The amount of magnesium in the skeletal calcite of the encrusting marine red alga Clathromorphum compactum varies seasonally in response to changes in water temperature. X-ray diffraction analyses of serial samples of this alga collected in the Gulf of Maine indicate more than a 40-percent change in composition during a year and demonstrate a more rapid calcification during warmer periods.Marine organisms deposit skeletal parts composed of a wide variety of mineral forms. Among the carbonatesecreting groups, the minerals calcite, aragonite, and a variety of magnesium calcites (1) are common (2, 3). Green algae deposit aragonite exclusively. Red algae deposit both aragonite and magnesium calcites, the latter containing up to 30 mole percent magnesium, calculated as MgCO3, in solid solution in the calcite (1).The coccolithophores deposit a calcite very low in magnesium.Clarke and Wheeler (4) and Chave (2) have shown that in calcite-secreting groups of marine organisms, the magnesium content of the whole calcitic tests increases almost linearly with water temperature over the range 0? to 30?C. Thus tropical forms of a given taxon have a higher magnesium content than their boreal counterparts. During an attempt to determine the rate of growth and calcification in an individual encrustation of the red alga Clathromorphum compactum, we found that seasonal changes in the magnesium content of the skeletal calcite could be detected.Because of the small radius of the symposium on Assessment of Radioactive Body Burdens in Man, Heidelberg, Germany, 11-16 May 1964 (International Atomic Energy Agency, in press). 4. J. Miettinen, ibid. 5. R. W. Perkins and J. M. Nielsen, Hanford Doc. No. HW-SA-3487. 6. We thank the PHS for the use of hospital facilities at Kotzebue, and M. C. Brewer, director of the Arctic Research Laboratory, for assisting in providing transportation and facilities in northern Alaska.Abstract. The amount of magnesium in the skeletal calcite of the encrusting marine red alga Clathromorphum compactum varies seasonally in response to changes in water temperature. X-ray diffraction analyses of serial samples of this alga collected in the Gulf of Maine indicate more than a 40-percent change in composition during a year and demonstrate a more rapid calcification during warmer periods.

Accurate determinations of the elemental composition of coal by classical methods can be quite difficult and are normally very time consuming. X-ray fluorescence utilizing the powder method, however, has the ability of providing accurate and rapid analyses. Unfortunately, well characterized standards, although available, are not plentiful. In addition, the durability or stability of ground and pelletized coal samples is poor resulting in deterioration with time. As a result, artificial coal standards were prepared from certified geological materials by fusing in lithium-tetra-borate in percentages approximating expected ash contents and compositions in coal. Since the lithium-tetra-borate comprises about the same percentage of the standard as does the carbon, hydrogen, and oxygen in coal, the ground and pelletized coal sample can be assayed against the fused calibration curves by compensating for the differences in the mass absorption coefficients of the two matrices.

Recent developments in analytical techniques and software have allowed the accurate quantitative determinations of both the major and minor elements in stainless steels by energy dispersive x-ray fluorescence. The successful analysis of 300 and 400 series stainless steel is reported utilizing this technique. The analysis of this type of material represents one of the most severe tests of the method due to numerous peak overlaps and interelement effects such as absorption and enhancement.Sixteen standards of ASTM 300 series and ten 400 series were prepared by polishing on a 220 grit aluminum oxide belt and subsequently washing the surface in absolute methanol. Analyses were performed with an EG&G ORTEC 6110 Tube Excited Fluorescence Analyzer utilizing a dual anode (Rh/W) x-ray tube. Peak deconvolutions and interelement corrections were made with a 16K PDP-11/05 computer utilizing the program FLINT (1). Utilization of spectral deconvolutions and interelement corrections yields a relative accuracy of approximately IX of the concentrations of the major elements.

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A rapid multielement analysis procedure for cement and ceramic type materials has been developed which uses pelletized powders and an exponential correction to the observed x-ray intensities. Only the more significant interactions are considered in an iterative process requiring a minimum of standards. The interaction coefficients are determined by a nonlinear multiple least squares fit of the standards. Average deviations obtained for the analysis of light elements in cement ranged from a low of 0.006% for K2O to a high of 0.13% absolute for SiO2.