Glasnik na hemicarite i tehnolozite na Makedonija

Bulletin of the Chemists and Technologists of Macedonia


Abstracts

Vol. 17, No. 1, 1998


Bulletin of the Chemists and Technologists of Macedonia, Vol. 17, No. 1, pp. 3–7 (1998)

GHTMDD – 300 ISSN 0350 – 0136

Received: March 16, 1998 UDC: 678.7:547.75:

Accepted: June 9, 1998

Original scientific paper

ELECTROCHEMICAL GRAFTING OF POLYPYRROLE WITH
POLY[ (METHYL METHACRYLATE)-CO-(2-(N-PYRROLYL) ETHYL METHACRYLATE)]

Nurcan Balci1, Ural Akbulut1, Levent Toppare1*, Dietmar Stanke2, Manfred L. Hallensleben2

1Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey
2Institute für Makromolekulare Chemie, Universität Hannover, Am Kleinen Felde 30, D-30167, Hannover, Germany

The electrochemical polymerization of pyrrole on poly[ (methyl methacrylate)-co-(2-(N-pyrrolyl) ethyl methacrylate)] (PMMA-co-PEMA-7) coated electrodes yielded electrically conducting graft films. During the electrosynthesis of the films sodium perchlorate (NaClO4) and tetrabutylammonium tetrafluoroborate (TBAFB) were utilized as the supporting electrolytes. The results of cyclic voltammetry studies indicated that both polypyrrole (PPy) and PMMA-co-PEMA-7 were electroactive. Thermal behaviors of the films were determined by using DSC, TGA and surface morphologies were studied with scanning electron microscopy. FT-IR and elemental analysis were used for the characterization of the samples.

Keywords: polypyrrole; copolymer; electroactive polymers; electrochemical grafting

 

R e z i m e

ELEKTROHEMISKA KALEM-POLIMERIZACIJA NA poliPIROL
VRZ POLI
[(METILMETAKRILAT)-KO-(2-(n-PIROLil)ETILMETAKRILAT)]

Nurcan Balci1, Ural Akbulut1, Levent Toppare1*, Dietmar Stanke2, Manfred L. Hallensleben2

1Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey
2Institute für Makromolekulare Chemie, Universität Hannover, Am Kleinen Felde 30, D-30167, Hannover, Germany

Elektrohemiskata polimerizacija na pirol vrz elektrodi prevle~eni so poli[(metilmetakrilat)-ko-(2-N-pirolil)etilmetakrilat)] (RMMA-ko-REMA-7) doveduva do sozdavawe na elektrosprovodlivi kalem-polimerni filmovi. Kako elektroliti vo tekot na elektrosintezata se koristeni natriumperhlorat (NaClO4) i tetrabutilamonium tretrafluoroborat (TBAFB). Rezultatite od cikli~nata voltametrija uka`uvaat na elektroaktivnost na dvata polimera: polipirolot (RRu) i RMMA-ko-REMA-7. Termi~koto odnesuvawe na filmovite e karakterizirano so pomo{ na DSC i TGA, a povr{inskata morfologija so SEM analiza. Filmovite se karakterizirani i so FT-IR i elementarna analiza.

Klu~ni zborovi: polipirol; kopolimer; elektroaktivni polimeri; elektrohemisko kalemewe


Bulletin of the Chemists and Technologists of Macedonia, Vol. 17, No. 1, pp. 9–15 (1998)

GHTMDD – 301 ISSN 0350 – 0136

Received: May 4, 1998 UDC: 678.744.01

Accepted: June 9, 1998

Original scientific paper

ON THE INFLUENCE OF POLY(BUTYL METHACRYLATE) POLYDISPERSITY
ON THE EXCLUDED VOLUME PARAMETERS

Gabriela Grigorescu1, Cãtãlina Ioan1, Silvia Ioan1 and Bogdan C. Simionescu2

1"P. Poni" Institute of Macromolecular Chemistry, Iasi 6600, Romania
2"Gh. Asachi" Technical University, Department of Macromolecules, Iasi 6600, Romania

The paper examines the influence of the molecular weight distribution types and the polydispersity indexes on the values of the root-mean-square radius of gyration, the second virial coefficient and the intrinsic viscosity for ultrahigh molecular weight poly(butyl methacrylate) (PBMA) obtained by plasma induced polymerization in different solvents.

