Chemistry pracs 100 years ago – 1893-1898
In the image below, the prac courses for Junior and Senior Chemistry are reproduced as they appeared in the University Calendar of 1898. The course for Junior and Medical students, time-tabled for thirty 3-hour sessions, included exercises on the common gases and acids (one of them HF, not something we would leave around in a first year lab these days). They also did a set of organic exercises and so, too, did the Senior students. But in both courses, the emphasis was heavily on chemical analysis, with first years learning how to identify the elements and second and third years how to measure them.
The photo below, from the University Archives, shows a prac class in progress. The year is 1893 and a Med I group is at work in the Junior lab. I can see wash bottles on every bench, made earlier as a glass-working exercise, and precipitates being filtered and washed. There are test tubes in racks and kits of reagent bottles. Light globes hang from the ceiling. The building, opened not long before, was "provided with the electric light".
"Wet" processes are being studied here. Elsewhere, the Junior course amounted to a canter through 50 years of "dry" qualitative analysis. By the mid-1800s, no analytical chemist would have been without a blowpipe. Developed originally by goldsmiths and glass blowers, this simple device consisted of a narrow-bore tube and a mouthpiece for blowing a fine jet of air into a flame. And I mean blowing, although sometimes there was a hand- or foot-operated mechanical blower, "to relieve the cheek muscles".
A skilled analyst used the blowpipe to direct a pointed oxidising or reducing flame onto a sample and was able to work out much about the composition of the sample by noting the volatility or fusibility of the material, the colour of the flame, the odour of the gas evolved ("the odour of rotten horse-radish" for example "indicates Se") and the nature of the residue.
Two events, however, marked the beginning of the end for the blowpipe as an analytical tool - the invention of the Bunsen burner which was almost as versatile as the blowpipe and easier to use; and, soon after, the publication of papers by Bunsen and Kirchhoff that took qualitative analysis to a new level.
Others before them had observed line emission by metal salts in a flame and also the black lines known as Fraunhofer lines in the otherwise continuous spectrum of sunlight. Bunsen and Kirchhoff, using a spectroscope of their own design, systematically recorded the emission lines of individual elements. They were then able to identify the elements in a sample with previously unimagined sensitivity; and, the clincher, to discover new elements (Rb and Cs in mineral spring waters). Meanwhile, Kirchhoff explained Fraunhofer lines as "reversed spectra", caused by atomic absorption in the sun's outer layers, and was busy drawing conclusions about the composition of the sun. Their "spectrum analysis" was a wonder of the age.
Junior and Medical students re-traced these steps in the prac course. For those going on to Senior Chemistry, prac turned largely quantitative. Second and third years were "required to make correct determinations" of a long list of salts and minerals and "certain of the following" which included ores, cements, coal, steel and manure.
The biggest shock for anyone today who had to do the Senior Prac in Liversidge's laboratory would be, I think, the analytical weighings. The lab was "well provided with balances for different purposes" and it needed to be. Most of the determinations were gravimetric and each involved a number of accurate weighings, perhaps 10 or 15, as replicates were taken to constant weight.
This would be no great chore using a present-day electronic analytical balance, with its single cushioned pan and in-built electromagnet. But the traditional analytical balance was a very different instrument. With two pans, light-weight beam, knife edge and set of reference masses, it was sensitive and accurate – and so tedious to use! In Fresenius' Quantitative Chemical Analysis, a prescribed textbook for prac in 1898, it took 4 closely packed pages to set down the rules for weighing and the tricks-of-the-trade. Shown above is a set of 19th Century weights and below, the use of a "rider" to determine fractions of a mg.
Fresenius, in the introduction of his book, had this to say about analytical chemistry: "The satisfaction enjoyed at the success of our efforts is surely in itself a sufficient motive for the necessary expenditure of time and labour, even without looking to the practical benefits which we may derive from our operations." I can hear our second years: "Yeah, right".
- I am grateful for the help of Reference Archivist Nyree Morrison.
- University Calendar of 1898
- Fresenius, C. R, Quantitative Chemical Analysis
- H.E. Roscoe and A. Schuster, Spectrum Analysis, Macmillan, 4th edn. (1885).
- J. Landauer, Blowpipe Analysis, Macmillan, 2nd edn. (1892).
- J.T. Stock, Development of the Chemical Balance, HM's Stationery Office (1969)