Gold, number

The gold numbers of the various protective colloids vary greatly and indeed the method offers a means for the detection of substances otherwise not easily identified, e.g. the starches. 

As typical of the gold numbers of various protective colloids the following values may be cited. 

Moseley stated that, within the limits of his researches, which covered all the elements between aluminum (number 13) and gold (number 79), there were spaces for three missing ones numbers 43, 61, and 75, and that, sinoe their X-ray spectra can be accurately predicted, it ought to be rather easy to find them. It was then believed that the celtium whose arc spectrum Professor Urbain had described in 1911 was element 72 (6, 13,14). 

Fig. 31. Scanning electron micrograph (SEM) and scanning Auger element maps for an array of four strips of gold numbers 1,3,6, and 8) and four of aluminum/alumina (numbers 2, 4, 5, and 7) on a silicon nitride substrate that was exposed to a mixture of HS(CH2),, C1 and CF3(CF2)8C02H in isooctane. The SEM and element maps are for the array viewed from above the schematic of the device (the height of the strips is not drawn to scale) is a side view [175]...

Was this your answer Copper (number 29), silver (number 47), and gold (number 79) are all in the same group in the periodic table (group 11), which suggests they should have similar—though not identical—physical and chemical properties. 

A colloidal species that adsorbs onto and acts to protect the stability of another colloidal system. The term refers specifically to the protecting colloid and only indirectly to the protected colloid. Example when a lyophilic colloid such as gelatin acts to protect another colloid in a dispersion by conferring steric stabilization. See also Gold Number, Protection. 

Different protective colloids have different protective powers. Zsigmondy showed that protective power of a protective colloid can be measured in terms of its gold number. 

Gold number may be defined as the number of milligrams of a protective colloid which will just stop the coagulation of 10 ml of a given gold sol on adding 1 ml of 10% sodium chloride solution . 

If no protective colloid is present in the gold sol, it will turn from red to blue. The smaller the gold number of a protective colloid, the greater is its protective power. 

Thus, starch has a high gold number, which shows that it is an ineffective protective colloid, while gelatin has a small gold number and is thus an effective protective colloid. 

Problem Gold number of starch is 25. Calculate its amount to be added intd 100 ml of gold sol so that it is not coagulated in presence of 10 ml of 10% NaCl solution. 

The lower the gold number, the better is the protective power colloid. of a protective... 

The relative efficiency of the various colloidal catalysts indicates that the gold number (7) of the protective colloid offers no guide to the selection of suitable colloidal support. On the basis of gold numbers, the gum arable catalyst should be far superior to the corresponding polyvinyl alcohol catalyst (8). 

Some alchemists even considered gold as condensed sunbeams [1] and used to represent it by the symbol of a circle, the hallmark of mathematical perfection. Let us recall in this respect, e.g., the Golden Section in geometry, the concept of a gold number in colloidal chemistry after R. A. Zsigmondy (Z. Anal. Chem. XL, 697 (1901)) and J. B. Richter and M. Faraday (Phil. Trans. CXLVII, 145 (1857), and the Golden Rule in quantum theory. 

The word gold has been used in many different fields, mostly to evoke perfection, like for example the famous gold section in geometry. In chemistry, the concept of a gold number is used to represent the protective action of colloid (Ref. [10], p. 738). This concept was... 

Biopolymer Gold number (mg/lOcm ) Rubin number (g/10 cm )... 

Heller and Pugh (1954) used a slight modification of Zsigmondy s gold number experiment to measure the effect that four samples of poly-(oxyethylene) had on the stabUity of a Faraday gold sol when potassium chloride was added. Their results are shown in Table 2.2. Listed therein are the values of the critical concentration of potassium chloride (cJ q), required to induce the red- blue transformation in the gold sol in the presence of the polymer at a given concentration (1 -0 g dm ). This concentration of polymer... 

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