A simple,automated device for the precise addition of liquids

Metering liquid reagents into reaction mixtures in a controlled andreproducible manner has often been a problem in syntheticchemistry. Carrying out the real simultaneous addition of two ormore liquid reagents (concurrent additions) is even more inconvenient.Difficulties increase when addition volumes become small,when addition times become long, or when the reagents are corrosiveor air-sensitive. We have constructed and tested an inexpensive,automated device for the slow, precise delivery of liquid reagentsinto laboratory-scale reaction mixtures. Controlled by a standardpersonal computer, this slow adder can accommodate liquidvolumes from hundreds of microlitres to litres and addition timesfrom minutes to days. Its glass and Teflon construction makes ituseful for nearly all reagents. By using multiple slow adders, trueconcurrent addition of several liquids can be easily achieved.