Investigation of Subsystems of Colloidal Agl by Radioactive Tracer Technique

Stable silver iodide sols were prepared in statu nascendi, i.e. by direct mixing of precipitation components. The sols contained 0.0001, 0.001 or 0.01 M Nal (pl = 4, 3 or 2) and 0.0001, 0.001 or 0.01 M/l Agl at 293 K. The following subsystem fractions were separated from the stable silver iodide suspensions by radioactive tracer technique with superspeed Sorvall SS-1 centrifuge and Beckman Model L Preparative ultracentrifuge: embrional, metaphasic, and roughly dispersed silver iodide. Formation and transformation of each subsystem was examined under various conditions (pl, age of sols, addition of coagulation electrolyte Mg-nitrate). The results described reveal a number of simultaneous processes in stable silver iodide suspensions: the embrya disappear and are transformed into the metaphase and solid phase; the methoric mass also disappears turning into the solid phase, i. e. the silver iodide particles grow. The method employed is described in detail and the results obtained show the dependence of the silver iodide subsystem structure on its age and conditions at which it is formed

Influence of Sodium and Iodide Ions on the Transformation of Metaphasic Silver Iodide into the Crystalline Silver Iodide

The influence of constitutive (Agl, l- ions) and nonconstitutive (Na+ ions) components of silver iodide hydrosols on the transformation rate of metaphasic silver iodide into crystalline silver iodide is studied. The simultaneous change of Agl, l - ions, and Na+ ions concentrations causes a complex change of the value of the constant k, (which is proportional to the aggregation rate constant k 2). Within a certain concentration range of constitutive components, the number of primary particles n 1° is directly proportional to the concentration of Agl, and the size of primary particles remains unchanged. Under such conditions, the value of the constant k, is only affected by the concentration of Na+ ions present in the system. For relatively high (pl = 1) and relatively low (pl = 4) concentrations of l- ions the values of the constants k, and b exhibit a sudden decrease

X-Ray Diffraction Analysis of Differently Prepared AgI. IV

The cubic/hexagonal ratio of Ag! formed by dilution of a solution of silver iodide in Na! and AgN03 solutions respectively, and the cubic/hexagonal ratio of Ag! formed in statu nascendi in mixed solvents has been investigated. The complex solution of Ag! + Na! (1, 2, 3, 4, and 8 M Na!) was diluted with water to 0.01 M Na!. The formed mixtures of cubic and hexagonal Ag! contained less cubic Ag! in systems of lower initial concentrations of Na! as compared with those of higher initial concentrations of Na!. By an increase in the amount of Ag! at constant Na! concentration the amount of cubic Ag! decreased: by aging this amount increased. By dilution of a complex solution of Ag! + AgN03 a larger amount of cubic Ag! was formed when the initial concentration of AgN03 was lower (1 M as compared to 8 M AgNOa). In Ag! sols prepared in water-methanol and water-ethanol mixtures, the amount of cubic and/or hexagonal modifications of Ag! changes, by an increase in the percentage of alcohol, in another way than it does in water-dioxane and water-acetone systems. By comparing the changes of the dielectric constant of the medium, the surface tension and the solubility of Ag! it can be concluded that complexly dissolved Ag! is probably the factor which most influences the formation of a a or ~ structure of Ag!

Investigation of Subsystems of Colloidal Agl by Radioactive Tracer Technique

Stable silver iodide sols were prepared in statu nascendi, i.e. by direct mixing of precipitation components. The sols contained 0.0001, 0.001 or 0.01 M Nal (pl = 4, 3 or 2) and 0.0001, 0.001 or 0.01 M/l Agl at 293 K. The following subsystem fractions were separated from the stable silver iodide suspensions by radioactive tracer technique with superspeed Sorvall SS-1 centrifuge and Beckman Model L Preparative ultracentrifuge: embrional, metaphasic, and roughly dispersed silver iodide. Formation and transformation of each subsystem was examined under various conditions (pl, age of sols, addition of coagulation electrolyte Mg-nitrate). The results described reveal a number of simultaneous processes in stable silver iodide suspensions: the embrya disappear and are transformed into the metaphase and solid phase; the methoric mass also disappears turning into the solid phase, i. e. the silver iodide particles grow. The method employed is described in detail and the results obtained show the dependence of the silver iodide subsystem structure on its age and conditions at which it is formed

