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Pubblico·9 membri
Gennady Bolshakov
Gennady Bolshakov

Quantitative Chemical Analysis

Published data on the use of household color-recording devices, such as office scanners, digital cameras, web cameras, mobile phones, and smartphones, in quantitative chemical analysis are generalized and systematized. The main approaches underlying the use of these devices for recording optical analytical signals are discussed. Methodological approaches used in the measurements and processing of the results are described. Examples of the determination of chemical compounds and ions using household color-recording devices are given.

Quantitative Chemical Analysis

WE welcome with pleasure a work which in the present state of our literature on Quantitative Chemical Analysis, may well be looked upon as a boon to the advanced chemical student. Fresenius's Quantitative Analysis has been so generally accepted by chemists as the standard book in this branch of Science, that we greatly regretted the unwarrantable liberties taken by the English editor in the late edition of our trusty author's work. The publishers, who did not, in justice to the accomplished author, recall that edition, may yet learn that the chemical public, at all events, know how to appreciate a good work on Quantitative Analysis. We confess to a feeling of relief, speaking as a teacher of chemical analysis, as we perused Mr. Thorpe's book; for although we have to differ from the author on some minor matters, we believe that this new work will speedily be found in the hands of every chemical student.

The described approach to measuring vinegar strength was an early version of the analytical technique known as titration analysis. A typical titration analysis involves the use of a buret (Figure 1) to make incremental additions of a solution containing a known concentration of some substance (the titrant) to a sample solution containing the substance whose concentration is to be measured (the analyte). The titrant and analyte undergo a chemical reaction of known stoichiometry, and so measuring the volume of titrant solution required for complete reaction with the analyte (the equivalence point of the titration) allows calculation of the analyte concentration.

The equivalence point of a titration may be detected visually if a distinct change in the appearance of the sample solution accompanies the completion of the reaction. The halt of bubble formation in the classic vinegar analysis is one such example, though, more commonly, special dyes called indicators are added to the sample solutions to impart a change in color at or very near the equivalence point of the titration.

As for all reaction stoichiometry calculations, the key issue is the relation between the molar amounts of the chemical species of interest as depicted in the balanced chemical equation. The approach outlined in previous modules of this chapter is followed, with additional considerations required, since the amounts of reactants are provided and requested are expressed as solution concentrations.

The stoichiometry of chemical reactions may serve as the basis for quantitative chemical analysis methods. Titrations involve measuring the volume of a titrant solution required to completely react with a sample solution. This volume is then used to calculate the concentration of analyte in the sample using the stoichiometry of the titration reaction.

The PREN value of the alloy may lead to a misleading prediction of pitting corrosion resistance because in the event of an imbalance of δ ferrite and austenite volume fraction, by Quantitative metallographic analyzes. In this work three laminated duplex stainless steels with different PRENs were characterized: UNS S32304 (Lean Duplex), UNS S31803 (Duplex) and UNS S32750 (Super Duplex), where several techniques of microstructural analysis were used, such as optical emission spectrometry, optical microscopy and scanning electron microscopy/EDS. For all the alloys studied, it was observed that the δ ferrite phase presents higher Cr and Mo contents than the austenite phase, which in turn had Ni contents higher than the δ ferrite. Therefore we can observe that the PRENN values for the Super Duplex alloy were generally higher, as well as in the ferritic and austenitic phase, at a level of 12.25% in relation to Duplex, and more than 50% higher than Lean Duplex, which leads to the definition of the alloy having greater resistance to pitting corrosion.

Course Info Register NowCourse DescriptionThe rapid advancement and increased ability to resolve chemical components has superseded the common procedures for forensic data analysis. Chemometrics is a disciplined blended in data science that aims to efficiently extract information from the expanding inventory of measurable chemicals. A methodological workflow rooted in big predictive analytics will be presented for statistically modelling changes in complex collected chemical data for applications in forensic consulting. After completion of this course, attendees will gain familiarity with concepts involving data pre-processing, statistical correlation, and multivariant statistical analysis. Case studies will be presented for the application of modern data science computer science techniques and creating supporting visuals using R and Python programming. Register for this Short Course.

The course will target intermediate data scientists interpreting complex quantitative chemical data sets. This course will also provide unique approaches to using modern programming languages and workflows to organize data analytics. Possible attendees include students, researchers, industry scientists, and data science consultants.

Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter.[1] In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separation isolates analytes. Qualitative analysis identifies analytes, while quantitative analysis determines the numerical amount or concentration.

Analytical chemistry consists of classical, wet chemical methods and modern, instrumental methods.[2] Classical qualitative methods use separations such as precipitation, extraction, and distillation. Identification may be based on differences in color, odor, melting point, boiling point, solubility, radioactivity or reactivity. Classical quantitative analysis uses mass or volume changes to quantify amount. Instrumental methods may be used to separate samples using chromatography, electrophoresis or field flow fractionation. Then qualitative and quantitative analysis can be performed, often with the same instrument and may use light interaction, heat interaction, electric fields or magnetic fields. Often the same instrument can separate, identify and quantify an analyte.

Analytical chemistry has been important since the early days of chemistry, providing methods for determining which elements and chemicals are present in the object in question. During this period, significant contributions to analytical chemistry included the development of systematic elemental analysis by Justus von Liebig and systematized organic analysis based on the specific reactions of functional groups.

Most of the major developments in analytical chemistry took place after 1900. During this period, instrumental analysis became progressively dominant in the field. In particular, many of the basic spectroscopic and spectrometric techniques were discovered in the early 20th century and refined in the late 20th century.[4]

Starting in the 1970s, analytical chemistry became progressively more inclusive of biological questions (bioanalytical chemistry), whereas it had previously been largely focused on inorganic or small organic molecules. Lasers have been increasingly used as probes and even to initiate and influence a wide variety of reactions. The late 20th century also saw an expansion of the application of analytical chemistry from somewhat academic chemical questions to forensic, environmental, industrial and medical questions, such as in histology.[6]

Modern analytical chemistry is dominated by instrumental analysis. Many analytical chemists focus on a single type of instrument. Academics tend to either focus on new applications and discoveries or on new methods of analysis. The discovery of a chemical present in blood that increases the risk of cancer would be a discovery that an analytical chemist might be involved in. An effort to develop a new method might involve the use of a tunable laser to increase the specificity and sensitivity of a spectrometric method. Many methods, once developed, are kept purposely static so that data can be compared over long periods of time. This is particularly true in industrial quality assurance (QA), forensic and environmental applications. Analytical chemistry plays an increasingly important role in the pharmaceutical industry where, aside from QA, it is used in the discovery of new drug candidates and in clinical applications where understanding the interactions between the drug and the patient are critical.

Inorganic qualitative analysis generally refers to a systematic scheme to confirm the presence of certain aqueous ions or elements by performing a series of reactions that eliminate a range of possibilities and then confirm suspected ions with a confirming test. Sometimes small carbon-containing ions are included in such schemes. With modern instrumentation, these tests are rarely used but can be useful for educational purposes and in fieldwork or other situations where access to state-of-the-art instruments is not available or expedient.

Quantitative analysis is the measurement of the quantities of particular chemical constituents present in a substance. Quantities can be measured by mass (gravimetric analysis) or volume (volumetric analysis).

The gravimetric analysis involves determining the amount of material present by weighing the sample before and/or after some transformation. A common example used in undergraduate education is the determination of the amount of water in a hydrate by heating the sample to remove the water such that the difference in weight is due to the loss of water. 041b061a72


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