Određivanje kalijum-jodida u kuhinjskoj soli

The samples of table salt bought in Belgrade supermarkets are analyzed in this paper. The method of indirect iodometry was used in the process of the analysis, and received results were converted into the content of KI in mg/kg of salt. Beside the content of KI, the content of NaCl was also determined, counted to dry meter and water content, and received results were compared with the requests determined by Regulations of Table Salt Quality Meant for Human Diet and by manufacturers' declaration. Received results show that the volumetric method of indirect iodometry, applied in this analysis, is very reliable for determination of potassium iodine in table salt, because of its high precision and reproducibility of the analysis results. All received results show that the samples of table salt which can be bought in supermarkets are according to the demands given by Regulations. Only one sample (evaporated salt) has significantly less mass of KI than it is determined by Regulations, but also by manufacturer's declaration. Measured humidity in the samples of table salt received from sea salt (sample 1) is higher than humidity in the samples received from rock salt as the result of magnesium presence in sea salt, which is hygroscopic material. Although samples 5 and 6 also originate from sea salt, their smaller humidity is the result of additional heating and salt processing.U radu su ispitivani uzorci kuhinjske soli koji se mogu nabaviti u beogradskim prodavnicama. U radu je primenjena metoda indirektne jodimetrije, a dobijeni rezultati su preračunavani na sadržaj KI u mg/kg soli. Osim sadržaja KI, određivan je i sadržaj NaCl, računato na suvu materiju i sadržaj vode, a dobijeni rezultati upoređeni su za zahtevima koji su predviđeni Pravilnikom o kvalitetu kuhinjske soli predviđenim za ljudsku ishranu i proizvođačkom deklaracijom. Dobijeni rezultati su pokazali da je volumetrijska metoda indirektne jodimetrije, primenjena u ovom radu, veoma pouzdana za određivanje kalijum-jodida u kuhinjskoj soli, usled velike preciznosti i reproduktivnosti rezultata ispitivanja. Svi dobijeni rezultati pokazali su da uzorci kuhinjske soli koji se mogu nabaviti u trgovini odgovaraju zahtevima Pravilnika, osim jednog uzorka (varena so) koji je sadržao znatno manju masu KI nego što je predviđeno Pravilnikom, ali i proizvođačkom deklaracijom. Izmerena vlažnost u uzorcima kuhinjske soli dobijene iz morske vode (uzorak 1.) veća je od vlažnosti u uzorcima dobijenim iz kamene soli kao posledica prisustva magnezijuma u morskoj vodi, koji je higroskopni materijal. Iako su i uzorci 5. i 6. poreklom iz morske vode, njihova mala vlažnost posledica je dodatnog zagrevanja i dorade soli

