The effect of sulfate ions on the growth of NaClO, faces (100) and (111) has been investigated. The heat of adsorption on the active centers of growth for both types of faces has been derived from kinetic experimental data. Direct adsorption measurements have been performed which gave the hcat of adsorption on the whole surface of each type of faces. A possible explanation of the experimental results is given.~CCJIeAoBaHO BJIMIIHHe CyJIL@aTHbIX HOHOB Ha POCT rpaHei% (100) M (111) XJIo-aICTMBHbIX MeCTaX poCTa AJIEi ABYX BPiAoB rpaHefi. TennoTa a n c o p 6 4~~1 RJIR BCefi rIoBepXHoCTM TeX me rpaHefi OIIpeAeneHa APiPeKTIIbIMM a~COp6UmOHHbIMM M3Mepe-IIHEMM. CAeJIaHa IlOnbITKa ZJM Ofi' bFICHeHMEi IIoJIy~eI-IHbIX pe3yJIhTaToB.paTa HaTpm. PI3 mmemyecmx ,qaHHbIx orIpeAeJrer-Ia TenaoTa ancop6qa~ iIa
The effective activation energies of crystal growth on the faces (100) of KCI, KBr, and K I crystals in water solutions have been determined. The values obtained have been compared with the respective crystal lattice energies according to Sletter and Mayer, as well as with the experimental ones. The activation energies of crystal growth are in strictest linear dependence on the heats of dehydration of the ions. This shows that the dehydration of the ions is most probably the ratecontrolling stage of the process of crystal growth in solutions. This concept is supported by the results of an experimental study of the rates of growth on the faces (1 11) and (100) of NaClO, crystals. OnpeneneHn Kaxcynwieca 3~e p r m i aKTmaqmi pocTa rpaHet (100) KpHcTannoB KC1, KBr y K1 E13 BOAHHX PaCTBOpOB. nOJIyW2HHbIe aHaW3HIlH COIIOCTaBJIeHbI C 3KCIlepHMeHTaJIbHbIMW EI C BWHCJIeHHbIMH no CneTTepy II MaBepy 3HePrHEI HpIIC-TanJIHYeCKAX PeIIleTOK COOTBeTCTBYIOUHX KpHCTaJIJIOB . 3HePrkIR aKTHBaUkiI1 np0-UeCCa pOCTa HaXOAIlTCH B na116onee RCHO BbIpaXeHHOfi JIHHefiHOfi 3aBEiCEiMOCTIl OT TaUHH a O H O B HBJIHBTCR KOHTPOJIIIPYH)II(AM 3TBnOM IIpOUeCCa POCTa KpHCTaJIJIOB I13 TennoT rHapaTaqm ~O H O B . TO ~O K~~E J B~~T , TO no Bcet BeposiTHocTn Aerunpapacmopa. rIoTsepmaeHHeM Tanoro B~~J I F I A~ IIBJIHEOTCFI EI AaHHbIe, nonpeaame np~1 HccaeaoBaHm cHopocTet pocTa rpaHet (111) II (100) KpmTannoB NaC10,.
