 to 20jzS, and the operation and main- 
 tenance, from 15 to 25 i per ton. From these 
 figures the total cost of flotation ranges from 
 
OIL, LABOR, AND MAINTENANCE 153 
 
 32 to 60^ per ton of ore, in a process where both 
 oil and acid are used. 
 
 In the case of the Potter process, Hoover 
 gives the cost per unit as about $1000, in- 
 cluding installation, for the Elmore vacuum 
 machine, about $1750 per unit, a capacity of a 
 unit ranging from 30 to 50 tons per day. 
 
 For the various flotation processes in use at 
 Broken Hill, we have an average figure of 3 s. 
 7 d. or 43^ per ton of ore. This figure does not 
 include the royalty of 1 shilling per ton of ore 
 treated. 
 
 From recent data published, the cost of flo- 
 tation in a certain mill is 35 per ton of crude 
 mill feed, or 60^ per ton of actually treated; 
 whereas in the same mill the cyanide process 
 costs 80^ per ton of crude mill feed, or $1.50 
 per ton of ore actually treated. 
 
 At the mill of the Consolidated Copper Co., 
 Miami, Ariz., about 14,500 tons of ore are 
 treated daily by the flotation process. Includ- 
 ing royally, the mining and milling costs about 
 $1.00 to $1.15 per ton of ore, which would make 
 the c&st of concentration almost corresponding 
 to the cost mentioned above. 
 
 At the mill of the Consolidated Arizona 
 Smelting Co., Humboldt, Ariz., the cost of 
 concentration by flotation, including coarse 
 crushing and flotation royalty, is slightly over 
 $1.00 per ton. For a period of six months, 
 the cost of flotation, exclusive of royalty, was 
 27 'i per ton. The power consumption of the 
 flotation machine is 32.7 kw. per hour. 
 
154 THE COST OF FLOTATION 
 
 The royalty charged by process owners for 
 the use of their processes is very high; Hoover 
 gives the average figure as 1 shilling or 25 j per 
 ton of ore treated. Few companies are willing 
 to pay such a high royalty and this naturally 
 has been one of the chief sources of trouble. 
 
 Judging from the figures given, one can see 
 that the cost of flotation for various processes, 
 localities, and ores varies greatly. To get the 
 cost of flotation for any particular ore, Stander 
 gives the following items, 1 which if taken into 
 consideration should give an approximate result : 
 power; oil, acid, or both; royalty, if any; labor; 
 supplies and repair work; heat (if a hot solu- 
 tion is required). 
 
 1 "The Flotation Process," by Stander, 1916. 
 
CHAPTER VIII 
 FORMULAS AND TABLES 
 
 Estimation of Consumption of Oil and Acid 
 per Ton of Feed 
 
 The following is a useful chart whereby the 
 consumption of oil and acid can be estimated 
 per ton of feed. 1 
 
 A concrete example showing how to use the 
 table may not be amiss: Assume that a plant 
 treats 450 tons per 24 hr. and that the con- 
 sumption of pine-oil is 160 cc. per minute, it is 
 desired to find the consumption of pine-oil in 
 pound per ton of feed. 
 
 From the point of intersection of the 100 
 cc. per minute line and the pine-oil line, follow 
 down and read the figure 2.95, which would be 
 the consumption in pound per ton at 100 cc. per 
 minute, and 100 tons of feed per 24 hr. 
 
 Inasmuch as the consumption of oil is greater 
 tha^n 100 cc. per minute and the tonnage treated 
 is greater than 100 tons per 24 hr., we must use 
 the third formula to arrive at our final figure. 
 Thus a 
 
 2.95 X 
 
 2.95 X X = 1.05 lb. per ton. 
 
 . 
 450 100 
 
 100 
 
 1 Min. & Sci. Press, May 20, 1916. 
 155 
 
156 
 
 FORMULAS AND TABLES 
 
 
 
 
 
 
 
 
 
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CALCULATION OF TONNAGE 
 
 157 
 
 Calculation of Tonnage of Feed to any 
 Particular Unit 
 
 For the application of this method the tonnage 
 of either the concentrate or the tailing produced 
 must be known and also the assay of all three 
 heads, tailings, and concentrate. The basis of 
 the method is the efficiency by assay of the 
 plant. 
 
 A concrete example, used in figuring the ton- 
 nage to a certain flotation plant, in which both 
 lead and a zinc concentrate were made, will be 
 clearer than the use of formulas and unknowns. 
 
