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the positions of several anomalous spectral lines. In 1875 de Boisbaudran^ reported the actual separation of a small quantity of the element. Its physical properties were found to be very close to those predicted by Mendel eeff. The new element was named after the country in which it was discovered-Gaul (France). Gallium is dis-3 6 tributed widely, * although in very small amounts (never (6) E. Einecke, "Das Gallium," Leipzig, Verlag von Leopold Voss, 1937. more than 0 .01$ in any material) over the whole of the earth's crust. It occurs in greatest concentration associated with the ores of aluminum, zinc and germanium. Pure, solid gallium is silvery white in appearance, and, on melting at 29.75°C., is very similar to liquid mercury. Gallium has a strong tendency to wet materials such as glass. Its very great alloying ability^*^ causes (7) Atomic Energy Commission, "Liquid Metals Hand book," Washington Govt. Printing Office, 1950.

0.061 ± 0.001 cm sec™1 with a transfer coefficient of 0.27. Note that the rate constant in this case does not change for a given potential step since the current and therefore the effective potential were almost constant during the time in which currents were measured. Each point on the plot represents one experiment.Attempts were also made to determine kinetic parameters for reduction of Cd(II) in 1.0M KNO3, Cd(II) in 1.0M KC1, and Co(III) tris(ethylenediamine) in 0.1M ethylenediamine/l.OM NaClO*. All three systems proved to have rate constants too large to be measured under the conditions of our experiments. As noted above, the shortest time at which meaningful data could be taken was 30 µ sec. For times of this order, the largest rate constant which could be determined, that is distinguished from diffusion control, is 0.8 cm sec™1. This lower limit of 0.8 cm sec™1 may be compared to the range of 0.6 to 5.0 cm sec™1 found by ac impedance methods for Cd(II) in nitrate and chloride media (11). Laitinen and Randles reported a rate constant of 0.13 cm sec™1 for Co(III) trisfethylenediamine) (12); however, Sluyters-Rehback and Sluyters demonstrated that the reduction of the similar system Co(III) in diethylenetriamine is diffusion controlled though complicated by adsorption of the cobalt complex (13).

Where Ha1.2.3. Hb1.2.3, and H c 1 . 2 , 3 are the heats of reaction of compounds a, b and c with reagents 1, 2, 3 (kcal/mole), respectively, Ma, Mb and M , are the molar concentrations of compounds a, b and c in sample (mmole/ml). AT1, AT,, and AT, are the measured temperature increases obtained with reagents 1, 2 and 3 ("C). Cl, Cz, and Cs are constants comprising the thermal capacity of the system (K equals the product of the density and the specific heat of the sample at the operating temperature) and the flow rates of the sample (Fs) and the three reagents (F,), It is assumed that this ratio is kept constant for each of the three reaction cells. Fs + F,These equations can be solved for Ma, M,, and M,, the concentrations in the sample of the three impurities. The arithmetical work involved in the solution of the equations involves considerable effort, especially if frequent analysis is required, and in these circumstances it would be advisable to arrange for the calculations to be handled by means of a data link to a computer.The principles of CFTA should have other applications in on-line analysis of organic or aqueous liquid streams and possibly, with suitable modifications in cell design, of gas streams. Choice of suitable reagents would make it possible to determine different types of impurities or added substances in sample streams. The reagent might be specific for a particular component of the sample or, as in this paper, a nonspecific reagent might be used which determines the total of various impurities present in the sample.The principles of CFTA might well find applications in the monitoring of effluents from liquid column chromatographs using a stream splitting device to isolate a portion of the total effluent for reagent addition. With suitable modifications the technique might also be applicable as a gas chromatographic detector. ACKNOWLEDGMENTSThe authors thank A. G. Barclay for his assistance in the early stages of the mechanical and electrical design of the instrument and B. W. Heys, D. I. Walmsley, and Miss V. M.Overend for their assistance during the development of the instrument.Investigation of the SCN-.catalyzed ac and dc polarography of gallium in strong acid media has been extended to ascertain the separate effects on the Ga(lll) reduction process of (a) ionic strength; (b) thiocyanate concentration; (c) added halide; (d) pH; and (e) changing Ga(lll) concentration. Results(a) through (c) intimated that reversible reduction may occur via anionic gallium [probably Ga(SCN)*-1 rathe! than cationic, and results obtained in (d) were not inconsistent with this notion. A subsequent anion exchange study using the C104-form of Dowex 1-X8 indeed verified that anionic Ga(lll) could be present in the SCNcontaining 6.OM NaC104 test solutions. Variation of corrected dc diffusion current vs. Ga concentration was linear over the range 0.01 m M to 5.0 m M Ga(lll) which enabled direct polarographic measurement of Ga(lll) down to the 1.0-ppm level. The Ga(lll) diffusion coefficient, DGa, was calculated to...

Constant current studies at the mercury pool electrode have yielded reversible cathodic-anodic chronopotentiograms for the gallium(mercury)-