Keywords: poly(butyl methacrylate); ultrahigh molecular weights; polydispersity indexes; root-mean-square radius of gyration; second virial coefficient; intrinsic viscosity

 

R e z i m e

ZA VLIJANIETO NA POLIDISPERZNOSTA NA POLI(BUTILMETAKRILAT) VRZ PARAMETRITE NA ISKLU^ENIOT VOLUMEN

Gabriela Grigorescu1, Cãtãlina Ioan1, Silvia Ioan1 i Bogdan C. Simionescu2

1"P. Poni" Institute of Macromolecular Chemistry, Iasi 6600, Romania
2"Gh. Asachi" Technical University, Department of Macromolecules, Iasi 6600, Romania

Vo trudot e ispituvano vlijanieto na vidot na molekularno-masenata raspredelba i indeksite na polidisperznost vrz vrednosta na radiusot na inercija, vtoriot virijalen koeficient i grani~niot viskoziteten broj za ultravisokomolekularen poli(butilmetakrilat) (RVMA) dobien so plazma-inicirana polimerizacija vo razli~ni rastvoruva~i.

Klu~ni zborovi: poli(butilmetakrilat); ultravisoki molekularni masi; indeksi na polidisperznost; radius na inercija; vtor virijalen koeficient; grani~en viskoziteten broj


Bulletin of the Chemists and Technologists of Macedonia, Vol. 17, No. 1, pp. 17–24 (1998)

GHTMDD – 302 ISSN 0350 – 0136

Received: December 29, 1998 UDC: 678.7.01/.02

Accepted: May 15, 1998

Original scientific paper

ABA TYPE BLOCK COPOLYMERS OF POLY(METHYL METHACRYLATE)
AND POLY(DIALKYL ITACONATE) WITH POLY(DIMETHYL SILOXANE) :
SYNTHESIS AND CHARACTERIZATION

Maja Cvetkovska1, Slobodanka ]oseva1, Snežana Tasevska1,
E. Elif Hamurcu2, Bahattin M. Baysal2,3

1The "Sv. Kiril & Metodij" University, Faculty of Technology and Metallurgy,
91000 Skopje, Republic of Macedonia
2TUBITAK – Marmara Research Center, Department of Chemistry, 41470 Gebze – Kocaeli, Turkey
3Bo¤aziçi University, Department of Chemical Engineering, 80815 Bebek – Istanbul, Turkey

A series of block copolymers of dibuthyl itaconate (DBI), dicyclohexyl itaconate (DCHI), and methyl methacrylate (MMA) were prepared by using diperoxycarbamate containing poly(dimethyl siloxane) units. Formation of ABA type block copolymers was illustrated by several characterization methods such as GPC, IR, viscosity, Inductivity Coupled Plasma Spectroscopy (ICP), and DSC techniques. Surface tension of block copolymers in various solvents and contact angle measurements showed that these siloxane containing copolymers would be effective modifiers in surface treatments.