Ispitivanje kinetike sušenja krompira u laboratorijskim uslovima

Chemistry is in its nature a fundamental science, but nowadays its results are increasingly used in practice. In such a way, many syntheses of important nutrition and industrial compounds (chemical technology), or destruction of harmful substances (chemical ecology) have been developed. The analytic part of chemistry (analytical chemistry) has found a significant usage even in optimization of technological processes of food technology. One of the oldest ways of food preservation is drying (dehydration). The basis of this process of preservation is to vaporize water, to dry enough the product, in order to stop the activity of enzymes and possibility of microorganisms’ development. Water in agricultural products is not free but bound to dry matter. Therefore, for its vaporizing it is necessary to bring enough heat. The part of the brought heat is used for vaporizing water, but one part of it becomes the energy for activation of several chemical reactions that decrease the nutritive values and the quality of future food. Therefore, the important engineering problem emerges: determination of optimal conditions for drying. For optimization of technological process of drying, it is necessary to do mathematical modeling of dependence of water vaporizing speed from environmental conditions beforehand. The aim of this paper is to determine potato pieces drying kinetics in laboratory dryer, in order to determine the optimal conditions for its industrial dehydration. It was established that in the first quarter of the time of drying evaporated 28.3% of total evaporation of water, and then in order by quarters: 53%, 14.1% and 4.6%, respectively. The greatest speed of drying was realized at moisture of potatoes about 50%.Hemija jeste, po svojoj prirodi, fundamentalna nauka, ali su danas njena saznanja sve više primenjena u praksi. Tako su razvijene mnoge sinteze važnih prehrambenih i industrijskih jedinjenja (hemijska tehnologija), ili razgradnja štetnih supstanci (hemijska ekologija). Analitički deo hemije (analitička hemija) našla je značajnu primenu čak i u optimizaciji tehnoloških postupaka tehnologije hrane. Jedan od najstarijih načina konzervisanja namirnica je sušenje (dehidracija). Osnova ovog postupka konzervisanja je da se voda ispari, da se proizvod dovoljno isuši, kako bi se sprečila aktivnost enzima i mogućnost razvoja mikroorganizama. Voda u poljoprivrednim proizvodima nije slobodna već je vezana za suvu materiju. Zato je za njeno isparavanje potrebno dovesti dovoljno toplote. Deo dovedene toplote se koristi za isparavanje vode, ali jedan njen deo postaje energija aktivacije za niz hemijskih reakcija koje umanjuju nutritivnu vrednost i kvalitet buduće hrane. Stoga se postavlja važan inženjerski problem: odrediti optimalne uslove sušenja. Za optimizaciju tehnološkog postupka sušenja neophodno je prethodno izvršiti matematičko modeliranje zavisnosti brzine isparavanja vode od uslova sredine. Cilj ovog rada je da utvrdi kinetiku sušenja komada krompira u laboratorijskoj sušari, kako bi se zatim utvrdili optimalni uslovi za njegovu industrijsku dehidraciju. Utvrđeno je da u prvoj četvrtini vremena sušenja ispari 28,3% ukupno isparene vode, a zatim redom po četvrtinama: 53%, 14,1% i 4,6%. Najveća brzina sušenja ostvarena je pri vlažnosti krompira od oko 50%

Određivanje brzine korozije u konzervama napunjenim graškom i boranijom za vreme skladištenja

This paper presents the results of examination of the corrosion behaviour of electrolytic tinplate in model solutions of salts in liquid contents (fills) of peas and string beans tins. The tins have been stored at the temperature of 25°C during the period of 18 months. The obtained results show that the corrosion currents and consequently corrosion rates, too, have higher values in the liquid contents (fills) of the tins than in the pure model solutions. Corrosion currents decrease noticeably in nitrogen atmosphere which speaks in favour of packaging of foodstuff in inert atmosphere. .U radu su dati rezultati ispitivanja korozionog ponašanja elektrolitičkog belog lima u model rastvorima soli i tečnom sadržaju (nalivu) konzervi graška i boranije. Na osnovu urađenih ispitivanja promene parametara tokom skladištenja a u model rastvorima i tečnim sadržajima (nalivima) konzervi graška i boranije, može se zaključiti da na proces korozije imaju uticaj komponente koje se nalaze u namirnicama koje su konzervirane, a isto tako i dodaci koji se dodaju u toku procesa proizvodnje. Takođe, ovi procesi su u konzervama vise izraženi za vreme skladištenja nego na početku određivanja. Struje korozije, a samim tim i brzine korozije belog lima, imaju vise vrednosti u nalivima konzervi od onih koje su određene u čistim model rastvorima. Korozivnost opada u sledećem nizu: naliv boranije - naliv graška - rastvor NaCl - rastvor NaCl i NaNO3. Struje korozije se osetno smanjuju u atmosferi azota, što govori u pri-log upotrebe pakovanja namirnice u inertnoj atmosferi. Dobijene - izračunate vrednosti brzine korozije pokazuju da je tokom skladištenja - stajanja 18 meseci brzina korozije nelakiranih konzervi reda veličine 102 i 103 mm/god, što je značajno manje od dopuštene (MDK) vrednosti od 0,12 mm/god, za lakirane konzerve. Na taj način, predpostavlja se da konzerve proizvedene od belog lima iz domaćih fabrika mogu biti bezbedne za čuvanje namirnica tokom višegodišnjeg vremenskog perioda.

