Draft:Analytical chemistry

Perhaps the Very First Chemical Analysis

Of course one may suggest, that humans perform chemical analysis since the most ancient time (mainly based on outer characteristics of matter, which may be defined by sense organs). Obviously, humans can do some simple things: to distinguish edible food from inedible, to define how dry is a piece of wool, and even (with proper training) to find bronze ore. But perhaps performing of the first real chemical analysis belongs to Archimedes. You've definitely heard the story of Eureka, but do you know it completely? If not, let me tell you it in short.

As it had written by Vitruvius, a King Hiero II after another war decided to make a votive crown for a temple, and supplied gold to a contractor, who made the crown. Everything would be okay, but Hiero got an information that the contractor hid a part of gold and substituted it with silver (that is cheaper). The crown is produced, but how to prove it contains silver... Hiero asked Archimedes to solve this problem. (Further the most famous part of the story goes: Archimedes pops out of a bath crying Eureka.)

How actually did Archimedes prove the crown contained silver? He took a vessel (filled with water to the brim) suitable for the crown's size, made ingots of equal with the crown weight (one gold and one silver), and assessed the quantities of water displaced by submersing of each of these objects (gold and silver ingots, and the crown). Archimedes replenished the vessel up to the brim after each submersion. Estimates were: the gold ingot displaced some water, the silver ingot displaced amount of water bigger than the gold ingot, the crown displaced intermediate amount of water. Thus Archimedes showed the contractor's theft, that is what Vitruvius says.

One can see, that Archimedes (aside he determined chemical composition of the crown) used attributes of Analytical chemistry: he used ingots as reference standards and he defined a reproducible procedure, so that we may consider this as the first chemical analysis.

Error

That was all, what Vitruvius told us. Nothing more. The following course of the story we will invent by ourselves.

The question what happened to the contractor (what King Hiero did to him) remains open. Imprisoned? Drove out? Killed? Anyway, let's try to defend our contractor.

Archimedes was able to come to his great conclusion basing on constancy of matter properties. Yes, the matter is constant, but were Archimedes' reference standards constant. Suggest to Archimedes to check it out. Let him make several gold ingots from different samples of this metal, and pass these ingots through his standard procedure. Native gold (the main source of gold in ancient times) often is impure, and contains 0,5 to 15% of other metals mostly silver, zinc, sometimes copper. Assessing a number of water quantities displaced by these gold ingots, Archimedes, sooner or later, would understand this. And after all, there is a mineral called electrum, that consist of gold and silver (15 to 50%). Knowing this Archimedes have to take into consideration the Error. Hiero might supply to the contractor not that pure gold, which was used for producing of the standard ingot. If so, then the contractor wasn't guilty. That may make Archimedes not just to assess displaced water quantity, but rather to measure, and what is better, to take pure gold out of native gold.

Nevertheless, Archimedes could not do that. In his times (circa 250 BC) about 1500 years remained till the emerging of acids dissolving noble metals...

Modern analytical chemists consider similar (and more subtle) errors in obligate manner. For example, they try to provide proper sampling, carry out parallel tests, and many more.

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  In nature, electrum may be hardly distinguished from gold. Credit to James St. John
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  Color of gold alloys depends on their composition. Credit to Metallos
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  Electrum ware may not look golden. Credit to Metropolital Museum of Art

Qualitative and Quantitative Analysis

Archimedes pointed that the crown was not pure, not 100% golden, say, it was of inappropriate quality. We call it qualitative analysis, and we may say: Archimedes performed qualitative analysis and proved presence of other elements among gold. He did elementary (simple), but still important job. By the way, notice how our language reflects this situation. And you already have understood that for more reliable proof we have to determine the exact quantity of gold, both supplied and used in the crown production, i.e. to perform quantitative analysis.

