Weight and Volume Methods

0 is a correction factor to account for the facts that the drops do not completely leave the tip, and that the surface tension forces are not truely vertical. Values of cp are reported in the literature. For this method, the tip must be completely wetted and the drops must form and detach slowly ( 1 min drop ). 

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E. Procedure. The procedure section should unambiguously describe the stepwise preparation of samples, standards, and blanks. Instrumental variables should be described. Weight and volume measurements should include the acceptable range. The procedure should also include methods for any calculations. Procedures should include, but are not limited to, the following recommended elements ... 

There are many ways to determine the weights and volumes to use in an application to a residue field trial. If calculated correctly, all of these methods are adequate. No... 

Tap density (ptap) is an extension of bulk density measurements, and the procedure used to measure the tap density again varies from lab to lab and can affect the final results. To measure tap density, a graduated cylinder is filled with powder and the weight and volume are recorded. The difference observed between procedures is the number of taps used for the measurement. In some cases, a particular number of taps is used, such as 200 [65], 500 [66], or even 1000 taps [67]. Other procedures involve tapping the cylinder for a number of times, recording the volume, and repeating the procedure until the volume remains constant [68]. This method ensures more consistent results. 

Density or specific gravity (relative density) is used whenever conversions must be made between mass (weight) and volume measurements. This property is often used in combination with other test results to predict oil quality, and several methods are available for measurement of density (or specific gravity). However, the density (specific gravity) (ASTM D1298 IP 160) is probably of... 

The sedimentation methods are normally used to measure the size of particles in a liquid medium because of the relatively high viscosity effects in liquids compared to gases. The particles in a liquid may become solvated, yielding increased weight and volume of the particle. Meanwhile, the buoyant effect on the solvated particle in the surrounding medium... 

Experiment 47. — Method Find the weight and volum.e of air exhausted by a pump from a bottle. 

This method involves the usual sourees of error sueh as those made in measuring weights and volumes. Two key potential sources of error are those occurring through poor repeatability of injection volumes and through inconsistent loss of sample in any sample preparation step. Both of these may be compensated for by the use of an internal standard method. 

Analytical TLC differs from PLC in that larger weights and volumes of samples are applied as a band across the entire layer width to thicker (0.5-2 mm) and sometimes larger layers, the purpose of which is the isolation and purification of 10-1000 mg of sample for further analysis. Multiple development of the plate is commonly used, and the separated substances are detected by a non-destructive method (e.g., under UV light and iodine vapors), and recovered by extraction from scraped layer material. PLC can be used to isolate sufficient pure drug compounds for confirmation by spectrometry in cases where analytical TLC is not adequate for identification. Examples of pharmaceutical applications of PLC include a new sesquiterpene trimer and phenylpropanoid glycosides. ... 

Such peak shapes correspond to special cases of P( ) size distributions, sometimes showing unphysical negative proportions of crystallites at some n values. Clearly, the maximum of information (the size distribution and the area-weighted and volume-weighted average sizes) will be obtained by using the Fourier analysis with a stabilization scheme, or Monte Carlo/Bayesian/maximum entropy methods. ... 

We shall first review the common units of weight and volume in the metric system and then describe methods of expressing results. The gram (g) is the basic unit of mass and is the unit employed most often in macro analyses. For small samples or trace constituents, chemists use smaller units. The milligram (mg) is 10 g, the microgram (/xg) is 10 g, and the nanogram (ng) is 10 g. The basic unit of volume is the liter (L). The milliliter (mL) is 10" L and is used conunonly in volumetric analysis. The microliter (/xL) is 10 L (10 mL), and the nanoliter (nL) is 10 L (1Q- mL). (Prefixes for even smaller quantities include pico for 10 and femto for 10" .)... 

A direct method is the analysis by weight and volume, indirect methods are gamma ray attenuation and electrical resistivity measurements. 

There are other methods for analyzing compoimds that don t require solvents for extraction. A sample of known weight and volume (liquid, solid, or liquid and solid mix), is put it in a closed vial, heated to the desired temp>erature, and maintained at that temperature while the... 

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