NATURE August 3, 1957 Vol

250 NATURE August 3, 1957 voL. 1ao

absence of any change in the slight influence of a hypoiodous acid and iodide in equal amounts. (The nearby ionizing electron discharge upon the speed hypoiodous acid and iodide take part in an equili• of pumping of the carbon monoxide {condensation brium to give a trace of iodine which is volatile.) coefficient), suggests that the gas molecules (neutral (3) The ratio of total iodine/chloride is higher in or ionized) are not taken up directly by the barium, warm, partly enclosed sea areas•. This is to be ex• but are first dissociated into oxygen and carbon. pected from the effect of temperature upon the Thus the reaction is one of oxidation in the presence equilibria mentioned in (1) and (2) 2, which results of carbon, and so the qualitative similarity between in a. marked increase in the content of volatile iodine the behaviour of barium towards oxygen and carbon molecules when sea water is cooled. monoxide is to be expected. Whereas the hypothesis accounts for these findings, In some details, there are important differences it should be noted that iodate and not hypoiodous between the reactions in the two cases. In the case acid would be the thermodynamically stable form of of oxygen, it was found• that the first monolayer of oxidized iodine in the sea. However, it seems likely o1'-ygen was only taken up if there were nucleation that the rate of iodate formation from hypoiodous centres in the surface of the barium film. Ordinarily, acid, a third-order reaction in near-neutral solution', such centres always exist in the surface of getter will be slow at the very low hypoiodous acid con• films deposited in a fraction of a minute and at centrations in sea water. Together with assimilation pressures greater than 10-• mm. of mercury. More• by powerfully reducing biological material this factor over, during the adsorption of the first monolayer will t end to prevent iodat e accumulating in the sea. of oxygen the speed of pumping increased. In the On the basis of the hypothesis, and given the case of carbon monoxide, the speed of pumping has necessary thermodynamic data, it should be possible been found always to decrease during the adsorption to predict the final oxidation states of marine of the first monolayer. Furthermore, no nucleation materials which undergo rapid oxidation-reduction centres are necessary. Once the first monolayer of reactions with iodide and hypoiodous acid or carbon monoxide has been absorbed, then the film iodine. of reaction products grows in a manner which can This work and the relevant calculations will be be explained with the aid of Mott's theory. presented in greater detail elsewhere. A fuller account of this work is being submitted T. I. SHAW for publication elsewhere. L. H. N. COOPER I wish to thank Mr. B. M. Cox for help with the Marine Biological Association of the United Kingdom, experimental work, Mr. M. E. Haine for helpful The Laboratory, criticism, and Dr. T . E. Allibone, director of the Plymouth. Research Laboratory, Associated Electrical Industries, April 18. Ltd., for permission to publish this communication. ' Sugawara, K., ]'aper read a t t he Regional Symposium on Physical R. N. BLOOMER Oceanography, Tokyo (October 1955). Research ' "Internationa l Critical Tables", 1st edit. (1926-33). Laboratory, ' Fellenberg, Th. Y .• Biochern. Z . , 152, 132 (1924). Associated Electrical Industries, Ltd., ·• lleyrnann, J. A., Nerl. TijdscM. Genee.,k., 1, 640 (1 927 ). Aldermaston, Berkshire. 'Reith, J. 1!' ., Rec. Trav. Chim. Pays-Bas., 49, 142 (1930). April 23. 'Skrabttl. A., Mh. Chem., 72, 223 11939).

' Smi thclls. C.. r., and Ransley, C. E., Proc. Roy. Soc., A, 155, 195 (1936). ' Wagener, S., Vacuwn, 3, 11 (1953). Colorimetric Estimation of Manganese 'Morrison, ,T., and Zcttcrstrom, R. B., J. App. Phys .• 26,437 (1955). • della Porta, P., Vacuum, 4, 284 (1954) (published Feb. 1957). TETRAMETHYLDIAMINODIPHENYLMETHANE ( 'tetra• 'llloomer, R. N. Nature, 179, 493 (1957). base') has been widely used for the colorimetric • llloomer, R. N., Brit. J. App. Phys. (in the p ress). estimation of quantities of manganese of the order of 'Mott, N. F., Trans. Farad. Soc., 43, 429 (1947). 0·01-0·1 µgm. 1-4. As generally applied, the test 'llloomer, R. N., Brit. J . ,!pp. Phys., 8, 40 (1957). involves the addition of t etrabase and potassium periodate in excess to a sodium acetate-acetic acid State of Iodine in Sea Water buffer containing manganese in solution. The in• tensity of the transient blue colour1-•--or more WATER from the upper layers of the ocean contains permanent green4--so produced is closely related to some 40 µgm./1. of iodine compounds. Sugawara1 has the concentration of manganese. The nature of the shown that about half this is iodide, while the reaction or of its end-products does not appear to remainder is an oxidized form, which he attributes to have been elucidated, although it is known that iodate. We find that various observations are more manganese hydroxide reacts with tetrabase to pro• readily explained on the hypothesis that the oxidized duce a blue colour•, and it has been suggested that form is principally hypoiodous acid. in the presence of periodate, manganese acts as a 3 (1) The ratio of oxidized form/iodide is about catalyst in the oxidation of tetrabase • unity1• Calculation from thermodynamic data• shows In a preliminary study of the reaction it has been this to be close to the ratio that would obtain between found that permanganate and hydrated manganese hypoiodous acid and iodide when in equilibrium with dioxide are equally effective in the production of the atmospheric oxygen, water and hydrogen ions at the blue colour in the absence of other oxidizing agents. pH of sea water. (2) It has been observed that sea The concentration of manganese necessary to produce water exposed to iodine-free air loses its iodine com• unit increase in colour intensity under these condi• pounds•; moreover, the iodine content of the tions is, however, 30-40 times greater than when 4 atmosphere near the sea rises to 1-2 µgm./m. 3• periodate is present. When manganese and periodate Data upon the relevant free energies2 show that this are present in excess, the molar concentration of is about the value to be expected if air is equilibrated tetrabase required to produce the same unit increase with sea water containing its iodine principally as in intensity is approximately twice that of perman-