Thin-Layer Chromatographic Detection of Phosphorothionate and Phosphorothiolothionate Pesticides Using 4-Amino-N,N-Diethylaniline

A thin-layer chromatographic method using a novel chromogenic reagent was developed to detect the phosphorothionate and phosphorothiolothionate groups of pesticides. On reaction with 4-am'mo-N,N-diethylaniline and subsequent exposure to bromine vapor, these compounds yield a deep magenta product. The chromogenic reagent is specific to these organophosphates and gives no response to phosphorothiolates and substituted phosphonates. The method is rapid and highly sensitive. The limit of detection is 0.05-0.5 μg.

Nickel-coated carbon fiber-reinforced tin-lead alloy composites

Nickel is deposited over pristine, surface-treated, and brominated P-100 carbon fibers using cementation and electroplating techniques. The fibers are brominated by bromine vapor for 48 h and then desorbed at 200 °C in air for 12 h. The anodic oxidation treatment is performed by etching fibers electrochemically in a dilute sodium electrolyte for 3 min or by immersing fibers in nitric acid for 72 h. Electroplated-coated fibers show better tensile properties than cementation-coated fibers. Tin-lead alloy composites reinforced by nickel-coated fibers (which are pristine, anodically oxidized, and brominated) are fabricated by squeeze casting. The composites containing coated carbon fibers with bromination or surface treatment have higher tensile and shear strength than the ones containing coated pristine carbon fibers. In addition, the composite containing coated carbon fibers with brominalion shows the best performance in the tensile properties.

Single Crystal X-Ray Diffraction Study of the Phase Transitions in Graphite-Bromine Intercalation Compounds

ABSTRACTReported here is the first observation of an incommensurate-commensurate phase transition at 316 ± 1 K upon heating stage-2 graphite-bromine prepared in bromine liquid. The transition during heating involved the movement of the 300 reflection toward a lower q value and the sharpening of the 010 reflection, thereby resulting in the commensurate structure characteristic of stage-2 prepared in bromine vapor. The transition was reversible. The previously reported comtmensurate-incommensurate transition occurred at 326, 329, 332, 338 and 348 K for stage 2 (in bromine liquid), stage 2 (in bromine vapor), stage 3, stage 4, and desorbed material, respectively. Disordering was observed upon completion of this transition.