Pursuing purity for 125 years
How pure is a material? The answer to this question is vital for chemical analysis. In a paper published by Carl Krauch in 1888, EMD became the first company in the world to commit itself to a defined level of purity. To mark the 125th anniversary of this publication, a lecture was recently held in which some of Krauch’s experiments were repeated.
Michael Arlt, Head of Central Analytics at EMD in Darmstadt
In 1851, a customer complained that EMD’s morphine was contaminated with narcotine. Although Emanuel Merck’s reply sounds very polite, if you read between the lines you can sense that Merck considered the customer’s complaint to be patently absurd.
The production process alone precluded such a possibility, Merck wrote. He went on to cite his company’s reputation and his own personal responsibility for ensuring the product’s quality: “I will always guarantee the purity of my preparations and will compensate you for any losses you may suffer as a result of a contaminated preparation.”
“All of life is chemistry, even love!“
Former university professor
A question of measurement standards
This first purity guarantee was well-timed and would have far-reaching consequences for EMD, a pharmacy founded in 1668 that later became a pharmaceutical and chemical company. By the mid-19th century, chemistry was already well on its way to becoming a science, and pharmacy was not far behind. This required precise measurements.
But measurements are only as precise as the measuring stick used. This applies to yardsticks for carpenters just as much as to the chemical analyses that early scientists used to investigate unknown materials and determine their composition. Such analyses were mainly done by examining the unknown materials reactions with known substances.
However, this method only worked correctly if the substances used in the analysis the reagents were of a defined purity. If the reagents are contaminated, chemists might not be measuring the reaction with the desired material, but with the unwanted additional substance present. It is a typical question of epistemology how we know what we know.
A control lab for monitoring EMD's own high quality standards, around 1900
In 1888, the 35-year-old pharmacist and doctor of chemistry Carl Krauch created an objective, demonstrable basis for Emanuel Merck’s purity pledge. The first edition of Krauch’s publication Die Prüfung der chemischen Reagentien auf Reinheit (“Inspecting the Purity of Chemical Reagents”) is only 60 pages long.
As the publication mentions that Krauch was a chemist at the “E. Merck chemicals factory“ in Darmstadt at the time, it enhanced the company’s reputation as a supplier of ultra-pure materials — especially for demanding analytical work, in which impurities at levels as low as one part in one quintillion (1:1018) can cause problems. This tiny amount corresponds to a pinch of salt dissolved in the 49 billion cubic meters of water in Lake Constance.
Carl Krauch (standing in the middle) surrounded by his EMD colleagues in 1886
Everything is a matter of chemistry — including love
Analytics is also one of the great passions of Georg Schwedt, who, as a college professor, held approximately 400 experiment lectures and several public school lab sessions in order to communicate a basic knowledge of chemistry to society at large. Schwedt, 70, is a professor emeritus of the Technical University of Clausthal in Germany. “All of life is chemistry,” says Schwedt, quoting the famous chemist Justus von Liebig. “Even love!” he adds.
Schwedt’s love of his subject really came across in the experiment lecture that he held in Darmstadt to mark the 125th anniversary of Krauch’s publication. During the lecture, Schwedt conducted six tests according to the instructions in the original publication. “I only have a list of the experiments,” he exclaims with youthful enthusiasm. “I just improvise everything else.” During his public lectures, Schwedt seems to veritably immerse himself in the compounds and their reactions. He also clearly and expertly explains their imponderables — in natural products, for example. “I’ve never had an experiment go wrong,” he reminisces. “I’ll quit if that ever happens.” Everything is going right in Darmstadt as well. A major feature of Schwedt’s experiments is that he doesn’t need much equipment because everything is chemistry in his eyes.
“My wife does most of the cooking because if I do it, it generally turns into a succession of experiments,” says Schwedt, who has written several instructive, entertaining, and successful books about the chemistry of cooking, baking, and frying, as well as household chemistry in general. “When I go to the supermarket, I hardly get around to doing any shopping because I’m always studying the labels..” However, Schwedt is by no means unworldly. He not only enjoys red wine, which is more to him than just “ethanol in an aqueous solution,” but also the molecular kitchen, in which chemical reactions are used to create new flavors and textures for meals.
"Merck’s guaranteed pure reagents," labeled "pro analysi" (for analysis), which were launched on the market in 1888, were groundbreaking. They created the basis for comparative chemical analysis, thanks to their manufacture according to binding standards of purity
Schwedt’s experiments in Darmstadt showed how Carl Krauch proceeded. Krauch used sensitive processes to demonstrate that professional manufacturing techniques do not lead to the presence of typical impurities in a compound, or that they lead to these impurities being present in such small amounts that they do not influence the analysis (see: “Color tempest in a glass with a snap-on lid”).
In performing his experiments, Schwedt demonstrated a purity principle that EMD employs as a matter of course and to which the company pledged itself in Carl Krauch’s publication of 1888: “From now on, the “E. Merck Company” will guarantee the purity of the reagents it markets in accordance with the methods described in the publication. This will mark the beginning of the procurement of reagents that are certified in accordance with the aforesaid guarantee.” Today, this quality pledge is upheld every day by around 700 employees at EMD’s Central Analytics department in Darmstadt and Gernsheim. “We can use almost all the analysis technologies that exist,” says Michael Arlt, Head of Central Analytics.
The department supports the entire company, including the environmental analytics unit, R&D, the goods receiving inspection unit, the quality assurance organization, and the customer complaints department. “For example, a manufacturer once sent us LC television sets with defective screens and asked us to analyze the liquid-crystal mixtures they contained,” says Arlt. Like Emanuel Merck in 1851, Arlt’s team came to the clear conclusion that the impurities could not be caused by the compounds supplied by EMD.
|Color tempest in a glass with a snap-on lid|
|All of the experiments in Georg Schwedt’s anniversary lecture are based on the instructions found in Carl Krauch’s publication. The experiments are often designed so that impurities lead to clear color changes during the test.
To check if sodium acetate has been contaminated with sodium carbonate, for example, Schwedt dissolves a small material sample in distilled water in a glass with a snap-on lid. He then adds phenolphthalein, which is a highly sensitive indicator of acidity.
“The redder the water gets, the more alkaline the sample is and the more intense the contamination,” says Schwedt. If the water is no more than a pale red, it shows that the sample meets the company’s purity pledge.