Chemistry in Education: How to Make Citric Acid and Sugar Crystals

Učenici osnovnih škola gotovo redovito izvode pokus krstalizacije modre galice i kuhinjske soli. Modra galica je otrovna i štetna za okoliš, a veće kristale kuhinjske soli teško je dobiti. Umjesto pokusa kristalizacije modre galice i kuhinjske soli bolje je izvesti pokus kristalizacije limunske kiseline i običnoga šećera. Te su tvari jeftine, lako dostupne, biorazgradljive i nisu štetne za okoliš. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Middle school students almost regularly perform experiments of crystallization of copper(II) sulphate pentahydrate and kitchen salt. Copper(II) sulphate pentahydrate is poisonous and harmful to the environment, and larger crystals of kitchen salt are difficult to obtain. Instead of experimenting with the crystallization of copper(II) sulphate pentahydrate and kitchen salt, it is better to carry out crystallization of citric acid and common (table) sugar. These materials are inexpensive, easily accessible, biodegradable, and not environmentally hazardous. This work is licensed under a Creative Commons Attribution 4.0 International License

How to Acquire an Idea of the Size of Atoms and Ions

U kemiji i nastavi kemije rabe se veličine pikometar i Avogadrov broj. Nastavnici lakoćom izgovore ili napišu, a učenici napamet nauče i reproduciraju te veličine, bez predodžbe o tomu koliko je 10–12 ili 1023. U ovom je radu pokazano kako vlastitom aktivnošću, u ovom slučaju rješavanjem jednostavnih problemskih zadataka iz područja strukturne kemije, učenici mogu samostalno doći do spoznaja o veličini atoma i usporediti ih s veličinama poznatih makro objekata. Time bi se spriječilo učenje napamet o veličinama čestica fundamentalno važnih u području nastave prirodnih znanosti. U ovo digitalno doba uz “nastavu na daljinu” i digitalizirane udžbenike suvremena škola ne treba tiskane udžbenike i “razrede”, već laboratorije i radionice te sportske dvorane i sportske terene gdje će učenici znanja, vještine i sposobnosti stjecati vlastitom aktivnošću. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Chemistry teaching uses quantities such as the picometer and Avogadro number. Teachers easily pronounce or write, and students learn to reproduce these quantities by heart, without any idea of how much numbers like 10–12 or 1023 actually are. This paper shows how students can, by solving simple problems, learn independently about the size of atoms and the meaning of Avogadro’s number. In the present digital age, “distance learning” and digitised textbooks, modern school does not need standard “classes” but laboratories, workshops, sports halls, and sports fields, where students could acquire knowledge, skills, and abilities by exerting their activities. This work is licensed under a Creative Commons Attribution 4.0 International License

The Endless Chain [AcOHg]nn+ Cation. Crystal Structure of Acetatomercury(II) Nitrate - Mercury(II) Acetate (1/1)

Acetatomercury(II) nitrate-mercury(II) acetate (llI), (AcOHg) N03 • Hg(AOch, not described so far in the chemical literature,\u27 was obtained by the reaction of mercury(II) nit rate hydrate with acetic anhydride. Orthorhombic-disphenoidal crystals, as shown by threedimensional X-ray diffraction analysis, are built of polymeric [AcOHg]nn+cations, nitrate anions and mercury(II)-acetate molecules. The mercury ions in the cation are bridged over by the acetate ion through both oxygen atom s separately at the Hg-O distances of 213(3) and 212(2) pm under the O-Hg-O arigle of 167(1)°. The mercury(II)-acetate molecule is in syn. conformation with the Hg-O distances of 204(3) and 209(3) pm and the O-Hg-O angle of 173(1)°. Crystal structure, determined from 1330 intensity data, was refined by full-rnatrix least-squares method to R = 0.076 and Rw = 0.090

Mercuration of Some Aliphatic Aldehydes. The Crystal Structure of 2,2-Bis(chloromercuri)butyraldehyde

Tris ( chloromercuri)acetaldehyde (1), 2,2-bis( chloromercuri)propionaldehyde (II) and 2,2-bis(chloromercuri)butyraldehyde (III) were obtained by mercuration of the corresponding aldehyde in an aqueous mercury(II) chloride solution containing sodium acetate. The mercurated aldehydes (II) and (III) are described for the first time. The crystal structure of (III) was determined by means of Patterson and Fourier syntheses based on threedimensional X-ray diffractometer intensity data and refined by the full-matrix least- squares method to an R value of 0.049. Crystals are orthorhombic, space group Pna21 with z = 4 formula units in the unit cell of the dimensions : a= 1114.6(6), b = 1121.3(5), c = 657.3(3) pm, Dots= 4.51and Deale = 4.38 Mg m-3• The structure consists of discrete moleculesof 2,2-bis(chloromercuri)butyraldehyde. The Hg-C bond lengthsare 216(2) and 209(2) pm. The Hg-C-Hg bond angle is 103(1) 0 and the C-Hg-Cl bond angles are 173(2)0 and 172(2)0 , respectively