 The concentrate tonnage is known and also 
 the assay (in zinc) of the heads, tailing, and con- 
 centrate. 
 
 Products. 
 
 Assay, Zn 
 per cent. 
 
 Symbol. 
 
 Feed . 
 
 5.7 
 
 H 
 
 Tailing 
 
 2.6 
 
 T 
 
 Concentrate 
 
 40 4 
 
 c 
 
 
 
 
 Then: 
 
 Ratio of concentration 
 
 C - T ^ 40. 4 -2. 6 
 " H- T~ 5.7-2.6 
 
 Efficiency of concentration 
 C X 100 40.4 X 100 
 
 12.1. 
 
 HxR 5.7X12.1 
 
 = 58.7 per cent 
 
 made 211 tons concentrate of 40.4 zinc, which 
 equals 85.2 tons of metallic zinc. 
 
158 FORMULAS AND TABLES 
 
 85.2 tons equals 58.7 per cent of zinc in the 
 original feed. 
 
 100 per cent 58.7 per cent = 41.3 per cent 
 zinc lost in the lead concentrate and tailing, 
 or 59.9 tons metallic zinc. 
 
 85.2 + 59.9 = 145.1 tons of metallic zinc in 
 the original feed. 
 
 145.1 -T- 0.57 = 2545.5 tons of feed to the plant. 
 
 The tonnage of concentrate or tailing could, 
 by knowing the feed tonnage, be equally well 
 calculated by this method. 
 
CALCULATION OF TONNAGE 
 
 159 
 
 2S, 
 "0*3 
 
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 J.sJl' 
 
 I 
 
 . 
 
 j O ft 
 
 
 
 ught. 
 
 Sl 
 
 H 
 
 >> 
 
 '03 
 
 O 
 
 II 
 
 II 
 
 r 
 
 "3 SP 
 
 Hi gj 
 1^11 
 
 S^o g g 
 
 81-14-s 
 
 d*|S6 
 
 asiss-g 
 
 25111 
 
 ,-J oj CO rjn lO O 
 
160 FORMULAS AND TABLES 
 
 Torque units should be distinguished from energy 
 units: Thus, foot-pound and kilogram-meter for energy, 
 and foot-pound and meter-kilogram for torque. 
 
 1 ft.-lb. 1 = 13,560,000 ergs = 1.356 joules = 0.3239 
 g.-cal. = 0.1383 kg.-m. = 0.001285 B.t.u. = 0.0003766 
 watt-hr. = 0.0000005051 h.p.-hr. 
 
 1 kg.-m. = 98,060,000 ergs = 9.806 joules = 7.233 
 ft.-lb. = 2.34 g.-cal. = 0.009296 B.t.u. = 0.002724 watt- 
 hr. = 0.000003704 h.p.-hr. (metric). 
 
 1 B.t.u. = 1055 joules = 778.1 ft.-lb. = 252 g.-cal. = 
 107.6 kg.-m. = 0.5555 Ib. -centigrade heat unit = 0.2930 
 watt-hr. = 0.252 kg.-cal. = 0.0003984 h.p.-hr. (metric) 
 = 0.0003930 h.p.-hr. 
 
 1 watt-hr. = 3600 joules = 2655.4 ft.-lb. = 860 g.-cal. 
 = 367.1 kg.-m. = 3.413 B.t.u. = 0.001341 h.p.-hr. 
 
 1 h.p.-hr. = 2,684,000 joules = 1,980,000 ft.-lb. = 
 273,700 kg.-cm. = 745.6 watt-hr. 
 
 1 kw.-hr. = 2,655,000 ft.-lb. = 367,190 kg.-m. = 1.36 
 h.p.-hr. (metric) = 1.34 h.p.-hr. 
 
 POWER 
 
 1 g.-cm. per sec. = 0.00009806 watt. 
 
 1 ft.-lb. per min. = 0.02260 watt = 0.00003072 h.p. 
 (metric) = 0.00000303 h.p. 
 
 1 watt = 44.26 ft.-lb. per min. = 6.119 kg.-m. per 
 min. = 0.001 kilowatt. 
 
 1 h.p. = 33,000 ft.-lb. per min. = 745.6 watts = 550 
 ft.-lb. per sec. = 76.04 kg.-m. per sec. = 1.01387 h.p. 
 (metric). 
 
 1 kw. = 44,256.7 ft.-lb. per min. = 101.979 kg.-m. per 
 sec. = 1.3597 h.p. (metric) = 1.341 h.p. 
 
