Gold solution

Titrimetric Methods. Frequently, the reduction of gold solutions leads to finely divided precipitates which are difficult to recover quantitatively. In such cases, the reduction of Au(III) to Au(0) by, eg, hydroquinone, can be followed potentiometricaHy (49). The end point in such titrations also can be determined with indicators such as benzidine (50) or o-anisidine (51). Alternatively, the reduction can be effected with excess hydroquinone which is then back-titrated with Ce(IV) (52). lodometric deterrnination of Au(III) also is useflil (53). 

Kolb, reconstruction of, 85 Gold-solution interface (Clavilier and Nguyen Van Huong), 77 Guidelli, and the methods for the determination of the potential of zero charge, 63... 

According to the procedure of sol deposition described in Section 2.3, more than 10% Au can be deposited on XC72R, thus allowing the use of the catalysts in fuel cells and other electrochemical applications [36]. In all the experiments the common mother gold solution 1 (Section 2.3) was used containing a low PVA amount (PVA Au = 0.05) in order to facilitate the adsorption step. Table 8 shows the results. According to ICP analysis, an almost total gold adsorption was obtained. 

Considerable research effort was focused on systems of colloidal gold of which a broad variety of synthetic procedures were reported [140 b, fj. While native colloidal gold solutions are only stable for a restricted time, Brust et al. [141] were able to overcome this problem by developing a simple method for the in situ preparation of alkyl thiol-stabihzed gold nanoparticles. This synthetic route yields air-stable and easy to handle passivated nanoparticles of moderate polydispersity, and is now commonly employed for the preparation of inorganic-organic core-shell composites. Such composites are used as catalytic systems with principally two different functions of the protective 3D-SAM layer. Either the metal nanoparticle core can be used as the catalytically active center and the thiol layer is only used to stabihze the system [142], or the 3D-SAM is used as a Hnker system to chemically attach further catalytic functions [143]. 

Heat the gold solution and the reducing solution separately on a stirring hot plate. 

When the gold solution reaches 60°C, stir vigorously and quickly add the reducing solution. 

In another application, the magnitude of the zeta potential is measured as a function of added counterions. The variation in zeta potential is found to be related to the stability of the colloidal suspension. The results of a gold colloidal suspension (gold solute) are reported as follows ... 

Mix 79 ml Reagent A with 1 ml Soln. B and heat to 60 °C while stirring. Prepare the reduction mixture according to Table 4.4 and heat to 60 °C, too. Add quickly the hot reaction mixture to the gold solution and continue heating and stirring for 15 min. When the color has changed to red, reflux for 10 min. 

Berthelot, op. cit., p. 304. Vincent de Beauvais, Lib. VIII, cliap. XIII, gives as the seven tests for gold solution, the touchstone, density, taste, the action of fire, fusion, sublimation. 

Stain the blots with the gold solution at room temperature on a shaker for 10-45 min until the protein bands are visible. Use sufficient gold solution to cover the blot easily... 

Slowly add 250 mL of citric acid solution to the gold solution. Leave to stir for 20-30 min. The color of the solution should develop into red (see Note 6). 

Freshly prepare a gold solution from an ampule of gold chloride crystals by adding 1 mL of a 1% aqueous gold chloride solution to 79 mL of distilled water. 

Warm the solutions to 60°C and quickly add the reducing mixture to the gold solution while stirring. The temperature is critical at this stage. Evidence of sol formation is the red color of the mixture. 

Add 100 pL of gold solution to each preparation, and incubate for 5 min at room temperature. 

Schmahl D, Steinhoff D. 1960. [Experimental carcinogenesis in rats with colloidal silver and gold solutions], Z Krebsforsc 63 586-591. (German)... 

Gold solution for additions prepare a gold 2.0 x 10-5 M solution in 0.1 M HC1 from the gold standard solution. 

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