Key words: triblock copolymers; poly(dibuthyl itaconate); poly(dicyclohexyl itaconate); poly(methyl methacrylate); poly(dimethyl siloxane); synthesis; characterization; solution properties

 

R e z i m e

ABA BLOK-KOPOLIMERI NA POLI(METILMETAKRILAT) I POLI(DIALKILITAKONATI)
SO POLI(DIMETILSILOKSAN) : SINTEZA I KARAKTERIZACIJA

Maja Cvetkovska1, Slobodanka ]oseva1, Sne`ana Tasevska1, E. Elif Hamurcu2, Bahattin M. Baysal2,3

1Tehnolo{ko-metalur{ki fakultet, Univerzitet Sv. Kiril i Metodij", 91000 Skopje, R. Makedonija
2TUBITAK – Marmara Research Center, Department of Chemistry, 41470 Gebze – Kocaeli, Turkey
3 Bo¤aziçi University, Department of Chemical Engineering, 80815 Bebek – Istanbul, Turkey

So pomo{ na diperoksikarbamat, so polidimetilsiloksanski blok, e sintetizirana serija blok-kopolimeri na dibutilitakonat (DBI), dicikloheksilitakonat (DCHI) i metilmetakrilat (MMA). Sintezata na ABA blok-kopolimeri e doka`ana so pove}e metodi za karakterizacija (GPC, IR, viskozimetrija, ICP i DSC). Povr{inskiot napon na blok-kopolimerite vo razli~ni rastvoruva~i, kako i rezultatite za kontaktniot agol uka`uvaat na toa deka blok-kopolimerite so siloksan mo`at da bidat efikasni modifikatori na povr{inskite svojstva.

Klu~ni zborovi: triblok-kopolimeri; poli(dibutilitakonat); poli(dicikloheksilitakonat); poli(metilmetakrilat); poli(dimetilsiloksan); sinteza; karakterizacija; svojstva na rastvori


Bulletin of the Chemists and Technologists of Macedonia, Vol. 17, No. 1, pp. 25–31 (1998)

GHTMDD – 303 ISSN 0350 – 0136

Received: July 15, 1997 UDC: 678.84

Accepted: April 10, 1998

Original scientific paper

AN INVESTIGATION OF THE RELATIONSHIPS BETWEEN SOME SYNTHETIC CONDITIONS AND THE PROPERTIES OF POLYSILOXANE ELASTOMERS PREPARED BY HYDROSILYLATION CROSSLINKING

Jelena D. Jovanovi}1, Milutin N. Govedarica2* and Petar R. Dvorni}2**

1Institute of General and Physical Chemistry, Studentski trg 12, YU-11000 Beograd
2Institute of Chemistry, Technology and Metallurgy, Center of Chemistry, Department of Polymeric Materials, Njegoševa 12, YU-11000 Beograd

The low temperature vulcanization process (LTV), performed in bulk at 37 ± 1oC, based on the platinum catalyzed hydrosilylation reaction of vinyl terminated dimethyl-siloxane polymers with dimethyl-methylhydridosiloxane copolymers was investigated. The effects of the catalyst concentration, of the maximum crosslink density and of the molecular weight of the dimethyl-methylhydridosiloxane copolymers on the vulcanization duration and on the hardness of the obtained elastomers were determined. Mathematical expressions for the investigated effects were also obtained.

Key words: low temperature vulcanization; hydrosilylation; vinyl terminated dimethylsiloxane; dimethyl-methylhydridosiloxane; elastomers properties

 

 

 

R e z i m e

ZAVISNOST ME\U NEKOI USLOVI NA SINTEZATA I SVOJSTVATA
NA POLISILOKSANSKI ELASTOMERI DOBIENI VO REAKCIJA
NA HIDROKSILILIRAWE

Jelena D. Jovanovi˘1, Milutin N. Govedarica2 i Petar R. Dvorni˘2

1Institut za op{tu i fizi~ku hemiju, Studentski trg 12, YU-11000 Beograd
2Institut za hemiju, tehnolohiju i metalurgiju, Centar za hemiju, Odeqewe polimernih materijala,
Wego{eva 12,
YU-11000 Beograd

Ispituvan e niskotemperaturen proces na vulkanizacija vo masa, kataliziran so platina, na 37 ± 1 oS, baziran vrz reakcija na hidrosililirawe na dimetilsiloksanski polimeri so krajni vinilni grupi i kopolimeri na dimetil-metilhidrosiloksan. Opredeluvano e vlijanieto na koncentracijata na katalizatorot za postignuvawe maksimalna gustina na vmre`uvawe, kako i na molekularnata masa na dimetil-metilhidrosiloksanot vrz vremeto na vulkanizacijata i tvrdinata na dobienite elastomeri. Za ispituvanite efekti se predlo`eni i soodvetni matemati~ki relacii.