Primena metode atomske apsorpcione spektrofotometrije (AAS) za određivanje sadržaja teških metala u prehrambenim proizvodima kojima su napunjene konzerve od lakiranog belog lima

Due to possibility of contamination of food products caused by a rapid pollution of environment, as a consequence of incidents and accidents, it is necessary to exert a regular and systematic control of the content of heavy metals in tins filled with food products for the purpose of disease prevention and protection of public health. Foodstuffs, which can be of heterogeneous chemical composition contain or a considerable quantity of water, organic acids, sodium-chloride, nitrates, anthocynes, etc. are added which are the potential co rodents of metals in contact with the contents of tins. The contamination of food products in tins can also occur because of a breakthrough of a protective tin lacquer, or a poor quality of a packaging material. The consequence of the corrosion of tins is the increase of concentration of metals, especially heavy metals, the deterioration of organoleptic characteristics of foodstuff and even the perforation of tins. The atomic absorbing spectropholometer is widely used in practice for determining the content of heavy metals because of its high sensitivity (10'6 g and less), accuracy (about 1%), selectivity and the possibility of application in defining the contents of more than 20 elements. The analyzed tins were filled with pasteurized sour cherry, pasteurized apricot mash, pasteurized plum halves and sterilized peas. The aim of this research was to define the content of heavy metals in food kept in lacquered tinplate tins. Furthermore, its aim was also to determine whether the content of heavy metals in foods, upon having been tinned for several months, changes and reaches the legal level and suchlike tins can be used in human nutrition.Usled mogućnosti kontaminacije prehrambenih proizvoda zbog rapidnog zagađenja životne sredine, kao posledica incidenata i akcidenata, neophodno je vršiti redovnu i sistematsku kontrolu sadržaja teških metala u konzervama napunjenim prehrambenim proizvodima, u cilju prevencije i zaštite zdravlja stanovništva. Namirnice, koje mogu biti heterogenog hemijskog sastava sadrže, ili im se dodaje znatna količina vode, organskih kiselina, kuhinjske soli, nitrata, antocijana i dr., koji su potencijalni uzročnici korozije metala u kontaktu sa sadržajem konzervi. Do kontaminacije prehrambenih proizvoda u konzervama može doći usled proboja zaštitnog laka konzerve ili lošeg kvaliteta ambalažnog materijala. Kao posledica korozije konzervi, dolazi do povećanja koncentracije metala, naročito teških metala, do pogoršanja organoleptičkih svojstava namirnice, pa i perforacije konzervi. Za određivanje sadržaja teških metala veliku primenu u praksi ima atomski apsorpcioni spektrofotometar, zbog visoke osetljivosti (10-6 g i manje), preciznosti (oko 1%), selektivnosti i mogućnosti primene za određivanje sadržaja preko 20 elemenata. Ispitivane konzerve punjene su pasterizovanom višnjom, pasterizovanom kašom kajsije, pasterizovanom polutkom šljive i sterilisanim graškom. Cilj ovoga rada bio je utvrđivanje sadržaja teških metala u prehrambenim proizvodima koji su se nalazili u konzervama od lakiranog belog lima. Takođe, cilj rada bio je da se utvrdi da li se sadržaj teških metala u prehrambenim proizvodima, nakon višemesečnog stajanja u konzervama, menja i dostiže zakonom dozvoljeni nivo i da li se takve konzerve mogu koristiti u ljudskoj ishrani

Kompleksometrijska određivanja - deo 2 - kompleksometrijsko određivanje Cu2+-jona

A copper-selective electrode of the coated wire type based on sulphidized copper wire was applied successfully for determining Cu(II) ions by complexometric titration with the disodium salt of EDTA (complexon III). By the formation of internal complex compounds with the Cu(II) ion, the copper concentration in the solution decreases, and all this is followed by a change of potential of the indicator system Cu-DWISE (or Cu-EDWISE)/SCE. At the terminal point of titration, when all the Cu(II) ions are already utilized for the formation of the complex with EDTA, there occurs a steep rise of potential, thus enabling us, through the first or second derivative to note the quantity of copper that is present in the solution. Copper-selective electrode showed a responsivity towards titration with EDTA as a complexing agent, with the absence of "fatigue" due to a great number of repeated measurings. Errors occurring during quantitative measurements were more a characteristic of the overall procedure which involve, because of the impossibility of the complete absence of subjectivity, a constant error, and the reproducibility of the results confirmed this fact. The disodium salt of EDTA appeared as a very efficient titrant in all titrations and with various concentrations ot Cu(II) ions in the solution, with somewhat weaker response at lower concentrations in the solution.U prvom delu rada prikazane su karakteristike dinatrijumove soli EDTA (kompleksona III), kao i mogućnost njene primene u kompleksometrijskim titracija-ma za kvantitativno određivanje različitih vrsta katjona, naročito Cu2+-jona. U drugom delu rada data je primena kompleksona III za određivanje bakra u vodenim rastvorima. Za određivanje završne tačke titracije korišćen je originalni tip jon-selektivne elektrode. Dokazana je primenljivost kompleksona III, teorijski objašnjena u prvom delu rada, za titrimetrijsko (kompleksometrijsko-potenciometrijsko) određivanje Cu2+- jona uz korišćenje indikatorskog sistema bakar-selektivna elektroda tipa prekrivena žica (modela DWISE i EDWISE)/ZKE, uz izraziti skok u završnoj tački titracije i dobru reproduktivnost rezultata određivanja

