THE FACTS ON FILE DICTIONARY OF INORGANIC CHEMISTRY

By SARAH BROWN

CONTENTS ENTRIES A TO Z THE VOLUME OF THE GAS THEORETICALLY BE- COMES ZERO IN PRACTICE, OF COURSE, SUB- STANCES BECOME SOLIDS AT THESE TEMPERATURES NEVERTHELESS, THE EXTRAPOLA- TION CAN BE USED TO CREATE A SCALE OF TEM- PERATURE ON WHICH –273 15 DEGREES CELSIUS (°C) CORRESPONDS TO ZERO (0°) THIS SCALE WAS ALSO KNOWN AS THE IDEAL-GAS SCALE; ON IT TEMPERATURE INTERVAL UNITS WERE CALLED DE- GREES ABSOLUTE (°A) OR DEGREES KELVIN (°K), AND WERE EQUAL IN SIZE TO THE CELSIUS DE- GREE IT CAN BE SHOWN THAT THE ABSOLUTE TEM- PERATURE SCALE IS IDENTICAL TO THE THERMODYNAMIC TEMPERATURE SCALE, ON WHICH THE TEMPERATURE INTERVAL UNIT IS THE KELVIN ABSOLUTE ZERO THE ZERO VALUE OF THER- MODYNAMIC TEMPERATURE; 0 KELVIN OR –273 15 DEGREES CELSIUS ABSORPTION A PROCESS IN WHICH A GAS IS TAKEN UP BY A LIQUID OR SOLID, OR IN WHICH A LIQUID IS TAKEN UP BY A SOLID IN ABSORPTION, THE SUBSTANCE ABSORBED GOES INTO THE BULK OF THE ABSORPING MATERIAL SOLIDS THAT AB- SORB GASES OR LIQUIDS OFTEN HAVE A POROUS STRUCTURE THE ABSORPTION OF GASES IN SOLIDS IS SOMETIMES CALLED SORPTION COMPARE AD- SORPTION ABSORPTION INDICATOR (ADSORPTION INDICA- TOR) AN INDICATOR USED FOR TITRATIONS THAT INVOLVE A PRECIPITATION REACTION THE METHOD DEPENDS UPON THE FACT THAT AT THE EQUIVALENCE POINT THERE IS A CHANGE IN THE NATURE OF THE IONS ABSORBED BY THE PRECIPI- TATE PARTICLES FLUORESCEIN – A FLUORESCENT COMPOUND – IS COMMONLY USED FOR EXAM- PLE, IN THE TITRATION OF SODIUM CHLORIDE SO- LUTION WITH ADDED SILVER NITRATE, SILVER CHLORIDE IS PRECIPITATED SODIUM IONS AND CHLORIDE IONS ARE ABSORBED IN THE PRECIPI- TATE AT THE END POINT, SILVER IONS AND NI- TRATE IONS ARE IN SLIGHT EXCESS AND SILVER IONS ARE THEN ABSORBED IF FLUORESCEIN IS PRESENT, NEGATIVE FLUORESCEIN IONS ABSORB IN PREFER- ENCE TO NITRATE IONS, PRODUCING A PINK COM- PLEX ABSORPTION SPECTRUM SEE SPECTRUM ABUNDANCE 1 THE RELATIVE AMOUNT OF A GIVEN ELEMENT AMONG OTHERS; FOR EXAMPLE, THE ABUNDANCE OF OXYGEN IN THE EARTH’S CRUST IS APPROXIMATELY 50% BY MASS 2 THE AMOUNT OF A NUCLIDE (STABLE OR RADIOACTIVE) RELATIVE TO OTHER NUCLIDES OF THE SAME ELEMENT IN A GIVEN SAMPLE THE NATURAL ABUNDANCE IS THE ABUNDANCE OF A NUCLIDE AS IT OCCURS IN NATURE FOR INSTANCE, CHLORINE HAS TWO STABLE ISOTOPES OF MASSES 35 AND 37 THE ABUNDANCE OF 35CL IS 75 5% AND THAT OF 37CL IS 24 5% FOR SOME ELEMENTS THE ABUNDANCE OF A PARTICULAR NU- CLIDE DEPENDS ON THE SOURCE ACAC ABBREVIATION FOR THE BIDENTATE A ACCELERATOR