Estimation of metals as sulphides : Estimation of bismuth,cadmium, lead,and indium

1. It has been shown, that under proper conditions bismuth, cadmium, lead and indium can be precipitated quantitatively as pure sulphides by alkali sulphides and the precipitate weighed directly for the estimation of the motal. 2. In the case of bismuth ammonium sulphide gives a pure precipitate of Bi₂0₃ which is washed with hot water and weighed directly. 3. In the case of cadmium sodium sulphide gives a pure orange coloured precipitate of the Bulphide which is washed with water and without any further treatment, weighed as CdS. 4. In the case of lead the solution is treated with alkali sulphide, the mixture is then acidified with. acetic acid and the pure precipitate of PbS after washing with water weighed directly without heating. 5. In the case of indium treatment with ammonium sulphide gives a pure precipitate of In₂S₃ which after washing and heating can be weighed directly for the estimation of the metal. Equally good results are obtained if the mixture is acidified with acetic acid after treatment with ammonium sulphide. 6. The given procedures provide for a convenient, quick and accurate estimation of the metals.     

Artificial intelligence–based models for the qualitative and quantitative prediction of a phytochemical compound using HPLC method

Isoquercitrin is a flavonoid chemical compound that can be extracted from different plant species such as Mangifera indica (mango), Rheum nobile , Annona squamosal , Camellia sinensis (tea), and coriander ( Coriandrum sativum L.). It possesses various biological activities such as the prevention of thromboembolism and has anticancer, antiinflammatory, and antifatigue activities. Therefore, there is a critical need to elucidate and predict the qualitative and quantitative properties of this phytochemical compound using the high performance liquid chromatography (HPLC) technique. In this paper, three different nonlinear models including artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine (SVM),in addition to a classical linear model [multilinear regression analysis (MLR)], were used for the prediction of the retention time (tR) and peak area (PA) for isoquercitrin using HPLC. The simulation uses concentration of the standard, composition of the mobile phases (MP-A and MP-B), and pH as the corresponding input variables. The performance efficiency of the models was evaluated using relative mean square error (RMSE), mean square error (MSE), determination coefficient (DC), and correlation coefficient (CC). The obtained results demonstrated that all four models are capable of predicting the qualitative and quantitative properties of the bioactive compound. A predictive comparison of the models showed that M3 had the highest prediction accuracy among the three models. Further evaluation of the results showed that ANFIS–M3 outperformed the other models and serves as the best model for the prediction of PA. On the other hand, ANN–M3proved its merit and emerged as the best model for tR simulation. The overall predictive accuracy of the best models showed them to be reliable tools for both qualitative and quantitative determination.     

A systematic scheme of qualitative analysis for anions. III

The completeness of precipitation of anions and basic radicals by the two group reagents, zinc acetate and cadmium nitrate, has been investigated. It has been shown that the two reagents precipitate many of the anions quantitatively and can thus be used for their gravimetric estimation.     

Thermolysis of sulphides precipitated by sodium sulphide : Sulphides of arsenic,mercury, rhenium,antimony and molybdenum

Thermolysis of the sulphides precipitated by sodium sulphide for direct determination in gravimetric analysis has been studied. It has been shown that the methods used for diying and weighing the precipitated sulphides of arsenic, mercury, rhenium, antimony and molybdenum are reliable.     

The application of thiosalts in analysis : Complete precipitation of sulphides

1. A new method of precipitating completely and quickly molybdenum, platinum and arsenic (in arsenates) as sulphide', has been described. 2. The new method is based upon the immediate formation of thiosalts of these metals by adding concentrated ammonium sulphide and the subsequent decomposition of the thiosalt by adding excess of hydrochloric acid. 3. The great usefulness of the method in qualitative analysis lies not only in the completeness of precipitation of the metals but also in the remarkable saving in the time taken to precipitate the metals. 4. It has been shown that the method is applicable also to till the other metals of the arsenic group. 5. Selenium which is precipitated by decomposing the thiosalt is easily soluble in ammonium sulphide while the selenium precipitate from a hot acid solution is generally in a form which is insoluble. 6. Vanadium can be precipitated completely with the arsenic group by this method if it is previously treated with hydrogen peroxide. 7. The use of the hydrogen sulphide gas has been replaced by a far more convenient reagent-concentrated ammonium sulphide.     

The application of thiosalts in analysis : Estimations based on decomposition of thiosalts part B. estimation of molybdenum and tin

1. It has been shown that molybdenum can be precipitated quantitatively by adding excess of concentrated ammonium sulphide to a molybdate solution and then decomposing the thiosalt with excess of hydrochloric acid. 2. The weight of the precipitate corresponds to the formula MoS₃.2H₂O and the quantity of metal can be estimated by multiplying the weight of the precipitate by a constant factor. 3. The same method is also applicable to the gravimetric estimation of tin. The precipitate of stannic sulphide is easily filterable and its weight corresponds to the formula SnS₂.2H₂O. 4. The general method in its simple form has not been found to be applicable to vanadium, platinum and gold.     

The application of thiosalts in analysis : Estimations based on decomposition of thiosalts Part C. Estimation of gold,platinum and antimony

The general method of forming and then decomposing the thiosalts has been applied to the gravimetric estimation of gold, platinum and antimony. In the case of gold and antimony the metals are weighed as Au₂S₃ and Sb₂S₃ respectively, while in the case of platinum, the precipitate of platinum sulphide is ignited and weighed as metal.     

The application of thiosalts in analysis: A new scheme of qualitative analysis - Part C

1. Seveial modifications for improving the efficiency of the new scheme of qualitative analysis have been proposed. 2. It has been shown that 1N sodium sulphide is a more efficient and convenient reagent and may be substituted for concentrated ammonium sulphide. 3. If sodium carbonate is added along with sodium, sulphide, barium, strontium and calcium are precipitated completely with the sulphides and hydroxides and the division of these metals into two groups is prevented. 4. It has been shown that the tedious separation of cerium and thorium from the iron group by means of oxalic acid is unnecessary and these metals can be tested for conveniently with the metals of the iron group. 5. The division of thallium into the iron and copper groups can be avoided and the metal precipitated completely with the copper group by adding potassium iodide in the treatment with 1N hydrochloric acid. 6. Modified procedures liave been provided tor the detection of nickel, tellurium and gold.     

Separations involving sulphides : Separation of thorium or titanium from some elements that form thiosalts

Sodium sulphide can be used to separate arsenic, antimony, tellurium, selenium, molybdenum, mercury, gold, platinum or rhenium from thorium and antimony, tellurium, selenium or mercury from titanium