Nessler tubes

Nessler tubes Cylinders of thin glass, generally graduated, used for comparing turbidities and colours of solutions. 

A. Standard series method (Section 17.4). The test solution contained in a Nessler tube is diluted to a definite volume, thoroughly mixed, and its colour compared with a series of standards similarly prepared. The concentration of the unknown is then, of course, equal to that of the known solution whose colour it matches exactly. The accuracy of the method will depend upon the concentrations of the standard series the probable error is of the order of + 3 per cent, but may be as high as + 8 per cent. 

It is advisable, wherever possible, to make a preliminary determination of the concentration of the unknown solution by adding from a burette a solution of the component in known concentration to a Nessler tube containing the reagents diluted with a suitable amount of water until the depth of colour obtained is practically the same as that of an equal volume of the unknown solution also contained in a Nessler cylinder and standing at its side. A series of standards on either side of this concentration is then prepared. 

The instrument is equipped with a prism so that the colour of the liquid under examination and that of the standard which has been selected on the disc are brought into juxtaposition, thus making it easier to compare the two. The Nesslerimeter is a similar type of instrument, made in a tall form to accommodate Nessler tubes. 

If necessary, dilute the sample to give an ammonia concentration of 1 mg L 1 and fill a 50 mL Nessler tube to the mark. Prepare a series of Nessler tubes containing the following volumes of standard ammonium chloride solution diluted to 50 mL 1.0,2.0,3.0,4.0,5.0, and 6.0 mL. The standards contain 0.01 mg NH3 for each mL of the standard solution. Add 1 mL of Nessler s reagent to each tube, allow to stand for 10 minutes, and compare the unknown with the standards in a Nessler stand (Section 17.4) or in a BDH Nesslerimeter. This will give an approximate figure which will enable another series of standards to be prepared and more accurate results to be obtained. 

Appearance. The specimen shall be thoroughly mixed and shall be examined by transmitted light for clarity, suspended matter, or sediment. This is most readily done by pouring some of the specimen into a test tube or Nessler tube... 

Hydrocarbons. Dil 15ml of the specimen to 45ml with distd w in a Nessler tube. Visually examine for cloudiness or opalescence during 30 minutes of standing... 

Introduce 100ml of ether under test into a Nessler tube, passing the sample thru a filter if it has any visible turbidity. Cap tbe tube with a transparent cover and place it in the "comparator", while side-by-side with it is placed one of the standards. Report as the color the number of the standard that most nearly matches the sample. In the event that the color lies midway between two standards, report tbe darker of the two. If, owing to differences In hue berw the sample and the standards, a definite match cannot be obtd, report the range ovet which an apparent match is ohtd, making a note that it is "off-hue ... 

Place an appropriate volume of standard lead solution which corresponds to each of five concentration levels in a Nessler tube, and add water to make up to 40 mL. Add 2 mL of dilute acetic acid and water to make up to 50 mL, and designate it as the test solution. Three tubes of test solution at each concentration level are prepared for separate runs. 

The control solution is prepared by pipetting 2 mL of dilute acetic acid in a Nessler tube of the same material with the test solution and adding water to make up to 50 mL. 

Add a drop of sodium sulfide TS to the test solutions, mix, and hold for 5 min. Put the Nessler tube containing the test solution of each lead concentration on a white background. Visually observe it from the upper side. Determine the lowest concentration where darkening can be visually observable and designate it as the detection limit. 

Method 3. Place an amount of the sample, directed in the monograph, in a quartz or porcelain crucible, heat continuously, gently at first, and then increase the heat until incineration is completed. After cooling, add 1 mL of aqua regia, evaporate to dryness on a water bath, moisten the residue with 3 drops of hydrochloric acid, add 10 mL of hot water, and warm for 2 minutes. Add 1 drop of phenolphthalein TS, add ammonia TS dropwise until the solution develops a pale red color, add 2 mL of dilute acetic acid, filter if necessary, wash with 10 mL of water, transfer the filtrate and washing to a Nessler tube, and add water to make 50 mL. Designate it as the test solution. 

Color. Prepare the standard color solution by introducing l.QOiO.Olg of CP iodine and 5.0+0.1g of CP KI to a 150-mi beaker, contg ca 25ml of distilled water as solvent. Transfer the so In quantitatively to 1000-ml volumetric flask, dilute to the mark with distd w and mix thoroughly. This soln shall not be used after 24hrs. For the test, fill a clean 50-ml Nessler tube to the mark with above color soln and fill the other 50-ml... 

For detn of color, fill to the mark a 100ml Nessler tube with the sample as received and compare the intensity of color with that of APHA50 contd in another Nessler ruhe by looking vertically downward thru the two solns against a white background... 

Prepare rhe APHA75 standard by diluting 15ml of APHA50 to 100 in a Nessler tube and compare the color with that of the sample which was previously heated in an oil hath at 22015°C for 2hrs and allowed to cool during 30 mins to RT... 

Appearance and Color. Pour the sample into a Nessler tube and inspect for transparency and absence of mechanical impurities. Compare its pale-yel color with APHA standards in the same manner as described under US specification tests. The APHA500 contains 500mg... 

To a 25 nil of condensate in a 50 ml Nessler tube was added from a pipette 5 ml of Nessler s reagent and distd w to the mark. Tbe presence of ammonia was indicated by the appearance of brown turbidity due to the formation of NHg,I - HjO and the intensity of this turbidity was detd colori-metrically using the Nalco Phototester, which was previously calibrated by using freshly prepd standards... 

Transfer ca a 3.0 g sample, weighed to 0.1 mg to a tail-form beaker of ca 180 ml capacity, add 20 ml coned HC1 and boil the mixt gently. From time to time replace the HC1 lost by evapn, and continue boiling until a KI-starch paper moistened with distd w is no longer colored by the vapor. Evap the soln to dryness, dissolve the residue in a little distd w and transfer the soln to a 50 ml Nessler tube. Add 5.0 ml of 10%... 

Simple colorimeters, used for routine analysis, are visual comparators related to Nessler tubes. The latter are made of flat-bottomed glass tubes with a volumetric mask and filled with reference solutions of varying concentrations (and possibly derivatising agents). The solution to be analysed, placed in an identical tube, is inserted beside the series of standard solutions. 

Natural bandwidth, 256 Natural width, 278 Nephelometry, 208 Nemst coefficient, 4 Nernst source, 175 Nessler tube, 207 Neutral marker, 116 Nier-Johnson, 296 NPD, 36... 

Vinyl Alcohol-Acetate Resin (VAAR). According to the US Military specification (Ref 6) the resin consists of a mixt of approx 28% solids and 72% solvent. The solids are approx 18% hydroxyl content by wt calcd as vinyl alcohol and 82% as vinyl acetate. The solvent is tech grade methyl acetate (82% pure). The spec requirements are Color - Equivalent to No 300 Pt Co std when a sample aliquot soln is compared visually using 100ml tail-form Nessler tubes against a white background... 

Water-Soluble Sulfates, Chlorides, and Nitrates. The procedures are applicable to pigments and extenders. The choice of hot or cold extraction depends on the properties of the pigment and should be agreed. The anions are determined by the usual analytical methods. For standards, see Table 1 ( Sulfates , Chlorides , and Nitrates ). Apparatus Nessler tubes or spectrophotometer, equipment for pH measurement. 

A standard series of solutions is prepared, each with a known concentration, having the same volume as the unknown, and being contained in identical fiat-bottomed tubes of equal diameter (Nessler tubes). The solutions should be compared in daylight and examined against a while background. 

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