Gold, crystals

But in metals it is relatively common for solid solutions to form. The atoms of one element may enter the crystal of another element if their atoms are of similar size. Gold and copper form such solid solutions. The gold atoms can replace copper atoms in the copper crystal and, in the same way, copper atoms can replace gold atoms in the gold crystal. Such solid solutions are called alloys. Some solid metals dissolve hydrogen or carbon atoms—steel is iron containing a small amount of dissolved carbon. 

P. Chen, I. V. Tomov, and P. M. Rentzepis, Time resolved heat propagation in a gold crystal by means of picosecond X-ray diffraction. J. Chem. Phys., 104(24), 10001-10007 (1996). 

Figure 2. (a) Bright field STEM image of small gold crystals on... 

Figure 6. Hiorofacetted region of a gold crystal, with the facet indexing marked. The atomic columns are black.

Wallenberg, L.R., Bovin, J.O. and Schmid, G. (1985) On the crystal-structure of small gold crystals and large gold structures. Surface Science, 156, 256-264. 

Heyraud and Metois (1980) studied shapes of small gold crystals in thermal equilibrium with their vapor in their samples only the (HI) and (100) facets were observed, since the range of temperatures investigated T 1000 C) is above the roughening temperature of the (110) facet. To observe some of the shapes described in this article, temperatures below the roughening and the deconstruction temperatures of the (110) facet should be considered. 

With respect to CO adsorption on neutral Aun clusters, our preliminary results show differences with previous calculations using cluster geometries extracted from the fee gold crystal. The adsorption energy of CO is minimum for the planar magic cluster Aue and shows maxima for the odd electron clusters Au5 and Au7, both with the CO absorbed on a bridge position, but the even-odd effect is not obtained for sizes larger than n=7. 

SYNTHESIS To a solution of 1.21 g 5-methoxyindole-3-carboxaldehyde in 15 mL nitroethane there was added 0.3 g anhydrous ammonium acetate, and the mixture was held at steam-bath temperature. Periodic assay by TLC showed the reaction to be complete in 1.5 h. The volatiles were removed under vacuum, and the residue (1.58 g of rusty red crystals) was recrystallized from 15 mL boiling isopropanol. After filtration and air-drying, there was obtained 1.24 g (82%) of 5-methoxy-3-(2-nitropropenyl)indole as dull gold crystals with a melting point of 178-179 °C. The literature value is 182-184 °C. 

HESSITE. A mineral telluride of silver. AgyTe. with some gold, crystallizing in the monoclinic syslem at normal temperatures isometric system above I49.5F (65.3 C). Crystalline form not ohvious at normal temperatures. Hardness. 2-3 specific gravity. 8.24-8.45 color, gray with metallic luster opaque. Named after G.H. Hess (1802— 1850). 

Q Gold crystallizes in a cubic close-packed structure, based on a cube with side a. Given that the density of metallic gold is 19.3 x 103 kg m-3 (density is mass divided by volume) and that a = 4.08 x 10-10 m, find the number of Au atoms per unit cell using the molar mass of 197Au(100%) = 197 g mol-1. Give your answer to 3 sig. figs. 

A solution 3.7 g 2,5-dimethoxy-3,4-(trimethylene)benzaldehyde in 15 g nitromethane was treated with 0.7 g anhydrous ammonium acetate and heated on the steam bath for 14 h. The volatiles were removed under vacuum, and the residue set up to 3.5 g dark crystals, which melted broadly between 126-138 °C. Recrystallization of the entire mass from 70 mL boiling EtOH gave 3.2 g burnished gold crystals with a mp of 129-137 °C. A further recrystallization of an analytical sample fromMeOH gave 2,5-dimethoxy-3,4-(tri me thylene)-B-nitiostyreneas yellow crystals with a mp of 146-147 CC. Anal. (C13H,5N04) C,H. 

Rymer and Butler (32) found that the lattice parameter of a very thin gold foil parallel to its surface is less than that of macroscopic gold crystals. 

A quantitative measurement of the depth of penetration of the diffracted electrons has been made previously by the author (1) by depositing silver vapor onto a gold crystal surface, using a calibrated silver source. Since the lattice structures are the same and the lattice constants differ by less than 0.4%, the silver was found to deposit as a thin crystal on the gold surface. Because of the different indices of refraction and certain fine-structure characteristics for the two metals, the diffraction beams from silver and gold were readily distinguished. 

Chryseosis corneae (deposition of gold crystals in the cornea) occurs rarely in patients treated with a cumulative dose of up to 500 mg of gold, but they occur in nearly all patients who have received 1500 mg or more (28). Deposition of gold as such has no chnical consequences. Gold can occasionally cause a keratitis or keratoconjunctivitis, but these are usually associated with skin involvement and are not a consequence of gold deposits in the cornea. 

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