Abstract. Complexation of oxonium and ammonium cations with two calix4arene amino acid derivatives, namely 5,11,17,23-tetra-tert-butyl-26,28,25,27-tetrakis-(O-methyl-D-α-phenylglycylcarbonylmethoxy)-calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-26,28,25,27-(O-

No abstract

Vizualizacija kemijskih procesa iznimno je važna i korisna u edukaciji kemije. Jedan od takvih pokusa je i kemijski vrt koji nastaje dodavanjem topljive soli metala u otopinu natrijeva silikata ili nekog drugog aniona s kojim metalni ion daje koloidni gel koji stvara polupropusnu membranu. Rastom kemijskog vrta nastaju cjevčice različitih veličina i oblika koje podsjećaju na stabalca i biljke u vrtu. U članku se opisuje izrada kemijskog vrta upotrebom lako dostupnih kemikalija. Taj pokus na jednostavan način predočuje precipitaciju povezanu s osmozom i izvrsno je edukativno sredstvo.

je evaporitni mineral kemijske formule Na 3 H(CO 3 ) 2 • 2H 2 O. U prirodi se često pojavljuje u zajednici s drugim mineralima, kao što su gips, halit, natron i drugi (https://www.mindat.org/min-4031.html). U starom Egiptu trona se upotrebljavala u postupku mumifikacije.*** Zainteresiranima preporučamo publikaciju "Pretpovijesni jantar i staklo" Arheološkog muzeja u Zagrebu iz 2006. **** Vapnenački skeleti mogu biti izgrađeni od minerala aragonita, kalcita i željezovitog kalcita. Kalcit i aragonit su niskotemperaturni i visokotemperaturni polimorfi kalcijeva karbonata (CaCO 3 ). Kalcit kristalizira u heksagonskom, a aragonit u rompskom sustavu.

Strong earthquake of M6.4 stroke Petrinja and neighbouring cities of Sisak and Glina in Croatia on December 29th 2020. It was preceded by two foreshocks of M5.2 and M5.0, and followed by a series of aftershocks of various magnitudes and intensities. We have analysed first 500 earthquakes and aftershocks of > M1.0 which occurred from December 28th 2020 to January 19th 2021, their frequency, focal depths, and coseismic surface phenomena. Correlation of focal depths revealed the source of earthquakes was faulting of hanging wall of a listric normal fault with NW-SE strike and dip towards NE. Major fault seems to have caused earthquakes with only minor magnitudes. The strongest two earthquakes of M6.4 and M5.2 were initiated on synthetic fault, whereas M5.0 earthquake was initiated on an antithetic fault. Almost 50% of all seismic energy of the first 500 analysed seismic events over M1.0 was released on 1 km and 10 km deep hypocentres. Focal mechanisms of major earthquakes and strong fore- and aftershocks indicate dextral-slip mechanism, which is also in accordance with the orientation of surface cracks, land faulting and sand volcano trains. Co-seismic surface phenomena are land cracks and fissures, land faults, sand volcanoes, eruptive springing of ground water, activation of landslides, and formation of dozens of collapse sinkholes which continued to form and grow for about a month following the major earthquake.