clean and free from any trace of grease or ot'her hydrophobic material which would prevent its being filled by capillary action. We have found that the following method gives consistent results.
After use the pipets are rinsed thoroughly with distilled water and immersed overnight in strong nitric acid. They are then washed thoroughly with tap water followed by standing in a detergent solution for an hour, then washed with tap water thoroughly and rinsed with distilled water several times.
Conclusion. This micropipet is simple both to construct and to use. It permits rapid mixing of the measured volume with a larger volume of fluid and thereby facilitates the determination of initial reaction rates using small reaction vessels. It has been employed with the 0.25ml, l-cm light path cells of the Uvispek spectrophotometer and with the l-ml cells of the Farrand spectrophotofluorometer, and should also be suitable for use with other instruments.
Summary. A micropipet is described which consists of a calibrated length of glass capillary cemented into and slightly protruding from the mouth of a larger glass tube. This construction permits rapid mixing of the contents of the capillary with a larger volume of liquid, when the latter is drawn into the larger tube and then expelled by means of a rubber bulb.