Ispitivanje površinskih karakteristika fosfogipsa primenom skenirajuće elektronske mikroskopije (SEM)

This paper presents the results of application of Scanning Electron Microscopy (SEM) to examinations of the samples of natural gypsum and phosphogypsum. Phosphogypsum has a well developed crystalline structure, and appear in two polymorphous forms, of rombic and hexagonal shape crystals. Natural gypsum has a poorly crystalline structure. The differences in crystalline structure influence the chemical behavior of these row materials.Elementarni sastav materije, bilo da je nepoznat ili da je potrebno proveriti sastav novog ili poznatog materijala koji će se koristiti u daljem radu, predstavlja čest zahtev u savremenoj analitičkoj praksi. Nekada se ovim zahtevima pridružuje i potreba da se utvrdi morfologija ili struktura površinske hrapavosti uzorka, njegova homogenost ili prisustvo defekata u strukturi. Elektronske mikroskopske i spektroskopske tehnike čiji je nagli razvoj, sve do komercijalnih sistema, od sedamdesetih godina do sada, omogućen pre svega dostignućima u elektronskim i kompjuterskim tehnologijama, postale su snažno oruđe za ostvarivanje pomenutih zahteva. U radu su prikazani rezultati primene skenirajuće elektronske mikroskopije (SEM) na ispitivanja površine uzoraka prirodnog gipsa i fosfogipsa, radi karakterizacije sastava i definisanja morfološkog sastava. SEM snimci prirodnog gipsa i otpadnog fosfogipsa ukazali su da ova dva gipsa, iako imaju iste hemijske (molekulske) formule – CaSO42H2O, imaju različitu strukturu: prirodni gips ima slabije izraženu kristalnu strukturu a otpadni fosfogips ima izrazitu kristalnu strukturu, pretežno rombičnog i heksagonalnog oblika, što ukazuje na njegov složeniji sastav od prirodnog a što je u skladu sa literaturnim podacima

