Gold calculations

The concentration of gold in seawater has been reported to be between 5 ppt (parts per trillion) and 50 ppt. Assuming that seawater contains 13 ppt of gold, calculate the number of grams of gold contained in 1.0 X 10 gal of seawater. 

R. Brill has carried out a series of experiments which indicate very clearly the influence of particle size on the sharpness of the Debye-Scherrer lines for iron powder. There is quite a powerful effect, the evaluation of which would be very profitable. Scherrer has already established in the work previously mentioned that the particle sizes of colloidal gold calculated by the use of his formula agree very satisfactorily with those obtained by the Zsigmondy method of direct counting. Later, Brill compared the different relations available for the computation with one another and obtained the data contained in Table 72. This includes a comparison of the relation originally given by Scherrer with the Laue formula modified by Brill and Pelzer. Various preparations of very fine-grained iron, which are of importance in the technique of catalysis in the ammonia process, served as material. 

Lead(II) iodide, Pbl2, is a dense, golden yellow, "insoluble" solid used in bronzing and in ornamental work requiring a golden color (such as mosaic gold). Calculate the molar solubility of lead(II) iodide in water at 25 °C, given that K p = 7.1 X 10 . ... 

Calculate the surface tension of gold at 970°C. Take your data from Fig. VII-10. 

STM and AFM profiles distort the shape of a particle because the side of the tip rides up on the particle. This effect can be corrected for. Consider, say, a spherical gold particle on a smooth surface. The sphere may be truncated, that is, the center may be a distance q above the surface, where q < r, the radius of the sphere. Assume the tip to be a cone of cone angle a. The observed profile in the vertical plane containing the center of the sphere will be a rounded hump of base width 2d and height h. Calculate q and r for the case where a - 32° and d and h are 275 nm and 300 nm, respectively. Note Chapter XVI, Ref. 133a. Can you show how to obtain the relevent equation ... 

Figure C2.17.13. A model calculation of the optical absorjDtion of gold nanocrystals. The fonnalism outlined in the text is used to calculate the absorjDtion cross section of bulk gold (solid curve) and of gold nanoparticles of 3 mn (long dashes), 2 mn (short dashes) and 1 mn (dots) radius. The bulk dielectric properties are obtained from a cubic spline fit to the data of [237]. The small blue shift and substantial broadening which result from the mean free path limitation are...

The calculation of the binding affinity with con.sidcration of all tbc.se effects for virtual screening is not possible. In order to circumvent thus difficulty, scoring functions arc used instead, c.g., the Liidi scoring function [80, or consensus scoring functions derived from FlevX score, DOCK score, GOLD score, ChemScore, or PMF score [81 ]. 

ICP-SFMS (Thermo Finnigan, Flement) with cold vapour generation was developed with a guard electrode and a gold amalgamation device using an Au-sorbent for sample pre-concentration to improve the sensitivity. Instrumental parameters of ICP-SFMS such as take-up time, heating temperature of Au-sorbent, additional gas flow, and sample gas flow were optimized. Detection limit calculated as 3 times the standard deviation of 10 blanks was 0,05 ng/1, RSD = 7-9 %. 

Example 2 Finely divided gold is agitated with an oxygen-saturated alkali-cyanide solution of pH = 12 containing 10 moldm of CN . Calculate the concentration of Au(CN)2 ions in solution at 25°C when the reaction is at equilibrium. The standard chemical potentials of the species involved (in kJ) are CN, 165 HjO, —237 Au(CN)f, 244 OH", —157. Assume that fl jo = 1, and take 2-303RT = 5710. 

The electrical current of a coplanar interdigilal gold/LPPP/gold device is space charge limited due to p-type charge earner traps localized in the bandgap [28]. This can be inferred from the field dependence of the dark current at room temperature. The thermally stimulated current spectrum exhibits two peaks, corresponding to two distinct trap levels ,1 and ,", which can be calculated from the rise in current, /, below the peak temperature ... 

Gold-copper, alloy (Au5Cu5, AuBCuB(S)), calculation of thermodynamic quantities, 136, 142 solid solution (CuAu), 129 Gold-lead, alloy (Au5Pb5), calculation of thermodynamic quantities, 136 Gold-nickel, alloy (Au5Ni8), calculation of thermodynamic quantities, 136, 142... 

Gold-thallium, alloy (Au5T15), calculation of thermodynamic quantities, 136... 

Silver-copper, energy of solutions, 142 Silver-gold, excess entropy, 132, 136 excess free energy, 136 Silver-lead, alloy (AgsPb5), calculation of thermodynamic quantities, 136 Silver-zinc, alloy (Ag5Zn5), 129... 

AuCN has a similar structure to AgCN and likewise dissolves in excess cyanide to form Au(CN)J this is important in the extraction of gold. It has been characterized as various salts (Tl, K, Bu4N, Cs) with Au-C 1.964A (Bu4N salt [91]). The thallium salt has short Au-Au (3.10A) and Au-Tl (3.50 A) interactions extended-Huckel calculations indicate the importance of relativistic effects in these covalent interactions. Isocyanides form stable complexes ... 

The stability of gold(III) compared with silver(III) has been ascribed to relativistic effects causing destabilization of the 5d shell, where the electrons are less tightly held. Hartree-Fock calculations on AuX4 (X = F, Cl, Br) indicate that relativistic effects make a difference of 100-200 kJ mol-1 in favour of the stability of AuXJ (Table 4.12) [110]. 

Example 2-3 The electropolymeric growth of 2 ng polyphenol onto a gold QCM crystal A = 1 cm2 /0 = 5 MHz) resulted in a frequency change of 12 Hz. Calculate the frequency change associated with the deposition of 4ng polyphenol onto a 0.5 cm2 crystal (/0 = 8 MHz). 

Values of the single-bond radii for the metals of the series silver to tin and gold to lead are also given in table 6, as calculated by equations (10c) and (11c) for the pure valence states A, B, C and D and for certain intermediate valencies, corresponding to resonance among these states. 

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