Corrosion of lead cable sheathing is of considerable importance to the electric and communication industries. When corrosion is encountered in an underground sheath, it may be of assistance, in combating the phenomenon, to know those limiting conditions under which the particular corrosion product can be formed. The authors studied the conditions of voltage and electrolyte composition under which the tetragonal or red modification of lead monoxide is formed at room temperature. The twenty-six solutes investigated are grouped into five classes according to the nature of the corrosion. Low salt concentration, voltage below 1.0 volt, and low solubility of the lead salt of the corroding anion are found to favor red lead monoxide formation.

This difference in volatility is in the same direction as the difference in carbon formation in the coaches for the two oils and perhaps of the same order of magnitude.The three factors listed earlier in the discussion as influencing the carbon residue test almost undoubtedly are those most