The most important quantitative tools of 19th century organic chemistry were the analytical balance and the Five-Bulb (Fünfkugel) Apparatus, usually called the "Kaliapparat" (interesting etymology), which Justus Liebig invented in 1831. These tools, together with well-chosen chemical transformations and clever reasoning, allowed 19th Century chemists to determine the nature of organic molecules and their reactions long before x-ray diffraction, structural spectroscopy, and chemical quantum mechanics were dreamt of.
By allowing efficient absorption of the
CO2 generated by combustion, the Kaliapparat made
it relatively easy to determine the amount of carbon
in a sample by weight. Liebig had an analytical balance
(right), made by a local cabinet
maker named Hoss, with which he could weigh 100 grams to an
accuracy of 0.3 mg. If burning a half-gram sample produced
something like a gram of CO2, he could weigh it
to an accuracy of better than 0.1%. The long arm of the balance swung slowly,
and the process of weighing was time consuming. Liebig could
smoke a cigar during the time it took to make a
Do you think you could measure the volume of
gaseous CO2 to 0.1% accuracy with
apparatus? [Consider the
influence of temperature and atmospheric
By allowing efficient absorption of the CO2 generated by combustion, the Kaliapparat made it relatively easy to determine the amount of carbon in a sample by weight.
Liebig had an analytical balance (right), made by a local cabinet maker named Hoss, with which he could weigh 100 grams to an accuracy of 0.3 mg. If burning a half-gram sample produced something like a gram of CO2, he could weigh it to an accuracy of better than 0.1%.
The long arm of the balance swung slowly, and the process of weighing was time consuming. Liebig could smoke a cigar during the time it took to make a high-precision weighing.
The delicate piece of glassware to the left is more that 150 years old, the last example of a Kaliapparat to survive from Liebig's laboratory. It is displayed in the Liebig Museum in Giessen, which is reasonably called the "Birthplace of Modern Organic Chemistry", because it is where Liebig taught from 1824 until 1852.
The Museum also has an exhibit, shown at the right, illustrating the stages a glass blower would go through in fabricating a Kaliapparat according to Liebig's 1837 instructions.
Students from all over the world flocked to Liebig's Giessen lab to learn how to be organic chemists. Of the first 61 Nobel Prizes in Chemistry, 44 were awarded to scientific descendants of students from this laboratory.
Not surprisingly many portraits of Liebig, like the one on the right, include a Kaliapparat (which in this 1852 photograph is connected backwards, with the combustion gases entering the smaller bulb).
If you didn't click on the Liebig Museum link above, click now to see an illustration showing 13 individuals in Liebig's lab in 1840.
The 22-year-old dandy at the far right is August Wilhelm Hofmann, whom we'll meet later in the course.
here to see other portraits
|Liebig's Kaliapparat remained in use for three quarters of a century and became a badge of honor for organic chemistry. Below it appears in the logo of the American Chemical Society, on the southwest corner of Sterling Chemistry Laboratory, and as a woodcarving in Yale's Chemistry Library. SCL was constructed in 1923, when some chemists were still familiar with the Kaliapparat, although it began disappearing from general use near the beginning of the 20th Century with the development of microanalytical methods involving samples 100 times smaller than Liebig's, balances 300 times more sensitive, and absorption of CO2 on a solid rather than in a solution.|
Logo of the American
Chemical Society Incorporation of the Kaliapparat in the
logo was suggested by J. L. Smith, one of the founders of
the ACS who had been a Liebig student in 1842.
Logo of the American Chemical Society
Incorporation of the Kaliapparat in the logo was suggested by J. L. Smith, one of the founders of the ACS who had been a Liebig student in 1842.
The Kaliapparat was so called in German because the apparatus contained a solution of kali (or caustic potash, i.e. KOH) to absorb CO2. The word kali derives in the alchemical tradition from the Arabic qalay, "to fry or roast in a pan", and al-qalay , "the substance that had been roasted", that is alkali; al being the definite article in Arabic (as in alchemy, alcohol, algebra, Alameda, etc.).
The sense of alkali is that certain plants were burned and their ashes were extracted with water, which was then evaporated in large iron pots to leave al-kali or pot-ash. This "fixed alkali" was mostly the carbonates of what we call alkali metals. Heated further the fixed alkali could lose carbonate by exchanging anions with lime (calcium hydroxide) to give "caustic potash", which subsequently could lose water to give the metallic oxides.
In the early 18th century it was realized that there were different alkalies: mineral alkali (soda), vegetable alkali (potash), and animal alkali (ammonia). The English word soda derived from suwwad, the Arabic name of a plant of which the ashes are rich in sodium carbonate. The name natron for sodium carbonate came from the Arabic narn, Hebrew neter, which derive from the Greek nitre (also the source of the word nitrate).
During a single week in 1807 Humphrey Davy in London, who had a humongous battery with 250 cells, electrolyzed both potash and soda as solids to prepare two new elemental metals and gave them the latinized names potassium and sodium. In 1813 Berzelius published in a British journal, Thomas Thomson's Annals of Philosophy, his system of atomic symbols as one- or two-letter abbreviations of Latin names for the elements. In this first paper he followed the British discoverer Davy in nomenclature and abbreviated potassium and sodium as Po and So. But within a year Berzelius decided in favor of kalium and natrium, names suggested by the Germans Klaproth and Gilbert, who thought that potassa and soda , labels for "impure substances of commerce", were inappropriate sources for naming elements.
This means that now you must memorize that the abbreviation for potassium is K (kalium), and for sodium Na (natrium).
Thanks to Hans von Zerssen of the Liebig Museum, Giessen.
Based on information from:
Oxford English Dictionary
S. Heilenz, Das Liebig-Museum in Giessen, Edition Giessen, 1996
Ringnes, J. Chem. Ed. (1989) 66, 731-738
Berzelius and Gilbert "Versuch einer lateinischen Nomenclature für die Chemie, nach electrisch-chemischen Ansichten", Annalen der Physik (1812) 42, p. 37
Berzelius "Essay on the Cause of chemical Proportions, and on some Circumstances relating to them : together with a short and easy Method of Expressing them" Annals of Philosophy (1814) 3, 362.
Thomson "Outline of Dr. Berzelius's Chemical Nomenclature", Annals of Philosophy (1814) 4, 450.