In collaboration with Dr. Georgette Taylor from the department of Science and Technology Studies at UCL we have been recreating the past and researching into past techniques and methodologies which are no longer in practice.

Recreating The Past - Blowpiping.

The use of blowpipes to produce an intense and extremely hot flame was, according to Berzelius at least, pioneered by jewellers long before it began to be used in chemical analysis. From the middle of the 18th century though, mineralogists such as Cronstedt began to use the same technique to assist with the analysis of minerals. Blowpipes were small and portable and enabled tiny portions of minerals to be quickly submitted to the fire without the need to build up heat (a lengthy process) in large furnaces.

At the end of the 18th century the technique developed a little further, distinguishing between different the different parts of the blowpipe flame and how it acted on the samples. The outer part of the flame, for example, removed the phlogiston of the sample, while the inner part (with the assistance of phlogiston rich charcoal) added it. With care, calxes could be reduced to the metals, and calcinated again at will. In the 18th century this was reconceptualised to accord with oxygen theory, and the outer part of the flame was used to oxidise the mineral, while the inner part could reduce it. This form of analysis also enabled the use of fluxes to show characteristic coloured glasses of particular metal oxides and, of course, characteristic flame colours. Blowpipe analysis was (allegedly) responsible, for the discovery of several elements: nickel, manganese, molybdenum, tungsten, tellurium, titanium, niobium, tantalum, cerium, cadmium, vanadium and indium. The somewhat alarming oxy-hydrogen blowpipe (a wall had to be built between operator and gas supply for safety) was also claimed to have been used in a successful reduction of barytes (as Barium Oxide was then called).

However, this technique is something of a lost art. Blowpipes are rarely, if ever, used today, although if you talk to some (fairly elderly) chemists and geologists they will admit to having been taught some of the basics in their distant youth. For the most part, chemists of today are entirely unfamiliar with the use of this key instrument of their science's past. It was as part of a historical project on analysis and synthesis in 19th century chemistry that we sought to investigate its use. Lacking any form of demonstration, Dr Taylor and I were forced to learn solely from the textbooks of the time, including Berzelius's 1820 treatise and Plattner's quantitative system of 1834. Blowpiping is a difficult skill to acquire, not least because the operator has to use circular breathing to ensure that the flame remains constant and steady of long periods of time. We discovered too that even a selection of careful and relatively detailed texts describing the practice are no substitute for the kind of demonstration that was, of course, unavailable to us.

While an oxidising flame was fairly simple to produce, an effective reducing flame was more elusive. However, with persistence, we were eventually (at some length) able to reduce a sample of black copper oxide to the metal. We also investigated the effect of the blowpipe on some minerals. Zeolites, so the textbooks tell us, were so named by Cronstedt after he witnessed their behaviour under the blowpipe. The term comes from the Greek zein 'to boil', and this is exactly what they appear to do. We recorded a short film and were able to show UCL chemists where these rocks, so familiar to them in their daily work, got their name.