 RESISTIVITY 
 
 1 ohm per cir. mil-ft. = 0.7854 ohm per sq. mil-ft. 
 = 0.001662 ohm per sq. mm.-m. = 0.0000001657 ohm 
 per cm. 3 = 0.0000000524 ohm per in. 3 
 
 1 ohm per sq. mil.-ft. = 1.273 ohms per cir. mil-ft. 
 1 The hyphen (-) as used here means " multiplied by." 
 
WEIGHT 161 
 
 = 0.002117 ohm per sq. mm.-m = 0.0000002116 ohm 
 per cm. 3 = 0.00000008335 ohm per in. 3 
 
 1 ohm per in. 3 = 15,280,000 ohms per cir. mil-ft. 
 = 12,000,000 ohms per sq. mil-ft. = 25,400 ohms per 
 sq. mm.-m. = 2.54 ohms per cm. 3 
 
 CURRENT DENSITY 
 
 1 amp. per sq. in. = 0.7854 amp. per cir. in. = 0.1550 
 amp. per sq. cm. = 1,273,000 cir. mils per amp. = 0.000001 
 amp. per sq. mil. 
 
 1 amp. per sq. cm. = 6.45 amp. per sq. in. = 197,000 
 cir. mils per amp. 
 
 1000 cir. mils per amp. = 1273 amp. per sq. in. 
 
 1000 sq. mils per amp. = 1000 amp. per sq. in. 
 
 METRIC SYSTEM WITH CONVERSIONS 
 
 10 milli- = 1 centi-. 10 deca- = 1 hecto-. 
 
 10 centi- = 1 deci-. 10 hecto- = 1 kilo-. 
 
 10 deci- = 1 (unit). 1 kilo- = 1 myria. 
 10 (units) = 1 deca-. 
 
 WEIGHT 
 
 METRIC UNIT is GRAM 
 
 Gram = weight 1 cubic centimeter of water at 4 C. 
 Gram = 15.4324 grains. 
 Gram = .03215 ounce troy. 
 -Gram = .00267923 pound troy. 
 Gram = .03527 ounce avoirdupois. 
 Gram = .00220462 pound avoirdupois. 
 Milligram = .0154324 grain. 
 Kilo or kilogram = 32.15 ounces troy. 
 Kilo or kilogram = 2.67923 pounds troy. 
 Kilo or kilogram = 35.27 ounces avoirdupois. 
 Kilo or kilogram = 2.20462 pounds avoirdupois. 
 Metric ton = 1000 kilos or kilograms. 
 Metric ton = 2204.62 pounds avoirdupois. 
 Metric ton = 1.10231 United States tons (2000 pounds). 
 Grain = .0648 gram. 
 Ounce troy = 31.10348 grams. 
 
162 FORMULAS AND TABLES 
 
 Pound troy = .37324 kilo or kilogram. 
 Pound troy = 373.24 grams. 
 Ounce avoirdupois = 28.3495 grams. 
 Pound avoirdupois = .45359 kilo or kilogram. 
 Pound avoirdupois = 453.59 grams. 
 Ton (2000 pounds) = .90718 metric ton. 
 Ton (2000 pounds) = 907.185 kilograms. 
 Assay ton = 29.1666 grams. 
 Assay ton = .0377 ounce troy. 
 Assay ton = .07814 pound troy. 
 Assay ton = 1 .0287 ounces avoirdupois. 
 Assay ton = .0643 pound avoirdupois. 
 
 CAPACITY 
 
 METRIC UNIT is LITER 
 Liter = 1000 cubic centimeters. 
 Liter = .26417 gallon (231 cubic inches). 
 Liter = 1.05668 quarts. 
 Liter = 33.81 liquid ounces. 
 Liter = 61.023 cubic inches. 
 Gallon (231 cubic inches) = 3.78543 liters. 
 Gallon (231 cubic inches) = 3785.43 cubic centimeters. 
 Liquid ounce = .029574. 
 
 VOLUME 
 
 Cubic meter = 35.314 cubic feet. 
 Cubic meter = 1.3079 cubic yards. 
 Cubic centimeter = .061 cubic inch. 
 Cubic foot = .02832 cubic meter. 
 Cubic yard = .7645 cubic meter. 
 
 LENGTH 
 
 METRIC UNIT is METER 
 
 Meter = 39.37 inches. Inch = 2.54 centimeters. 
 
 Meter = 3.280833 feet. Foot = 30.48 centimeters. 
 
