Journal
of the University of Chemical Technology and Metallurgy, XXXVII, 2002, Book
2Journal
of the University of Chemical Technology and Metallurgy, XXXVII, 2002, Book
2
KINETICS OF FILLING POROUS ANODIC ALUMINA FILMS WITH SHALLOW PORES
A. Girginov, A. Zahariev, M. MachkovaPITTING CORROSION OF Cr-Mn-N STEEL. EFFECTS OF THE TEMPERATURE AND pH OF 3.5% NaCl MODEL SOLUTION
B. Tzaneva, L. Fachikov, R. RaicheffENOLIC ESTERS OF INDOMETHACIN WITH 2 - ARYL (HETEROARYL) - 1H - INDENE - 1,3 (2H) - DIONES AND 2-ARYL (HETEROARYL) - 2, 3 - DIHYDROPHENALENE- 1, 3 -DIONES
N. Stoyanov, Zl. Jordanova, St. Damjanova, J. HristovaSPECTROPHOTOMETRIC DETERMINATION OF SILVER WITH BROMOPYROGALLOL RED AND
1,10-PHENANTROLINE IN THE PRESENCE OF GELATIN
Chr. Ivanova, S. PopovaSPECTROPHOTOMETRIC ANALYSIS OF SILVER-TIN ALLOYS WITH COPPER AND ZINC ADDITIVES
Chr. Ivanova, S. PopovaCONCENTRATION FLAMMABILITY LIMITS I. ALKANOLS
Z. Zdravchev, M. Hristova
KINETICS OF FILLING POROUS ANODIC ALUMINA FILMS WITH SHALLOW PORES
A. Girginov, A. Zahariev, M. Machkova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: assen@uctm.eduReceived 10 December 2001
Accepted 19 December 2001
The kinetics of formation of complex anodic alumina films is investigated. For this purpose porous matrixes with shallow and deep pores are filled by re-anodization in non-dissolving electrolyte. The porous films are formed in two electrolytes - H2SO4 and (COOH)2, which are usually used as a medium for obtaining porous films on aluminium. Depending on the thickness of the porous films, two types of kinetic curves can be specified. During the re-anodization of shallow pore matrixes a change in the rate of the process is observed. This change corresponds to the moment of complete filling the porous film. When matrixes with deep pores are filled the pores remain partially unfilled and the re-anodization occurs only in the pores. In this case the rate remains constant. Depending on the porosity of the films the voltage of the complete filling of the matrix and the charge needed for that are different.
Keywords: porous alumina films, re-anodization, complex alumina films, porous matrix.
PITTING CORROSION OF Cr-Mn-N STEEL. EFFECTS OF THE TEMPERATURE AND pH OF 3.5% NaCl MODEL SOLUTION
B. Tzaneva, L. Fachikov, R. Raicheff
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: fachikov@uctm.eduReceived 19 November 2001
Accepted 23 January 2002
The pitting corrosion behaviour of Cr-Mn-N steel samples in a 3,5% model aqueous solution of NaCl has been investigated in a wide range of variations of both the bath temperature and pH. The experiments have been performed with samples of Cr14,N,Mn15 austenitic steel upon bath condition varied within the ranges: 0-80oC and 1.0-9.0 pH. Various methods (potentiodynamic, galvanostatic, optical and electron microscopy, etc.) have been employed to characterize the pitting corrosion of the steel samples. The results obtained indicated that the steel tested demonstrates a strong ability to develop pitting corrosion. The origin spots of the pitting are located mainly in the zones around the non-metallic formation of the steel (carbides, oxides and sulphides).
Keywords: pitting corrosion, stainless steel, manganese, nitrogen, and sodium chloride solutions.