Heterogeneous Exchange Processes. XXII. AgI- 131I- Exchange

The dependence of the course of the heterogeneous AgI-131!exchange process on the age of the sol and on the concentration of the free iodide ion in the liquid phase was investigated in stable silver iodide sols. Generally the results obtained show a course of heterogeneous exchange in stable sols similar to that shown by the results obtained in coagulated suspensions of AgI in previous investigations. The experiments have shown that the exchange process -is sharply accelerated by adding the coagulating electrolyte. The investigations of this phenomenon allow the analysis of the change of the dispersity states and colloido-chemical characteristics of stable silver iodide sols

Mehanokemijske i termičke transformacije amorfnih i kristalnih alumosilikata

Preparation of amorphous aluminosilicates precursors with defined properties is a very important factor for further studies of nucleation and crystal growth of zeolites during their thermal and hydrothermal transformation into zeolites and special ceramics. This study presents the effect of an intensive mechanical force (ball-milling) on the properties of zeolite A and zeolite A with partially exchanged sodium ions with other cations (Li+, K+, Cs+, NH4+). The influence is studied of different cations on the mechanical and thermal stability of the zeolite framework and the formation of amorphous phases, as well as their transformation into nonzeolitic crystal phases after thermal treatment.Priprava amorfnih alumosilikatnih prekursora definiranih svojstava bitan je čimbenik za studij nukleacije i kristalnog rasta zeolita tijekom njihovih termalnih i hidrotermalnih transformacija u zeolite i specijalne keramičke materijale. U ovom radu je prikazan učinak jakih mehaničkih sila na strukturna svojstva zeolita A i zeolita A u kojem su Na+ ioni djelomično ili potpuno zamijenjeni različitim kationima (Li+, K+, Cs+, NH4+). Prikazan je utjecaj različitih kationa na mehaničku i termičku stabilnost zeolitne građe i dobivanje amorfnih prekursora kao i njihove termičke transformacije u nezeolitne kristalne faze

The working capacity of patients having undergone mutilating neck surgery on account of malignant growths and the care of the community for their future

Raspravlja se o radnoj sposobnosti radnika i seljaka iza velikih mutilirajućih operativnih zahvata na vratu zbog malignoma. Pored toga je obraćena velika pažnja na brigu zajednice za budućnost tih bolesnika.The working capacity of patients having undergone mutilating neck surgery on account of malignant growths and the care of the community for their future. The ever increasing number of practically cured patients who had been suffering from a tumor of the larynx has made it necessary to make a. detailed analysis of the working capacity of such patients and to direct them in their physical and emotional rehabilitation efforts after surgical treatment. Most of the patients regain their working capacity within a period of 3-6 months following laryngectomy, while this period may last from 6 months up to 2 years after laryngedomy and radical neck resection. The cause of the failure of professional rehabilitation is due to the psychological crisis into which every single patient falls after an operation and might also be searched for in the attitude of the people he lives with. Another negative factor is the indispensability of breathing through tracheostoma, which factor in itself disqualifies such patients for a number of callings. The rehabilitation of speech as such does not present an essential component in the working capacity of the patient, however, it is of great importance in overcoming post-operative crises. In analysing the working capacity of 47 laryngectomees, a striking difference between beneficiaries of the social insurance scheme for workers and those not falling under it becomes apparent. Apart from the economic factor, the possibilities offered for gradual and individual adaptation of the convalescent to physical efforts make all the difference. The termination of clinical treatment ought not to be the end of our concern for such patients. Circumstances should be arranged for rehabilitation in all the cases where the physical condition of the patient makes such steps possible. Measures ought to be taken to secure the livelihood of such patients who in spite of all efforts remain incapacitated, regardless of the fact whether they are entitled to social insurance benefits or not. Cases where long lasting constructive plastic surgery is needed and also incurable patients present a special problem. It is not possible to send them home on account of the specific conditions of their nutrition and the special care they require, neither can they be hospitalized in smaller institutions. It would therefore appear to be indispensable to secure for such patients a medical institution, where patients could undergo adequate therapy between two surgical interventions, while others again would receive optimum care till the end of their days

