Transmittance reading

Initial transmittance reading was 88.0. initial transmittance reading was 85.1. initial transmittance reading was 89.4. hInihal transmittance reading was 15.4. 

The transmittance readings should be taken within 5 to 10 minutes after red color development. The developed red color is stable on standing up to at least 2 hours when working with crystalline dihydrotriazole only however, when phenyl azide is used, as it must be in an actual analysis for Compound 118, some of its nonvolatile thermal decomposition products develop colors on standing. 

A standard 5 ppm iron sample gave a transmittance reading of 52.8%. What is the concentration of an unknown iron sample if its transmittance is 61.7% ... 

Secondly, the baseline for the peak must be well defined. The baseline for the entire spectrum is the portion of the trace where there are no peaks. It does not usually correspond to the 100% T line. Thus, two percent transmittance readings must be taken, one for the baseline (corresponding to where the baseline would be if the peak were absent—a blank reading) and one for the minimum percent transmittance, the... 

Convert all percent transmittance readings to absorbance. Subtract the absorbance at the baseline from the absorbance at the tip of the 817 cm"1 peak in each spectrum. 

A portion of the incident light, however, may be refiected by the surface of the cell or absorbed by the cell wall or solvent. To focus attention on the compound of interest, elimination of these factors is necessary. This is achieved using a reference cell identical to the sample cell, except that the compound of interest is omitted from the solvent in the reference cell. The transmittance (T) through this reference cell is Jj divided by Jq the transmittance for the compound in solution then is defined as Is divided by Jjj. In practice the reference cell is inserted and the instrument adjusted to an arbitrary scale reading of 100 (corresponding to 100% transmittance), after which the percent transmittance reading is made on the sample. As we increase the concentration of the compound in solution, we find that transmittance varies inversely and logarithmically with concentration. Consequently, it is more convenient to define a new term, absorbance (A), that wUl be directly proportional to con-... 

The National Institute of Standards and Technology (NIST) provides standard reference materials (SRMs) to verify the wavelength accuracy and accuracy of absorbance (transmittance) readings. SRM 930E for UV- s analysis consists of a set of three neutral density glass filters of standard thickness with nominal... 

Each time a series of samples is run, the absorbance of one or more blank solutions is read versus pure solvent and, if appreciable (sO.Ol A with a Spectronic 20), this is subtracted from all analyte solution readings. Actually, if file blank solution is essentially colorless (i.e., its absorbance is small), this solution is often used in place of the solvent for adjusting the 100% transmittance reading. Any blank absorbance is then automatically corrected for (subtracted). This method... 

Several spectrophotometers have scales that are read either in absorbance or in percent transmittance. What would be the absorbance reading at 20% T1 At 80% r What would the transmittance reading be at 0.25 absorbance At... 

After excitation and plate development the data in columns 2 and 3 of Table 8-6 were obtained from densitometer readings. The percentage transmittance readings of Table 8-6 must be converted to relative intensity readings by reference to the plate calibration curve previously prepared and... 

Into an impinger bubbler flask, 25 ml of ethyl Cellosolve absorber medium is introduced. A 3-10-litre sample of air is collected at a rate of 1 litre per minute. After sampling is complete, the colour is allowed to develop for 1 h. The final volume is adjusted to 25 ml with absorber medium and the transmittance read at 450//m in 2-5-cm cells. The micrograms presence of TDI and 3,3 -diisocyanato-4,4 -dimethylcarbanilide is determined from a previously prepared calibration curve. The micrograms of TDI are determined separately from the A-l-naphthylethylene diamine procedure. 

When the level transmitter span is small, one must be careful to ensure that both purge systems are equalized—that is, that they have the same flow rate and same length of same diameter impulse or purge line. Failure to accomplish this equalization may result in an ofl t in transmitter reading that will not be detect by conventional calibration procedures. This consideration is particularly critical for specific gravity measurement by AP. 

The use of IR and MR spectrometry for qualitative measurements is extensive and wide ranging, and for this purpose transmission spectra are conventionally recorded as a function of wavenumber. In order to make quantitative measurements, it is necessary to convert the transmittance readings to absorbance. A, the relation between the two being ... 

If the vertical coordinate of the spectrum is linear with percent transmittance, then the percent transmittance reading at, say, the bottom of a sample band is taken to be proportional to /. The percent transmittance at the same wavelength is read for the background point, that is, where the recorder pen would be if there were no sample band. This is taken as proportional to Iq. From these values for I and Iq the background corrected sample absorbance can be calculated as logjoC / )-... 

A dispersive instrument is patterned after a double-beam spectrophotometer. Radiation at two fixed wavelengths passes through a cell containing the process stream to provide a continuous measurement of the absorption ratio. At one wavelength, the material absorbs selectively at the other wavelength, the material does not absorb or else exhibits a constant but small absorption. The ratio of transmittance readings is converted directly into concentration of absorber and recorded. This type of instrument can handle... 

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