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The pains and pleasures

of industrial analytical chemistry

One should keep in mind that industrial analysis is not necessarily a routine, boring occupation. It can be frustrating at times but it can also be fascinating, instructive, humorous, and even exciting. It is usually pleasant if one dedicates himself to learning about what goes on in chemical systems. The key to enjoying analytical work lies in knowing that the results will be useful and important.

Problem - solving in analytical chemistry

An analytical chemist should know enough about existing methodologies to choose the best one for application to a given sample, perhaps modifying it if necessary to fit the particular situation, and that there is also an analytical science which seeks the improvement of analytical methodologies with regard to scientific problems. Nowadays, with more and more instrumental methods in vogue, the analysts and determinators are coming closer together.

To be a good chemist one must first be a good analytical chemist. We can teach instrumental analysis in industry, but we should not teach basic chemistry.

Mercury? Questions and answers

Some of you may be interested in the question of mercury and its determination in the environment. This is a fascinating question with many aspects. It illustrates again the importance of analytical chemists looking at the whole picture.

Swedish scientists had developed a gas chromatographic method for the determination of alkyl and aryl mercuric compounds extracted from fish with benzene and dilute hydrochloric acid. They were interested in those compounds because of their use as slimicides, but it turned out that regardless of what compound was used, the mercury found in fish was present as a monomethylmercuric ion.

A number of questions about the behavior of mercury remain to be answered. Several theories have been proposed as to how mercury might have gone from inorganic form in water or a bottom sediment, into a methylated form of a fish. One theory assumes anaerobic conversion in the mud to volatile dimethyl mercury which enters fish via the gills. Another assumes aerobic conversion to monomethyl mercury by bacteria, with subsequent transfer up to the food chain. Still another assumes that a fish itself can methylate mercury taken in either through the gills as elemental vapor, or via the stomach as inorganic ions, or in an adsorbed state in silt particles. Before all these questions can be answered, we need to develop highly sensitive methods for each individual form of mercury. At present the most sensitive methods can go down only to about 0.05-ppm inorganic mercury in water.

At the conference on environmental mercury contamination in 1970 in Ann Arbor, Michigan, USA a number of sources from which mercury may enter the environment was mentioned. Among them were the burning of fossil fuels, use of mercurial compounds for fungicides in agricultural seed treatments, use of elemental mercury in the electrical industry for manufacture of batteries and mercury vapor lamps, use of mercuric catalysts, and the disposal of domestic sewage sludge. It will be up to analytical chemists to evaluate all of the sources and to provide the data on which proper action can be based. This will be true not only for mercury, but also for all environmental contaminants.

It is interesting that both Finish and Swedish chemists have found fairly high content in fish from certain lakes in northern parts of their countries, remote from any known source of pollution.

Another interesting fact is that mercury will be found in the hair of a person who has been exposed to it. The average person has about one or two ppm in his hair or even more.

Having analyzed sections of the hair of a long- haired person and having known its growth rate, one can approximate the time and intensity of exposure. Most of these analyses have been done by neutron activation, which is advantageous because very small samples can be employed. However, hair can be analyzed by the atomic absorbance method following the digestion procedure used for fish analysis. A 100-mg sample is sufficient for hair in the range of 1 to 10 ppm.

Exercises

I. Translate into Vietnamese paying attention to the finite and non- finite forms of the verb:

1. Having developed a gas chromatographic method for the determination of alkyl and aryl compounds the Swedish scientists got interested in those compounds.

2. Swedish scientists developed a gas chromatographic method for the determination of alkyl and aryl mercuric compounds extracted from fish.

3. The chemists extracted fairly high mercury contents from fish.

4. The scientists found high mercury contents in fish from certain lakes, remote from any known source of pollution.

5. Mercury found in fish was present as a monomethylmercuric ion.

II. Translate into Vietnamese paying attention to the pronoun ((one)):

1. One should keep in mind that industrial analysis is not necessarily a boring occupation.

2. It is pleasant if one dedicates himself to learning about what goes on in chemical systems.

3. An analytical chemist should know enough about existing methodologies to choose the best one for application.

4. To be a good chemist one must first be first of all a good analytical chemist.

III. Translate into Vietnamese paying attention to the Model Verbs + Perfect infinitive:

1. It was realized that drying may have caused some denaturation, but whatever the change it should not have affected the amino acid composition of the proteins.

2. It goes without saying that any of the acid derivatives (amide, ester, etc.) might have been prepared either from benzotrichloride or benzoic anhydride instead of from benzoic acid

3. The mercaptans obtained could have been oxidized in alkaline solutions to disulfides.

4. Zincate solutions could have been prepared by dissolving ZnO in aqueous KOH.

5. It accounts for the observation of Hauer that an X-ray fibre diagram could not be obtained when raw rubber was stretched very slowly, for in this case the region of maximum flow may never have been passed through and the molecular extension necessary for crystallization thus not achieved.

IV. Read the following model of a summary:

The article ((The pains and pleasures of industrial analytical chemistry)) discusses what an analytical chemist should know about existing methodologies and presents a gas chromatographic method for determination of alkyl and aryl

mercuric compounds extracted from fish with benzene and dilute hydrochloric acid.

The paper provides examples of fairly high mercury content in fish from certain lakes of Sweden and Finland, which are remote from any known source of pollution and of finding mercury in the hair of a person exposed to it.

The article illustrates and describes the importance of an analytical chemist who should use the best methodology to a given sample modifying it to the fit the particular situation.