Well, and here is yet another couple of words about those, who were a milestone on a path of development of chemistry in general, and analytical chemistry in particular. Wikipedia says (referencing  to a chemist Thomas Thomson) that nitric acid was obtained by Raymond Lully (who lived circa 1232–1316), the same Thomas Thomson mentions that Lully "could form aqua regia by adding sal ammoniac or common salt to nitric acid, and he was aware of the property which it had of dissolving gold". Back then it were days of alchemy. Lully wasn't a single alchemist, there were many others before him and after, he is just serving a bolster in our narrative. And please don't get him the first who might obtain nitric acid.

Diagram showing qualitative acid test for gold. A quantitative variant might exist.

Alchemists, people mostly known for their cherished dream to find a philosopher's stone, that is able to turn any metal into gold. Hmm... gold again?! Having these two acids alchemists became able to do in chemical way that Archimedes did in physical. But it seems like the first quantitative analysis was connected with gold too. Even Wikipedia says that the modern word "titration" (which stands for classical volumetric quantitative analysis) descends from the French word tiltre (1543), meaning the proportion of gold or silver in coins or in works of gold or silver; i.e., a measure of fineness or purity.

But let's have a look at alchemists from a slightly different angle. Some alchemists (who wanted to get rich in gold) sought a philosopher's stone. However the philosopher's stone itself is a thing worth more than gold. Existence of such a thing, itself may make gold, in fact cheap. And this may make alchemists to be not interested in deception in quantitative assays of gold. We can find a confirmation of that in Paracelsus, who said that alchemy should not serve to obtaining gold, it should serve medicine preparation.

Paracelsus himself believed in that the best medicine is a pure active principle, that could be extracted from a remedy. He considered it would be a compound of five extractions by five different ways (the three of them were known to him, the two others — were not). Extraction ways corresponded to five (or four one) Aristotelian elements. These ways were: liquid extraction (approximately means water element or mercury), ashing (fire element or sulfur), distillation (ether). The missing ways motivated alchemists as Paracelsus to continue their searches. Their ideas, albeit being wrong, gave development to separation methods, without which transition to quantitative analysis would not be possible. Also this transition was possible due to creation measuring instruments.

By the way, without separation Robert Boyle and Antoine Lavoisier (who have thrown al-prefix out of alchemistry) barely could understand that chemical elements are not fire, water, air and earth, but rather oxygen, nitrogen, sulfur, phosphorus, and others, more than a hundred of which are known today. They were excited about till what limits the separation of matter is possible.

While Robert Boyle and other alchemists judged about prime elements, matter discretion and what substances are included in mixed bodies, there was a man who made a great deal for analytical chemistry in practice, it is Georgius Agricola. He developed, aside finding ore veins and manufacturing metals, much of basics of assaying ores. He assayed an ore by fire or in very hot furnaces, he also applied fluxes to ores and couldn't not to observe hiss of CO₂ on processing carbonates by vinegar, or changing a color of a flame from one or another ore. That's how classical flame tests appeared. Thus he contributed to qualitative analysis. However quantitative analysis was rather strongly improved by him too. For instance, in his main work De Re Metallica, one can find such indications:

It is necessary that the assayer who is testing ore or metals should be prepared and instructed in all things necessary in assaying, and that he should close the doors of the room in which the assay furnace stands, lest anyone coming at an inopportune moment might disturb his thoughts when they are intent on the work. It is also necessary for him to place his balances in a case, so that when he weighs the little buttons of metal the scales may not be agitated by a draught of air, for that is a hindrance to his work.

Instrumental Methods

Volta's eudiometer. Credit to Museo Galileo

By that time (the end of 1500s) humanity stepped through a threshold of a new concept on what elements are, and got directed towards more accuracy and convenience of analysis. Equipped laboratories were created on the patterns of Agricola's and even better, and certain scientists were pretty successful and productive, as Carl Wilhelm Scheele, or Pelletier & Caventou tandem, at those labs, achieving great analytical results and making historic discoveries...

