Sodium hydroxide, 500 g
Molar mass (M) 40,0 g/mol
Density (D) 2,13 g/cm³
Boiling point (bp) 1390 °C
Melting point (mp) 323 °C
ADR 8 II
CAS No. [1310-73-2]
excl. VAT. | 500 g per Pack Qty.
Art. No. 6771.3
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Sodium hydroxide ≥98 %, p.a., ISO, in pellets
|Suitable (as desiccant) for||Alkaline fluids (e.g. amines)|
|Not suitable (as desiccant) for||Acids, acid derivatives, phenols|
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The most common technique for measuring the amount of nitrogen in organic matter is the Kjeldahl method, which is used in a wide range of sectors such as environmental analysis, food analysis, water analysis and agricultural analysis, as well as in the pharmaceutical and chemical industries. In this traditional method, a precisely weighed sample is broken down using concentrated sulphuric acid, a process which digests its organic contents and reacts nitrogen to form ammonium sulphate.(CHNO)(s) → CO2 (g) + SO2 (g) + H2O (g) + NH4SO4 (solv, H2SO4)A catalyst or catalyst mixture consisting of copper, selenium, mercury and/or titanium is added to speed up the reaction. Sodium or potassium sulphate is used to give the sulphuric acid a higher boiling point. If the nitrogen is contained in a nitro, nitroso or azo compound, however, the mixture must be reduced with zinc before digestion takes place.
The nitrogen is now present in the sulphuric acid as ammonium sulphate. Adding a strong base (such as NaOH) neutralises the sulphuric acid and liberates ammonia from the solution.NH4SO4 (solv) + 2 NaOH (aq) → Na2SO4 (aq) + 2 NH3 (g) + 2 H2O (l) The ammonia is led into an acid (such as boric acid) by means of steam distillation.B(OH)3 (aq) + 2 H2O (l) + NH3 (g) → B(OH)4- (aq) + NH4+ (aq) The resulting strong base (borate ion) is back-titrated with a strong acid (hydrochloric acid or sulphuric acid). The excess weak boric acid is not captured in the process. A Tashiro's indicator that changes colour in the acid is used for titration. The amount of acid that has been used up can then be converted into the amount of nitrogen in the sample. NH4+ (aq) + B(OH)4- (aq) + HCl (l) → NH4Cl (aq) + B(OH)3 (aq) + H2O (l)To calculate the protein content of the sample, the varying nitrogen content of the amino acids must be checked and the relevant conversion factors applied. The nitrogen contained in food derives mainly from proteins, but different samples may also contain other sources of nitrogen.
Determination of biological oxygen demand (BOD)
BOD (biochemical oxygen demand) is a measure of the amount of oxygen that microorganisms need to break down the organic material in a water sample over a specific period of time. It is important to calculate the oxygen concentration at the start and end of the measuring time, which is usually five days and is expressed as an index (BOD5). Chemical, electrochemical or physical methods are used for this calculation.
Desiccants can absorb water and bind it chemically (reversibly or irreversibly) or physically. The main desiccants can be subdivided into four categories:
- non-renewable chemical desiccants
- renewable chemical desiccants
- silica gels
- molecular sieves
|Acetic acid anhydride||-||-||+||-|
|Acetic acid ethyl ester||4 Å||+||-||+|
|Acetic acid methyl ester||4 Å||+||-||+|
|Diisopropyl ether||4 Å||-||+||-|
|Dimethyl formamide||4 Å||-||-||-|
|Xylene (Isomer compound)||4 Å||-||+||-|
Carl ROTH provides suitable acids and bases for different requirements!
- High purity
- High batch consistancy
- Detailed specifications
- Good price-performance ratio
|Assay (acidim.)||≥98 %|
|Carbonate (as Na2CO3)||≤1 %|
|Total nitrogen (as N)||≤0,001 %|
|Chloride (Cl)||≤0,005 %|
|Sulphate (SO4)||≤0,005 %|
|Phosphate (PO4)||≤0,001 %|
|Silicate (SiO2)||≤0,01 %|
|Heavy metals (as Pb)||≤0,0005 %|
|Aluminium (Al)||≤0,002 %|
|Calcium (Ca)||≤0,002 %|
|Iron (Fe)||≤0,001 %|
|Magnesium (Mg)||≤0,0005 %|
|Potassium (K)||≤0,05 %|
|Nickel (Ni)||≤0,001 %|
|Lead (Pb)||≤0,001 %|
|Arsenic (As)||≤0,0001 %|
|Zinc (Zn)||≤0,001 %|