CHEMISTRY GLOSSARY

praseodymium    →   praseodimij

Praseodymium was discovered by Carl F. Auer von Welsbach (Austria) in 1885. The origin of the name comes from the Greek words prasios didymos meaning green twin. It is silvery white, moderately soft, malleable, ductile metal. Reacts slowly with oxygen. Reacts rapidly with water. Metal ignites and burns readily. Praseodymium is obtained from same salts as neodymium. Used with neodymium to make lenses for glass maker’s goggles since it filters out the yellow light present in glass blowing. Alloyed with magnesium creates a high-strength metal used in aircraft engines. Misch metal, used in the manufacture of pyrophoric alloys for cigarette lighters, contains about 5 % praseodymium metal. (Typically composition of misch metal are Ce:Nd:Pr:La:Other rare earth=50:18:6:22:4).

practical salinity    →   praktični salinitet

Practical salinity S_P is defined on the Practical Salinity Scale of 1978 (PSS-78) in terms of the conductivity ratio K₁₅ which is the electrical conductivity of the sample at temperature t₆₈ = 15 °C and pressure equal to one standard atmosphere, divided by the conductivity of a standard potassium chloride (KCl) solution at the same temperature and pressure. The mass fraction of KCl in the standard solution is 0.0324356 (32.4356 g of KCl in 1 kg of solution). When K₁₅ = 1, the Practical Salinity P S is by definition 35. The conductivity of that reference solution is C(35,1568,0) = 42.914 mS/cm = 4.2914 S/m (Siemens per meter). Note that Practical Salinity is a unit-less quantity. Though sometimes convenient, it is technically incorrect to quote Practical Salinity in "psu". When K₁₅ is not unity, S_P and K₁₅ are related by the PSS-78 equation

At a temperature of t₆₈ = 15 °C, R_t is simply K₁₅ and Practical Salinity S_P can be determined from the above equation. For temperatures other than t₆₈ = 15 °C, Practical Salinity S_P is given by the following function of R_t (k = 0.0162)

radium    →   radij

Radium was discovered by Marie and Pierre Curie (France) in 1898. The origin of the name comes from the Latin word radius meaning ray. It is silvery-white radioactive metal. Reacts with oxygen and water. Highly radiotoxic. Carcinogen by inhalation, ingestion, or exposure. Radium is found in uranium ores at 1 part per 3 million parts uranium. Used in treating cancer because of the gamma rays it gives off.

redox potential    →   redoks potencijal

Redox potential is the potential of a reversible oxidation-reduction electrode measured with respect to a reference electrode, corrected to the hydrogen electrode, in a given electrolyte.

salinity    →   salinitet

Salinity (S) is a measure of the quantity of dissolved salts in seawater. It is formally defined as the total amount of dissolved solids in seawater in parts per thousand (‰) by weight when all the carbonate has been converted to oxide, the bromide and iodide to chloride, and all organic matter is completely oxidized.

Chlorinity is the oldest of the salinity measures considered and is still a corner-stone in the study of dissolved material in seawater. Based on the principle of constant relative proportions it provides a measure of the total amount of dissolved material in seawater in terms of the concentration of halides. The relationship between chlorinity (Cl) and salinity as set forth in Knudsen’s tables is

In 1962, however, a better expression for the relationship between total dissolved salts and chlorinity was found to be

Practical Salinity (S_P) was introduced as a replacement for Chlorinity. Practical Salinity is is relatively easy to measure using standard conductometers, measurements are more precise and less time consuming than measurements of Chlorinity and accurate measurements can even be made in situ. Practical salinity S_P is defined on the Practical Salinity Scale of 1978 (PSS-78) in terms of the conductivity ratio K₁₅ which is the electrical conductivity of the sample at temperature t₆₈ = 15 °C and pressure equal to one standard atmosphere, divided by the conductivity of a standard potassium chloride (KCl) solution at the same temperature and pressure. The mass fraction of KCl in the standard solution is 0.0324356 (32.4356 g of KCl in 1 kg of solution).

Note that Practical Salinity is a unit-less quantity. Though sometimes convenient, it is technically incorrect to quote Practical Salinity in "psu". For most purposes one can assume that the psu and the ‰, are synonymous.

The global average salinity of ocean waters is about 35 ‰, that is, about 35 g of solid substances are dissolved in 1 kg of seawater.

saturated fat    →   zasićena mast

Saturated fats are fats in foods that are solid at room temperature. They come chiefly from animal sources (beef, whole-milk dairy products, dark meat poultry) but also from tropical vegetable oils (coconut, palm).

Schellbach’s burette    →   Schellbachova bireta

When colourless liquids are used, parallax mistake is avoided by use of Schellbach’s burette. On the inside wall opposite to graduation scale it has a melted in ribbon from milky glass in the middle of which a blue line is found. The level of liquid is now spotted very easily because of light breaking in the meniscus blue line now looks like a double spike.

solution composition    →   sastav otopine

Solutions are homogenous mixtures of several components. The component which is found in a greater quantity is called the solvent and the other components are called solutes. Quantitative composition of a solution can be expressed by concentration (amount, mass, volume and number), by fraction (amount, mass, and volume), ratio (amount, mass, and volume) and by molality. Amount, mass, and volume ratio are numerical, nondimensional units and are frequently expressed as percentage (% = 1/100), promile (‰ = 1/1000) or parts per million (ppm = 1/1 000 000). If it is not defined, it is always related to the mass ratio.

silver/silver-chloride electrode    →   srebro/srebrov klorid elektroda

Silver/silver-chloride electrode is by far the most common reference type used today because it is simple, inexpensive, very stable and non-toxic. It is mainly used with saturated potassium chloride electrolyte, but can be used with lower concentrations such as 3.5 mol dm^-3 or 1 mol dm^-3 potassium chloride. Silver/silver-chloride electrode is a referent electrode based on the following halfreaction

sugar    →   šećer

Sugar is any of a group of water-soluble carbohydrates of relatively low molecular weight and typically having a sweet taste. The group comprises mainly monosaccharides (glucose, fructose, galactose), disaccharides (sucrose, lactose, maltose), and trisaccharides (raffinose). Many monosaccharides and disaccharides fairly commonly found in nature bear names reflecting the source from which they were first isolated. For example, glucose is also known as grape sugar, lactose as milk sugar, and maltose as malt sugar. In everyday usage, the name is often used to refer specifically to sucrose (table sugar, cane sugar, beet sugar).