An acid is a chemical compound that reacts with metals to form salts by releasing hydrogen.
Their general properties are sour taste, the power of changing vegetable blues into reds, of evolving hydrogen in presence of magnesium, of decomposing chalk with effervescence, and of being in various degrees neutralized by alkalis. An acid has been defined as a compound of hydrogen, the whole or a part of which is replaceable by a metal when this is presented in the form of a hydroxide; being monobasic, dibasic, or tribasic, according to the number of replaceable hydrogen atoms in a molecule. Some acids also contain oxygen and these are called oxy-acids. Varying amounts of oxygen in an acid are reflected in its name ending -ous or -ic, and the salts formed from such acids are similarly named ending in -ite and -ate. Research Acid
Gold is a bright yellow coloured, rare, precious metal element with the formulae Au and a relative hardness of 3 occurring in nature in widely distributed small amounts. The main source of gold is in gold-quartz veins where gold was deposited from mineral bearing solutions. When the veins weather, the gold is separated from the quartz and mechanically settles on the stream floor as a placer deposit. The fineness of gold is measured in carats. 24 carat gold is pure, 22 carat gold is 22 parts gold to two parts other metals and so on. Gold is seldom used for any purpose in a state of perfect purity on account of its softness, but is combined with some other metal to render it harder. Standard gold, or the alloy formerly used for the gold coinage of Britain, consists of twenty-two parts of gold and two of copper (being thus 22 carats fine). Articles of jewelry are made of every degree of fineness up to 22 carats, i.e. 22 parts of gold to 2 of alloy.
Gold is one of the most ductile and malleable of all the metals It is one of the heaviest of the metals, and not being liable to be injured by exposure to the air, is well suited for making coins and jewelry. Its ductility and malleability are very remarkable. It may be beaten into leaves so exceedingly thin that one grain in weight will cover 56 square inches. It is also extremely ductile; a single grain may be drawn into a wire 500 feet long, and an ounce of gold covering a silver wire is capable of being extended upwards of 1300 miles. It may also be melted and remelted with scarcely any diminution of its quantity. It is soluble in nitro-muriatic acid or aqua regia, and in a solution of chlorine. Its specific gravity is 19.3, or it is about nineteen times heavier than water.
The alloy of gold and silver is found already formed in nature. It is of a paler yellow than pure gold, while the copperalloy has a colour bordering upon reddish yellow. Palladium, rhodium, and tellurium are also met with as alloys of gold.
Gold has been found in larger or smaller quantities in nearly all parts of the world. It is commonly found in reefs or veins among quartz, and in alluvial deposits. Among the latter may be ranked the deposits in river beds, from which the gold is obtained by dredging. Dredging is even employed where the water has to be brought by artificial means. When gold is in rock, quarrying, crushing, washing, and treatment with mercury are employed. The rock is crushed by machinery, and the crushed material is treated with mercury, which dissolves the gold, forming a liquid amalgam, after which the mercury is volatilized, and the gold left behind. Two other processes are also in use, viz. the chlorination and the cyanide. In the former the gold is transformed into soluble gold chloride, and the metal is obtained from this solution by means of sulphuretted hydrogen. The cyanide process is especially useful for ores containing tellurium, or for ores in a fine state of division, and con^sists in dissolving the metal in potassiumcyanide solutions, from which it can be obtained by various means. The gold obtained by these methods always contains silver, from which it is separated by the process known as 'parting'.
In alluvial (or placer) deposits it is extracted by washing, in the form of dust, grains, laminae, or nuggets. After the gravel has been turned over and the nuggets have been taken out, the remainder is washed to recover the finer particles of gold. In washing in the pan - 'panning out' - a quantity of the 'dirt', free from stones, is put into a shallow dish with a slight depression in the middle. It is then mixed with water, and the dish held with one side lower than the other, while by a gentle motion the sand and other lighter bodies are washed over the edge of the pan, and the heavy matters containing the gold remain at the bottom. The 'dolly' or 'tossing tub' is a circular tub for washing rather fine stuff that has been sifted. The 'cradle' consists of a short box or trough two meters long, mounted on a kind of rockers, and slightly inclined to allow the mud to run off. A box, with a bottom of iron plate perforated with holes, is placed over the higher end of the trough. The 'pay dirt' (i.e. gravel or sand containing a sufficient amount of gold to be profitably worked) is thrown into this box, and water is run or poured upon it. The finer portion is thus carried through the holes, and directed by an inclined plate into the trough. The cradle is rocked from side to side, the light matters are carried away by the water, and the particles of gold and other heavy matters lodge behind the 'rimes', or transverse bars of wood, with which the bottom of the trough is fitted, and are afterwards collected.
