Jacob Block

Interference of the ammoniiun ion in Mohr's method for the determination of chloride

The ammonium ion has been found to interfere in the Mohr method for the determination of chloride.

On the use of X-ray powder diffraction for determining low levels of chrysotile asbestos in gypsum-based bulk materials: use of a synchrotron source

Abstract The use of synchrotron X-ray powder diffraction for the quantitative analysis of very low levels (0.25–3.5wt%) of chrysotile asbestos in bulk samples is examined. A study of chrysotile in a pure alumina matrix indicates that the detection limit is ca. 0.1wt% and the quantification limit ca. 0.2wt%. A second study using a more complex matrix, chrysotile in a gypsumvermiculite mixture, indicates a quantification limit between ca. 0.25 and 0.5wt% for dehydrated samples. The sensitivity of the method can be increased if appropriate chemical pre-treatments using sodium ethylenediamminetetraacetate (EDTA) are performed to remove the gypsum, which is the major component of the mixture. A study of the EDTA treated materials shows no change in the chrysotile and confirms the use of this procedure.

Preparation of orthorhombic YBa2Cu3O7−δ by spray-drying formate solutions

Abstract A simple, low cost process has been developed for the preparation of orthorhombic YBa2Cu3O7−δ superconducting powder by spray-drying formate solutions. Yttrium oxide, cupric oxide and barium carbonate are dissolved in formic acid and spray-dried. The spray-dried powder is “charred” at 95°C prior to calcination to avoid undesirable melting and/or dissolution. The charred powder is calcined to produce phase-pure, superconducting YBa2Cu3O7−δ product. Superconducting powder can also be prepared from acetate solutions.

Magnesium scales from seawater distillation

Abstract Seawater evaporation tests were run in the presence of typical distillation plant corrosion products, such as Fe, Ca and Ni. It was assumed that scales formed in this environment are more typical of the “real world” than scales formed under conditions with little or no corrosion taking place. Two types of tests were run, beaker tests using seawater and metal coupons, and flow tests using seawater and Cu-Ni tubing. By reducing the total alkalinity to less than 80 ppm, we were able to eliminate the formation of aragonite, and concentrate on the identification of the lesser known magnesium scales. Using X-ray diffraction spectroscopy, two different magnesium scales were identified. One, as expected, was brucite [Mg(OH)2], which was obtained under conditions of high temperature (110–120°C) and little or no residual CO2 in the brine. The other scale identified was iowaite [4Mg(OH)2·FeOCl·H2O], which was obtained at lower temperatures (100–110°C) and at higher residual CO2 in the brine. No evidence was found for the formation of hydromagnesite [3Mg(OH)2·MgCO3·3H2o], a scale previously proposed by other investigators. Tests with commercially available, threshold agent, Darex 41, tend to confirm the existence of two distinct Mg scales, since no threshold effect was observed for Mg(OH)2 formation, but a threshold effect was observed for the Mg scale formed at lower temperatures, i.e., iowaite.

Effect of iron and copper during scale suppression by threshold compounds

Abstract When a plant is run on threshold agents of the polyacrylic type, the resultant high brine pH can cause iron, if present, to precipitate on heat transfer surfaces as Ca(Mg 0.67 Fe 0.33 )(CO 3 ) 2 (ferroan dolomite), or as Mg 6 FeCO 3 (OH) 13 ·4H 2 O (brugnatellite). Both deposits severely inhibit heat transfer. The soluble iron contributing to these formations can be complexed by adding agents such as the phenol-substituted ethylenediamine diacetic acids. Above concentrations of 0.2 to 0.4 ppm, copper will precipitate the polymers onto heat transfer surfaces; this too can be alleviated by chelating agents. Such treatment can be costly, but fortunately only temporary where the metal ions emanate from the internal corrosion associated with acid treatment. Supersaturation of calcium carbonate and magnesium hydroxide by threshold agents will raise brine recycle pH to more than 9, eliminate carbonic acid attack and thus drastically reduce corrosion rates of copper and ferrous alloys in one to two days. Thus, the principal objective of such specific metal treatment is to “hold off” the negative effects of dissolved metals until corrosion subsides in the brine circuit.