Klu~ni zborovi: niskotemperaturna vulkanizacija; hidrosililirawe; dimetilsiloksan so krajni vinilni grupi; dimetilmetilhidrosiloksan; svojstva na elastomerite


Bulletin of the Chemists and Technologists of Macedonia, Vol. 17, No. 1, pp. 33–39 (1998)

GHTMDD – 304 ISSN 0350 – 0136

Received: February 22, 1998 UDC: 615.222.073/.074

Accepted: May 15, 1998

Original scientific paper

DRUG DISSOLUTION PROFILES AND PHYSICO-CHEMICAL STABILITY EVALUATION OF CONTROLLED-RELEASE SOLID DISPERSION GRANULES

Katerina Gora~inova1, Ljiljana Klisarova2, Angel Simov1, Emilija Fredro-Kumbarad`i1,
Kristina Mladenovska
1, Marija Glavaš1

1Institute of Pharmaceutical Technology, Faculty of Pharmacy, The "Sv. Kiril & Metodij" University,
Vodnjanska 17, 91 000 Skopje, Republic of Macedonia
2Institute of Chemistry, Faculty of Natural Sciences and Mathematics, The "Sv. Kiril & Metodij" University,
P.O.B. 162, 91 001 Skopje, Republic of Macedonia

Physico-chemical stability and drug dissolution profiles of the prepared solid dispersions containing Verapamil HCl as active substance were evaluated using different experimental methods during 60-months real-time stability studies. During the stability studies no drug decomposition or changes in the active substance content appeared. Physical characterization of the solid dispersions showed no changes in the drug/polymer network during ageing. The initial amorphous appearance of the drug substance in the solid dispersions was maintained during ageing. Although the drug dissolution profiles showed differences compared to series tested immediately after preparation, the drug release dependence upon HPMCP HP 55 was maintained even more pronounced at higher pH values.

Key words: solid dispersions; stability studies; controlled release; Verapamil HCL; ethyl cellulose; HPMCP HP 55

 

R e z i m e

FIZI^KO-HEMISKA STABILNOST NA CVRSTI DISPERZII SO VERAPAMIL-HIDROHLORID I NEGOVO KONTROLIRANO OSLOBODUVAWE

Katerina Gora~inova1, Qiqana Klisarova2, Angel Simov1, Emilija Fredro-Kumbaraxi1,
Kristina Mladenovska
1, Marija Glava{1

1Institut za farmacevtska tehnologija, Farmacevtski fakultet, Univerzitet Sv. Kiril i Metodij",
Vodwanska 17, 91 000 Skopje, Republika Makedonija
2Institut za hemija, Prirodno-matemati~ki fakultet, Univerzitet
Sv. Kiril i Metodij",
p. fah 161, 91001 Skopje, Republika Makedonija

Be{e ispituvana stabilnosta na podgotvenite cvrsti disperzii so verapamil-hidrohlorid so upotreba na razli~ni eksperimentalni metodi (IC spektroskopija, UV spektroskopija, difrakcija so H-zraci, tenkoslojna hromatografija pod visok pritisok, testovi na disolucija) vo tek na 60 meseci. Za vreme na ispituvawata na stabilnosta ne be{e zabele`an raspad i/ili promena na kvantitativniot sostav na aktivnata supstancija. Fizi~koto karakterizirawe na cvrstite disperzii poka`a deka ne doa|a do promeni vo strukturata na cvrstite disperzii za vreme na stareeweto. Isto taka be{e za~uvana amorfnosta na vklopenata aktivna supstancija vo cvrstite disperzii. Iako osloboduvaweto na verapamil-hidrohloridot za vreme na stareeweto se razlikuva od po~etnoto, sepak zavisnosta na osloboduvaweto na aktivnata supstancija od polimerot HPMCP HP 55 be{e zadr`ana, a duri i ponaglasena pri povisoki rN vrednosti.

