Chemistry Dictionary

In this site we focused on the the areas of science incluod analytical chemisty, general chemistry, inorganic chemistry, organic chemistry, physical chemistry, and spectroscopy.(Online Chemistry Dictionary )

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31.5.17

The Function of Analytical Chemistry

  9:29 AM    

The Function of Analytical Chemistry  

Chemical analysis is an indispensable servant of modern technology whilst it partly depends on that modern technology for its operation. The two have in fact developed hand in hand. From the earliest days of quantitative chemistry in the latter part of the eighteenth century, chemical analysis has provided an important basis for chemical development.
For example, the combustion studies of La  Voisier and the atomic theory proposed by Dalton had their bases in quantitative analytical evidence.  The transistor provides a more recent example of an invention which would have been almost impossible to develop  without sensitive and accurate chemical analysis. This example is particularly interesting as it illustrates the synergic development that is so frequently observed in differing fields. Having underpinned the  development of the transistor, analytical instrumentation now makes extremely wide use of it. In modern technology, it is impossible to over-estimate the importance of analysis. Some of the major  areas of application are listed below.  

Fundamental Research
  The first steps in unraveling the details of an unknown system frequently involve the identification of its constituents by qualitative chemical analysis. Follow-up investigations usually require structural  information and quantitative measurements. This pattern appears in such diverse areas as the  formulation of new drugs, the examination of meteorites, and studies on the results of heavy ion  bombardment by nuclear physicists.  

Product Development  
The design and development of a new product will often depend upon establishing a link between its  chemical composition and its physical properties or performance. Typical examples are the  development of alloys and of polymer composites.  

Product Quality Control 
 Most manufacturing industries require a uniform product quality. To ensure that this requirement is  met, both raw materials and finished products are subjected to extensive chemical analysis. On the one  hand, the necessary constituents must be kept at the optimum levels, while on the other impurities such  as poisons in foodstuffs must be kept below the maximum allowed by law.  

Monitoring and Control of Pollutants  
Residual heavy metals and organochlorine pesticides represent two well-known pollution problems.  Sensitive and accurate analysis is required to enable the distribution and level of a pollutant in the  environment to be assessed and routine chemical analysis is important in the control of industrial  effluents.  

 Assay 
 In commercial dealings with raw materials such as ores, the value of the ore is set by its metal content.  Large amounts of material are often involved, so that taken overall small differences in concentration  can be of considerable commercial significance. Accurate and reliable chemical analysis is thus  essential.  Medical and Clinical Studies  The levels of various elements and compounds in body fluids are important indicators of physiological  disorders. A high sugar content in urine indicating a diabetic condition and lead in blood are probably  the most well-known examples.  


Tage: analytical, biochemistry, chemistry experiments, chemistry lab, inorganic chemistry, research, chemicals, chemical reaction, chemical formula, chemical science, chemistry dictionary, green chemistry, chemistry quiz

Source:
1-Freefullpdf for Scientific Publications
2-Principles and Practice of Analytical Chemistry

  

Analytical Chemistry

  9:21 AM    


The Scope of Analytical Chemistry

Analytical chemistry has bounds which are amongst the widest of any technological discipline. An analyst must be able to design, carry out, and interpret measurements within the context of the fundamental technological problem with which he or she is presented. The selection and utilization of suitable chemical procedures require a wide knowledge of chemistry, whilst familiarity with and the ability to operate a varied range of instruments is essential. 

Finally, analysts must have a sound knowledge of the statistical treatment of experimental data to enable them to gauge the meaning and reliability of the results that they obtain. When an examination is restricted to the identification of one or more constituents of a sample, it is known as qualitative analysis, while an examination to determine how much of a particular species is present constitutes a quantitative analysis. Sometimes information concerning the spatial arrangement of atoms in a molecule or crystalline compound is required or confirmation of the presence or position of certain organic functional groups is sought. Such examinations are described as structural analysis and they may be considered as more detailed forms of analysis. Any species that are the subjects of either qualitative or quantitative analysis are known as analytes. 