Osiromašeni uranijum I - uranijum, radioaktivnost i zakonska regulativa

Depleted uranium is a highly toxic and low radioactive waste; an off-product of the uranium enrichment process and represents dangerous radioactive waste for man and the environment. Up to the 1970-ies was stored, but from the beginning of the seventies it has been used for missile hard core production which seems to be very efficient for armor brakes (penetration). But except for its immediate efficiency, for which there is no dought, depleted uranium remains at the location in the form of tiny particles and smog as an "invisible threat", being almost permanently dangerous for people and environment (4,5-109 years). That is the reason of the great publicity, which in the last decade, from the Gulf War (1991) when munition with depleted uranium was massively used for the first time, which grew into a real campaign against this munition which is unselective, inhumane and causes consequences for both the conquered and conquerors. In the name of humanity, the environment and finally the protection of life on Earth, the campaign has lead to a proposal to ban its usage. On the other - hand, from the military viewpoint, these are - ideal weapons. As the ideal - does not exist, in a series of papers we shall try to present the cycle of depleted uranium movement, from the separation of unusable material (which implies expensive for storage, but cheal almost free of cost, for giving to possible users) in the process of nuclear fuel enrichment to use for munitions production. The last stage is not complete consequences of the use of munitions with depleted uranium, because they are unpredictable, unselective and eternal. In the first part of the serial the fundamental terms connected with the process of radiation to which people are permanently exposed are given and also legal regulations for health protection. Also, a review of all the terms connected with radiation are given, as well as the scale of degrees of human exposure to radiation. A review of the properties of uranium, as the last element of the periodical system of elements which can be found in nature, its origin and migration in the environment are also given, and the data for natural and depleted uranium compared. Finally, the origin and structure of nuclear fuel is given with strict emphasis of the fact that it is waste material.Osiromašeni uranijum je toksičan, nus proizvod procesa obogaćivanja uranijuma i predstavlja vrlo opasan radioaktivni otpad. Sve do sedamdesetih godina XX veka bio je skladišten, da bi početkom sedamdesetih počeo da se koristi za izradu tvrdog jezgra (penetratora) projektila. Međutim, osim trenutne efikasnosti koja nije sporna, osiromašeni uranijum, u vidu veoma sitnih čestica i aerosola predstavlja opasnost po ljude i životnu sredinu gotovo večito (4,5 , 10g godina). To je i razlog velikog publiciteta koji je poslednje decenije XX veka, od Zalivskog rata 1991. god. kada su projektili sa osiromašenim uranijumom prvi put masovno upotrebljeni, prerastao u pravu kampanju protiv ove municije koja je neselektivna, nehumana i izaziva posledice i kod pobednika i kod pobeđenih. U ime zaštite ljudi, životne sredine i života na Zemlji uopšte, vodi se kampanja za potpunu zabranu korišćenja osiromašenog uranijuma, koji je, sa druge strane, po vojnim kriterijuma - idealan. U nekoliko radova prikazaće se ciklus kretanja osiromašenog uranijuma, od odvajanja kao beskorisnog materijala pri procesu obogaćivanja nuklearnog goriva do primene za izradu municije. Poslednja etapa - posledice primene municije punjene sa osiromašenim uranijumom jesu i biće predmet mnogih izučavanja i analiza u budućnosti. U ovom radu dati su osnovni pojmovi vezani za proces zračenja kojem je čovek neprekidno izložen, kao i zakonska regulativa koja se odnosi na zaštitu čoveka od zračenja. Takođe, dat je prikaz svih pojmova koji se odnose na zračenje, kao i normativi stepena izloženosti čoveka zračenju. Analiziraju se, između ostalog, svojstva uranijuma kao poslednjeg elementa u periodnom sistemu elemenata koji se nalazi u prirodi, njegovo poreklo i migracija u životnoj sredini, pri čemu su upoređeni podaci vezani za prirodni i osiromašeni uranijum. Na kraju, daje se nastanak i sastav osiromašenog uranijuma koji nastaje pri procesu kruženja u nuklearnom gorivnom ciklusu, gde se decidirano podvlači da je to otpadni materijal

Osiromašeni uranijum, III - komercijalna primena osiromašenog uranijuma - proizvođači municije i oružja od osiromašenog uranijuma

Depleted uranium is a highly toxic and low radioactive waste produced during the uranium enrichment process. Up to the seventies of the XX century it was stored and has also been used for making missile hard cores, which is very efficient for armor penetration. However, except for its immediate efficiency, for which there is no doubt, depleted uranium contaminates the location in the form of tiny particles and smog as an "invisible threat", dangerous for peo­ple and the environment almost forever (4.5 , 109 years). That is the reason for the great publicity, which in the last decade, from the Gulf War (1991) on wards, when munitions with depleted uranium were mas­sively applied for the first time, escalated in to a real campaign against its use as an unselective, inhuman and dangerous material which causes con­sequences for both the conquered and conquerors. In the name of humanity, the environment and the quality of life on Earth, a campaign has been led with the goal of banning its usage. The cycle of depleted uranium movement, from the separation of unusable material in the process of nuclear fuel enrichment to its use for munitions pro­duction has been presented. In a series of three papers published in Chemi­cal Industry (No 4, 5 and 10, 2001). This paper, as the third part of the series, gives information about the produ­cers of ammunition with depleted uranium of all sizes (caliber) and all the fi­elds and test areas where such kinds of munitions have been tested in the past.U trećem delu serije posvećene problematici osiromašenog uranijuma navode se proizvođači municije koja u svom sastavu sadrži i osiromašeni uranijum. Analiziraju se tipovi municije, najčešće primenjeni kalibri municije kao i poligoni na kojima je municija testirana

