Determination of Elemental Sulfur from S-Rich Soil and Fertilizer by Titrimetric Method

In the present study the emphasis was given on two points, one is find out the effective extractants solvent and another is method of determination. Importance also was given on extraction ratio between solvent used as extractants and the amount used or dilution of the sample, shaking time and the incubation period on the basis of which after shaking how much time is required for settle down the solution just before titration/determination. The better result was obtained in 45 minutes to one hour after extraction was completed. Among three extractants, determination of elemental sulfur (ES), acetone can be used as an effective extractant for both S-rich fertilizer and soil sample (% recovery values obtained were 99.0 and 97.0% respectively). On the contrary, the % recoveries with toluene and xylene the values obtained from S-rich fertilizer and S-rich soils were 97.0 and 93.0 and 92.0 and 87.0% respectively. Determination was done with titrimetric method. Colorimetric always time consuming, values obtained with spectrophotometer is sometimes variable and expensive due to using of power supply. In titrimetric method where a high degree of accuracy and precision is not required. It is rapid and suitable for routine analysis in laboratories without using specialized equipment. temperature greater than 25°C has reported to show lower recoveries of ES [5]. According to Ref. [3] 5 minutes are adequate for the removal of ES from soil with acetone, but Ref. [6] have suggested that complete extraction of sulfur was achieved only after 3 hour. But in solubility tests approximately 45 minutes were required to dissolve pure sulfur in acetone. Amount of soil used varied between 0.2 and 0.1 g (ovendry weight basis), depending on the expected ES concentration. The minimum extraction ratio between extractants and the sample should be 100:1 or depending on sample containing more than 50% of ES (then ratio should be 175:1). ES in soils is generally determine only those soils having ES less than 100 mg Kg-1 and sulfur concentration in excess of 50000 mg Kg-1 could be measured. Lower ratios produced excessive color interference even with the use of a color blank. Increasing the extractant to soil ratio did not affect the recovery of ES. ES of soil In the present inquisition 0.2 g sample was mixed to the 20 ml of each extractant, i.e., acetone, toluene and xylene at the ratio of 1:100. The solution was shaken thoroughly on suitable shaking machine for 45 minutes to 1 hour and allowed to stand for overnight. Then the solution was filtered through Whatman no.44. Now 2 ml of aliquot was taken in 50 ml white porcelain basin, 2 ml of Potassium cyanide (KCN, 0.1M: 0.6519 g/100 ml) was added to the sample solution to give thiocyanide which was then titrated with 0.025M AgNO3 (4.2467 g/L) in presence of 2 ml of 0.33 M formalaldehyde (1 ml of Conc.HCOH/100 ml) to bind residual cyanide ions.. For this reason same amount of KCN was added in the solution as to the amount of aliquot in the procedure to Chemical Sciences Journal C h em ica l Sciences Jurna l


Introduction
Elemental sulfur (E S ) is employed to produce acidity in the soil and as well as reclaim alkaline lands and as a fertilizer for crops. One pound of sulfur added to the agricultural land will makes three pounds of sulfuric acid. On the other hands, one part of sulfur being equal to five parts of gypsum in reclamation. Early attempts at analyzing soils and fertilizer for sulfur content were confined to the determination of sulfate ions, later total sulfur were made and organic sulfur was reported as the difference between total and sulfate ions. For elemental sulfur determination of fertilizer very few works has been reported although so many procedures have been developed for the soil related methods.

Elemental sulfur (E S ) from soil
So many methods have been prepared by different analyst in different time extraction methods based on using different type of organic solvent (without considering whether it is costly or volatile) in different ratio between the extractants and the amount of sample to be used for bringing E S in solution with shaking period in various incubation time and the method of evaluation (colorimetric or titrimetric) is very important for this determination. E S can be extracted from soils with acetone, ether, pyridine, with steam of distillate with chloroform; Schoenberg reagent, Ref. [1] isolated free sulfur from soil with steam and extracted the distillate with chloroform. In Ref. [2,3] used a modification of Morris method to determine E S that is based upon the reaction of sulfur with sodium sulphite to give thiosulfate. The determination of E S in acetone extracts originally prepared by Ref. [4] involved the direct precipitation of E S by solvent exchange. When applied to the analysis of soil extracts the method is subject to interference from acetone-soluble organic matter and the procedure should not be used uncritically for highly organic soils. Preliminary investigation s were conducted to determine i) the most suitable extractant for E S polluted forest floor materials, and ii) the effect of soil moisture and the extraction time on the recovery of added E S .
Temperature may also affect in the recoveries of E S . Drying soil at

Determination of Elemental Sulfur from S-Rich Soil and Fertilizer by Titrimetric Method
Md Didar-ul-Alam* and Mohammed Naushad Alam Soil, Water and Environment, Dhaka University, Dhaka, Bangladesh

Abstract
In the present study the emphasis was given on two points, one is find out the effective extractants solvent and another is method of determination. Importance also was given on extraction ratio between solvent used as extractants and the amount used or dilution of the sample, shaking time and the incubation period on the basis of which after shaking how much time is required for settle down the solution just before titration/determination. The better result was obtained in 45 minutes to one hour after extraction was completed. Among three extractants, determination of elemental sulfur (E S ), acetone can be used as an effective extractant for both S-rich fertilizer and soil sample (% recovery values obtained were 99.0 and 97.0% respectively). On the contrary, the % recoveries with toluene and xylene the values obtained from S-rich fertilizer and S-rich soils were 97.0 and 93.0 and 92.0 and 87.0% respectively. Determination was done with titrimetric method. Colorimetric always time consuming, values obtained with spectrophotometer is sometimes variable and expensive due to using of power supply. In titrimetric method where a high degree of accuracy and precision is not required. It is rapid and suitable for routine analysis in laboratories without using specialized equipment. temperature greater than 25°C has reported to show lower recoveries of E S [5]. According to Ref. [3] 5 minutes are adequate for the removal of E S from soil with acetone, but Ref. [6] have suggested that complete extraction of sulfur was achieved only after 3 hour. But in solubility tests approximately 45 minutes were required to dissolve pure sulfur in acetone. Amount of soil used varied between 0.2 and 0.1 g (ovendry weight basis), depending on the expected E S concentration. The minimum extraction ratio between extractants and the sample should be 100:1 or depending on sample containing more than 50% of E S (then ratio should be 175:1). E S in soils is generally determine only those soils having E S less than 100 mg Kg -1 and sulfur concentration in excess of 50000 mg Kg -1 could be measured. Lower ratios produced excessive color interference even with the use of a color blank. Increasing the extractant to soil ratio did not affect the recovery of E S .

E S of soil
In the present inquisition 0.2 g sample was mixed to the 20 ml of each extractant, i.e., acetone, toluene and xylene at the ratio of 1:100. The solution was shaken thoroughly on suitable shaking machine for 45 minutes to 1 hour and allowed to stand for overnight. Then the solution was filtered through Whatman no.44. Now 2 ml of aliquot was taken in 50 ml white porcelain basin, 2 ml of Potassium cyanide (KCN, 0.1M: 0.6519 g/100 ml) was added to the sample solution to give thiocyanide which was then titrated with 0.025M AgNO 3 (4.2467 g/L) in presence of 2 ml of 0.33 M formalaldehyde (1 ml of Conc.HCOH/100 ml) to bind residual cyanide ions.. For this reason same amount of KCN was added in the solution as to the amount of aliquot in the procedure to