Further Reading

Beckman JR and Randolph AD (1977) Crystal size distribution dynamics in a classified crystalliser: part II, simulated control of crystal size distribution. American Institute of Chemical Engineers Journal 23: 510-520.

Eek RA, Pouw HAA and Bosgra OH (1995) Design and experimental evaluation of stabilising feedback controllers for continuous crystallisers. Powder Technology 82(1): 21-35.

Eek RA, Dijkstra SJ and van Rosmalen GM (1995b) Dynamic modelling of suspension crystallizers, using experimental data. American Institute of Chemical Engineers Journal 41(3): 571-584.

Kramer HJM, Bermingham SK and van Rosmalen GM (1999) Design of industrial crystallisers for a required product quality. Journal of Crystal Growth 198/199: 729-737.

Miller SM and Rawlings JB (1994) Model identification and control strategies for catch cooling crystallisers. American Institute of Chemical Engineers Journal 40: 1312-1327.

O Meadhra RS, Kramer HJM and van Rosmalen GM (1995) A model for secondary nucleation in a suspension crystallizer. American Institute of Chemical Engineers Journal 42(4): 973-982.

Randolph AD and Larson MA (1988) Theory of Particulate Processes, 2nd edn. New York, Academic Press.

Randolph AD, Chen L and Tavana A (1987) A feedback control of CSD in a KCl crystallisation with fines dissolver. American Institute of Chemical Engineers Journal 33: 582-591.

J. A. Gamble, School of Earth Sciences,

Victoria University of Wellington, New Zealand

Copyright © 2000 Academic Press

Magmas are hot (eruption temperatures range between 600°C and 1400°C), multicomponent, but generally silicate-dominated melt systems formed by processes of partial melting in the interior of the earth. Silicon and oxygen are the major constituents of most magmatic systems, apart from those of the carbonatite association, where NaCO3 and CaCO3 are significant components. This article considers crystallization in silicate-dominated melt systems. In addition to Si and O, Ti, Al, Fe3 +, Fe2 +, Mn, Mg, Ca, Na, K and P comprise the constituents commonly referred to as the 'major elements'. It has become conventional to refer to these in terms of their oxides, expressed in weight percent (Table 1). Furthermore, magmas typically contain dissolved volatile species, dominated by H2O, but including SO2, H2S, Cl2, F2, CO2, CO and traces of noble gases such as He, Ar and

Randolph AD, Beckman JR and Kralievich ZI (1977) Crystal size distribution dynamics in a classified crystalliser: part 1, experimental and theoretical study of cycling in a potassium chloride crystallisation. American Institute of Chemical Engineers Journal 23: 500-510.

Rawlings JB, Miller SM and Witkowski WR (1993) Model identification and control of solution crystallisation processes. Industrial and Engineering Chemistry Research 32: 1275-1296.

Rawlings JB, Sink CW and Miller SM (1995) Control of crystallisation processes. In: Meyerson A (ed.) Handbook of Industrial Crystallisation, pp. 103-130. Boston: Butterworth Heinemann.

Redman T, Rohani S and Strathdee G (1997) Control of the crystal mean size in a pilot plant potash crystalliser. Transactions of the Institute of Chemical Engineers 75A: 183-192.

Rohani S (1995) Control of crystallisers. In: Mersmann A (ed.), Crystallisation Technology Handbook. New York: Marcel Dekker, Inc.

Xe. Elements such as Rb, Sr, Ba, Zr, Nb, the rare earth elements, Pb, Th and U are present in trace amounts (typically |g g_1 or ppm) and are called 'trace elements'.

After magmas form, they may move away and separate from their source regions, due principally to

Table 1 Major oxide chemical analyses (wt%) of typical volcanic igneous rocks. All data are from the author's database of chemical analyses

Element oxide

Basalt

Andesite

Dacite

Rhyolite

SiO2

49.86

60.35

66.68

73.89

TiO2

1.38

0.78

0.58

0.33

AI2O3

15.96

17.53

16.5

13.69

Fe2Os

5.47

3.37

2.42

1.47

FeO

6.47

3.17

1.93

0.89

MnO

0.32

0.18

0.06

0.08

MgO

6.27

2.79

1.43

0.39

CaO

9.1

5.87

3.51

1.22

Na2O

3.16

3.63

4.03

3.43

K2O

1.55

2.07

2.71

4.53

P2O5

0.46

0.26

0.15

0.08

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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