Klu~ni zborovi: cvrsti disperzii; ispituvawe na stabilnosta; kontrolirano osloboduvawe; verapamil-hidrohlorid; etilceluloza; hidroksipropil-metil-celuloza ftalat


Bulletin of the Chemists and Technologists of Macedonia, Vol. 17, No. 1, pp. 41–44 (1998)

GHTMDD – 305 ISSN 0350 – 0136

Received: December 19, 1997 UDC: 543:58

Accepted: May 5, 1998

Short communication

FLAVONOIDS OF VERBASCUM SCARDICOLUM
AND MELAMPYRUM SCARDICUM

Pan~e Naumov, Igor Kuzmanovski and Marina Stefova

Institute of Chemistry, Faculty of Natural Sciences & Mathematics, The „Sv. Kiril & Metodij" University,
P.O. Box 162, 91001 Skopje, Republic of Macedonia

Aerial parts of two endemic plant species, Verbascum scardicolum and Melampyrum scardicum, were examined for the presence of twenty-one flavonoid and two phenolic acids by RP HPLC. The components were detected by comparison with standards. From the inflorescences of V. scardicolum luteolin 7-O-glucoside was isolated and purified by chromatographic methods. In the leaves’ extract of V. scardicolum, caffeic acid was detected. The M. scardicum extract showed the presence of luteolin, luteolin 7-O-glucoside and apigenin 7-O-glucoside. The results were compared with literature data for the other species of Verbascum and Melampyrum.

Key words: flavonoids; Verbascum; Melampyrum; reverse-phase high performance liquid chromatography

 

R e z i m e

FLAVONOIDI KAJ
VERBASCUM SCARDICOLUM I MELAMPYRUM SCARDICUM

Pan~e Naumov, Igor Kuzmanovski i Marina Stefova

Institut za hemija, Prirodno-matemati~ki fakultet,Univerzitet Sv. Kiril i Metodij",
p. fah 162, 91001 Skopje, R. Makedonija

Nadzemni delovi od dva endemi~ni rastitelni vida, Verbascum scardicolum i Melampyrum scardicum, se ispitani za prisustvoto na dvaeset i eden flavonoid i dve fenolni kiselini so reverzno-fazna visokoefikasna te~na hromatografija. Komponentite se detektirani so sporedba so standardi. So hromatografski metodi od cvetovi na V. scardicolum izoliran i pre~isten e luteolin 7-O-glukozid. Vo ekstraktot od listovi na V. scardicolum e detektirana kofeinska kiselina. Vo ekstraktot od M. scardicum e utvrdeno prisustvo na luteolin, luteolin 7-O-glukozid i apigenin 7-O-glukozid. Rezultatite se sporedeni so literaturni podatoci za drugi vidovi od rodovite Verbascum i Melampyrum.

Klu~ni zborovi: flavonoidi; Verbascum; Melampyrum; reverzno-fazna visokoefikasna te~na hromatografija


Bulletin of the Chemists and Technologists of Macedonia, Vol. 17, No. 1, pp. 45–52 (1998)

GHTMDD – 306 ISSN 0350 – 0136

Received: February 2, 1998 UDC: 546.683.3 – 386:543.42

Accepted: May 15, 1998

Original scientific paper

SPECTROPHOTOMETRIC CHARACTERISTICS OF THALLIUM(III) COMPLEXES WITH IODOACETIC ACID AND TERTIARY AMINES

Dragan S. Mihajlovi}1 and Traj~e Stafilov2

1A.D. Tehni~ka kontrola, 91000 Skopje, Republic of Macedonia
2Institute of Chemistry, Faculty of Natural Sciences and Mathematics, The "Sv. Kiril & Metodij" University,
P.O. Box 162, 91001 Skopje, Republic of Macedonia

