Blank test

Reduction of a nitro compound to a hydroxylamine. Dissolve 0-5 g. of the compound in 10 ml. of 50 per cent, alcohol, add 0-5 g. of solid ammonium chloride and about 0 5 g. of zinc powder. Heat to boiling and allow the ensuing chemical reaction to proceed for 5 minutes. Filter from the excess of zinc powder and test the filtrate with ToUen s reagent see Section III,70,(i). An immediate black or grey precipitate or a silver mirror indicates the presence of a hydroxylamine formed by the reduction of the nitro compound. Alternatively, warm the filtrate with Fehling s solution a hydroxylamine will precipitate red cuprous oxide. (A blank test should be performed with the original compound.)... 

Dodge has based a process for the determination of benzaldehyde. A strong (2 5 N) alcoholic potash solution is required for the estimation, which is performed. by allowing a mixture of 10 c.c. of this solution with 1 to 2 grams benzaldehyde to stand at the ordinary temperature for twenty-four hours, after which the unabsorbed pota is titrated back with N/2 hydrochloric acid. A blank test is also made, and from the amount of potash entering into reaction, the percentage of aldehyde can be calculated. The process breaks down in the assay of natural oil of bitter almonds, probably due to the presence of benzaldehyde cyanhydrin. 

A blank test should be performed to ensure the absence of chlorine in the materials employed. 

Blind-probe, /. blank test, -schlauch, m. flexible tube closed at one end. -strom, m. (Elec.) wattless current, -versuch, m. blank test, -wert, m. blank value, reagent value, -wlderstand, m. (Elec.) reactance. 

Benzoic acid is sparingly soluble in water (which is a disadvantage) and must therefore be dissolved in 95 per cent ethanol. The mode of use is similar to that already described for potassium hydrogenphthalate (Section 10.27, Procedure B). For a 0.1 M solution, of, say, sodium hydroxide, weigh out accurately 0.4 g portions of the acid into a 250 mL conical flask, add 10- 20 mL of ethanol, shake until dissolved, and then titrate the solution with the strong alkali using phenolphthalein as indicator. A blank test should be made with the same volume of ethanol and the indicator deduct, if necessary, the volume of the alkali solution consumed in the blank test. 

The film formed during the blank test was left on the glassy carbon surface. Upon addition of further mercury nitrate, 20-50 til of a 5 g/1 solution were... 

The limit of detection (LoD) has already been mentioned in Section 4.3.1. This is the minimum concentration of analyte that can be detected with statistical confidence, based on the concept of an adequately low risk of failure to detect a determinand. Only one value is indicated in Figure 4.9 but there are many ways of estimating the value of the LoD and the choice depends on how well the level needs to be defined. It is determined by repeat analysis of a blank test portion or a test portion containing a very small amount of analyte. A measured signal of three times the standard deviation of the blank signal (3sbi) is unlikely to happen by chance and is commonly taken as an approximate estimation of the LoD. This approach is usually adequate if all of the analytical results are well above this value. The value of Sbi used should be the standard deviation of the results obtained from a large number of batches of blank or low-level spike solutions. In addition, the approximation only applies to results that are normally distributed and are quoted with a level of confidence of 95%. 

For higher accuracy in the low polymer concentration range, two different methods were used. In the case of PAA, potentiometric titrations of solutions of PAA were performed with 0.01 N NaOH using a Brinkman model, Westbury, NY, automated titrator. Blank tests indicated no interfering species. Known amounts of PAA were used to prepare a calibration curve immediately after titration of the samples containing unknown amounts of polymer. The starting point of the titration was pH 4.0, and the end point was reached near pH 8. Total volumes of 75 or 100 cc were used for the titrations, and the ionic strength was controlled at 0.01 M NaCl. 

Determination of Carboxylic Group Terminals. The carboxylic group terminals were determined by alkali titration (12.). After 200 mg of the sample was dissolved in T.5 ml of benzyl alcohol in a nitrogen atmosphere at 110 °C, the solution was titrated with 0.05N potasL- Vum hydroxide using phenolphthalein as an indicator. A blank test was carried out by the same method but omitting the sample. 

