Soxhlet extractor is a laboratory apparatus designed to extract substances with a low solubility in the extracting solvent. The method described by the German chemist Franz von Soxhlet (1848-1926) in 1879 is the most commonly used example of a semi-continuous method applied to extraction of lipids from foods. In the Soxhlet extractor, the sample soaks in hot solvent that is periodically siphoned off, distilled and returned to the sample. During each cycle, a portion of the non-volatile compound dissolves in the solvent. After many cycles the desired compound is concentrated in the distillation flask. The solvent in the flask is then evaporated and the mass of the remaining lipid is measured.
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
Potential vs. SHE / V | ||
---|---|---|
t / °C | 3.5 mol dm-3 | sat. solution |
15 | 0.212 | 0.209 |
20 | 0.208 | 0.204 |
25 | 0.205 | 0.199 |
30 | 0.201 | 0.194 |
35 | 0.197 | 0.189 |
Sucrose (saccharose), or ordinary table sugar, is a disaccharide in which α-D-glucopyranose and β-D-fructofuranose are joined at their anomeric carbons by a glycosidic bond. There are no hemiacetals remaining in the sucrose and therefore sucrose is not a reducing sugar and does not exhibit mutarotation. Sugar is a white crystalline sweet compound found in many plants and extracted from sugar cane and sugar beet. It is used as a sweetening agent in food and drinks. If heated to 200 °C, sucrose becomes caramel. When sucrose is hydrolyzed it forms an equimolar mixture of glucose and fructose. This mixture of monosaccharides is called invert sugar. Honeybees have enzymes called invertases that catalyze the hydrolysis of sucrose. Honey, in fact, is primarily a mixture of glucose, fructose, and sucrose.
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).
Titar (T) is a mass of titrated matter which is equivalent to 1 cm3 of solution. It is shown as T = 2.356 mg HCl / 1.0 cm3 NaOH, 0.1000 moldm-3, and it is usually shown in a table form. If the concentration of used standard solution (c) differs from one outlined in the table data (c0), the factor of correction (f) is induced
Titar is usually used in industrial operational laboratories where from titar tables mass or percentage of the ingredient in question is directly read.
Unsaturated fatty acid is a fatty acid whose carbon chain can absorb additional hydrogen atoms. Their carbon chain has one or more double or triple valence bond per molecule. The most important of these are:
Oleic (9-octadecenoic acid) | CH3(CH2)7CH=CH(CH2)7COOH |
Linoleic (9,12-octadecadienoic acid) | CH3(CHCH2)3(CH2CH=CH)2(CHCH2)7COOH |
Linolenic (9,12,15-octadecatrienoic acid) | CH3(CH2CH=CH)3(CHCH2)7COOH |
Human eye can only see electromagnetic radiation of wavelengths form 400 nm to 760 nm. This narrow part of electromagnetic spectrum is called visible radiation. Visible (white) light is a mixture of light of all kind of colours, it can be separated, with the help of a glass prism, into its component colours - visible light spectrum, and each colour corresponds to a certain area of wavelengths:
Colour | Wavelength / nm |
---|---|
purple | 400 - 450 |
blue | 450 - 500 |
green | 500 - 570 |
yellow | 570 - 590 |
orange | 590 - 620 |
red | 620 - 760 |
Hardness is defined as the concentrations of calcium and magnesium ions expressed in terms of calcium carbonate. These minerals in water can cause some everyday problems. They react with soap and produce a deposit called soap curd that remains on the skin and clothes and, because it is insoluble and sticky, cannot be removed by rinsing.
Hard water may also shorten the life of plumbing and water heaters. When water containing calcium carbonate is heated, a hard scale is formed that can plug pipes and coat heating elements. Scale is also a poor heat conductor. With increased deposits on the unit, heat is not transmitted to the water fast enough and overheating of the metal causes failure. Build-up of deposits will also reduce the efficiency of the heating unit, increasing the cost of fuel.
There are two types of water hardness, temporary and permanent.
Temporary Hardness is due to the bicarbonate ion, HCO3-, being present in the water. This type of hardness can be removed by boiling the water to expel the CO2, as indicated by the following equation:
Permanent hardness is due to calcium and magnesium nitrates, sulphates, and chlorides etc. This type of hardness cannot be eliminated by boiling.
Water supply classification | |
---|---|
Hardness | Concentration of Calcium carbonate (mg/L) |
Soft Water | 0 to 75 |
Medium Hard Water | 75 to 150 |
Hard Water | 150 to 300 |
Very Hard Water | over 300 |
Generalic, Eni. "Periodic table." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
Glossary
Periodic Table