New method for spectrophotometric determination of thallium in the presence of large amount of cadmium is described. This method is developed on the basis of the investigation of thallium(III) complexes with iodoacetic acid and ternary amines. The complexes are soluble in water and/or in organic solvents and show an absorption peak at 365–405 nm, depending upon the amine and solvent used. For a practical application, hexamethylenetetramine and pyridine was used as an organic base. The spectra of the solutions of In(III), Ga(III), Cd(II) and Zn(II) in the presence of CH2ICOOH and tertiary amines do not have an absorption band in the spectral region above 320 nm. It may be utilized for spectrophotometric determination of thallium in presence of large amount of these elements. The molar absorption coefficient of the complex of thallium with iodoacetic acid and hexamethylenetetramine is about 4500 mol–1dm3cm–1 in isobutylmethyl ketone and isoamylacetate and 6000 mol–1dm3cm–1 in propanol-water mixture (1+2), while the complex with pyridine has a molar absorption coefficient 5800 mol–1dm3cm–1. Spectrophotometric method for determination of thallium in cadmium metal by iodoacetic acid and pyridine was developed. For content of thallium between 0.05 and 0.15 %, average standard deviation was 0.0016 % Tl, while between 0.15 and 0.40 % Tl standard deviation was 0.0022 %.

Keywords: thallium; determination in cadmium; spectrophotometry; ternary complexes; iodoacetic acid; hexamethylenetetramine; pyridine

 

R e z i m e

SPEKTROFOTOMETRISKI KARAKTERISTIKI NA TALIUM(
III) KOMPLEKSI SO JODOOCETNA KISELINA I TERCIERNI AMINI

Dragan S. Mihajlovi}1 i Traj~e Stafilov2

1A.D. Tehni~ka kontrola, 91000 Skopje, Republika Makedonija
2Institut za hemija, PMF, Univerzitet
Sv. Kiril i Metodij",
p. fah 162, 91001 Skopje, Republika Makedonija

Talium(III) formira acidokompleksi so jodoocetnata kiselina, koi davaat `olti ternerni kompleksi so tercierni amini. Kompleksite se rastvorlivi vo voda i/ili vo organski rastvoruva~i i davaat lenta so maksimum na 365‡405 nm, zavisno od upotrebeniot amin. Za prakti~na primena se koristeni heksametilenetetramin i piridin kako organski bazi. Spektrite na rastvorite na In(III), Ga(III), Cd(II) i Zn(II) vo prisustvo na CH2ICOOH i tercierni amini nemaat apsorpciona lenta vo oblasta nad 320 nm. Ova mo`e da se iskoristi za spektrofotometrisko opredeluvawe na talium vo prisustvo na golemi koli~estva od ovie elementi. Molarniot apsorpcionen koeficient na taliumot so jodoocetnata kiselina i heksametilentetramin e okolu 4500 mol–1dm3cm–1 vo izobutil keton i izoamil actetat i 6000 mol–1dm3cm–1 vo prisustvo na smesa od propanol‡voda (1+2), dodeka kompleksot so piridinot ima molaren apsorpcionen koeficient od 5800 mol–1dm3cm–1. So primena na ovie ispituvawa razvien e spektrofotometriski metod za opredeluvawe na talium vo kadmium so primena na jodoocetna kiselina i piridin. Za sodr`ina na talium od 0,05 do 0,15 % e dobiena standardna devijacija od 0,0016 %, dodeka za sodr`ina na talium od 0,15 do 0,40 % standardnata devijacija iznesuva 0,0022 %.

