Silver fineness

SILVER / SILVER CHLORIDE MIXTURE. SILVER FINELY -DIVIDED... 

For from one quintal of earth of the mine Two arrobas are yielded of silver fine. ... 

Silver Fineness. Figure 4 contains data for the silver fineness of about 400 Sasanian coins as determined by the direct (neutron Howit-... 

Figure 4. Silver fineness as determined by neutron Howitzer analysis for about 400 Sasanian drachms. Alternating open and closed circles are used to assist visually in associating data points with ruling monarchs listed at top of graph.

Germsui Black Salve. Lard, 24 parts white oxide of zinc and Peruvian balsam, of each 3 parts nitrate of silver, finely pulverized, 1 part. This formula is taken from tho Hamburg Pharmacopoeia. 

But still the alkahest remained an enigma, and so further experiments were made with silver and mercury. For those with silver, fine silver was reduced with nitric acid to the salts of the metal, carefully washed in distilled water, sublimated by special process, finally yielding up a white oil which had a very soothing effect on highly nervous cases. 

Fineness Term used to define the degree of purity of gold or silver. Fineness is given as parts of the metal concerned per 1000 parts by weight. 

Silver Fines (Wet, Grey) — 212 100 8 u - - very dilute FeCIs bleaching powder and muratic acid solution, aeration none, agitation by boiling. Alloy C — 12 days... 

Add a known volume ofo oaM.AgNOj solution (in excess) and boil the solution until the silver chloride has coagulated. Filter through a conical 5 cm. funnel, ensuring that the filter-paper does not protrude above the r m of the funnel. Wash the silver chloride and the filter-paper several times with a fine jet of distilled water. To the united filtrate and washings add i ml. of saturated ferric alum solution. The solution should be almost colourless if it is more than faintly coloured, add a few drops of concentrated nitric acid. Then titrate with 0 02M-ammonium thiocyanate solution until the permanent colour of ferric thiocyanate is just perceptible. (Alternatively the chloride may be determined potentiometrically.)... 

The Stedman-type column is shown in Fig. 11, 56, 25. The characteristic features are (i) the use of a fine stainless steel wire cloth formed into conical discs, and (ii) an accurately fitting Pyrex glass jacket, produced by shrinking Pyrex glass on mandrels to the required inside dimensions. Modifications incorporating a silvered vacuum jacket and an electrically-heated jacket are marketed. This column is said to possess high efficiency but is expensive. It is generally employed in conjunction with a total-condensation variable take-off still head. 

Sodium anthraquinone-p-sulphonate ( silver salt ). Place 60 g. of fuming sulphuric acid (40-50 per cent. SO3) in a 250 or 500 ml. round-bottomed flask and add 50 g. of dry, finely-powdered anthra-quinone (Section IV,145). Fit an air condenser to the flask and heat the mixture slowly in an oil bath, with occasional shaking, so that at the end of 1 hour the temperature has reached 160°. Allow to cool and pour the warm mixture carefully into a 2 litre beaker containing 500 g. of crushed ice. Boil for about 15 minutes and filter off the unchanged anthraquinone at the pump. Neutralise the hot filtrate with sodium hydroxide and allow to cool, when the greater part of the sodium anthra-quinone-p-sulphonate separates as silvery glistening plates ( silver salt ). Filter these with suction and dry upon filter paper or upon a porous plate. A second crop of crystals may be isolated by concentration of the trate to half the original volume. The yield is 40-45 g. 

Silver is also recovered during electrolytic refining of copper. Commercial fine silver contains at least 99.9% silver. Purities of 99.999+% are available commercially. 

Yttrium has a silver-metallic luster and is relatively stable in air. Turnings of the metal, however, ignite in air if their temperature exceeds 400oC. Finely divided yttrium is very unstable in air. 

The commercially available photochromic glasses contain a fine dispersion of silver halide crystallites which ate about 10 nm in diameter and about... 

Cadmium Sulfide Photoconductor. CdS photoconductive films are prepared by both evaporation of bulk CdS and settHng of fine CdS powder from aqueous or organic suspension foUowed by sintering (60,61). The evaporated CdS is deposited to a thickness from 100 to 600 nm on ceramic substates. The evaporated films are polycrystaUine and are heated to 250°C in oxygen at low pressure to increase photosensitivity. Copper or silver may be diffused into the films to lower the resistivity and reduce contact rectification and noise. The copper acceptor energy level is within 0.1 eV of the valence band edge. Sulfide vacancies produce donor levels and cadmium vacancies produce deep acceptor levels. 

Deposits. Selenium forms natural compounds with 16 other elements. It is a main constituent of 39 mineral species and a minor component of 37 others, chiefly sulfides. The minerals are finely disseminated and do not form a selenium ore. Because there are no deposits that can be worked for selenium recovery alone, there are no mine reserves. Nevertheless, the 1995 world reserves, chiefly in nonferrous metals sulfide deposits, are ca 70,000 metric tons and total resources are ca 130,000 t (24). The principal resources of the world are in the base metal sulfide deposits that are mined primarily for copper, zinc, nickel, and silver, and to a lesser extent, lead and mercury, where selenium recovery is secondary. 

Commodity exchanges require good deUvery silver buUion to be 999 parts per 1000 fine silver. Samples of specifications for silver are given in Table 6. ... 

Silver Sulfide. Silver sulfide, Ag2S, forms as a finely divided black precipitate when solutions or suspensions of most silver salts are treated with an alkaline sulfide solution or hydrogen sulfide. Silver sulfide has a dimorphic crystal stmcture. Transition from the rhombic (acanthite) to the cubic (argentite) form occurs at 175°C. Both crystal stmctures are found in nature. 

At room temperature, sulfur unites readily with copper, silver, and mercury and vigorously with sodium, potassium, calcium, strontium, and barium to form sulfides. Iron, chromium, tungsten, nickel, and cobalt react much less readily. In a finely divided state, zinc, tin, iron, and aluminum react with sulfur on heating (19). 

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