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AMMONIA SOLUTION STRENGTH DETERMINATION
Apparatus, Reagents,—The usual volumetric and gravimetric apparatus. For analysis the student may take the bench reagent labelled 5E. NH4HO. For the standard acid pure H2SO4 of specific gravity 1.840 or thereabouts is most suitable. Pure Na2CO3 (prepared as before) is necessary for standardising the acid. Method, Reactions.—A certain volume of the ammonia solution is taken at a temptrature of 16°
METHODS OF ASSAYING
Assuming that assaying be defined as “the estimation of the commercially important elements in their ores, alloys, or products,” the following classification of methods, though not exhaustive, may be adopted for convenience. METHODS OF ASSAYING. As examples of these methods repeatedly come under the student’s notice, only a few words of explanation will be given here. I. Dry (OF Fire)
Effects of Impurities on Scorification
Method of Experiment.—A number of charges of a quartzose ore are prepared, and weighed quantities of certain substances are added to the various charges. The effects on the charge and dish are noted. Apparatus.—The muffle furnace, pulp scales, and accessories. Reagents.—Quartz, grain lead, borax glass, copper, iron, cobalt, and manganese. In place of cobalt and manganese the oxides of these
Effect of Impurities on Cupellation
Method of Experiment.—Weighed quantities of other metals will be added to weighed quantities of silver and lead, and after cupellation the coloration of the cupel and the appearance of the bead indicate to a certain extent the impurity present. Apparatus.—The muffle furnace, balance, and accessories. Reagents, etc—Gold, silver, lead, copper, tin, antimony. Details of Experiment.—Weigh out five charges approximately as
Iron or Nail Method Assay Method
The Iron or Nail Method Principle: Sufficient soda is added to flux the silica, and an excess to give a fluid alkaline slag in which the FeS formed by the iron introduced and the sulphur in the pyrites may dissolve. The sulphur present acts to a certain extent as a reducer. One gram FeS2, is capable of reducing 8 gms.
Assay Blister Copper
This material may be taken as containing 96 to 98% copper, a few ounces of gold per ton (varies considerably with different ores), some hundreds of ounces of silver per ton, and small quantities of impurities. Though the estimation of silver has so far not been considered, the student will find it convenient to estimate both silver and gold when
ESTIMATE SILVER IN GALENA
To estimate how much silver is present in galena, the student has already assayed this ore for lead, and by cupelling the buttons so obtained he will obtain some idea as to the silver contents of the ore; but to obtain accurate results the ore must be specially treated either by crucible assay or by scorification. The student is advised
DRY ASSAY OF MERCURY ORES
The following estimation is given as an exercise in distillation. The method has been used to advantage, being convenient and requiring little apparatus. For refined methods of distillation and absorption of the mercury by gold plates consult “Beringer,” “Furman,” etc. Method. — In cinnabar the mercury is combined with sulphur. To separate these, the ore is mixed either with iron
Fire Clay Composition & Properties
For practice the student may take either “ Stourbridge ” or “ Dinas ” fireclay and sand. The following table gives their average composition. The Dinas sand consists almost entirely of SiO2 (free), but in the Stourbridge clay the SiO2 is mostly combined with Al2O3. The clay is preferable for practice. For reference regarding the composition of clays, the student
Magnetite Concentration Methods
Table of ContentsElimination of ImpuritiesMagnetic SandsBriquettingSeparation of Magnetite as an Impurity Magnetite is the most strongly magnetic of all minerals, and it is therefore natural that the earliest application of magnetism to ore dressing was for its concentration from gangue. Magnetite ores occur in large bodies in almost all countries, and on account of the high iron tenor of the
Magnetic Separators for Weakly Low Magnetic Minerals
Table of ContentsWetherill Rowand Separator Type “E” SeparatorHomboldt-Wetherill Cross-Belt SeparatorMechernich SeparatorMotor-Type SeparatorPrimosigh Separator For Dry OresUlrich SeparatorPayne Magnetic SeparatorInternational SeparatorUbaldi SeparatorHumboldt-Wetherill Type VI SeparatorWetherill Parallel SeparatorWetherill Horizontal SeparatorWetherill Inclined Separator Wetherill Rowand Separator Type “E” Separator The machine consists essentially of a belt which conveys the ore between the poles of a series of magnets, so arranged that the belt
Electromagnetic Separators for Strongly Magnetic Minerals
Table of ContentsBall-Norton Belt SeparatorMonarch or Ball-Norton Double-Drum SeparatorDellvik-Grondal SeparatorGrondal Type II SeparatorGrondal Type III SeparatorGrondal Type IV SeparatorGrondal Type V SeparatorThe Grondal Slime SeparatorWetherill Type F SeparatorFroeding SeparatorEricksson SeparatorForsgren SeparatorEdison SeparatorEdison Belt SeparatorBall-Norton Single-Drum Cobbing SeparatorWenstrom SeparatorNew Wenstrom Cobbing SeparatorGrondal Cobbing SeparatorDings SeparatorHumboldt-Wetherill Tandem Separator Type VIICleveland-Knowles SeparatorStern-Type Wet SeparatorPrimosigh Wet SeparatorLeuschner Table SeparatorHumboldt Single-Roller Separator for Wet SeparationHerbele
Indirect Titration
The action of permanganate of potash upon a ferrous solution is one of oxidation, hence it is evident that if any other oxidising agent is present it will count as permanganate. In such a case the titration can be used (indirectly) to estimate the quantity of such oxidising agent, by determining how much less of the permanganate is used. For
Titrometric Assays
Table of ContentsStandard SolutionsStandardising Within the limits of the error of experiment, a definite volume of a solution or gas represents a certain weight of metal or other substance, hence the exact weight may be determined by experiment. The error of experiment may be reduced to insignificant dimensions by repeating the experiment, and taking the mean of three or four determinations.