There is much in common between the techniques and methods used in a qualitative and quantitative analysis. In both cases, a sample is prepared for analysis by physical and chemical 'conditioning', and then a measurement of some property related to the analyte is made. It is in the degree of control over the relation between a measurement and the amount of analyte present that the major difference lies. For a qualitative analysis, it is sufficient to be able to apply a test which has a known sensitivity limit so that negative and positive results may be seen in the right perspective. Where a quantitative analysis is made, however, the relation between measurement and analyte must obey a strict and measurable proportionality; only then can the amount of analyte in the sample be derived from the measurement. 
To maintain this proportionality it is generally essential that all reactions used in the preparation of a sample for measurement are controlled and reproducible and that the conditions of measurement remain constant for all similar measurements. A premium is also placed upon careful calibration of the methods used in a quantitative analysis. These aspects of chemical analysis are a major pre-occupation of the analyst.






Tage: analytical, biochemistry, chemistry experiments, chemistry lab, inorganic chemistry, research, chemicals, chemical reaction, chemical formula, chemical science, chemistry dictionary, green chemistry, chemistry quiz

Source:
1-Freefullpdf for Scientific Publications
2-Principles and Practice of Analytical Chemistry

  

4.5.17

Determination of lead by edta titration Back Titration

  11:34 AM    

Determination of lead by EDTA titration Back Titration

Complexometric titration of a lead Pb with EDTA is very simple, this type of determination of lead by EDTA titration is according to EDTA titration. This method is useful for determination of lead in water and solutions.

PRINCIPLE

Lead may be titrated with EDTA over several pH ranges using a variety of indicators
by direct or back procedures. In This experiment, we describe the determination of lead
by Complexometric back titration at pH 10 using Eriochrome black T as an indicator. The
color change and mechanism of titration are:

Determination of lead by EDTA titration Back Titration
Determination of lead by EDTA titration Back Titration


REAGENTS

1- Lead ions solution (analyte)
2- Eriochrome black T indicator
3- Standardized 0.01 M zinc sulfate solution
4- 0.01 M EDTA solution


PROCEDURE

1- Pipette 25.0 mL of Lead ions solution into a 250.0 mL and add an excess known amount of 0.01 M EDTA solution (V EDTA) and add 2-3 mL buffer solution pH 10.
2- Add 50mg of Eriochrome black T indicator and titrate rapidly with standard 0.01 M zinc sulfate solution until the color changes from blue to wine red. Record the used volume (as VZn).
3- Repeat the titration twice.

Atomic weight of Lead= 207.2 g/mol

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2.5.17

determination of aluminum by back titration

  8:58 AM    

Determination of aluminum  (Al+3) by back titration using EDTA titration

PRINCIPLE:

               Complexometric back titration generally performs when the metallic ions form a
stable complex with EDTA in a slow reaction or when a metal ion blocks an indicator. The
blocked indicator cannot release metallic ions, thus no color change will be observable at
the endpoint of the complexometric direct titration. Both conditions exist in the case of
aluminum ion, thus the ion is best determined by complexometric back titration along
with heating to enhance the complexation of Al-EDTA.

In this analysis, an excess known amount of EDTA is added to the Aluminum
sample solution followed by a pH 10 buffer solution where the Al-EDTA complex can
form. To prevent aluminum ion blocking the indicator and to facilitate the Al-EDTA
complexation, heating the mixture prior to adding the indicator Eriochrome black T wherein
its free form is a blue color. The amount of unchelated EDTA can be then determined using
complexometric back titration with standardized zinc or Magnesium solution. At the endpoint,
a change to wine-red color is observable. This change is due to the formation of Zn- or Mg-
Eriochrome black T complex. 
determination of aluminum by edta titration

REAGENTS: 

1- Aluminum ions solution (analyte)
2- Eriochrome black T indicator 
3- Standardized 0.01 M zinc sulfate solution (titrant).
4- 0.01 M EDTA solution


PROCEDURE:

1- Pipette 25.0 mL of Aluminum ions solution into a 250.0 mL and add an
excess known amount of 0.01 M EDTA solution (V EDTA) and add sufficiently
buffer solution pH 10 just to make the solution ammoniacal.
2- Boil the mixture for a few minutes to ensure complete complexation of
Aluminum. Then, cool to room temperature and adjust the pH to 10.
3- Add 50mg of Eriochrome black T indicator and titrate rapidly with standard
0.01 M zinc sulfate solution until the color changes from blue to wine red.
Record the used volume (as V Zn).
4- Repeat the titration twice.

CALCULATIONS:

Showing posts with label EDTA titration

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