 Kilometer = 3280.833 feet. Foot = .3048 meter. 
 Kilometer = .62137 mile. Mile = 1.60935 kilometers. 
 Centimeter = .3937 inch. Mile = 1609.347 meters. 
 
WEIGHTS AND MEASURES 163 
 
 AREA 
 
 Square meter = 10.764 square feet. 
 Square meter = 1550.3 square inches. 
 Hectare or square hectometer = 2.4711 acres. 
 Square kilometer = 247.1 acres. 
 Square inch = 6.452 square centimeters. 
 Square foot = 929 square centimeters. 
 Square foot = .0929 square meter. 
 Square mile = 2.59 square kilometers. 
 Acre = .40469 hectare. 
 Acre = 4046.9 square meters. 
 
 UNITED STATES WEIGHTS AND MEASURES 
 AVOIRDUPOIS WEIGHT 
 
 27.34375 grains = 1 dram. 
 
 16 drams = 1 ounce (oz.). 
 
 437.5 grains = 1 ounce. 
 
 16 ounces = 1 pound (lb.). 
 
 7000 grains = 1 pound. ' 
 
 100 pounds = 1 hundredweight. 
 
 2000 pounds = 1 short ton (usually used). 
 
 2240 pounds = 1 long ton (seldom used). 
 
 TROY WEIGHT 
 
 24 grains = 1 pennyweight (dwt.). 
 20^ pennyweights = 1 ounce (oz.). 
 480 grains = 1 ounce. 
 12 ounces = 1 pound (lb.). 
 5760 grains = 1 pound. 
 
 APOTHECARIES' WEIGHT 
 
 20 grains = 1 scruple. 480 grains = 1 ounce. 
 
 3 scruples = 1 dram. 12 ounces = 1 pound. 
 
 8 drams = 1 ounce. 5760 grains = 1 pound. 
 
164 FORMULAS AND TABLES 
 
 
 
 LENGTH 
 12 inches = 1 foot. 4 rods = 1 chain. 
 
 3 feet = 1 yard. 66 feet = 1 chain. 
 5| yards = 1 rod. 320 rods = 1 mile. 
 16J feet = 1 rod. 5280 feet = 1 mile. 
 
 AREA 
 
 144 square inches = 1 square foot. 
 9 square feet = 1 square yard. 
 30J square yards = 1 square rod. 
 160 square rods = 1 acre. 
 640 acres = 1 square mile. 
 
 VOLUME 
 
 1728 cubic inches = 1 cubic foot. 
 27 cubic feet = 1 cubic yard. 
 
 CAPACITY 
 
 Liquid 
 
 4 gills = 1 pint. 
 
 2 pints = 1 quart. 
 
 4 quarts = 1 gallon (231 cubic inches). 
 
 63 gallons = 1 hogshead. 
 
 31J gallons = 1 barrel 
 
 Dry 
 
 2 pints = 1 quart. 
 
 4 quarts = 1 gallon (268.8025 cubic inches). 
 2 gallons = 1 peck. 
 4 pecks = 1 bushel (2150.42 cubic inches). 
 
 AVOIRDUPOIS AND TROY CONVERSIONS 
 
 Ounce troy = 1.09714 ounces avoirdupois. 
 Pound troy = 13.166 ounces avoirdupois. 
 Pound troy = .822857 pound avoirdupois. 
 Ounce avoirdupois = .91145 ounce troy. 
 Pound avoirdupois = 14.583 ounces troy. 
 Pound avoirdupois = 1.21528 pounds troy. 
 
THERMOMETER READINGS 165 
 
 Ton (2000 pounds avoirdupois) = 29,166f ounces troy. 
 Ton (2000 pounds avoirdupois) = 2430.56 pounds troy. 
 
 MONEY 
 
 ENGLISH 
 
 4 farthings = 1 penny (d). 1 pound = 7.3224 grams 
 4 pence = 1 shilling (s). gold. 
 
 20 shillings = 1 pound (). 1 pound = $4.8665 United 
 1 pound = 113.001 grains States money, 
 gold. 
 
 MEXICAN 
 
 100 centavos = 1 peso. 1 peso = .87 or J troy ounce 
 
 1 peso = 417.74 grains sil- (approximate) silver, 
 ver. 1 peso = 27.073 grams sil- 
 
 ver. 
 
 UNITED STATES >"'*., 
 
 100 cents = 1 dollar ($). 1 dollar = 23.22 grains gold. 
 
 VALUE OF GOLD 
 
 1 ounce troy = $20.67. 
 
 1 pennyweight (dwt.) = ^ ounce troy. 
 