And somehow unnoticed (as a dawn) an era of instrumental analysis came in that period. Wikipedia (as in 2022) says that the first instrumental analysis was flame emissive spectrometry developed by Robert Bunsen and Gustav Kirchhoff who discovered rubidium (Rb) and caesium (Cs) in 1860. Their brilliant idea was to combine classical flame tests and known since Isaac Newton dispersive prism to build a spectroscope for obtaining spectra of light emitted in those tests. They investigated this interesting property of elements and were lucky (with certain effort) to come across with spectral lines that never seen before.

However, as always, we may count history of instrumental methods from an earlier date. In 1777 Alessandro Volta proposed an instrument — with rather unusual for modern us name — eudiometer. The name derives from Greek words "eudios", which means "clear" and "metreo", which means "to measure". The appliance measured clearness of air, and Volta's eudiometer determined presence of natural methane (and other flammable gases) in air. It was set up like this: a glass tube closed at one side with a cork, the tube was filled with a portion of air from the other side and got closed. After that an electric charge was applied on electrodes within the tube. In the presence of methane appearing spark exploded the air, and the cork popped up. That pointed the air was not suitable for breath. Did you know that natural methane has no color and odor as well as gases common for air, but is toxic? This analytical instrument was innovative enough for that time, because it used electricity for the first time in history.

Anyway, one may consider a method instrumental, when analyte is elusive for human sense (or hard to catch), but a used device detects it and signals to a human about it. Substances have different physical properties, which are not that obvious as density (mass and volume, which been defined by Archimedes at the first) or color, either smell... They are: optical absorption, optical rotation, retention time, and many more, and modern analytical chemistry actively uses devices measuring these and classical properties as well.

Why Analytical Chemistry is Chemistry

An attentive reader may ask, if, nowadays, analysis is based on physical phenomena, and the days of classical chemical analysis are gone, then why Analytical chemistry is still chemistry? Here is the answer without preludes. The object of Analytical chemistry is still chemical and will be. It is chemical composition of objects that surround us. However, many fields of analytical chemistry, are referred as simply "analysis", e.g. environmental analysis, forensic analysis, pharmaceutical analysis.

There is a discipline tightly connected with analytical chemistry — Laboratory Techniques, and practicing analysts are familiar with both in more or less extent.

The division of labor, of course making one people to develop analytical procedures (for example to decide what precipitator is the best for gravimetric assay of Calcium: sulfate, carbonate or oxalate), while others doing the very work. The formers and the laters are both qualified workers, who studied analytical chemistry.

Analytical Chemistry in Human Life

Adjustment of the optical stand for cathodoluminescent spectrometers. Credit to Kseniia Orekhova

Analytical chemistry supports the main human interest. Before it was gold, then the list was widen; included medicines. Henry D. Thoreau wrote, that "the crop of English hay is carefully weighed, the moisture calculated, the silicates and the potash", but by the 21 century those crops, "rich and various, unreaped by man" are measured too. Analytical chemistry captures new spheres, one by other, as human interests grow.

Analytical chemistry is a technology, a product of which is information, and as any other information this one requires respective relation.

Analytical chemistry accompanies civilization with its problems. It substantiates mining of ores, and checks ecology of life spaces; it detects nutritional value of crops, and depletion of soils; it estimates how good our food, or how bad our blood; it finds out what substance cures us and what intoxicates; and many more.

Future

Here I wanted to write an exciting passage to the beautiful tomorrow, but it seems like things go along a time ago founded course to automation and miniaturization (everything to rid people of hard, dull or dangerous routine). Imagine, for instance, an appliance, which determines activity of certain genes of a person from a drop of his/her blood so that a doctor could give a right dose of a medicine to him or her. It's not a miracle, just well-known chemical reaction carried out in micro-capillaries surrounded by micro-detectors. The way to the future of analytical chemistry is not a walk in a park. History knows that one's dreams would smash to smithereens like in Elizabeth Holmes's.

Hope, this lecture has kindled your interest to continue the study.