Mohr pipette

Capacitance cell as shown in Fig. 1 oscillator as described in the text and Fig. 2 frequency counter (range at least 0.5 to 5 MHz) shielded coaxial cables with connectors five 50- or 100-mL volumetric flasks a 5-mL Mohr pipette acetone wash bottle rubber pipette bulb. 

Figure 1-1 Pipettes. A,Volumetric (transfer). B, Ostwald-Folin (transfer). C, Mohr (measuring), D, Serological (graduated to the tip).

Analytical chemistry began in the late eighteenth century with the work of French chemist Antoine-Laurent Lavoisier and others the discipline was further developed in the nineteenth century by Carl Fresenius and Karl Friedrich Mohr. As a pharmacist s apprentice in Frankfurt, Germany, Fresenius developed an extensive qualitative analysis scheme that, when it was later published, served as the first textbook of analytical chemistry. He built a laboratory at his house that opened in 1848. Here he trained students in gravimetric techniques that he had developed. Mohr developed laboratory devices such as the pinch clamp burette and the volumetric pipette. He also devised a colorimetric endpoint for silver titrations. It was his 1855 book on titrimetry, Lehrhuch der Chemisch-Analytischen Titromethode, that generated widespread interest in the technique. 

Into a 250-ml beaker having an internal diameter of 6—6.5 cm and 100-ml calibration mark and containing 75-80 ml of standard hard water, 5 ml of EC is added, using a Mohr-type pipette, while stirring using a glass rod,... 

The precipitable halide halogens in a 15-ml volume of seawater sample are determined by titration with a silver nitrate solution using a chromate end point, the Mohr titration. The silver nitrate solution is standardized against 15 ml of a seawater standard of known chlorinity ( Eau de Mer Normale ), obtainable from the Depot d Eau Normale, Laboratoire Hydrographique, Charlottenlund Slot, Copenhagen, Denmark. Corrections are made to allow for temperature and density, so as to convert titration values to chlorinity, from which salinity values are obtained. Special Knudsen-type automatic pipettes and burettes are used. 

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