Methods for detecting liquid ammonia content and instruments used

Please ask an expert for help; I urgently need information on this topic. Please have the administrator share it throughout the forum – I’m afraid I’ll lose points if I post it repeatedly:handshake

GB 536-1988 Liquid anhydrous ammonia; GB/T 8570.1-1988 Liquid anhydrous ammonia – Sampling of laboratory samples; GB/T 8570.2-1988 Liquid anhydrous ammonia – Determination of ammonia content; GB/T 8570.3-1988 Liquid anhydrous ammonia – Determination of residue content by gravimetric method; GB/T 8570.4-1988 Liquid anhydrous ammonia – Determination of residue content by volumetric method; GB/T 8570.5-1988 Liquid anhydrous ammonia – Determination of moisture content by Karl Fischer method; GB/T 8570.6-1988 Liquid anhydrous ammonia – Determination of oil content by gravimetric method and infrared spectroscopy; GB/T 8570.7-1988 Liquid anhydrous ammonia – Determination of iron content by o-phenanthroline spectrophotometry. The instrument is a glass container called a liquid ammonia purity tester; you can inquire about it

Thank you; I’ve asked a friend to help me find out the details of these standards. This post was last edited by pwq1973 on 2009-3-30 at 19:34.]

200 ml of liquid ammonia was collected using a Lysenko receiver; after natural evaporation, the remaining substance in the receiver was rinsed clean with distilled water and transferred to an Erlenmeyer flask. A few drops of bromocresol green-methyl red were added, and the mixture was titrated to the endpoint using 0.1 mol H2SO4.

Testing for oil and iron content is troublesome. I wonder if there are any factories that conduct tests in these areas? Are there any tests for lead content as well?

Manufacturers that have infrared spectrometers and spectrophotometers should be able to conduct such tests; the operation is not very difficult – what’s important is to have the appropriate instruments. Lead content can be quantified using an atomic absorption spectrophotometer