Where practicable, the method known as 'sluicing' is often adopted for treating alluvial deposits. The 'sluices' consist of troughs called 'flumes', in sections about 3.5 meters long, inclined on trestles. The bottom of the sluice-box is crossed by 'riffle' bars of wood or iron. The smallest of the sluices consists of two such sections. Into the upper one the gravel is thrown, and the lower end is closed by an iron grid to keep back the pebbles and large stones, while the sand, etc, pass through to the lower trough. In this it deposits ite gold and heavy matters behind the riffle bars. In the longer sluices (say 75 meters long) the lower end of the upper section is not blocked, but near it the bottom consists of an iron grating - the 'grizzly'. The large stones are washed forward over the grating, but the sand and fine particles carried by the water fall through it on to the second section of the sluice. In some cases the fine sand, after passing through the first section of the sluice, falls on inclined tables covered witli blankets, rough cloth, or hides witli. the hairy side up, over which it flows in a thin stream. These 'blanket-strakes' serve to arrest and recover the fine gold. In other cases amalgamated copper plates are employed for the same purpose.
Where water is plentiful, 'hydraulic mining' is the cheapest mode of working. Under this system, 'deep leads' (which are alluvial deposits covered over with more recent matter in ancient river beds) and other alluvial deposits are worked by washing down the gravel by means of a powerful jet of water.
In quartz mining - and the case is similar with the hard, solid 'banket' formation of South Africa that contains tlie gold - the ore to be crushed is first passed through a 'stone-breaker' or 'ore crusher', and is further crushed by the 'stamps' or other grinding mill. The ordinary stamp-battery consists, in its lower part, of a cast-iron 'mortar-box', fitted on one or both sides with a fine screen. At the bottom of this box is a row of iron blocks called 'dies', upon which the stamps, or heavy cylindrical cast-iron blocks, are made to rise and fall by means of cams, being thus kept pounding away at the ore in the mortar-box. A stream of water is admitted, and carries the crushed material through the screens. Mercury is fed into the mortar-boxes in small quantities, and much of the gold is retained there on amalgamated copper plates. Slightly inclined amalgamated plates arranged in steps are placed in front of the battery, and over these the crushed orepulp passes slowly, the gold being retained by the amalgamated surfaces. The remaining product, or 'tailings', which may still contain some gold, is then treated either by 'concentration' and the concentrates chlorinated, or the whole is treated by the cyanide process.
For the concentrating process 'vanners' are generally employed. These consist of a slightly sloping table, formed of an endless travelling belt of rubber, which is stretched over rollers and so mounted as to be capable of violent agitation (the vibrations numbering 200 a minute) while moving slowly in an upward direction. The pulp is led on at the higher end, and the flow of water carries the light matters down the slope, the separation being greatly assisted by the shaking movement. The heavy matters only are carried forward by the belt over the higher end, and pass into a box below, being then known as 'concentrates'.
At one time large supplies of gold were obtained from Peru, Bolivia, and other parts of the New World. A rich source of the supply has long been the UralMountains, whence gold is still obtained. An immense increase in the world's production was caused by the discovery of gold in California in 1848, and Australia in 1851, while the South African gold-fields caused a similar increase. It is only since 1886 that the Transvaal became a great gold-producing area, the chief locality being the Witwatersrand.
In Western Australia many mines were opened at the end of the 19th century, and the Yukon district of Canada (Klondike) was also recognized as a gold-field in the 19th century. There are also gold-mines in India that have been worked with great success. Gold has been found in various parts of the United Kingdom, as in Sutherlandshire, Wicklow, and many places in Wales.
ITE is an abbreviation for Institute of Tool Engineering
ITE is an abbreviation for Interim Test Equipment
ITE is an abbreviation for Intersite Transportation Equipment Research ITE
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Acid
