Apparatus constant

Compressed air line apparatus constant flow type 1000-2000... 

C is an apparatus constant. Usually C, a, and KH are temperature dependent, but a and Kh more so than C. Also In (a) behaves analogously to VPIE and normally increases as temperature falls according to 1/T or 1 /T2 (Chapter 5), while KH typically increases exponentially as temperature falls. These two criteria conflict so far as the best choice of temperature is concerned, and for good separations it is necessary to determine the optimum compromise. With a and KH set by the selection of operating system and temperature, resolution is proportional to Vg/Vc. For maximum resolution the vapor volume is increased by electing open tubular columns, i.e. wetted wall columns with minimal liquid loading, and therefore minimal capacity. 

There are claimed advantages and disadvantages for both techniques. Both have sensitivities of about 10 cc per quantum state for moderate power laser sources. Of course increased laser power provides increased sensitivies in either case. One advantage (we feel) to the LIF technique for NO detection is that a single calibration of the apparatus constant (photon collection and detection efRciencies) is valid for pressure from 10" torr to one atmosphere. 

For any polymerisations which are not internally of first order, the apparatus constant A must be determined. This can be done as follows Let the volume of solution in the dilatometer be Vj + nr h (where is the volume of the body of the dilatometer, r the i.d. of the capillary and h the height of the meniscus in the capillary), and let the dependence of the volume... 

With this apparatus, constant pH can be maintained by using a combination glass electrode along with an automatic titrimeter and digital buret. 

Since the relative positions of the resonance peaks are dependent on the strength of the applied magnetic field or that of the applied radiofrequency, they must be normalized, in order to obtain spectra which are independent of the apparatus constants. 

The apparatus constant can be eliminated by using the so-called relative specific response the relative specific response of a compound is the ratio of the specific responses of the compound and of a deliberately chosen reference compound (r). Hence, the relative specific responses of the compound under determination and of the calibration standard,7 // and/ (cf., eqns. 12—14), respectively,are... 

The relative specific response characterizes unambigously the specificity of detection (with a given detector and under given conditions) and is relatively little dependent on the variations in instrumental parameters (cancellation of the apparatus constant). Therefore, the relative specific response is the most suitable basis for the definition of the mass-specific response factor. This factor can be defined as the inverse of the relative specific response hence, for compounds i and s we have... 

A H amount (mcal/mg) of energy change per unit mass of sample K apparatus constant (mcal/mcal )... 

The apparatus constant shall be determined as follows. First prepare the melting curves for pure tin, indium, potassium nitrate, and potassium perchlorate. Next using the value of heat of fusion found in the literature, determine the relationship between the temperature and the apparatus constant Calculate the apparatus constant at the extrapolated decomposition temperature, and, in the abovementioned equation, use the value so obtained. 

DSC(l) data were obtained with a Model DSC20 apparatus (Shimadzu Co., Ltd.) at Yoshida laboratory, The University of Tokyo. A sealed cell made of soft stainless steel was used as the sample cell K 1. The extrapolated decomposition temperature 1" was taken as the decomposition start temperature (Tdsc or Tdta). In DSC(l),the peak area was obtained by weighing the peak-area cutout. The apparatus constant, k, which is used to determine the DSC decomposition heat (Qdsc(1)) from the peak area, was determined by obtaining the values of heat of fusion for potassium nitrate, indium, tin, and potassium perchlorate. 

DTA(2) data were obtained with a Model DT-40 DTA apparatus (Shimadzu Co., Ltd.) at Yoshida laboratory. Since the DSC apparatus developed problems frequently, an attempt was made to use a DTA apparatus in screening tests for the hazards of reactive substances. The sample cell used was the same as in DSC(l). Qdta(2) was determined by using the apparatus constant, k, at each temperature as obtained in the DTA evaluation of the standard substances listed above. The DTA curve was stored on a floppy disk by a Model PC-9801 personal computer (NEC), and the values of Tdta and peak area were determined with the base line leveled. The peak area was calculated as the product of output voltages ( V) times temperature (0 C) and, by multiplying the resulting peak area by the apparatus constant, Qdta(2) was determined. 

