ROBERT C. PLUMB
chemical principles exemplified
Worcester Polytechnic Institute Worcest.r, M o m c h u r l t s 01609
Trace Elements Make Australia Fertile lliustrating principles of enzymatic kinetics Information provided by A. J . V. Janes, Muresk Agricultural College, Western Australian Institute of Technology Farming in Australia is widely dependent upon the addition of certain trace elements to the soil. The benefits of these trace elements to the Australian economy are incalculable. The prospect for Australia has been changed from one of restricted population based on a restricted agriculture to one of great potential. It seems likely that never have such small amounts of simple chemicals had such a major effect upon a society. From a geological viewpoint much of Australian soil is very old. The rocks and minerals were formed about two billion years ago. The soils derived from these are of course younger, hut in some cases, are known to be as old as 250 million years. Leaching, by geochemical action, has reduced the levels of cobalt and copper and other metals such as zinc and manganese below the levels necessary for highly productive agriculture; hence soil science has developed as one of the most important applied chemistly fields in Australia; Australian scientists lead the work in their knowledge of trace element chemistry in agriculture. Through this applied science Australian agriculture has grownfrom farming in a hostile environment to the point where Australia is not only self-sufficient but is a leading exporter to world markets. If soil is deficient in cobalt, grass can still grow normally hut sheep which graze on the grass show symptoms of general starvation. A copper deficiency decreases growth in pasture and crops and causes "rickets" in lambs and strinev wool with drastic economic consequences. AdditionsUbf small amounts of trace elements dramatic results. For example 2 oz of molybdenum trioxide per acre, on certain soils; can increase the yield of clover from well below 2000 lh/acre to over 4000 lh/acre, a return of more than 20,000 to 1 on a weight basis. Trace elements are commonly applied to soils in the wheat belt areas with first year financial returns of more than 1000%. Literally millions of people are affected by the "magic" manipulation of growth performed by farmers in Australia; the chemist, with his specialized knowledge, can obtain insights into how the "magic" operates. Of course all of the roles of trace elements are not understood hut much is known. A principle role of trace metals is in enzymes which catalyze important biochemical reactions. For example, copper is essential in the functions of mitochondia of cells. One of the final steps in the degradation of the chemical energy of glucose involves cytochrome oxidase, a n enzyme containing copper in which the
electron transfer reaction occurs. Both plants and animals employ this reaction; remove the traces of copper in the soil and plants and animals become deficient in the cytochrome oxidase enzyme and life stops. Cobalt is required in the diet of animals and humans where i t is used a s cobalamin, vitamin BIZ. Its ahsence in humans produces
pernicious anemia and is correctable by dosages of a few micrograms a day. Interestingly, plants can grow in the ahsence of cobalt but animals, depending on the plants for vitamin Bn, develop the symptoms of pernicious anemia if the soil is deficient.
Anthropology and Surface Chemistry Illustrating the importance of surface to volume ratio Contribution by William D. Hobey, Worcester Polytechnic Institute A parameter often important in the behavior of particles is the surface-to-volume ratio. Small bubhles in a liquid rise more slowly than large bubbles because the buoyancy varies as the volume while the viscous drag varies as the surface area. Metallic particles, when sufficiently small, may sinter (fuse together) because the surface energy per unit mass, which is decreased by the sintering, is greater for the smaller particles than for larger ones. A larger scale effect of surface to volume ratio, less well known to chemists, appears in the evolution of hody stature of man himself a t extremes of climate.* As an example of this we can compare the shape of a Negro, such as a Dinka or a Nuer from the Nilotic Sudan, with that af an Eskimo from the frozen wastes of Greenland. The typical Nilotic Negro is extremely tall with a straight narrow body and long thin limbs. The average height of a Dinka, for example, is well over six feet, and men of six foot seven or six foot eight are by no means uncommon. Ths Eskimo, by contrast, is extremely short and stocky, and his body is well covered with a layer of fat. One of the properties of these characteristic shapes is that the surface area of the Dinka's skin is very much greater in proportion to his body volume than that of the Eskimo. He is, in fact, designed like a highly efficient radiator which enables the heat of his body to be carried away swiftly and efficientlyinto the surrounding atmasphere. With the Eskimo exactly the reverse is the case. His more or less globular shape conserves his body heat to the fullest eatent, as the radiating surface is proportionately much smaller.
The prototypic Neanderthal who lived in then colder climates 180,000 to 40,000 years ago has a hody build similar to the Eskimo. The tendancy to minimize the surface-to-volume ratio in cold climates is particularly evident in the facial features of the northern (or late) Mongoloids, which include the Eskimoes and the Tungus of Eastern Siberia. Here2 the protuberances are flattened out by a slight recession of the nose, and by a corresponding forward movement of the cheekbones, or 'molars', thus reducing the surface area to a minimum. The browridges are reduced and the region around the eye has became well padded with fat. This fat gives protection to the wlnersble nasal sinuses and, banked up round the eye-balls, reduces the visible part of the eyes to the characteristic Mongoloid slits. This arrangement protects the eyeball from cold and the retina from excessive snow glare. The fatty pads round the nose also help to smooth out the facial contours, and provide additional insulation for the nasal passages so that the air can be warmed to the maximum extent on its way to the lungs.
' Carrington, Richard, "A Million Years of Man," World Publishing Co., Cleveland and New York, 1963, pp. 127-8. Op. eit., pp. 133-4. Volume 51. Number 10. October 1974
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