 1 pennyweight = $1.03^. 
 
 1 grain = 4.306 cents (United States). 
 
 1 gram = $0.6646. 
 
 1 gram = .03215 or ^ T (approximate) ounce troy. 
 
 1 kilo = $664.60. 
 
 1 kilo = 32.15 ounces troy. 
 
 CONVERSION OF THERMOMETER READINGS 
 
 
 Freezing point. 
 
 Boiling point. 
 
 Fahrenheit 
 
 degrees. 
 
 degrees. 
 01 o 
 
 Centigrade 
 
 32 
 
 212 
 
 1 /-v/-v 
 
 
 
 
 1UU 
 
 To convert Fahrenheit to Centigrade, subtract 32 and 
 multiply by f . 
 
166 
 
 FORMULAS AND TABLES 
 
 To convert Centigrade to Fahrenheit, multiply by f 
 and add 32. 
 
 WEIGHT AND MEASURE OF WATER 
 
 1 pound (avoirdupois) water = 27.68122 cubic inches. 
 1 pound (avoirdupois) water = .0160192 cubic foot. 
 1 gallon (United States liquid) water = 231 cubic inches. 
 1 gallon (United States liquid) water = .13368 cubic foot. 
 1 gallon (United States liquid) water = 3.78543 liters. 
 1 gallon (United States liquid) water = 8.3389 pounds 
 
 (avoirdupois). 
 
 1 cubic foot water = 62.42 pounds (avoirdupois). 
 1 cubic foot water = 7.48052 gallons. 
 1 cubic foot water = 28.318 liters. 
 1 ton water = 339.84 gallons. 
 1 ton water = 32.941 cubic feet. 
 1 ton water = 907.2 liters. 
 1 liter water = 2.2046 pounds (avoirdupois). 
 
 WEIGHT OF ROCK AND SAND 
 
 
 Cubic feet 
 per ton. 
 
 Weight in 
 pounds per 
 cubic foot. 
 
 Sulphide ore in place 
 
 11-13 
 
 182-154 
 
 Sulphide ore broken 
 
 15-18 
 
 133-111 
 
 Oxidized ore in place 
 
 14-18 
 
 143-111 
 
 Oxidized ore broken 
 
 22-24 
 
 91-81 
 
 Quartz in place. (Specific grav- 
 ity, 2.65) 
 
 12 
 
 165 
 
 Quartz broken 
 
 21 
 
 94 
 
 Earth in bank 
 
 18 
 
 111 
 
 Earth, dry and loose 
 
 27 
 
 74 
 
 Clay 
 
 17 
 
 118 
 
 Loose sand 
 
 25 
 
 80 
 
 Mill tailing. (Specific gravity, 
 2.7) 
 Sand collected under water 
 Transferred sand (before 
 leaching) 
 
 21.5 
 26 
 
 93 
 
 77 
 
 Leached sand (that has been 
 transferred) 
 
 24 
 
 83.3 
 
 
 
 
AUTOMATIC WEIGHTS, 1917 
 
 167 
 
 INTERNATIONAL ATOMIC WEIGHTS, 1917 
 
 Element. 
 
 Sym- 
 bol. 
 
 Atomic 
 weight. 
 
 Element. 
 
 Sym- 
 bol. 
 
 Atomic 
 weight. 
 
 Aluminium 
 Antimony 
 
 Al 
 Sb 
 
 27.1 
 120 2 
 
 Neodymium 
 Neon 
 
 Nd 
 
 Ne 
 
 144.3 
 20 2 
 
 Argon 
 
 A 
 
 39.88 
 
 Nickel 
 
 Ni 
 
 58 68 
 
 Arsenic 
 
 As 
 
 74.96 
 
 Niton (radium em- 
 
 
 
 Barium 
 
 Ba 
 
 137.37 
 
 anation) 
 
 Nt 
 
 222.4 
 
 Bismuth 
 
 Bi 
 
 208.0 
 
 Nitrogen 
 
 N 
 
 14.01 
 
 Boron . 
 
 B 
 
 11.0 
 
 Osmium 
 
 Os 
 
 190.9 
 
 Bromine 
 
 Br 
 
 79.92 
 
 Oxvgen 
 
 o 
 
 16 00 
 
 Cadmium 
 
 Cd 
 
 112.40 
 
 Palladium . . 
 
 Pd 
 
 106.7 
 
 Ccesium . . 
 
 Cs 
 
 132.81 
 
 Phosphorus. . . . 
 
