Zsigmondy

The model proposed by Zsigmondy—which in broad terms is still accepted to-day—assumed that along the initial part of the isotherm (ABC of Fig. 3.1), adsorption is restricted to a thin layer on the walls, until at D (the inception of the hysteresis loop) capillary condensation commences in the finest pores. As the pressure is progressively increased, wider and wider pores are filled until at the saturation pressure the entire system is full of condensate. 

R. Zsigmondy, Z. Anal Chem., 40, 697 (1901) Colloids and the EItramicroscope, J. Alexander, TransL, John Wiley Sons, Inc., New York, 1909. 

R. Zsigmondy (Gottingen) demonstration of the heterogeneous nature of colloid solutions by methods which have since become fundamental in modem colloid chemistry. 

The topic of gold nanospheres attracted the interest of several famous nineteenth century scientists such as Michael Faraday, Richard Zsigmondy, and Gustov Mie [43]. Interest diminished in the mid-twentieth century although some excellent contributions were made by Turkevich [42, 44], Frens [45], and Brust [46] in that period regarding the controlled preparation of nearly monodisperse colloidal suspensions. 

This relationship permits of experimental verification by direct observation of the diffusion coefficient and the measurement of the radius of the particle. Svedberg Zeit. Phys. Chem. LXVII. 105, 1907 Archiv f Kemi, etc., K. Svmska Vetensk. Akad. Stockholm, B, IV. 12,1911) employed colloidal gold prepared by reduction with phosphorus according to the directions of Faraday and Zsigmondy. 

It has been noted that for substances which do not yield ions in solution, such as charcoal, the charge is always produced by the preferential adsorption of an ion from the solution, e.g. the hydrogen ion. For substances which yield ions in solution, e.g. the hydroxides, it is evident that the charge can be accounted for by superficial ionisation (see Zsigmondy, Kolloidchemie Wolfgang-Pauli, Trans. Farad. Soc. xvi. 6,1921), e.g. ... 

On the assumption of a somewhat mobile double layer, electrostatic attraction between particles may occur, due to this displacement effect, even if the total net charge be not zero, i.e. coagulation may take place before the isoelectric point is reached. The data of Zsigmondy on gold particles, and of Powis Zeit. Phys. Ohem. Lxxxix 186, 1915) on oil particles, have indeed shown that the optimum point for precipitation is not actually at the isoelectric point, although in the case of gold, practically complete discharge of the double layer had to take place before coalescence. 

Coalescence does not immediatelyfollow after contact. Zsigmondy has noted, in the case of gold sols, under the ultramicroscope, that the small primary particles coalesce on contact to form secondary particles, that a primary will coalesce with a secondary, but two secondary particles do not coalesce. 

The following data were obtained by Zsigmondy Zeit. Phys. Ohem. XCII. 600, 1918) for the rate of decrease of primary particles in a gold suspension undergoing coagulation ... 

Similar results have been obtained by Westgren and Reitstdtter Zeit Fhys. Ghem. xcil. 760, 1918) with gold suspensions somewhat coarser than those employed by Zsigmondy and by Kruyt and von Arkel (Rec. d. Trav. Ghim. d. Pays- Bas, xxxix. 656,1920) for selenium. 

Kermack and Wright Biochem. J. XVII. 635,1923) have shown that gelatine at a of 4 T exerts but little protective power on a negative gum benzoin sol, acid gelatine precipitates the colloid in small concentrations whilst alkaline gelatine protects it. Similar observations have been made by Zsigmondy on the effect of casein on gold, but its exact isoelectric point was not established. 

Zsigmondy R, Thiessen PA (1925) Das kolloide Gold. Akademische Verlagsge-sellschaft mbh, Leipzig... 

Several theories have been formulated in order to explain the difference between the state of the adsorbate during adsorption and desorption. For example, Zsigmondy postulated that hysteresis was caused by a difference of contact angle during adsorption and desorption. 

Kirchner, F., and R. Zsigmondy, 1904. Uber die Ursachen der Farbemanderunden von Gold-Gelatinepraparaten, Ann. Phys., 15, 573-595. 

The tiny particles in colloidal gold were not seen directly until the early twentieth century, when the Austrian chemist Richard Adolf Zsigmondy invented the ultramicroscope, a device capable of resolving such small objects. For elucidating the nature of colloids Zsigmondy was awarded the Nobel Prize in chemistry in 1925. 

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