E. Scarano
and M. Forina University of Genoa Genoa, Italy
Microburet for Deoxygenated or Gas-Saturated Liquids
In our analytical research work we have often been concerned with the delivery of smallvolumes of liquids from a buret with its point dipped in a solution, meeting the two following requirements 1) Amounts of chemical species however minute (such as those coming from the tip of a usual buret by diffusion) were not tolerated to come into the solution during the experiment,
Figure 1. Diagram of micmburet 1, Closing device (shown in detail in Fig. 21; 2, rubber disc and Nylon sphere (latter mode with a Ramel; 3, gas and liquid inlet; 4, gar outlet; 5, deoxygmation and gor-raturolion chamber; 6, NyIon thread; 7, gmund gloss loin?.
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Figure 2. lrlghll De. toil of closing device; 8, Nylon cap; 9, hypodermic steel needle; 10, b r a s knob; 11, rubber disc> 12, brorr d i x with screws to block tho Nylon thread and to close tho oriflco of the steel needle.
Chemical Educafion
2) The liquid, in some cases, had to be deoxygenated or gassaturated
The above indicated requirements were fulfilled with the buret with the closure on the tip as described here. Figure 1 shows the assembled buret, Figure 2 shows the details of the closing device. The steel needle is soldered to the brass knob. Connection between the steel needle and the Nylon cap, and between the latter and the glass neck of the buret are gas-tight. Delivery of the liquid isobtained by turning the brass knob. Due to the small pitch of the threading, the delivery is highly controllable. For deoxygenated or gas-saturated liquids, the buret is first placed horizontally; with a suction through 4 liquid is forced into 5, by the way of 3. The gas is then allowed to bubble through the liquid for a preset time, and forced to pass alternately through 4 and the tip of the buret. Then the buret is placed vertically; the liquid fills the graduated part of the buret; and its level is adjusted to the zero mark. The tip of the buret is washed and dried, and the buret is placed in the working cell. During the complete experiment the gas is continuously passing by way of 3 into 4. Two kinds of burets have been constructed: 1- and 0.1-ml full capacity, with graduations of 10 and 1 rl, respectively. Of course, due to the Nylon thread inside, standardization of the buret is necessary. This operation, however, is readily and easily accomplished. In addition to our own uses, the buret has been found very well-suited for water determination with the Karl Fischer procedure by Dr. R. Andruzzi, of the Chemical Institute, Faculty of Engineering, University of Rome (Italy).
