chapter  3
36 Pages

Seeking the Natural: Laboratories and the ‘Knowability’ of Milk

One task of this chapter is to illustrate the obstinate reluctance of the material – the milk, the laboratory equipment, the equations – to cooperate in the process of analytical exploration. For liquids in general, Bernadette Bensaude-Vincent finds that hydrometers are the perfect illustration of this phenomenon.2 Whereas, by the late eighteenth century, the precision balance had already allowed a simplification of the interrogation and analysis of solids, the specific gravity of liquids remained difficult to apprehend and difficulties with designing, manufacturing and using the hydrometer confirmed instead nature’s ‘complexity and the limits of our rationalization of the real world’. Hydrometers were, in her words, a materialization of archimedes’ law, but they were, throughout our period, capable of little more than approximate measurement: ‘à peu près’ [almost]. even the great Lavoisier was unable to make one that could be used in all liquids, and eventually the world of hydrometry fragmented into many different sub-fields, each geared to the measurement of one commercially significant fluid. By 1800 there were lactometers for milk, saccharometers for sugar in the brewing process, acidimeters for laboratory reagents, salinometers for measuring salt in solution, and so on. these were not designed to be interchangeable, although the underlying principle is universal and local adaptations do seem to have been common. For instance, the London Hospital in the 1840s was using a urinometer (suitably sterilized one hopes) to measure the specific gravity of milk and in 1865 Payen claimed that Baumé’s areometer, designed to test the strength of alcohol, was regularly pressed into service for milk analysis in French wine-producing districts.3