Specific gravity fractions

Horton and Aubrey (34) handpicked pure vitrain samples from coals and separated them into five different specific gravity fractions. They then analyzed these for 16 minor elements. They concluded that for the three vitrains they studied, beryllium, germanium, vanadium, titanium, and boron were contributed almost entirely by the inherent (organically combined) mineral matter and that manganese, phosphorus, and tin were associated with the adventitious (inorganically combined) mineral matter. 

Figure 2. Germanium in specific gravity fractions of a sample from the Davis Coal Member. Upper washa-bility curve. Lower distribution of germanium in individual fractions.

Nickel in a sample from the Colchester (No. 2) Coal Member (Figure 4) is definitely concentrated in the heavier specific gravity fractions. However, the washability curve remains well above the abscissa and does not appear to approach the origin in the cleanest fraction (purest... 

Two trace element studies are being done to answer some of these questions. The first study, funded by the Environmental Protection Agency, concerns coal washing and is designed to determine the distribution of certain trace elements in coal. The various specific gravity fractions of coal are separated by a sink-float procedure. Commercially available organic fluids are used as the separation media. 

Specific Gravity Fraction % Coal in Fraction Mercury Concentration (ag/g)... 

Fluorine. Tables X, XI, and XII show the results obtained for fluorine in the coal-washing study with coals from Pennsylvania, Iowa, and West Virginia. In all three coals, the fluorine appears to be associated with the mineral matter in the coal. Therefore, removal of the higher specific gravity fractions would lower the fluoride content of the remaining coal. 

Kentucky. The cadmium appears to be so distributed in the coal that removal of the high specific gravity fraction of the coal does not affect the cadmium concentration in the remaining coal. This result is different from that encountered with the other trace elements. Other coals will be studied to see if they exhibit the same cadmium distribution as the Hazard No. 4 coal. 

Figure 12. Comparison of the elements in various specific gravity fraction of the top part of bed 9.

Oil of Turpentine.—This is a common adulterant for the volatile oils and is not always easy to detect. In most cases use is made of the specific gravity, fractional distillation and rotatory power, and the characters of oil of turpentine are described in Chapter IX (see also Oil of Lemon). 

Table 19.13. Infrared Absorption Frequencies for the Various Specific Gravity Fractions before and after Heating at 850°C (Quinaux and Richelle, 1967)...

One other technique for the investigation of trace elements in coal applies the float-sink principle in which comminuted coal can be separated into several specific gravity fractions by flotation in mixtures of liquids such as perchloroethylene and naphtha a liquid such as bromoform (CHBrj) can also be employed for further subfractionation. This procedure can virtually be employed as a fractionation technique to remove significant proportions of the mineral matter from coal without resorting to the use of heat. 

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