Gold crystallinity

Fig.2. Gold crystalline surface imaged at atomic resolution by in-situ STM in 0.01 M CUSO4 and 0.05 M H2SO4 in Millipore water with E = 200 mV and = -110 mV (filtered), d = 0.02 nm, It = -3 nA.

Fig. 3. Gold crystalline surface oxidized ex-situ at ambient pressure for 24 h. Two layers of gold oxide are seen to the upper left, and to the lower right the gold was only partially oxidized. Along the mid-diagonal, rows of individual atoms are observed. In-situ STM images, electrolyte 0.01 M CUSO4 and 0.05 H2SO4 in MiUipore water, E = 400 mV, Et =-91 mV, d = 0.5 mn, /, = 1.2 nA.

BNCP forms a yeUow-gold crystalline solid which is typical for octahedral cobalt(ni) complexes having six coordinating nitrogens (as in the case with CP). BNCP crystallizes in a mcmoclinic system [38]. The density of the BNCP monocrystal is 2.05 g cm [27]. 

In addition to tire standard model systems described above, more exotic particles have been prepared witli certain unusual properties, of which we will mention a few. For instance, using seeded growtli teclmiques, particles have been developed witli a silica shell which surrounds a core of a different composition, such as particles witli magnetic [12], fluorescent [13] or gold cores [14]. Anotlier example is tliat of spheres of polytetrafluoroetliylene (PTFE), which are optically anisotropic because tire core is crystalline [15]. 

Stannous Oxide. Stannous oxide, SnO ((tin(II) oxide), mol wt 134.70, sp gr 6.5) is a stable, blue-black, crystalline product that decomposes at above 385°C. It is insoluble in water or methanol, but is readily soluble in acids and concentrated alkaHes. It is generally prepared from the precipitation of a stannous oxide hydrate from a solution of stannous chloride with alkaH. Treatment at controUed pH in water near the boiling point converts the hydrate to the oxide. Stannous oxide reacts readily with organic acids and mineral acids, which accounts and for its primary use as an intermediate in the manufacture of other tin compounds. Minor uses of stannous oxide are in the preparation of gold—tin and copper—tin mby glass. 

Other Cesium Compounds. Cesium acetate [3396-11-0], CsOOCCH, mol wt 191.95, theoretical cesium content 69.24 wt % cesium trifluoroacetate, CF COOCs, mol wt 245.93, theoretical cesium content 54.04 wt % cesium—precious metal compounds such as cesium dicarbonyltetrachloromthenium, [22594-81-6] Cs2RuCl4(CO)2, mol wt 564.71, mthenium content of 17.9 wt %, a yellow crystalline powder and cesium tetrachlorogold [13682-60-5], CsAuCl, mol wt 471.7, gold content of 41.8 wt % a yellow powder are all known. 

Sodium cyanide [143-33-9] NaCN, is a white cubic crystalline soHd commonly called white cyanide. It was first prepared in 1834 by heating Pmssian blue, a mixture of cyanogen compounds of iron, and sodium carbonate and extracting sodium cyanide from the cooled mixture using alcohol. Sodium cyanide remained a laboratory curiosity until 1887, when a process was patented for the extraction of gold and silver from ores by means of a dilute solution of cyanide (see Metallurgy, extractive). A mixture of sodium and potassium cyanides, produced by Edenmeyer s improvement of the Rodgers process, was marketed in 1890. 

Potassium cyanide [151 -50-8] KCN, a white crystalline, deUquescent soHd, was initially used as a flux, andlater for electroplating, which is the single greatest use in the 1990s. The demand for potassium cyanide was met by the ferrocyanide process until the latter part of the nineteenth century, when the extraordinary demands of the gold mining industry for alkah cyanide resulted in the development of direct synthesis processes. When cheaper sodium cyanide became available, potassium cyanide was displaced in many uses. With the decline in the use of alkah cyanides for plating the demand for potassium cyanide continues to decline. The total world production in 1990 was estimated at about 4500 t, down from 7300 t in 1976. 

AgPh is a colourless solid [144] that is rather insoluble in non-donor solvents and appears to be polymeric (AgPh) (n > 10) in addition mixed compounds (AgPh) .AgN03 (n = 2,5) can also be obtained that involve silver clusters. Mesitylsilver is a thermally stable (but light-sensitive) white crystalline solid in the solid state it is tetrameric (in contrast to the pentameric copper and gold analogues) ... 

The properties of alloys are affected by their composition and structure. Not only is the crystalline structure important, but the size and texture of the individual grains also contribute to the properties of an alloy. Some metal alloys are one-phase homogeneous solutions. Examples are brass, bronze, and the gold coinage alloys. Other alloys are heterogeneous mixtures of different crystalline phases, such as tin-lead solder and the mercury-silver amalgams used to fill teeth. 

Based on the fact that pi-acids interact with the trinuclear gold] I) pi-bases, TR(carb) and TR(bzim), the trinuclear 3,5-diphenylpyrazolate silver(I) complex was reacted with each. Mixing [Au3(carb)3] or [Au3(bzim)3] with [Ag3(p,-3,5-Ph2pz)3] in CH2CI2 in stoichiometric ratios of 1 2 and 2 1 produced the mixed metal/mixed ligand complexes in the same gold-silver ratios. The crystalline products were not the expected acid-base adducts. It is suspected that the lability of the M-N bond (M=Au, Ag) in these complexes results in the subsequent cleavage of the cyclic complexes to produce the products statistically expected from the stoichiometry of materials used [74]. As a result of the lability of Au-N and Ag-N bonds, and the stability of... 

The pentafluorophenyl group imparts greater crystallinity to the complexes and as a result many complexes have been studied by X-ray crystallography. Although vith other metal centers C Fs-CaFs or CfiFs-CfiHs n-n stacking interactions are observed [21, 22], there are not many examples in gold chemistry and they have been sho vn very recently [23]. 

Bayon, R., Coco, S., Espinet, P., Fernandez-Mayordomo, C. and Martin-Alvarez, J.M. (1997) Liquid-Crystalline Mono- and Dinuclear (Perhalophenyl) gold(l) Isocyanide Complexes. Inorganic Chemistry, 36(11), 2329-2334. 

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