Cut and weigh technique

A final point of consideration is the measurement time required. Certainly electronic integration is by far the fastest and the ball and disc integrator would also be considered fast. The manual methods in increasing slowness would be peak height, height and width, triangulation, planimeter, and finally cut and weigh technique. 

As the cut and weigh method above, the planimeter method is a perimeter method that makes use of a surveyor s or draftsman s instrument called a planimeter. Using this technique the baseline is drawn as usual. The perimeter of the peak is then traced using the eyepiece containing cross-hairs of the planimeter. 

Sieves may also be calibrated by a counting and weighing technique applied to the fraction of particles passing the sieve immediately prior to the end of an analysis. These will have a very narrow size range and the average particle size may be taken as the cut size of the sieve. A minimum number ( ) of particles need to be weighed to obtain accurate volume diameters let this weight be m and the particle density be / then ... 

Calculate the enthalpy of the reaction endotherm by a suitable technique (e.g. area can be measured by planimetry, cutting and weighing, etc.). 

Several techniques have been used to determine the orthobaric densities of the liquid and gas. The simplest method is that proposed by van Eck and recently used by the Reporter. A series of heavy-walled tubes are partially filled with varying but known amounts of the substance under investigation. Each is heated slowly in turn until the meniscus disappears out of either the top or bottom of the tube, i.e. the vapour phase completely condenses or the liquid gas completely evaporates. The temperature at which the tube becomes completely filled with vapour or liquid is noted. The volume of each tube is then found by weighing it in water and then cutting the tube open, emptying it and weighing the pieces in water. This method enables the densities of liquid and vapour to be calculated over a series of temperatures. This method is simple but time-consuming, and requires considerable experimental care. 

In the mercury pump technique, the volume of a 25-g sample of shale is obtained by pressuring a chamber to 24 psig with and without the shale sample. In the mtid balance technique, shale cuttings are added in the mud balance cup until they weigh the equivalent of a cup of water. The volume of shale can be expressed as... 

The intensity (or area) of a spectrum is calibrated with standards such as a, a -diphenyl-//-picrylhydrazyl (DPPH), potassium peroxylamine disulfonate [Fremy s salt K2NO(SO,)2], or carbon One gram of DPPH contains 1 5 X 1021 unpaired spins, and the strong pitch standard (0 1% powdered coal in KC1) has 3 x 1015 spins/cm of length A computer is useful for integrating the spectral area Alternatively, techniques have been developed m which the absorption line is cut out from the paper trace, weighed, and compared with that of a standard sample... 

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