ENOLIC ESTERS OF INDOMETHACIN WITH 2 - ARYL (HETEROARYL) - 1H - INDENE - 1,3 (2H) - DIONES AND 2-ARYL (HETEROARYL) - 2, 3 - DIHYDROPHENALENE- 1, 3 -DIONES
N. Stoyanov, Zl. Jordanova, St. Damjanova, J. Hristova
University of Rousse,
Technological college, 7200 Razgrad,
E-mail: ihtbt@infotel.bgReceived 18 January 2002
Accepted 8 February 2002
The interaction of indomethacin with 2-substituted-1,3-indandiones and 2,3-dihydrophenalene-1,3-diones is described. It is established that as a result of this interaction esters of indomethacine with the corresponding enolic forms are obtained. The newly synthesized 8 indomethacinic derivatives are characte-rized with elemental analysis and IR-spectral data. Preliminary results for the biological activity of some of the newly synthesized compounds are reported.
Keywords: Indandiones, phenalenediones, activated esters, anticoagulant, enolacetates.
SPECTROPHOTOMETRIC DETERMINATION OF SILVER WITH BROMOPYROGALLOL RED AND 1,10-PHENANTROLINE IN THE PRESENCE OF GELATIN
Chr. Ivanova, S. Popova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: christina@top.bgReceived 17 December 2001
Accepted 20 December 2001
An improved method for the spectrophotometric determination of silver with bromopyrogallol red (BPR) and 1,10-phenantrolinå (Phen) has been developed. The stabilization of the ternary complex with gelatin results into a several fold increase of the concentration region of applicability of this method, particularly in the higher concentrations range (up to 2.4 g Ag/cm3). The preser-vation of the complex [Phen.AgPhen+]2BPR2- under the mentioned conditions was confirmed. The accuracy and the sensitivity of the method were increased. A higher selectivity in the presence of EDTA was achieved. The established optimal concentration conditions of the determination are: silver - up to 60 g/25.0 cm3; EDTA - 2.0x10-3 M; Phen - 1.2x10-4 M; BPR - 2.4x 10-5 M; 0.4 M acetate buffer solution with pH 6.5-6.7; gelatin - 6x10-3%.
Keywords: spectrophotometric analysis, silver, bromopyrogallol red, 1,10-phenantroline.
SPECTROPHOTOMETRIC ANALYSIS OF SILVER-TIN ALLOYS WITH COPPER AND ZINC ADDITIVES
Chr. Ivanova, S. Popova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: christina@top.bgReceived 17 December 2001
Accepted 20 December 2001
A scheme for the spectrophotometric analysis of dental silver-tin alloys with copper and zinc additives has been developed. A sample of the alloy (~ 0.1 g) was dissolved with concentrated H2SO4. The stannic ion was determined with quercetin ( max - 435 nm) in the medium of 0.15 M H2SO4 and 40 % ethanol. The copper was determined with 4-(2-pyridylazo)resorcinol ( max - 528 nm) in a tartarate buffer solution with pH 2.8. An improved variant for the silver determination is proposed. It is based on the formation of a ternary blue coloured complex with bromopyrogallol red and 1,10-phenantroline ( max - 636 nm) stabilized with 6x10-3 % gelatine, at pH 5.8 in the presence of EDTA. The tin interference was eliminated by standard silver solution containing the determined amount of the stannic ion in the analyzed sample. Zinc was determined by an improved variant of the dithizone method by single extraction with a 10-3 % dithizone solution in carbon tetrachloride at pH 5.0-5.4, masking the Ag+ and Cu2+ with thiosulfate.
Keywords: spectrophotometric determination, silver, tin, copper, zinc.
CONCENTRATION FLAMMABILITY LIMITS I. ALKANOLS
Z. Zdravchev, M. Hristova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: mariana_hristova@hotmail.comReceived 01 February 2002
Accepted 27 February 2002
New methods are proposed for the estimation of the concentration flammability limits of alkanols as function of their molecular mass and boiling point. These alkanols are of interest as components of mixed solvents used in lacquer and varnish process industries. Corresponding expressions are obtained on the basis of the standard deviations methods. The derived expressions permit the estimation of the concentration flammability limits with a satisfactory accuracy for practical purposes.
Keywords: concentration flammability limits, estimation, alkanols, flammability characteristics.
