Assaying is the estimation of the amount of pure metal, and especially of the precious metals, in an ore or alloy. In the case of silver the assay is either by the dry or by the wet process. The dry process is called eupellation from the use of a small and very porous cup, called a cupel, which is usually made of well-burned and finely-ground bone-ash or of magnesia. The cupel, being thoroughly dried, is placed in a fire-clay oven about the size of a drain-tile, with a flat sole and arched roof, and with slits at the sides to admit air. This oven, called a muffle, is set in a furnace, and when it is at a red heat the assay, consisting of a small weighed portion of the alloy wrapped in sheet-lead, is laid upon the cupel. The heat causes the lead to volatilize or combine with the other metals, and to sink with them into the cupel, leaving a bright globule of pure metallic silver, which gives the amount of silver in the alloy operated on. In the wet process the alloy is dissolved in nitric acid, and to the solution are added measured quantities of a solution of common salt of known strength, which precipitates chloride of silver. The operation is concluded when no further precipitate is obtained on the addition of the salt solution, and the quantity of silver is calculated from the amount of salt solution used.
An alloy of gold is first cupelled with lead as above, with the addition of three parts of silver for every one of gold. After the cupellation is finished the alloy of gold and silver is beaten and rolled out into a thin plate, which is curled up by the fingers into a little spiral or cornet. This is put into a flask with nitric acid, which dissolves away the silver and leaves the cornet dark and brittle. After washing with water the cornet is boiled with stronger nitric acid to remove the last traces of silver, well washed, and then allowed to drop into a small crucible, in which it is heated, and then it is weighed. The assay of gold, therefore, consists of two parts: cupellation, by which inferior metals (except silver) are removed; and quartation, by which the added silver and any silver originally present are got rid of. The quantity of silver added has to be regulated to about three times that of the gold. If it be more the cornet breaks up, if it be less the gold protects small quantities of the silver from the action of the acid. Where, as in some gold manufactured articles, these methods of assay cannot be applied, a streak is drawn With the article upon a touchstone consisting of coarse-grained Lydian quartz saturated with bituminous matter, or of black basalt. The practised assayer will detect approximately the richness of the gold from the colour of the streak, which may be further subjected to an acid test. The Goldsmith's Company of London is the statutory assay-master of all England. Research Assaying
The 1003 aiming projector is a German, lightweight illuminating source sometimes fitted to the Heckler and Koch MP5sub-machine-gun. The 1003 aiming projector consists of a 100-watt halogenquartzbulb in a metal lamp and a 12-volt, 4.5 amp battery. In use the 1003 aiming projector allows illumination of a target at ranges of up to 100 metres in total darkness, with a light bright enough to dazzle the target, for a period not exceeding ten seconds during which six aimed shots may be fired before the light is turned off and the firers position changed. Research 1003 Aiming Projector
Flint-glass is a species of glass, so called because pulverized flints were originally employed in its manufacture. It was extensively used for domestic purposes. Its dispersive power in regard to light renders it invaluable in the manufacture of the object-glasses of telescopes and microscopes, as by combining a concave lens of flint-glass with one or two convex lenses of crown-glass, which possesses much less dispersive power, a compoundlens is formed in which the prismatic colours arising from simple refraction are destroyed, and the lens rendered achromatic. Quartz and fine sand were later substituted for flint in the manufacture of this glass. Research Flint-Glass
The materials used for electrical insulation are numerous and of the most diverse nature, including the majority of non-metallic substances. There is no definite dividing-line between conducting and
insulating materials, as the majority of insulating materials allow some electric current to flow, though usually only a very small amount. Rather, the British Standards Institute defines an insulating material as one which offers a relatively high resistance to the passage of an electric current. The best insulating materials - those offering the highest resistance to the flow of electric current - are respectively: air, fused quartz, clear mica, paraffinwax, yellow beeswax and quartz. Research Insulating Materials
Omnis Quartz is a database manager operating within the Windows environment. This environment uses pull-down menus, scaleable fonts, scrollable lists, dialog boxes, overlapping windows and most of the other elements common to this graphical interface. These elements are used to make selections, assemble sequences of commands from the set of Quartz programming commands and functions and to define the look and functions of the database application, when completed. End-users will interact with database applications through layout windows. While the number of windows in a layout cannot be greater than twelve, multiple windows may be opened at once. Only the uppermost window is active and available for data entry. Layout windows can hold a maximum of 120 fields from up to twelve files, with files being opened when a layout is chosen for data entry. With most databases, any programming instructions are usually held separately, often as text files.
Omnis Quartz stores the programming instructions - the sequences - as part of the menu structure. A sequence of commands can be associated with every menu line - sequences can be up to 5K long with a storage limit of 30K for each menu. Each of the menu lines has a number and can also be assigned a name to appear on the menu line. When 'writing' an application, a window opens to show the sequences associated with each line of the menu. Sequences may be called by other sequences or accessed from push buttons or menu choices on entry layouts. Quartz comes into its own for turnkey applications where the advantages of the Windows interface can be fully exploited. Research Omnis Quartz
In mechanics, torsion is the strain produced in a solid body when parallel planes are turned relatively to one another round an axis perpendicular to them. If one end of a cylindrical wire is kept fixed and the other end is twisted by a mechanical force, and if under this twisting stress the wire turns through an angle, then it is found that, so long as the angle is not too great, it is proportional to the applied force, that is if the applied force or couple is doubled, the angle through which the end of the wire is twisted is also doubled.
If the length and radius of the wire are known, and also the strength of the twisting force, then the angle through which the wire twists varies directly with the length of the wire multiplied by a constant depending upon the material of the wire. Since the angle varies inversely as the fourth power of the radius of the wire, the deflection produced by the twisting force increases very rapidly as the wire becomes smaller, for example if the wire's radius is halved the angle of twist is multiplied by 2 to the power of 4, or in other words 16. In measuring small torsions, therefore, a very thin wire or thread is chosen, and for this purpose quartz fibres of extreme tenuity are employed.
Most substances behave very differently in their ability to recover from torsion. Quartz, steel, glass etc will suffer a considerable torsion and when it is removed regain their original forms. Copper and lead on the other hand, will not recover from even small twists.
One of the important applications of torsion is in a spring, and it is because of its ability to recover that steel is typically used for springs. Research Torsion
Agate is a semi-precious stone siliceous semi-pellucid compound mineral, consisting of bands or layers of various colours blended together, the base generally being chalcedony, and this mixed with variable proportions of jasper, amethyst, quartz, opal, heliotrope, and carnelian. The varying manner in which these materials are arranged causes the agate when polished to assume some characteristic appearances, and thus certain varieties are distinguished, as the ribbon agate, the fortification agate, the zone agate, the star agate, the moss agate, the clouded agate, etc. In Scotland they are cut and polished under the name of Scottish pebbles. Research Agate
In geology, aggregate is a term applied to rocks composed of several different mineral constituents capable of being separated by mechanical means, such as granite, where the quartz, feldspar, and mica can be separated mechanically. Research Aggregate
Amethyst is a purple or bluish-violet coloured precious stone comprised of quartz coloured with manganese. It is so named from the ancient Greek's belief that it had the power to cure drunkenness. Research Amethyst
Anatase is one of the crystalline forms of titanium oxide, and an important source of the metal titanium. Anatase has the formulae TiO2 and a relative hardness of 6. It is found in granite, gneiss, micaschist, metamorphic limestone, and dolomite. Anatase may be present as an accessory mineral in the rocks or in a quartzvein traversing it. It is used as a coating for welding rods and as a source of titanium. Research Anatase
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Assaying
