Nitrate standard

Mercury(II) chloranilate 700 Mercury(II) nitrate standard soln. of, 359 Mercury/mercury( II )-EDTA electrode (mercury electrode) 586 potentiometric titration of metallic ions with EDTA and, 588 prepn. of, 587 Mercury thiocyanate 700 Metaphosphoric acid in homogeneous precipitation, 426 Metal apparatus 93 Metal ion buffer 53... 

In Nebraska, state regulations require that the chemical makeup of animal feed sold in the state be accurately reflected on the labels found on the feed bags. The Nebraska State Agriculture Laboratory is charged with the task of performing the analytical laboratory work required. An example is salt (sodium chloride) content. The method used to analyze the feed for sodium chloride involves a potentio-metric titration. A chloride ion-selective electrode in combination with a saturated calomel reference electrode is used. After dissolving the feed sample, the chloride is titrated with a silver nitrate standard solution. The reaction involves the formation of the insoluble precipitate silver chloride. The electrode monitors the decrease in the chloride concentration as the titration proceeds, ultimately detecting the end point (when the chloride ion concentration is zero). 

Refs on Analysis of NG 1) Marshall 2(1917), pp 739—40 (Estimation of small quantities by reaction with phenol disulfonic acid to form. PA and colorimetric measurement against K nitrate standards) 2) Koehler et al, AnnChimAnal-ChimAppl 2, 271-2(1920) CA H 3794(1920) (Devarda method) 3) W.W. Becker, lECAnalEd 5, 152-4(1933) CA 27, 2909U933)(Redox method for NG and NGc in the presence of DNT)... 

Dilute 0.5,1.0,2.0, 5.0, and 10.0 mL of the secondary standard to 100 mL, respectively. This would give a series of standards of strength 0.05, 0.1, 0.2, 0.5, and 1.0 mg N03-N/L, respectively. Check the efficiency of the column by comparing one of the reduced nitrate standards to a nitrite standard at the same concentration. If the reduction efficiency falls below 75%, use freshly prepared Cu-Cd granules. 

Prepare three nitrate standards at concentrations 1, 10, and 50 mg/L. To 10 mL of each standard in 40 mL beakers, add 10 mL buffer solution, respectively. Immerse the tip of the electrode in the solution while stirring. Record the stable millivolt reading for each standard. Prepare a calibration curve plotting N03-N concentrations in the abscissa and millivolts in the ordinate. The plot should be a straight line with a slope of 57 3 mV/decade at 25°C. After this, rinse and dry the electrode immerse in the sample-buffer mixture and record the stable potential reading. Determine the concentration of N03-N in the sample from the calibration curve. 

The alkyl nitrates also can be detected by chemiluminecent reactions similar to those for the PANs. The alkyl nitrates are converted to NO by hot catalysts, and the NO is detected by O3 chemiluminescence as described in Section l.E.l. The detector can be calibrated with an NO standard, which is more readily available, more reliable, and more easily transported than an alkyl nitrate standard. However, O3 chemiluminescence is less sensitive, by one or two orders of magnitude, than BCD. The alkyl nitrates can also be converted to NO2 by thermal decomposition with a postcolumn pyrolyzer consisting of a heated quartz tube. The NO2 can then be determined by luminol chemiluminescence. The sensitivity of this type of detector is comparable to that of the BCD. Both types of chemiluminescence detectors respond only to oxidized nitrogen species, therefore the halocarbon interference is eliminated. 

S04 see Conservative Elements). The analytical results reported by W. Dittmar in 1884 for waters collected during the British RMS Challenger Expedition (1872-1876) from the world s oceans were almost the same as today s values. The constancy of major chemical composition has led oceanographers to define salinity as a fundamental property together with temperature to calculate the density of sea water. It was routine for classic physical oceanographers to titrate sea water for chloride (plus bromide) ion with silver nitrate standard solution, until the mid 1960s when salinity could be determined more practically by measurement of conductivity. 

If the chloride content of the water sample is unknown this should first be determined by pre-titration with silver nitrate standard solution of appropriate normality. Take 100 ml of the filtered water sample with a chloride content of 1 - 15 mg, or a smaller volume diluted to 100 ml with distilled water. The pH should lie between 7 and 9 (acid- or alkaline-reacting waters should first be neutralized with chloride-free reagents). Add 1 ml of potassium chromate solution. 

Excess NADH is then oxidized to NAD to eliminate interference with color development when NO2 from Reaction 18-9 is measured colorimetrically by reactions such as 18-7. For quantitative analysis in the field, a small, battery-operated spectrophotometer can be used with a set of nitrate standards. Alternatively, color can be compared visually with a chart showing colors from several standards. Commercial field kits allow analysis in the range 0.05-10 ppm nitrate nitrogen. Laboratory apparatus provides a precision of 2% when measuring 0.2 ppm NO3 nitrogen, with a detection limit of 3 ppb. Nitrate reductase has been applied to the measurement of nitrate in a classroom aquarium. ... 

Nitrate standard solution 1.011 g of dry potassium nitrate (KNO3) is dissolved and made up to 1 L with pure water. The stock solution contains 10 mmol/L nitrate and is stable. 

Whenever beginning a series of analyses, the redactor should be reactivated by passing a high concentration nitrate standard (>20/imol/L) through it for several minutes. If the standard peak of the on-line calibration is reduced by more than 10 %, the redactor should be reactivated or replaced. 

The water used as ZW and for the preparation of the nitrite and nitrate standards should be free from nitrate or nitrite. The efficiency determination may be performed using pure water for ZW and standards. 

Analyse triplicates of the two nitrite and nitrate standards (2 and 20 /tmol/L, as outlined before) without any modifications to the nitrate manifold. The efficiency is calculated from the mean absorbances (or equivalent spectrophotometer readings) as in the manual method... 

Silver Nitrate, Standard Alcohtdic Solution (0.1 mol/ L)—Dissolve 17 g of AgNOj in 1(X) mL of water in a l-L volumetric flask and dilute to 1 L with 2-propanol (99 %) (Note 4). Store in a dark bottle and standardize at intervals frequent enough to detect a change of 0.0005 or greater in molarity. 

Silver Nitrate, Standard Alcoholic Solution (0,010 mol/L)—Prepare daily by dilution of the 0.1 N standard. Pipet 100 mL of the 0.1 mol/L standard into a 1-L volumetric flask and dilute to volume with 2-propanol. Calculate the exact molarity. 

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