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Tashiro’s indicator solution

0,75 g/l methyl red sodium salt + 0,375 g/l methylene blue in ethanol 50 % (v/v), denatured
Examples of effect: Flammable; liquids form compounds with the air which can become explosive; produce flammable gases with water or can self-combust. Safety: Keep away from open flames and sources of heat; close containers tightly; store in a fire-safe manner.
Warning
H226
i flammable liquid and vapour
P210 P280 P303+P361+P353 P305+P351+P338
i keep away from heat, sparks, open flames, hot surfaces. No smoking, wear protective gloves/eye protection, IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water/shower, IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing
Pack Qty.
Pack.
Density (D) 0,934 g/cm³
Flash point (flp) 27 °C
ADR 3 III
WGK 1
UN-Nr. 1170

pH indicator, mixed indicator

€18.85/Pack Qty. 

excl. VAT. | 250 ml per Pack Qty.

Art. No. 2624.1

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Product details



Tashiro’s indicator solution 0,75 g/l methyl red sodium salt + 0,375 g/l methylene blue in ethanol 50 % (v/v), denatured

Technical Information
Colour conversion violet - green 
Handling area pH 4,2 - 6,2 
Tashiro’s indicator solution
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2624.1 250 ml plastic €18.85
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Downloads / MSDS


General information

Determination of Nitrogen according to Kjeldahl

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.


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