 P 
 
 31.04 
 
 Calcium 
 
 Ca 
 
 40 07 
 
 Platinum 
 
 Pt 
 
 195 2 
 
 Carbon . . 
 
 c 
 
 12.005 
 
 Potassium 
 
 K 
 
 39 10 
 
 Cerium 
 
 Ce 
 
 140.25 
 
 Praseodymium . . 
 
 Pr 
 
 140.9 
 
 Chlorine 
 
 Cl 
 
 35.46 
 
 Radium 
 
 Ra 
 
 226.0 
 
 Chromium 
 
 Cr 
 
 52.0 
 
 Rhodium 
 
 Rh 
 
 102 9 
 
 Cobalt 
 Columbium 
 
 Co 
 Cb 
 
 58.97 
 93.1 
 
 Rubidium 
 Ruthenium 
 
 Rb 
 
 Ru 
 
 85.45 
 101.7 
 
 Copper . 
 
 Cu 
 
 63.57 
 
 Samarium 
 
 Sa 
 
 150 4 
 
 Dysprosium 
 
 Dy 
 
 162.5 
 
 Scandium 
 
 Sc 
 
 44 1 
 
 Erbium 
 
 Er 
 
 167 7 
 
 Selenium 
 
 Se 
 
 79 2 
 
 Europium 
 
 Eu 
 
 152.0 
 
 Silicon 
 
 Si 
 
 28 3 
 
 Fluorine 
 
 F 
 
 19.0 
 
 Silver. 
 
 Ag 
 
 107 88 
 
 Gadolinium 
 
 Gd 
 
 157 3 
 
 Sodium 
 
 Na 
 
 23 00 
 
 Gallium 
 
 Ga 
 
 69.9 
 
 Strontium 
 
 Sr 
 
 87 63 
 
 Germanium 
 
 Ge 
 
 72.5 
 
 Sulphur 
 
 s 
 
 32 06 
 
 Glucinum.. 
 
 Gl 
 
 9 1 
 
 Tantalum 
 
 Ta 
 
 181 5 
 
 Gold-. . . 
 
 Au 
 
 197 2 
 
 Tellurium 
 
 Te 
 
 127 5 
 
 Helium 
 
 He 
 
 4.00 
 
 Terbium 
 
 Tb 
 
 159 2 
 
 Holmium 
 
 Ho 
 
 163 5 
 
 Thallium 
 
 Tl 
 
 204 
 
 Hydrogen. * 
 
 H 
 
 1 008 
 
 Thorium 
 
 Th 
 
 232 4 
 
 Indium 
 
 In 
 
 114 8 
 
 Thulium 
 
 Tin 
 
 168 5 
 
 Iodine 
 
 I 
 
 126.92 
 
 Tin . 
 
 Sn 
 
 118 7 
 
 Iridium 
 
 Ir 
 
 193 1 
 
 Titanium 
 
 Ti 
 
 48 1 
 
 Iron 
 
 Fe 
 
 55 84 
 
 Tungsten 
 
 W 
 
 184 
 
 Krypton 
 
 Kr 
 
 82 92 
 
 Uranium 
 
 u 
 
 238 2 
 
 Lanthanum 
 
 La 
 
 139 
 
 Vanadium 
 
 V 
 
 51 
 
 Lead 
 
 Pb 
 
 207 20 
 
 Xenon 
 
 Xe 
 
 130 2 
 
 Lithium 
 
 Li 
 
 6 94 
 
 Ytterbium (Neo- 
 
 
 
 Lutecium. . 
 
 Lu 
 
 175 
 
 ytterbium) 
 
 Yb 
 
 173 5 
 
 Magnesium 
 Manganese 
 
 Mg 
 Mn 
 
 24.32 
 54 93 
 
 Yttrium 
 Zinc 
 
 Yt 
 Zn 
 
 88.7 
 65 37 
 
 Mercury 
 
 Hg 
 
 200 6 
 
 
 Zr 
 
 90 6 
 
 Molybdenum 
 
 Mo 
 
 96.0 
 
 
 
 
 
 
 
 
 
 
168 
 
 FORMULAS AND TABLES 
 
 MAXIMUM SOLUBILITIES 
 (!N WATER AT ORDINARY TEMPERATURES) 
 
 Parts in water. 
 
 Aluminum sulphate (A1 2 (864)3) 1 part in 3. 
 
 Calcium carbonate (CaCOs) Insoluble. 
 
 Calcium chloride (CaCl 2 ) 1 part in If. 
 