The crystallization kinetics of zinc oxalate a t different supersaturations was studied by a turbidimetry method. It was found that the curves optically registered by this method can be quantitatively characterized a t initial supersaturations lower than 4.51. The graphically differentiated curves showed that the maximum crystallization rate could be fitted by equation Vmax z K ( C -Co)2, where C and C, are the initial and the equilibrium concentrations, respectively. The crystallization rates after the maximum follow the same equation depending on the absolute supersaturation a t a given moment. A linear dependence between the rate constants and the supersaturations a t the maximum crystallization rates is found, This dependence is determined by the inversely proportional correlation of the distances between the steps of growth with the supersaturation given by equation (8). The activation growth energy E* = 7.1 kcal/mole is determined from the straight line obtained. Die Kristallisationskinetik von Zinkoxalat bei verschiedenen Ubersattigungen wirdanhand einer turbidimetrisehen Methode untersucht. Es wird festgestellt, da8 die nach dieser Methode optisch registrierten Kurven bei Ausgangsiibersattigungen unter 4,51 quantitativ charakterisiert werden konnen. Die graphisch differenzierten Kurven zeigen, daB fur die maximale Kristallisationsgeschwindigkeit die Gleichung Vmax = K ( C -C,)2 giiltig ist, in der C und C, die Ausgangs-bzw. Gleichgewichtskonzentration bezeichnen. Nach dem Maximum folgen die Kristallisationsgeschwindigkeiten derselben Gleichung in Abhiingigkeit von der absoluten Ubersattigung in einem bestimmten Augenblick. Zwischen den Geschwindigkeitskonstanten und den Ubersattigungen bei den maximalen Kristallisationsgeschwindigkeiten besteht eine lineare Abhiingigkeit, die durch das umgekehrt proportionale Verhiiltnis der Abstiinde zwischen den Wachstumsstufen zu der von Gleichung (8) angegebenen Ubersiittigung bestimmt wird. Die Aktivierungsenergic des Kristallwachstums E * = 7 , l kcal/mol wird aus der erhaltenen Gerade bestimmt,
This paper is a review of our experimental research on the influence of the supersaturation, flow velocity and temperature on the linear crystallization rate of different faces of model crystal systems. The obtained experimental results are discussed in the light of the new theoretical treatments on crystal growth from low temperature solutions.B pa6o~e paCCMOTpeHbl HaWH 3KCIIepHMeHTaJILHbIe HCCJIeAOBaHHR 0 BJIHRHHH IlepeCbImeHLIFI, CKOPOCTH IIOTOKa H TeMIle11aTypbI Ha JIHHefiHyIO CKOPOCTb pOCTEi pa3JIH' iHLIX I'paHeR MOAeJIbHOfi KpHCTaJIbHOfi CHCTeMbI. npOBeDeH0 o 6 c y m n e~~e pe3yJlbTaTOB 3KCIlePHMeHTOB B CBeTe HOBbIX TeOpeTHqeCHl' lX llOCTaHOBOK 0 pOCTe KpHCTaJIJIOB H3 HH3KOTeMnepaTypHblX PBCTBOPOB.I n the course of many years we have conducted research on the influence of some factors on the linear crystallization rate (LCR) for different faces of crystal systems.These studies have both a theoretical significance for the elucidation of the niechanisrn of crystallization from solutions and a practical value in connection to the preparation of single crystals and crystalline products with definite physicochemical parameters. The experiments were performed in an apparatus in which a circulating solution flows past the growing crystal. I n the first models of the apparatus (BLIZNAKOV, KIRKOVA; BLIZNAKOV) the circulation was accomplished with the help of a valve system with a maximal flow velocity of 1-2 cm/s. To increase the flow velocity a new version of the apparatus was designed recently (NIKOLAEVA, KIRKOVA 1977/78) with which the flow velocity reaches -20 cm/s. This permitted the hydrodynamics effect on the process to be also investigated.I n the present work our experimental studies on the influence of the flow velocity, supersaturation and temperature on the LCR of different faces of crystal systems will be summarized. We will attempt to explain the results in the light of the new theoretical treatments of crystal growth froni low temperature solutions and we will compare them with the experimental data of other research workers. 1.Influence of the flow velocity on the crystal growth-plotting of the R ( o ) relationThe complex hydrodynamic processes which influence the crystal growth from solutions are still not theoretically clear and the experimental results in this field are too few. The last generally indicate that a t low supersaturation values, when the velocity of the flow past the growing crystal increases, the crystal growth rate tends to a constant value. With an increase in the supersaturation, this value is reached a t constantly increasing flow velocities and at high supersaturations it is not reached at all (BOURNE, DAVEY 34, 1976; BELYUSTTN, LEVINA 1974; TREIVUS 1979). This is explained by the increasing role of the volume diffusion with the increase in super-50 *
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