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THE relation between the properties of electric logs and the fluid used in drilling a well is briefly discussed in this paper, and the fact that the resistivity of the drilling mud and its filtrate can appreciably affect such logs is shown.Apparatus was designed and a procedure established to determine the effect of various factors on the resistivity of drilling mud. Five muds commonly employed in California were tested and the following observations were made:1. The effect of raising the temperature from 80°F. to 180°F. is to decrease the resistivity of the mud or filtrate approximately SO per cent.2. The resistivity of the mud in most cases closely approximates that of its filtrate.3. The change in the resistivities of muds caused by ithe:addition of chemical is not the same function of the amount of chemical added for each mud.4. The effect produced by increased sodium chloride content is to reduce markedly the resistivity of the mud and its filtrate.5. Weighting materials, such as Baroid and limestone, tend to increase the resistivity of drilling mud.6. Cement and counteracting reagents reduce mud resistivity.

The Raman spectrum of AsF3 was found to consist of four lines with the frequencies ω1(1), 707; ω2(1), 341; ω3(2), 644; and ω4(2), 274 cm—1. The selection rules require a pyramidal molecule. Electron diffraction data for AsF3, AsCl3 and PCl3 are used to establish the bond angles. The entropies of the three trihalides were calculated, and the standard free energies of formation of AsCl3(l) and AsCl3(g) were determined to be —65,190 cal. and —62,718 cal., respectively, at 25°.