The following methods are applicable for the determination of lead limits: 1 Principle: The sample is treated by adding ammonium citrate, potassium cyanide, and hydroxylamine hydrochloride to eliminate interferences from ions such as iron, copper, and zinc. At a pH of 8.5–9.0, lead ions form a red complex with dithizone; this complex is extracted using trichloromethane, and comparison with standard series is made to conduct limit tests or quantitative analyses. 2 Reagents Unless otherwise specified, the reagents used in this standard are all deionized water or lead-free water. 2.1 Nitric acid (GB 626-78). 2.2 Sulfuric acid (GB 625-77). 2.3 Ammonia water (GB 631-77)(1+1): If it contains lead, it must be redistilled using a all-glass distiller. 2.4 Hydrochloric acid (GB 622-77). 2.5 Trichloromethane (GB 682-78): It shall contain no oxides. 2.6 Phenol red indicator: 0.1% ethanol solution. 2.7 Diammonium hydrogen citrate (HGB 3294-60): 50% solution. Weigh 100 g of diammonium hydrogen citrate, dissolve it in 100 ml of water, add 2 drops of phenol red indicator, and adjust the pH to 8.5–9.0 using ammonia solution (1+1); if the color changes from yellow to red, add another 2 drops. Extract several times with dimethyl sulfoxide in chloroform, using 10–20 ml each time, until the chloroform layer remains green. Discard the chloroform layer after washing twice, using 5 ml each time, and then dilute with water to a total volume of 200 ml. 2.8 Hydroxylamine hydrochloride (HG 3-967-76): 20% solution. Weigh 20 g of hydroxylamine hydrochloride, dissolve it in 40 ml of water, add 2 drops of phenol red indicator, and adjust the pH to 8.5–9.0 using ammonia solution (1+1); if the color changes from yellow to red, add 2 more drops. Extract several times with dimethyl sulfoxide in chloroform, using 10–20 ml each time, until the chloroform layer remains green. Wash the mixture twice more with chloroform, 5 ml each time. Discard the chloroform layer, make the solution acidic by adding hydrochloric acid (1+1), and then bring the volume to 100 ml with water. 2.9 Potassium cyanide: 10% solution. 2.10 Diphenylthiourea (dithiourea) (HGB 3343-60): 0.05% solution in trichloromethane, stored in a refrigerator; purified by the method described below if necessary. Weigh 0.5 g of finely ground dithizone and dissolve it in 50 ml of trichloromethane. If there are any residues, filter them using filter paper into a 250 ml separatory funnel. Extract the mixture three times with ammonia solution (1+99), 100 ml each time. Filter the extracts through cotton and transfer them to a 500 ml separatory funnel. Adjust the pH to acidic using hydrochloric acid (1+1). The precipitated dithizone is then extracted three times with 200 ml, 200 ml, and 100 ml of trichloromethane respectively; the combined trichloromethane solutions are used as a dithizone stock solution. 2.10.1 Dithizone working solution: Pipette 1.0 ml of the dithizone stock solution, add 9 ml of trichloromethane, and mix well. Using a 1 cm cuvette and adjusting the zero point with trichloromethane, the absorbance (A) is measured at a wavelength of 510 nm. The volume (V) of the dithizone stock solution required to prepare 100 ml of dithizone working solution (with 70% transmittance) is calculated using equation (1). 10(2-lg70) 1.55 V=--------------------- =---------- ………… (1) A A 2.11 Lead standard solution: Precisely weigh 0.1598 g of high-purity lead nitrate (HG 3-1309-80), add 10 ml of 1% nitric acid, dissolve it, and then transfer the solution quantitatively into a 100 ml volumetric flask; dilute to the mark with water. 1 ml of this solution is equivalent to 1 mg of lead. Before use, dilute with water to a concentration of 1 ml equivalent to 10 μg of lead. 2.12 1% Nitric Acid: Take 1 ml of nitric acid (GB 626-78) and dilute it with water to 100 ml. 3 Instruments: All glass instruments used shall be soaked in 10–20% nitric acid for more than 24 hours, rinsed repeatedly with tap water, and finally washed thoroughly with water. 3.1 Spectrophotometer. 3.2 125ml separatory funnel. 3.3 250 ml Erlenmeyer flask or 250 ml triangular flask. 4 Sample Preparation 4.1 The “sample preparation” of inorganic samples can be carried out according to the methods specified in the respective standard texts. 4.2 The “sample preparation” of organic samples is generally carried out in accordance with the following procedures, in addition to those specified in the respective standard texts. 4.2.1 Wet digestion: Weigh 5.0 g of the sample and place it in a 250 ml Kjeldahl flask or Erlenmeyer flask. Add 10 ml of nitric acid to soak the sample; after waiting for a while (or overnight), heat it slowly. Once the reaction has slowed down, allow the mixture to cool slightly. Then add 5 ml of sulfuric acid along the wall of the flask, and heat it again slowly until the solution inside begins to turn brown. Continue adding nitric acid drop by drop (high-chloric acid can also be added if necessary); during this process, care must be taken to prevent explosions. Keep heating until all the organic matter has decomposed, and at that point white smoke consisting of large amounts of sulfur dioxide will be produced. The final solution should be colorless or slightly yellowish. After cooling, the solution is transferred to a 50 ml volumetric flask. The Kjeldahl flask or Erlenmeyer flask is washed several times with a small amount of water, and the washings are added to the volumetric flask as well. Water is then added up to the mark, and the mixture is mixed thoroughly for later use. Each 10 ml of solution corresponds to 1.0 g of sample. Take a crucible and conduct a reagent blank test using the method described above. 4.2.2 Dry digestion: This method is suitable for samples that are not suitable for wet digestion. Weigh 5.0 g of the sample into a porcelain crucible, add an appropriate amount of sulfuric acid to moisten the sample, carefully carbonize it, then add 2 ml of nitric acid and 5 drops of sulfuric acid. Heat carefully until all white fumes have dissipated, transfer the mixture to a high-temperature furnace, and ash it at 550°C until complete decomposition occurs. Remove after cooling. Add 1 ml of nitric acid (1+1) solution, heat to dissolve the ash, transfer the sample solution to a 50 ml volumetric flask (filter if necessary), wash the crucible with a small amount of water, and add the washings to the volumetric flask as well. Add water to the mark and mix thoroughly for later use. Each 10 ml of solution corresponds to 1.0 g of sample. Take a crucible and conduct a reagent blank test using the method described above. 5 Determination 5.1 Limit test: An appropriate amount of the sample solution and the lead standard solution (with a lead content of not less than 5 μg) are placed in separate 125 ml separatory funnels, to which 1% nitric acid is added up to 20 ml in each. To both the sample solution and the lead standard solution, add 1 ml of 50% ammonium citrate solution, 1 ml of 20% hydroxylamine hydrochloride solution, and 2 drops of phenol red indicator. Adjust the mixture to a red color using ammonia solution (1+1), then add 2 ml of 10% potassium cyanide solution to each. After mixing, add 5.0 ml of dithizone solution and shake vigorously for 1 minute. After allowing the mixture to separate into layers, filter the trichloromethane layer through absorbent cotton into a 1 cm cuvette. Measure the absorbance at a wavelength of 510 nm, using trichloromethane as the zero point; alternatively, perform a visual comparison. The absorbance or color intensity of the sample solution should not be greater than that of the lead standard solution. If the sample is treated, the lead limit standard should also be treated in the same manner. 5.2 Quantitative determination: Transfer 10.0 ml (or an appropriate amount) of the sample solution and an equal amount of reagent blank into separate 125 ml separatory funnels, and add 1% nitric acid to each until a volume of 20 ml is reached. 0.0, 0.1, 0.3, 0.5, 0.7, and 1.0 ml of the lead standard solution were taken (corresponding to 0, 1, 3, 5, 7, and 10 μg of lead, respectively). Place them in separate 125 ml separatory funnels. Add 1% nitric acid to each until the volume reaches 20 ml. To the sample solution, reagent blank solution, and lead standard solution, 1 ml of 50% ammonium citrate solution, 1 ml of 20% hydroxylamine hydrochloride solution, and 2 drops of phenol red indicator were added. The mixture was adjusted to a red color using ammonia solution (1+1), after which 2 ml of 10% potassium cyanide solution was added to each solution; these were then mixed well. 5.0 ml of dithizone working solution was added to each sample, and the mixture was shaken vigorously for 1 minute. After allowing it to settle and separate into layers, trichloromethane was filtered through absorbent cotton into 1 cm cuvettes. The absorbance was measured at a wavelength of 510 nm, with the zero tube used as the reference point, and a standard curve was prepared. 5.3 Calculation (A1-A2)×1000 C=-------------------------------- ………………… (2) V2 m×------ ×1000 V1 Where: C – the lead content in the sample, in mg/kg or mg/L; A1 – the lead content in the sample solution, in μg; A2 – the lead content in the reagent blank solution, in μg; m – the mass (volume) of the sample, in g(ml); V1 – the volume to which the sample is brought to standard concentration after processing, in ml; V2 – the volume of the sample solution taken for testing, in ml