Određivanje sadržaja fluorida u vodi za piće i čajevima fluorid-selektivnom elektrodom

Potentiometric analysis of fluoride content (as F- ion) in solutions by using fluoride ion-selective electrode is simple, reliable and cheap. Very small concentrations of fluoride-ions (to 10-6 mol/dm3) can be determined by fluoride selective electrode, with regulation of ion strength of a solution and control of concentration of hydroxide ions and interfering ions of metals. The influence of pH and complexing ions of metals can be successfully regulated by the TISAB solution and by preserving pH value in the range from 5.00 to 7.00. The content of fluorides in the samples can be determined by the method of direct potentiometer, and in the case of very low concentration by standard addition method. In this paper it was analyzed the determination of fluoride ions concentration in bottled mineral waters and water from Belgrade plumbing in two Belgrade districts (Palilula and Novi Beograd) and in tea, by using the fluoride selective electrode. It was determined that the content of fluoride ions in bottled mineral water significantly differs from values given on declaration, and that content of fluoride ions varies over a period of time. The content of fluoride ions in water from plumbing in two Belgrade districts at the time of analysis was significantly increased and exceeded values given in Regulation for drinking water quality. The received results from the analysis of fluorides in teas show that fluorides exist in teas in different concentrations. There are also differences between the same kinds of tea, which is noted with mint (Mentha piperitae folium), as a consequence of differences between soils where it was planted. As taking of fluorides, according to World Health Organisation recommendation (WHO), is limited in the range from 2 to 4 mg per day, it is necessary to give the content of fluorides on all products that are used in human consumption.Potenciometrijsko određivanje sadržaja fluorida (kao F-jon) u rastvorima upotrebom fluoridne jon-selektivne elektrode je jednostavno, pouzdano i jeftino. Fluorid-selektivnom elektrodom mogu se odrediti veoma niske koncentracije fluorid-jona (do 10-6 mol/dm3), uz regulisanje jonske jačine rastvora i kontrolisanje koncentracije hidroksid-jona i interferirajućih jona metala. Uticaj pH i kompleksirajućih jona metala može se uspešno regulisati rastvorom TISABa i održavanjem pH vrednosti u oblasti od 5,00 do 7,00. Sadržaj fluorida u uzorcima može se odrediti metodom direktne potenciometrije, a u slučaju veoma niskih koncentracije, metodom standardnog dodatka. U radu je vršeno određivanje koncentracije F--jona u flaširanim mineralnim vodama ('Vujić voda', 'Rosa', 'Duboka', 'Voda-voda', 'Aqua viva', 'Knjaz Miloš') i vodi iz beogradskog vodovoda sa dve beogradske opštine (Palilula i Novi Beograd) i u čajevima (Divlja nana (Mentha piperitae folium), Čaj od žalfije (Salviae officinalis), Čaj od kantariona (Hypericum perforatum), 'Domaća nana' (Mentha piperita L.), Čaj od kamilice (Chamomillae flos)), upotrebom fluorid-selektivne elektrode. Uočeno je da sadržaj fluorid-jona u flaširanim mineralnim vodama znatno odstupa od vrednosti koje su date na deklaraciji, ali i da sadržaj fluorid-jona varira tokom vremena. Sadržaj fluorid-jona u vodi iz vodovoda sa dve beogradske opštine, u vreme analiziranja je znatno povećan i premašuje vrednosti propisane Pravilnikom o kvalitetu vode za piće. Dobijeni rezultati ispitivanja fluorida u čajevima ukazuju da se fluoridi nalaze u čajevima u različitim koncentracijama. Do razlike dolazi i među istim vrstama čaja, što je zabeleženo kod nane (Mentha piperitae folium), što je posledica pre svega zemljišta na kojem je nana uzgajana. Kako je, saglasno preporukama Svetske zdravstvene organizacije (SZO), unošenje fluorida limitirano u opsegu 2 do 4 mg dnevno, na svim proizvodima koji se koriste u humanoj upotrebi potrebno je navesti i sadržaj fluorida