Analytical chemistry unit operations

In some respects, hydrometallurgy can be described as wet analytical chemistry carried out on a large scale. Many different dow sheets can be designed with various types of unit operations and most metals can be extracted from a complex ore and recovered at the desired level of purity. A viable hydrometaHurgical process, however, must achieve that goal at an economically acceptable cost. 

Chemicals, Apparatus, and Unit Operations of Analytical Chemistry... 

PART I Tools of Analytical Chemistry 1 7 Chapter 2 Chemicals, Apparatus, and Unit Operations of Analytical Chemistry 20... 

The general analytical process is shown in Figure 1.1. The analytical chemist should be involved in every step. The analyst is really a problem solver, a critical part of the team deciding what, why, and how. The unit operations of analytical chemistry that are common to most types of analyses are considered in more detail below. 

An increase in emphasis in instrumentation took hold beginning in the 1940 s and led within a decade to the establishment of numerous experiments in process control in the 1950 s. Industrial and analytical chemistry gradually faded from the scene, although certain aspects of analytical laboratory courses and industrial chemical analysis laboratory remained in many curricula until the 1950 s. With the arrival of such textbooks as Zimmerman and Lavine (1955) and McCormack (1948), a broad pattern of unit operations experiments following established procedures was a common feature of all of the existing curricula. 

There are many dcliniiions of aulomalion. bui (he practical meaning is the performance of operations without human intervention. In the context of analytical chemistry, automation may involve operations like the preparation of samples, the measurement of responses, and the calculation of results. Tigure 3,1-1 illustrates the common steps in a typical chemical analysis and the automation methods used. In some cases, one or more of the steps shown on the left of the figure can be omitted. For example, if the sample is already a liquid, the dissolution step can he omitted. Likewise, if the method is highly selective, the separation step may be unnecessary. The steps listed in Figure 33-1 are sometimes called unit operations. 

For the most part, analytical instrumentation has been at a micro-level for some time already, particularly the electronics related to detection and so on. As the instrument vendors see the market developing, the interfaces between the instruments and the microprocess unit operations will need to be retrofitted. Because reactions are so rapid in microreactors, one can explore more unique types of chemistries. In particular, the ability to remove heat so effectively allows complex condensation reactions to be carried out. 

The large amount of data produced by an automated analytical system has to be processed by an on-line computer. Owing to the miniaturization of analytical and electronic components multi-channel nutrient analysers may be designed as rather compact and handy units, even fit to be used on small vessels. However, they are very complex and by no means switch on-measure-switch off machines. Well trained personnel, skilled in analytical chemistry, mechanics and data processing, and a great deal of experience is required to reliably operate nutrient analysers. Automated analysis is most profitable in every day routine measurements of large sample numbers. A few occasional nutrient samples, however, are better analysed by manual methods. 

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