The crystal structure of Li^Phs has been determined. The face-centered cubic cell contains 80 Pb atoms in space group F23; the cell constant is 20.08 A. The packing of the Li and Pb atoms is analogous to that found for LiPb, LisPb3, Li3Pb and Li7Pb2; these structures resemble the body-centered cubic array present in Li metal, with the appropriate number of Li atoms replaced by Pb.

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The conditions under which electrolytically generated iodine can be used for secondary coulometric titrations and the end point determined by an amperometric method have been investigated. Tripositive arsenic in quantities from 64 to 1200 micrograms has been titrated in solutions having a pH value of 8 with an average error without regard to sign of 0.6 microgram.

The structures of the compounds BasPb a, BaPb, and BaPb a have been determined. BasPb a has the body-centered tetragonal D8~ structure with a =9.038 +_0.010, c = 16.843-+0.017 A; the space group is I4/mcm and there are four formula units per unit cell. The room temperature modification of BaPb has the orthorhombic Bf structure with a =5.29 -+0.01, b= 12.60_+0.02, c =4.78 _+0-01 A; the space group is Cmcm and there are four formula units per unit cell. BaPb a is rhombohedral with a = 9-565 _+ 0.009 A, a = 44 ° 47' + 3'; the space group is R3m and there are three formula units per primitive cell.

The crystal structures of LiaPb and LilPbz have been determined. The LisPb cell is face-centered cubic with a = 6.687 A.; the Li7Pbz cell is hexagonal with a = 4.751 A. and c = 8.589 A. Two other compounds with Li/Pb mole ratios of approximately 2.5 and 4.0 have been characterized by cooling-curve data and by X-ray diffraction patterns. The arrangement of the atoms in LisPb is similar to that in lithium metal with the appropriate number of lithium atoms replaced by lead atoms; LilPbz has a similar but slightly modified arrangement.