Gasometric Assays
Gasometric methods are not much used by assayers, and, therefore, those students who wish to study them more fully than the limits of this work will permit, are recommended to consult Winkler and Lunge’s text-book on the subject. The methods are without doubt capable of a more extended application. In measuring liquids, ordinary variations of temperature have but little effect,
Oxidising Agents used in Assaying
The chief oxidising agents (which are also de-sulphurisers) are the following: Nitre, or Potassic Nitrate.—This salt fuses very easily to a watery liquid. It oxidises most combustible substances with deflagration, and thereby converts sulphides into sulphates, arsenides into arsenates, and most metals into oxides. In the presence of strong bases, such as soda, the whole of the sulphur is fully
De-Oxidising Agents used in Assaying
The de-oxidising agents most in use are the following: Charcoal.—Powdered wood charcoal; it contains more or less hygroscopic moisture and about 3 or 4 per cent, of ash. The rest may be considered carbon. Carbon heated with metallic oxides takes the oxygen ; at low temperatures it forms carbon dioxide, and at higher ones, carbon monoxide. Other conditions besides that
Assaying Iridium Determination Method
Occurs in nature alloyed with osmium as osmiridium or iridosmine, which is “ rather abundant in the auriferous beach sands of Northern California” (Dana). It occurs in bright metallic scales, which do not alloy with lead, and are insoluble in aqua regia. Iridium also occurs in most platinum ores, and forms as much as two per cent, of some commercial
Assaying Platinum Determination Method
Platinum occurs in nature in alluvial deposits associated with gold and some rare metals, generally in fine metallic grains, and, occasionally, in nuggets. It is a grey metal with a high specific gravity, 21.5 when pure and about 18.0 in native specimens. It is fusible only at the highest temperature, and is not acted on by acids. It is dissolved by
Flatting Gold
Small buttons, such as are got in assaying most gold ores, are placed on a polished steel anvil and flattened by one or two blows with a hammer. The flattened discs are heated to dull redness on a clean cupel and are then ready for parting. Somewhat larger buttons may be similarly treated, but they should be annealed (i.e. heated to redness and allowed
Inquartation
The method of separating the gold from the silver in gold-silver alloys by boiling with nitric acid does not act equally well in all cases. An alloy half silver half gold, rolled to thin sheet and boiled for half an hour with nitric acid, may still retain more than two-thirds of its silver. An alloy of 1 part gold and
ASSAY FOR CYANIDE BY TITRATION WITH SILVER NITRATE
Table of ContentsCYANIDESDetermination of the acidity of an oreExamination of cyanide solutions for metalsExamination of an ore for “ cyanicides” The determination of the quantity of a cyanide is made by finding how much silver nitrate is required to convert the whole of the cyanide into potassium silver cyanide or one of the allied compounds. It will be seen from
Gold Parting Process
Table of ContentsParting in FlasksParting in glazed crucibles or dishesAssaying with checks – SurchargeParting in special apparatusSilver in gold bullion The thin sheet of metal is dropped into hot dilute nitric acid and boiled for five or six minutes after the brisk action of the acid on the metal has ceased. At this stage nearly all the silver has gone
Remove Lead from Gold or Silver
Large quantities of lead carrying gold and silver are sold to refiners in bars weighing about 100 lbs. each. The assay of these alloys presents no special difficulties, but the sampling of them is a question which may be profitably discussed. A molten metal may be conceived to have all the physical states observed in ordinary liquids, although these cannot