 Calcium hydroxide (slacked lime Ca(OH) 3 ) . 600. 
 
 Calcium oxide (unslacked lime CaO) 800. 
 
 Calcium sulphate (CaSO 4 ) " 500. 
 
 Calcium sulphite (CaSOs) nsoluble. 
 
 Copper sulphate (CuSOi) part in 4. 
 
 Iron oxide, hydroxide, and sulphide nsoluble. 
 
 Iron sulphate (copperas FeSO4) part in 4. 
 
 Lead acetate (Pb (C 2 H 3 O 2 )2) " 2. 
 
 Lead carbonate (PbCOs) nsoluble. 
 
 Lead oxide (litharge PbO) 
 
 Lead sulphate (PbSO 4 ) 
 
 Lead sulphite (PbSO 3 ) 
 
 Lead chloride (PbCl 2 ) 1 part in 93. 
 
 Magnesium sulphate (MgSCh) 1 3. 
 
 Mercuric chloride (HgCl 2 ) 15. 
 
 Oxalic acid (C 2 O4H 2 2 H 2 O) 10. 
 
 Potassium bicarbonate (KHCOs) 3. 
 
 Potassium carbonate (K 2 CO 3 ) 1. 
 
 Potassium cyanide (KCN) I (boiling). 
 
 Potassium ferrocyanide (K4Fe(CN) 6 ) 3. 
 
 Potassium hydroxide (KOH) 1. 
 
 Potassium iodide (KI) " |. 
 
 Potassium sulphate (K 2 SO 4 ) 9. 
 
 Silver nitrate (AgNOs) ft. 
 
 Sodium bicarbonate (NaHCOs) 1 " 10. 
 
 Sodium bisulphate (NaHSCM 1 3. 
 
 Sodium carbonate (Na 2 CO 3 ) 1 4. 
 
 Sodium hydroxide (NaOH) 1 1. 
 
 Sodium sulphate (Na 2 SO4) 1 4. 
 
 Zinc carbonate (ZnCOs) Insoluble. 
 
 Zinc cyanide (Zn(CN) 2 ) 
 
 Zinc hydroxide (Zn(OH)2) 
 
 Zinc sulphate (Zn(SO) 4 ) 1 If. 
 
 FORMULAS FOR CIRCLES AND CIRCULAR TANKS 
 
 Circumference of circle = diameter X 3.1416. 
 
 . . . diameter 2 
 Area of circle = = X 3.1416. 
 
 a 
 
 Volume of cylindrical tank = area of bottom X height. 
 
