Sampling sample dividers

The number of grams in a sample divided by the number of equivalents in the same sample gives the gram-equivalent weight of the material. 

Mechanical methods also exist for dividing up particulate material into suitably sized samples. Samples obtained by these means are usually representative of the bulk material within limits of less than 1 per cent, and are based upon the requirements established by the British Standards Institution. Sample dividers exist with capacities of up to 10 L and operate either by means of a series of rapidly rotating sample jars under the outlet of a loading funnel, or by a rotary cascade from which the samples are fed into a series of separate compartments. Sample dividers can lead to a great deal of time-saving in laboratories dealing with bulk quantities of powders or minerals. 

Units may be combined together into derived units to express a property more complicated than mass, length, or time. For example, volume, V, the amount of space occupied by a substance, is the product of three lengths therefore, the derived unit of volume is (meter)3, denoted m3. Similarly, density, the mass of a sample divided by its volume, is expressed in terms of the base unit for mass divided by the derived unit for volume—namely, kilogram/(meter)3, denoted kg/m3 or, equivalently, kg-m-3. The SI convention is that a power, such as the 3 in cm3, refers to the unit and its multiple. That is, cm3 should be interpreted as (cm)3 or 10-6 m3 not as c(m3), or 10 2 m3. Many of the more common derived units have names and abbreviations of their own. 

Some intensive properties are ratios of two extensive properties. For example, the property density, d, mentioned above, is a ratio of the mass, m, of a sample divided by its volume, V ... 

The density, d, of a gas, like that of any substance, is the mass of the sample divided by its volume, d = tn/V. Because the densities of gases are so low, they are usually expressed in grams per liter (g-L ). The density of air, for instance, is about 1.6 g-L-1 at SATP. Because the mass of the sample is equal to the amount in moles times the molar mass, m = nM, and n = PV/RT, it follows that... 

The membrane retention fraction R may be defined as membrane-bound moles of sample, divided by the total moles of sample in the system ... 

The reduced stress is defined as the force per cross-sectional area of the undeformed sample, divided by the term X-X- with X being the relative elongation L/L0. With undiluted rubber, this is not found experimentally. In most cases, however, the elastic behaviour in a moderate elongation range is satisfactorily described fcy the empirical Mooney-Rivlin equation, which predicts a linear dependence of on reciprocal elongation X- (32-34)... 

An alternative method of calculation of unsaturation involves substitution of heteroatoms with hydrocarbon moieties. All the elements with valence 1 are substituted for CH3 groups, all the elements with valence 2 for CH2 groups, all the elements with valence 3 for CH groups, and all the elements with valence 4 for C. The formula obtained is compared with that of the alkane with the same number of carbon atoms. The difference between the number of hydrogen atoms in the alkane and in the sample divided by 2 gives the R value. For the above examples one will get ... 

The number-average molecular weight M , defined as the total weight of a polymer sample divided by the total number of moles in it (Eqs. 1-15 and 1-16), is given by... 

Second, easily flowing granules or powder may be riffled. This is recommended for fertilizers Oohnson, 1990b). Riffle boxes (sample dividers or splitters) are available to BS812 and BS1377 from ... 

Procedure. Take a representative of the bulk fertilizer sample and reduce in size by cone and quartering, or use a sample divider. Then grind and sieve to 0.2 mm (No. 70 or 70 mesh), mix thoroughly and immediately transfer to an airtight container. Weigh 0.0500 g (in duplicate) into a 50-ml micro-Kjeldahl... 

Calculation. Subtract the weight of the empty crucible from that of the crucible plus NDF to obtain the weight of NDF in 0.5 g sample. Divide by the sample weight and multiply by 100 to obtain the % NDF in the freeze-dried sample. Multiply this figure by 100/(100-moisture content) to obtain the % NDF in DM. Subtract the empty crucible weight from the weight of crucible plus ash and multiply by 100/weight of NDF to obtain the % ash in the NDF. 

Calculation. Subtract the blank reading from the sample reading in pg K ml read from the graph. This is equal to the g kg of potassium in the sample. Divide the pg K mM by 10 to obtain the % K in the sample. If the sample was not oven-dried, use the separate moisture determination to correct the result to K in DM. 

There are many laboratory devices available for the reduction of the primary sample to an analysis sample. The three most important methods used in the pharmaceutical industry are (i) scoop sampling, (ii) cone and quartering, and (iii) the spinning riffler or rotary sample divider (Fig. A-3). 

Density is the amount of mass contained in a sample divided by the volume of the sample ... 

Let s assume we have a 1.000 L sample of the gas, which weighs 5.380 g. We know the temperature, volume, and pressure of the gas and can therefore use the ideal gas law to find n, the number of moles in the sample. Dividing the mass by the number of moles then gives the molar mass. 

Two processes of sample division and reduction are covered (1) procedure A, in which manual riffles are used for division of the sample and mechanical crushing equipment for reduction of the sample, and (2) procedure B, in which mechanical sample dividers are used for division of the sample and mechanical crushing equipment for reduction of the sample. A third process that is, in reality, a combination of procedures A and B may be used at any stage. 

By sample mean X we understand the value that is the arithmetic average of property values Xj, X2, X3, Xp When we say average, we are frequently referring to the sample mean, which is defined as the sum of all the values in the sample divided by the number of values in the sample. A sample mean-average is the simplest and most important of all data measures of location. 

The soil HMBC (SHMBC) is the ratio of the IC50 of a metal in a soil sample divided by the IC50 of a metal in a reference soil. 

Figure 2.4 Systematic sampling. Systematic sampling divides the site into grid cells. Soil samples are collected from within each of these units, their locations geo-referenced. A drawback may be the missing of hot spots. ...

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