The fraction of the analyte determined in a blank test sample or test portion, after spiking with a known quantity of the analyte under predefined conditions. 

The above assembly consists of a selfsealing Kipp-Hein gas generator for furnishing comparatively air-free C02, a Trautz-Nierderl gasometer to measure the amt of gas used either in the determination or in the blank test a gas burner for heating the... 

As the quantity of water-soluble constituents in the various hido powders varies greatly, it is always necessary, before using a hide powder for tannin determinations, to determine the quantity of soluble constituents by a blank test according to the method described here. 

Fig. 9.6-11 demonstrates the stability of lard stabilized with C02-rosemary extracts, expressed as the Peroxide Number (POZ), compared to BHA (Butylhydroxyanisole), and pure lard, as a blank test value. 

To distinguish between colour changes caused by ageing of the paint rather than by the rubber a blank test assembly may be used. A blank is an assembly prepared and tested in the same manner as the samples under test but the rubber is replaced by an inert material such as aluminium. 

Carry out a blank test, in duplicate. When making a series of Carbamite estimations, perform one blank test before and the other at the completion of the series... 

Figure 8.20 shows a typical experimental result obtained for a mixture of Ti02-AC (activated carbon) particles, which was exposed to ca. 2 ppm of NO in air for a period of 5 h at relative humidity of 50%. The lines of NO (blank) and N02 (blank) were recorded in a separate experimental run (blank test) in which... 

Hide powder this should be white, woolly and free from any substances soluble in cold water and capable of reducing permanganate—this is shown by a blank test. 

Lipase activity was determined by adding 2 mL of the extract to an emulsion of olive oil (10% olive oil, 5% Arabic gum in 100 mmol/L of phosphate buffer, pH 7.0.) and incubating at 37°C and 200 rpm for 15 min. The reaction was stopped with the addition of a solution of ethanol and acetone (1 1). The fatty acids released in the hydrolysis were titrated with a solution of 0.04 N NaOH (5). Blank tests were performed by titration of a sample of emulsion without incubation, adding the enzyme extract sample just before the beginning of titration. One unit of lipase activity corresponds to the amount of enzyme that produces 1 pmol of fatty acids/min in the reaction conditions just described. 

Experiment . Selectivity Blank Test Extract selectivity blanks from six different lots. 

The S2p peaks appear at a binding energy of 161.8 eV in pure nickel sulfide and at 168.7 eV in nickel sulfate (Fig. 3). No indication of die presence of sulfate species can be observed in the freshly sulfided and Blank tested samples. In the samples treated in the presence of water, a peak corresponding to sulfate can be observed. Its intensity is one order of magnitude lower than the intensity of the sulfide peak. This peak did not show any clear evolution as a function of the treatment time. 

As a test reaction for the catalytic activity the hydrogenation of dimethylitaconate was employed. No reaction takes place in the blank test, when the carrier Al-MCM-41 itself is used as catalyst. The immobilised rhodium complexes give enantioselectivities up to 92 % ee of dimethyl-(R)-methylsuccinate with a turn over number of 4000 for the S,S-Me-Duphos ligand. The corresponding supported catalysts with R,R-Diop and S,S-Chiraphos ligands lead to enantioselectivities of 34 % ee and 47 % ee with lower activities. With the (+)-Norphos ligand the favoured enantiomer is dimethyl-(S)-succinate which is formed with 47 % ee. 

Blank Tests Where a blank determination is specified in a test or assay, it is to be conducted using the same quantities of the same reagents and by the same procedure repeated in every detail except that the substance being tested is omitted. 

Acidity (as H2SO4) Dilute 9 mL (10 g) of sample in 90 mL of carbon dioxide-free water, add methyl red TS, and titrate with 0.02 N sodium hydroxide. The volume of sodium hydroxide solution should not be more than 3 mL greater than the volume required for a blank test on 90 mL of the water used for dilution. 

Blank Test Perform a blank test on each lot of Hide Powder. Transfer 7.2 g of Hide Powder EFT, accurately weighed, into a 300-mL Erlenmeyer flask containing 100 mL of water. Proceed as directed in the Sample Test, beginning with Shake the flask for 20 min.. .. Calculate the weight difference. 

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