 Volume of cone = 
 
 area of base X height 
 
INDEX 
 
 PAGE 
 
 Acidity and alkalinity 118 
 
 Acid, probable effect on flotation 118 
 
 Adhesion 46 
 
 Adsorption 44 
 
 explanation of 44 
 
 and absorption 44 
 
 in flotation 44 
 
 temperature and pressure upon 46 
 
 Amount of frothing agent in tests 116 
 
 Apparatus for measuring oil added in tests 123 
 
 Bubbles, basic factor in making 20 
 
 Bubbles 92 
 
 bursting of, cause, etc 92-93 
 
 Callow test set 146-149 
 
 Calculation of tonnage of feed to any particular unit 157 
 
 Capillary attraction 34 
 
 phenomena 34 
 
 attraction, result of 36 
 
 Case testing machine 143 
 
 Coal-tar creosote, character of froth 99 
 
 Coal-tar products 87-88 
 
 Coal-tar cresols 88 
 
 Colloids ; . . 8 
 
 terminology of 8-10 
 
 chemistry, concept of 10-12 
 
 classification of 13 
 
 properties of 14 
 
 condition, control of 19 
 
 Contact angle ' 28 
 
 definition of 28 
 
 in flotation 29-33 
 
 169 
 
170 INDEX 
 
 PAGE 
 
 Cost of flotation 151-154 
 
 Cresol, or cresylic acid froths 101 
 
 Crude-wood, turpentines 89 
 
 Dealers in flotation 104-106 
 
 Dineric interface 50 
 
 Disposal of froth 125 
 
 Effect of temperature on flotation tests 119 
 
 Effect of addition agents in flocculating ganguc- 
 
 slimes 120-121 
 
 Electric charges on suspended particles 43 
 
 Electrical phenomena in flotation 53-64 
 
 Electrical theory, requirements for 53 
 
 Electrification of bubbles 55 
 
 Electrical theory, Ralston's 57 
 
 Callow's 57 
 
 Baines' 53-56 
 
 DurelPs objection to 57 
 
 Fahrenwald's experiments 58-64 
 
 Emulsification 48 
 
 effect upon flotation 48 
 
 theory of 49-51 
 
 Emulsion, definition of 48 
 
 modifying agents 49 
 
 Equation of Gibbs 45 
 
 Film flotation 126 
 
 Filters, size of pores in 15 
 
 Flotation, concentration by 1 
 
 definition of 2 
 
 Flotation processes, classification of 4 
 
 Flotation, theory of 7 
 
 oils used in 87 
 
 of oxidized ores by use of hydrogen sulphide ..... 80 
 
 by use of sulphur vapor 82 
 
 by various solutions 81 
 
 by use of sulphuretted oil 83 
 
 by use of colloidal sulphur 83 
 
 by the Murex magnetic process 83-85 
 
INDEX 171 
 
 PAGE 
 
 Flotation oils, cost of 106-108 
 
 consumption of in the United States 109 
 
 Forms for flotation tests 117-118 
 
 Formulas and tables, chapter on 155 
 
 Froths and bubbles 92-93 
 
 Froths formed by flotation oils 93-95 
 
 Froths, disposal of 125 
 
 Frothing agents in tests, amounts used 116 
 
 Fuel-oil 88 
 
 Gas-oils 89 
 
 Grinding for flotation tests 112-115 
 
 Grinding for flotation, fineness of 115 
 
 Hoover testing machines 138-140 
 
 Interfacial tension 47 
 
 Iron pipe mill 115 
 
 Janney test machine 131-138 
 
 Kinds of frothing agents 116 
 
 Macquisten tube 127 
 
 Mechanical frothing apparatus 131-138 
 
 Mohr pipette 123 
 
 Oils and other reagents in flotation 86 
 
 used in flotation 56-57 
 
 collectors or oilers : . . . 89 
 
 f rothers or f earners 89 
 
 Oxidized ores 79 
 
 the flotation of 59 
 
 classification of methods 59-60 
 
 Osmosis 37-38 
 
 definition of 37 
 
 relations to colloids 38-39 
 
 Osmotic phenomena 37 
 
 pressure, influence of added substances upon 39 
 
172 INDEX 
 
 PAGE 
 
 Preferential flotation 64 
 
 vs. selective flotation 64 
 
 classification of methods 65 
 
 roasting processes 65-70 
 
 by use of a chemical solution 70-72 
 
 controlling methods 72-77 
 
 furnishes new evidence to strengthen electrical 
 
 theory 74-78 
 
 Pebble mill 114 
 
 Pine-oil, characteristics of froth 96-99 
 
 Pneumatic flotation test apparatus 146-150 
 
 Potter-Delprat apparatus 130 
 
 Roy and Titcomb test machine 145 
 
 Separatory funnels for testing 146 
 
 Slide machine for testing 140-142 
 
 Speed of agitation in tests 119 
 
 Surface films 25 
 
 Surface tension 20 
 
 definition of 20 
 
 effects of added substances upon 20-23 
 
 phenomena . 23-24 
 
 the force of 24 
 
 effect of oil on , 28 
 
 Suspensoids and emulsoids 17 
 
 properties of 17 
 
 Tables, chapter of 155 
 
 Tests. 110 
 
 important points t9 test for 110 
 
 preliminary considerations 110 
 
 methods of grinding for 110-113 
 
 effect of temperature upon 119 
 
 acidity and alkalinity in 118 
 
 amount of frothing agent in 116 
 
 fineness of grinding for 115 
 
 addition agents in 120 
 
 speed of agitation for 119 
 
 Test tubes for flotation. . 129 
 
INDEX 173 
 
 PAGE 
 
 The purpose of oil in flotation 89 
 
 The qualities of flotation oil 90-92 
 
 The cost of flotation oils 106-107 
 
 Types of machines and their operation 126 
 
 classification of 126 
 
 Viscosity 39-44 
 
 examples illustrating 40 
 
 molecular dispersoids 42 
 
 suspensoids 43 
 
 Wood creosote bubbles 100 
 
 Wood-testing machines 128 
 
UNIVERSITY OF CALIFORNIA LIBRARY 
 BERKELEY 
 
 Return to desk from which borrowed. 
 This book is DUE on the last date stamped below. 
 
 mmc.n 
 
 IAR 1 6 1954 
 
 ML itiurmuLum LI 
 
 arm it i 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 , 
 
 
 
 
 100m-ll,'49 (B7146sl6)476 
 
*+ 
 
 VA 03125