Mean Activity Coefficients of KCl in KCl + SrCl2 + H2O Ternary System at 288.15 K Determined by EMF Method.

In this work, the studies of thermodynamic mean activity coefficients of KCl in the KCl-SrCl2-H2O ternary system have been made. A cell without liquid junction battery cell, K-ISE|KCl(mA), SrCl2(mB)|Cl-ISE, was used to study the activity coefficients in this mixed system KCl-SrCl2-H2O at 288.15 K by the electromotive force method. The total ionic strengths ranges are 0.0100-1.0000 mol·kg-1 with different ionic strength fractions yb of SrCl2, that is, yb = (0, 0.2, 0.4, 0.6, and 0.8). The results show that the K-ISE and Cl-ISE have a good Nernst response. Accordingly, the electromotive forces of the mixed system were measured by using the ion selective electrode listed above, and the mean activity coefficients are also determined with Nernst equation. Using the activity coefficient data, the mixed ion interaction parameters θK,Sr and ψK,Sr,Cl of Pitzer equations at 288.15 K were fitted by Matlab with linear regression method, respectively. Furthermore, those parameters were applied to calculate the values of the mean activity coefficients of SrCl2. Finally, the osmotic coefficients, water activity, and the excess Gibbs free energy of this system were evaluated by Pitzer's equations.

[Determination of Iodine and Iodate in Brine and Seafood Simultaneously by Ultraviolet Absorption Spectrometry].

The iodide in samples was oxidized to iodate by bromine water, which could be removed by formic acid, and iodate could be transformed to I3- with excess of I- in phosphoric acid, the iodate in samples could be transformed directly to I3- with excess of I- in phosphoric acid. The I3- solution had strong absorption at 350 and 288 nm, and the absorbance had a linear relationship to the concentration of I3- in a certain range. Total content of iodide and iodate had been detected after samples were oxidized by bromine water and the content of iodate had been detected directly, and the content of iodide was obtained by difference of the two results. Based on this, the method had been established to detect iodide and iodate in brine and seafood simultaneously by ultraviolet absorption spectrometry. The volumes of bromine water, formic acid, phosphoric acid and potassium iodide had been optimized. The effect of illumination, temperature and time also had been discussed. The optional reagents condition for iodide was: 2 drops of 3% bromine water, 0.5 mL of 10% formic acid, 4 mL of 20% phosphoric acid and 1 mL of 100 g x L(-1 KI. The optional reagents condition for iodate was: 0. 2 mL of 20% phosphoric acid and 1 mL of 100 g x L(-1) KI. The absorbance were determined after reacting for 30 min at room temperature and natural light conditions. Under the optimized conditions, the concentration of iodide and iodate in the range of 0 - 1.2 and 0 -1.5 mg x L(-1) were well agreed with Lambert Beer law. The sample blank was detected for twelve times and the detection limit of iodide and iodate were 1.54 and 14.8 µg x L(-1) respectively. The RSD of twelve times determination of 0.8 mg x L(-1) of iodide and iodate were 0.097% and 0.067%, respectively. The iodide and iodate in Zhabuye brine, Hong Feng underground brine, kelp, seaweed and sea cabbage had been detected, the recovery experiments also had been conducted at the same time, the recovery of iodide and iodate were between 80% - 120%. All the results met the requirement of analytical chemistry.

[Pretreatment of Aluminum-Lithium Alloy Sample and Determination of Argentum and Lithium by Spectral Analysis].

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Flame Atomic Absorption Spectrometry (FAAS) and Visible Spectrometry (VS) was applied for determination of Ag and Li in lithium-aluminium alloy standard sample and test sample, their respective advantages and disadvantages were compared, the excellent selectivity of ICP-OES was confirmed by analyses of certified standard sample. Three different sample digestion methods were compared and discussed in this study. It was found that the better accuracy would be obtained by digesting sample with chloroazotic acid while the content of Li was measured by FAAS, and it was better to digest sample with hydrochloric acid and hydrogen peroxide while determining Ag and Li by ICP-OES simultaneously and determining Ag by FAAS and VS. The interference of co-existing elements and elimination methods was detailedly discussed. Ammonium hydroxide was added to adjust the sample solution into alkalescent and Al, Ti, Zr was precipitated by forming hydroxide precipitation, Mg and Cu was formed complex precipitation with 8-hydroxyquinoline in this condition, then the interference from matrix element to determinate Ag by FAAS was eliminated. In addition, phosphate was used to precipitate Ti to eliminate its interference for determination of Li by FAAS. The same treatment of determination for Ag by FAAS was used to eliminate the interference of matrix element for determination of Ag by VS, the excess of nitrate was added into sample and heated to release Ag+ from silver chloride complex, and the color of 8-hydroxyquinoline was eliminated because of decomposed by heating. The accuracy of analysis result for standard sample was conspicuously improved which confirms the efficient of the method to eliminate interference in this study. The optimal digestion method and eliminate interference method was applied to lithium-aluminium alloy samples. The recovery of samples was from 100.39% to 103.01% by ICP-OES determination for Ag, and from 100.42% to 103.01% by ICP-OES determination for Li. The recovery ranged from 95.91% to 99.98% by FAAS determination for Ag, and ranged from 98.04% to 99.98% for FAAS determination of Li. The recovery was from 98.00% to 101.00 by VS determination for Ag, the analysis results all meet the analysis requirement.