Microchemistry and ultramicrochemistry; history and development

Abstract

Since the end of the last century new techniques have been developed to make it possible to perform chemical experiments on a smaller and smaller scale. The historical development ofgravimetry at a macro-, micro- and ultramicro-level, is represented in a cologarithmic diagram, correlating the sensitivity of the balance, the amount of compound to be evaluated and the weight of sample normally taken. Reference is made to the techniques of micro- and ultramicro-gravimetry used in the laboratory ofB. B. Cunningham at the University of California (Berkeley), and attention is directed to exercises made by graduate students in this laboratory. Titrimetry, with amounts of the microliter, is easy to make, for instance by means of the pipettes and burettes designed byP. Kirk. Ultramicro Kjeldahl determinations, for instance, are very useful for biological purposes; they can be effected by the diffusion technique ofConway, without transfer of solution. On the other hand, for the manipulation of radioactive compounds, operations in “gloved boxes” assure a satisfactory protection at a level lower than 100 millicuries. At a ultramicro level,spectrophotometry can be used with success and is a very promising method today. The sensitivity in the detection and evaluation of traces by means of different analytical procedures is compared graphically. A review is given of some analytical, preparative and physico-chemical methods used in micro- and ultramicro-chemistry.