Spektroskopski studij sintetskog forsterita dobivenog iz zeolitnih prekursora

Important ceramics materials are prepared from aluminosilicate based precursors using novel methods, offering at the same time a better control over many important properties. Forsterite, due to its good refractoriness with melting point at 2163 K, excellent electrical insulation properties even at high temperatures, low dielectric permittivity, thermal expansion and chemical stability, is a material of interest to engineers and designers especially as an active medium for tuneable laser and is also a material of interest to SOFC (Solid oxide fuel cells) manufacturers. The aim of this study is to investigate the synthesis of crystalline forsterite using different zeolite precursors previously activated by ball milling. Synthetic forsterite was synthesized from different zeolite precursors and MgO combining highenergy ball milling and thermal treatment of the mixture under determined conditions of time and temperature for each operation. In this research are studied the solid-state phase transformations taking place at temperatures below 1273 K. The obtained products were characterized using different spectroscopy techniques in comparison with surface analysis method and X-ray diffraction.Važni keramički materijali pripremljeni su iz alumosilikatnih prekursora, pri čemu su primijenjene novije metode, koje istodobno daju mogućnost intervencije u procese nastajanja i kontrolu nad mnogim svojstvima. Forsterit je silikatni materijal posebno interesantan inženjerima i konstruktorima procesne opreme, osobito u laserskoj tehnici i području gorivih čvrstih oksidnih ćelija (SOFC), zbog svoje kemijske stabilnosti, dobrih vatrostalnih karakteristika, tališta od 2163 K, izvrsnih električkih izolacijskih svojstava, male električne permitivnosti i slabog termičkog širenja. Cilj ovog rada je istraživanje na području sinteze kristalnog forsterita uz upotrebu različitih zeolitnih prekursora koji su prethodno aktivirani mljevenjem kugličnim mlinom. Sintetski forsterit dobiven je iz smjese MgO i različitih zeolitnih prekursora, kombinirajući visoko energijsko mljevenje i termičku obradu u kontroliranim vremenskim i temperaturnin uvjetima. U ovom istraživanju studirane su fazne transformacije čvrstog stanja koje se odvijaju na temperaturama ispod 1273 K. Dobiveni proizvod je opisan pomoću različitih spektroskopskih tehnika, analizom specifične površine i rendgenskom difrakcijom

Spektroskopski studij sintetskog forsterita dobivenog iz zeolitnih prekursora

Important ceramics materials are prepared from aluminosilicate based precursors using novel methods, offering at the same time a better control over many important properties. Forsterite, due to its good refractoriness with melting point at 2163 K, excellent electrical insulation properties even at high temperatures, low dielectric permittivity, thermal expansion and chemical stability, is a material of interest to engineers and designers especially as an active medium for tuneable laser and is also a material of interest to SOFC (Solid oxide fuel cells) manufacturers. The aim of this study is to investigate the synthesis of crystalline forsterite using different zeolite precursors previously activated by ball milling. Synthetic forsterite was synthesized from different zeolite precursors and MgO combining highenergy ball milling and thermal treatment of the mixture under determined conditions of time and temperature for each operation. In this research are studied the solid-state phase transformations taking place at temperatures below 1273 K. The obtained products were characterized using different spectroscopy techniques in comparison with surface analysis method and X-ray diffraction.Važni keramički materijali pripremljeni su iz alumosilikatnih prekursora, pri čemu su primijenjene novije metode, koje istodobno daju mogućnost intervencije u procese nastajanja i kontrolu nad mnogim svojstvima. Forsterit je silikatni materijal posebno interesantan inženjerima i konstruktorima procesne opreme, osobito u laserskoj tehnici i području gorivih čvrstih oksidnih ćelija (SOFC), zbog svoje kemijske stabilnosti, dobrih vatrostalnih karakteristika, tališta od 2163 K, izvrsnih električkih izolacijskih svojstava, male električne permitivnosti i slabog termičkog širenja. Cilj ovog rada je istraživanje na području sinteze kristalnog forsterita uz upotrebu različitih zeolitnih prekursora koji su prethodno aktivirani mljevenjem kugličnim mlinom. Sintetski forsterit dobiven je iz smjese MgO i različitih zeolitnih prekursora, kombinirajući visoko energijsko mljevenje i termičku obradu u kontroliranim vremenskim i temperaturnin uvjetima. U ovom istraživanju studirane su fazne transformacije čvrstog stanja koje se odvijaju na temperaturama ispod 1273 K. Dobiveni proizvod je opisan pomoću različitih spektroskopskih tehnika, analizom specifične površine i rendgenskom difrakcijom