Klu~ni zborovi: talium; opredeluvawe vo kadmium; spektrofotometrija; ternerni kompleksi; jodoocetna kiselina; heksametilenetetramin; piridin


Glasnik na hemi~arite i tehnolozite na Makedonija, god. 17, br. 1, str. 53‡59 (1998)

GHTMDD – 307 ISSN 0350 – 0136

Pristignato: 10 april 1998 UDC: 541.131 : 543.551:

Prifateno: 5 maj 1998

Nastava ‡ Education

DIREKTNO KULOMETRISKO OPREDELUVAWE NA FARADEEVATA KONSTANTA EKSPERIMENT ZA SREDNO I VISOKO OBRAZOVANIE

DIRECT COULOMETRIC DETERMINATION OF FARADAY’S CONSTANT
A HIGH SCHOOL AND COLLEGE EXPERIMENT

Vladimir M. Petru{evski, Metodija Najdoski i Qup~o Pejov

Institut za hemija, Prirodno-matemati~ki fakultet,
Arhimedova 5, Skopje, Republika Makedonija

So primena na direkten kulometriski metod opredelena e vrednosta na Faradeevata konstanta. Izvedena e elektroliza na voda (t. e. razreden rastvor od sulfurna kiselina) vo Hofmanov aparat. Koli~estvoto na izdvoen vodorod e presmetano preku izmereniot volumen na gasot, vo ramkite na aproksimacijata za idealen gas.

Klu~ni zborovi: Faradeeva konstanta; direktna kulometrija; {kolski hemiski eksperimenti

 

The value of Faraday’s constant was determined using the direct coulometric method. Electrolysis of water (i.e. diluted solution of sulphuric acid) was carried out in Hoffmann’s apparatus. The quantity of evolved hydrogen was calculated by measuring the volume of the hydrogen gas, employing the ideal gas approximation.

Keywords: Faraday’s constant; direct coulometry; college chemical experiments


Glasnik na hemi~arite i tehnolozite na Makedonija, God. 17, br. 1, str. 61‡66 (1998)

GHTMDD – 308 ISSN 0350 – 0136

Pristignato: 10 april 1998 UDC: 542.06:

Prifateno: 5 maj 1998

Nastava ‡ Education

EKSPERIMENTI ZA FENOMENI [TO SE VO VRSKA
SO GOLEMINATA NA ^ESTI^KITE

PARTICLE SIZE PHENOMENA EXPERIMENTS

Metodija Najdoski i Vladimir M. Petru{evski

Institut za hemija, Prirodno-matemati~ki fakultet, Univerzitet "Sv. Kiril i Metodij",
Arhimedova 5, p. fah 162, MK‡91001 Skopje, Republika Makedonija

Lesno mo`e da se poka`e deka dokolku {ipka cink se potopi nekolku minuti vo rastvor od bakar (II)sulfat, taa brzo se prekriva so crna skrama (ili duri i prav, ako rastvorot e koncentriran). Vo soglasnost so elementarnite poznavawa na hemiskata reaktivnost, crnata supstanca treba da se identificira kako bakar. Zo{to, toga{, bojata e crna? Pri dobro poznatata reakcija me|u cink i hlorovodorodna kiselina ~estopati mo`e da se zabele`i formirawe na crn prav (pocrnuvawe na cinkot"). [to pretstavuva, od hemiska gledna to~ka, crnata supstanca?

Klu~ni zborovi: hemiski eksperimenti; demonstracii; fenomeni vo vrska so goleminata na ~esti~kite; rasejuvawe na svetlina

 

It can be easily shown that if a zinc rod is immersed for several minutes in CuSO4 solution it is readily covered with a black layer (or even powder, if the solution is concentrated). According to some elementary knowledge of chemical reactivity, the black substance should be identified as copper. So, why is it black? During the well-known reaction between zinc and hydrochloric acid, a formation of black powder ("zinc blacking") may be noticed very often. What is the chemical nature of that black substance?

Keywords: chemistry experiments; chemical demonstrations; particle size phenomena; light scattering


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