Binding of Mercury(II) by N-(2-mercaptopropionyl)glycine. Synthesis, IR and NMR Characterization. Crystal Structure of the 1:2 Solvate of Bis[N-(propionyl-2-thiolato)-glycine]mercury(II) with 4-Methylpyridine

Bis[N-(propionyl-2-thiolato)glycine]mercury(II), Hg[SCH(CH3)CO-NHCH2COOH]2, was obtained by the reaction of an aqueous solution of N-(2-mercaptopropionyl)glycine and mercury(II) acetate. From the 4-methylpyridine (γ-picoline) solution it crystallizes as a 1:2 solvate, Hg[SCH(CH3)CONHCH2COOH]2 ⋅ 2C6H7N, in the triclinic system, space group P1̅ with a = 4.810(5) Å, b = 9.711(4) Å, c = 15.615(8) Å, α = 105.76(4)°, β = 103.44(4)°, γ= 94.01(4)°, Z = 1, R = 0.027. Two N-(propionyl-2-thiolato)glycine molecules are bonded centrosymmetrically to mercury over sulfur atoms as mercaptide at a distance of 2.341(2) Å. Hg(mpgH)2 molecules are connected by centrosymmetrically related hydrogen bonds N1−H⋅⋅⋅O3 of 2.922(5) Å into chains along [100]. Each molecule also forms two hydrogen bonds O1−H⋅⋅⋅N2 of 2.612(6) Å with two γ-picoline molecules. The structure of complexes and binding to sulfur were substantiated by 1H and 13C NMR spectroscopy on the basis of mercury induced Chemical shifts, H−H and C−H coupling constants and connectivities in twodimensional homo- and heteronuclear correlated spectra

Tireotoksična kriza u 75-godišnje bolesnice

A 75-year-old female patient was admitted to the Intensive Care Unit with the signs of thyrotoxic crisis. Although hyperthyroidism had been previously suspected, thyrosuppressive therapy was not initiated on time. This along with other adverse factors like acute urinary infection contributed to deterioration and unfavorable development of the disease. Clinical improvement was noticed 24 hours from the introduction of combined therapy with propylthiouracil, propranolol, hydrocortisone and cardiotonics for rapid atrial fibrillation caused by atherosclerotic and thyrotoxic heart, supplemented with sedatives and necessary medical care. Shortly upon normalization of the thyroid hormone levels, RJ therapy was administered as a final solution. Pancytopenia verified before the initiation of thyrostatic therapy also contributed to this solution. The intention of this case report is to point to the yet possible occurrence of thyrotoxic crisis, which is nowadays extremely rare owing to appropriate management of hyperthyroidism. Nevertheless, may the disease failed to be recognized on time and therapy is introduced too late, along with other unfavorable factors such as acute infection, the disease can still occur sporadically. Although the mortality rate has been drastically lowered, it is still rather high, i.e. about 7%, therefore these patients should be treated at intensive care unit.Žena u dobi od 75 godina primljena je u Jedinicu za intenzivno liječenje pod slikom tireotoksične krize. Iako se je već ranije sumnjalo na hipertireozu, tireosupresivna terapija nije započeta na vrijeme, što je uz negativne pridružene čimbenike (akutna mokraćna infekcija) doprinijelo nepovoljnom razvoju bolesti. Kombinirana terapija propiltiouracilom, propranololom, hidrokortizonom te kardiotonicima zbog brze atrijske fibrilacije u sklopu aterosklerotskog i tireotoksičnog srca, uza sedative i ostale potporne mjere dovela je do kliničkog poboljšanja već nakon 24 h. Ubrzo nakon normalizacije hormona štitnjače primijenjena je RJ terapija kao definitivno rješenje, čemu je doprinijela i pancitopenija dokazana jo. prije započete terapije tireostaticima. Ovim prikazom želi se ukazati na jo. uvijek moguću pojavu tireotoksične krize koja je danas zahvaljujući primjerenom liječenju hipertireoze izrazito rijetka, no uz neprepoznavanje bolesti i zakašnjelu terapiju te nepovoljne druge čimbenike (npr. akutni infekt) jo. se uvijek može sporadično susresti. Iako je smrtnost drastično smanjena, ipak je jo. uvijek dosta visoka i iznosi oko 7%, zbog čega i takvi bolesnici zahtijevaju smještaj u jedinice za intenzivno liječenje