In the case of DTA, the apparatus constant varies with the temperature therefore, the... 

It is commonly assumed that the calibration factor, K, by means of which, according to Eq. (8), the measurement data are converted into the number-average molecular weights, depends only on the solvent, the temperature, and an apparatus constant. ... 

Here G2 is the apparatus constant related to the sensitivity of the spectrometer at 100 kHz. 

G3 is the apparatus constant related to the sensitivity of the spectrometer with the analyzer inserted, and A is the Mueller matrix for the analyzer. The above equation can be approximated as... 

To eliminate the apparatus constant and determine the dielectric constant, we com-... 

Given a value of for the chosen reference gas from Table 1, adjusted if necessary to the experimental temperature and pressure with Eq. (6), and given the value of the frequency shift obtained with this gas, Eq. (5) may be used to obtain the apparatus constant K. Once K is known, Eq. (5) may be used to determine the dielectric constant of the subject gas, say HCl, from the frequency shift obtained with that gas. 

Since the capacitance of the cell, C eii, varies somewhat with temperature owing to thermal expansion and contraction of the metal parts, it is advisable to determine the apparatus constant K for each temperature at which the cell is to be used. If this is to be done with CO2 as the reference gas when the cell is cooled with Dry Ice, care must be taken to limit the filling pressure to significantly less than 1 atm to avoid condensation of CO2 in the cell. 

In order to determine the apparatus constant iioffAll that appears in Eq. (13), measurements are made on a material of known susceptibihty. Eor this purpose, a common standard is an aqueous solution of nickel chloride, about 30 percent NiCl2 by weight. Prepare 100 mL of such a solution with an accurately known weight fraction of NiCl2 in air-free distilled water. When this and other solutions are weighed on the Gouy balance, record the ambient temperature. 

From the given by this expression and the density of the NiCl2 solution, the volume susceptibility x can be calculated from Eq. (2). With this and the measured weight difference, determine and report the apparatus constant appearing in Eq. (13). 

The apparatus constant requires again the application of some standard. Ultimately, HRS measurements are also referenced against quartz as in EFISHG, but this cannot be done directly. Initially, the solvent has been used as an internal reference (Clays and Persoons, 1991, 1992). However, the )3 values of common solvents are very small and large errors in their determination have been noted unless sources of error (like scattering from small undissolved particles) were carefully excluded. The value for methanol has been found to be five times lower than initially reported as shown by subsequent measurements on carefully purified solvents (Morrison et al., 1996). It is therefore advisable to use a standard solution of p-nitroaniline as an external reference (Morrison et al., 19% Wortmann et al., 1997). 

It would be helpful if various workers would adopt a few standard experimental arrangements, since the value of 6 and its variation with D and v could quickly be determined for each technique. An alternative would be to run a known reaction with each new method of stirring, thus establishing an "apparatus constant." Sometimes a knowledge of 6 is useful in determining the mechanism of a reaction. For example, in the dissolution of Cu in 02 aturated NH3 solutions, studied by Halpern (28), the overall reaction is... 

This list includes the apparatus constantly used by a single student, who should be provided with each piece, and be held responsible for its returp in... 

The apparatus constant k is obtained by calibration measurement. With the measured attenuation U = lo exp(-pdp) the porosity p is simply determined, lo represents the intensity of the primary beam. To calculate the porosity p one gets the condition ... 

In another method, the pressure of air required to force a thread of liquid along a capillary tube until the surface at the free end of the tube is plane is measured. Achmatov measured the pressure p to drive a liquid into two joined horizontal tubes of radii R, r and used the formula /7=2or(l/r—1/jR) if one liquid is a standard, p=cK, where K is an apparatus constant. 

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