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 : A new and more comprehensive scheme of qualitative analysis

The scheme of qualitative analysis based on the formation and decomposition of thiosalts has been enlarged by including within it practically all the basic radicles -which are likely to be met with in the analysis of ores and alloys, etc. Besides the rare elements already included in the original scheme rhodium, ruthenium, osmium, palladium, iridium, gallium, indium, rhenium, tantalum, niobium, germanium, scandium and the rare-earths and alkalis have been fitted into the more comprehensive scheme. An outline of procedures for the separation of metals into groups in the more comprehensive scheme of qualitative analysis is given.     

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

A brief outline is given of the new scheme of qualitative analysis for common elements based upon the decomposition of thiosalts.     

The application of thiosalts in analysis : Estimations based on decomposition of thiosalts part e. estimation of antimony in antimonate

1. It has been shown that pentavalent antimony can bo precipitated quantitatively by decomposing its thiosalt with a large excess of 2N hydrochloric acid and weighed as Sb₂S₅ 2. In the case of platinum, 12N hydrochloric acid can be substituted for acetic acid in the decomposition of the thiosalt. 3 Lead can be quantitatively estimated as sulphide by sodium sulphide if ammonium acetate is also added.     

Separations involving sulphides: Separation of zinc from some elements that form thiosalts

It has been shown that 2 N sodium sulphide reagent can be used for separating arsenic, antimony, tellurium, selenium, molybdenum, mercury, gold, platinum or rhenium from zinc.     

The application of thiosalts in analysis : A new scheme of qualitative analysis - part a

1. A new scheme of qualitative analysis for mixtures containing the common as well as the so-called “rare” elements has been discussed. 2. The new scheme is based upon the immediate formation of thiosalts by metals of the arsenic group (and vanadium) on adding concentrated ammonium sulphide solution and the subsequent decomposition of the thiosalts with excess of hydrochloric acid. 3. This scheme has the following advantages over the classical scheme now in use: a. The slow precipitation of the copper and arsenic groups by hydrogen sulphide in hydrochloric acid solution has been replaced by a more simple and rapid method of precipitating the sulphides completely. A considerable saving of time taken in analysis is thus effected. b. The use of the hydrogen sulphide gas which is extremely inconvenient especially in large classes of students, has been eliminated and its place has been taken by concentrated ammonium sulphide—a reagent which can be easily prepared and used as a shelf reagent. c. The use of yellow ammonium sulphide which does not give a satisfactory separation of the copper group from the arsenic group has been eliminated. d. As the main features of the new scheme are similar to those of the classical scheme the student who has been trained in the old technique can take to the new scheme without much difficulty.     

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: Separations of alkaline earth metals from some elements that form thiosalts

It has been shown that 2N sodium sulphide reagent can be used for separating strontium, calcium or magnesium from arsenic, antimony, tellurium, selenium or molybdenum.     

The application of thiosalts in analysis a new scheme of qualitative analysis: Insoluble substances in qualitative analysis

A scheme has been proposed for the systematic detection of compound's in the insoluble residue obtained in qualitative analysis of the common elements.     

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 : Estimations based on decomposition of thiosalts Part A. Estimation of arsenic,selenium and tellurium

1. It has been shown that the complete precipitation of arsenic sulphide (from arsenates) by decomposing the thiosalt provides a, lemarkably convenient and rapid method for its estimation which is in marked contrast to the tedious methods so far available for this purpose. 2. The method of precipitating the sulphide bv decomposing the thiosalt is also applicable to the estimation of tellurium for which no perfectly iclicibic gravimetric method had so far been devised. 3. Selenium also can be estimated gi avimetrically by this method and it provides a convenient alternative to the well-known method based upon I eduction to the metal. 4. The precipitates obtained in the case of arscnic, tellurium, and selenium correspond to the formulae As₂S₅, TeS₂ and SeS₂, respectively.     

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     

Separations involving sulphides : Separation of bismuth,cadmium and indium from various other elements that form thiosalts

It has been shown that 2N sodium sulphide reagent can be successfully used in separating tellurium, molybdenum, antimony or rhenium from bismuth., platinum, gold, selenium, rhenium, arsenic, molybdenum or tellurium from cadmium; platinum, gold, selenium, rhenium, arsenic, molybdenum, tellurium or antimony from indium.It is not possible to separate quantitatively arsenic, platinum, gold or selenium from bismuth; antimony from cadmium; and tin from bismuth, cadmium or indium.     

The application of thiosalts in analysis : A new and more comprehensive scheme of qualitative analysis Analysis of the insoluble residue

Modified procedures have been given to provide for the detection of some additional insoluble substances in the more comprehensive scheme of qualitative analysis.     

Estimation of metals as sulphides: Atmospheric oxidation of alkali sulphides

The atmospheric oxidation of sodium and ammonium sulphide reagents has been studied. It has been shown that if the reagents are prepared by passing hydrogen sulphide from 2–4 minutes in alkali hydroxide solutions at a temperature below 5° C they remain unoxidized for a considerable time, and the sulphide precipitates produced by them in gravimetric analysis are therefore free from sulphur.     

Mechanochemistry of sulphides

At present mechanochemistry of sulphides appears to be a science with a sound theoretical foundation exhibiting a wide range effectiveness in different areas of science and technology. For traditional application mechanochemistry is of exceptional importance in extractive metallurgy of sulphidic ores where many technological processes have been developed. Metal sulphides can be also utilized in emerging nanotechnology with application as advanced luminescence, optoelectronic, magnetic and catalytic materials.     

Seperations involving sulphides : Separation of alkaline earth metals from some elements that form sulphides

It has been shown that 2N sodium sulphide reagent can be used efficiently for separating. 1.Barium from rhenium, platinum, gold, bismuth, palladium, lead or cadmium. 2.Strontium, calcium and magnesium from rhenium, platium, gold, mercury, bismuth, palladium, lead or cadmium     

Reactions of sulphides in molten cryolite

The freezing point depression of cryolite (Na₃AlF₆) by the addition of Al₂S₃ and FeS was investigated. It was found that for contents of up to 10 wt.% Al₂S₃, it brings into the melt three new species. X-ray analysis of solidified melts of the system Na₃AlF₆–Al₂S₃ showed that it contained chiolite, Na₅Al₃F₁₄ and Na₂S. Chiolite originates from a reaction between Na₃AlF₆ and AlF₃. This suggests that the system Na₃AlF₆–Al₂S₃ is a part of the reciprocal system NaF, AlF₃//Na₂S, Al₂S₃. The solubility of FeS in cryolite melt is so low that it cannot be determined by the thermal analysis. When FeO is added to the Na₃AlF₆–Al₂S₃ melt, Fe²⁺ cations and S²⁻ anions react under the formation of solid FeS. A similar reaction was observed for Ni²⁺ and S²⁻ ions.