Automatic burets

Squibb automatic buret, laboratory supply houses Schellbach automatic buret, laboratory supply houses. 

Summary. Most of the automatic burets which have been discussed have been primarily refinements of models that were introduced many years ago. In the adaptations of automatic burets to microchemistry, some burets have eliminated major drainage errors and contact of titrant with mercury and have provided readily readable volumes on dials or mechanical counters. These improvements are reflected in increased... 

Fig. 2-4. Typical batch reactor configuration. pH is controlled by a combination pH electrode and automatic buret connected to an autotitrator a syringe sampler allows for removal of a subsample of suspension an addition port permits injection of solute an inert gas is bubbled through the suspension by means of a gas dispersion tube and the system is vented through a gas trap a thermometer allows for temperature monitoring and the suspension is mixed with an overhead stirrer.

It remains to be mentioned that contrary to what we believed together with others, the solutions of quaternary alkoxides appear to be quite stable at room temperature when well protected from carbon dioxide and humidity. We kept solutions of tetrabutylammonium ethoxide or iso-propoxide in ethanol—benzene 1 10 in automatic burets at 25 to 30°C during a rather humid summer season and after two months they were practically unchanged, giving the same titration curves as before. 

Approximately 0.001 M porphyrindin. This solution is made up immediately before use in double-distilled water at 0-4 . There is a decrease of the titer of about 10% per 6 hours the solution should be standardized immediately before and immediately after use against the standard ascorbic acid. It will be found convenient to store the porphyrindin in a small automatic buret the reservoir of which is kept in ice. The porphyrindin is then run up into the buret only when needed. 

Calibrate the detector tube pump for proper volume measurement at least quarterly. Simply connect the pump directly to the bubble meter with a detector mbe in-line. Use a detector mbe and pump from the same manufacturer. Wet the inside of the 100 cc bubble meter with soap solution. For volume calibration, experiment to get the soap bubble even with the zero ml mark of the buret. For piston-type pumps, pull the pump handle all the way out (full pump stroke) and note where the soap bubble stops for bellows-type pumps, compress the bellows fully for automatic pumps, program the pump to take a full pump stroke. 

Electronic devices such as automatic titrators and digital burets may be used in place of the traditional glass buret and manual titration. Such devices provide electronic control over the addition of titrant and thus, with proper calibration, are accurate, high-precision devices. These will be discussed in Section 4.9. 

There are also various devices that are commonly used for titrations in place of the glass burets previously described. A digital buret, for example, is an electronically controlled bottle-top dispenser that delivers 0.01-mL increments from a reagent bottle containing the titrant. There are also automatic titrators, such... 

In the laboratory for the electroplating facility at Molex, Inc., Lincoln, Nebraska, seventeen plating baths set up for tin and tin-lead electroplating must be tested three times daily for acid content. The procedure involves an acid-base titration using standard sodium hydroxide as the titrant. Because the volume of samples is so large, an automatic bottle-top buret is used with a 2-gal bottle filled with the standard sodium hydroxide solution. 

Clayton Allsman, a laboratory technician for Molex, Inc., titrates a plating bath sample for acid content using an automatic bottle-top buret. 

The critical datum is not a buret reading, as it was in the case of the volumetric method. Rather, the amount of iodine used is determined coulometrically by computing the coulombs (total current over time) needed to reach the end point. The coulombs are calculated by multiplying the current applied to the anode-cathode assembly (a constant value) by the total time (seconds) required to reach the end point. The modern coulometric titrator automatically computes the amount of moisture from these data and displays it. 

The special apparatus (Fig. 2) consists of two 500 ml Erlenmeyer flasks A and B having slightly rounded bottoms and fitted with Teflon -coated magnetic stirring bars and injection ports, a mercury-filled bubbler back-up prevention valve C, and a mercury-filled automatic dispenser D with airtight-connected insert delivery tube of a buret E. 

The whole dilatometer is immersed in an open bath thermostat, and the temperature is kept constant within =t0.05°C. The position of the motor buret syringe is converted into an electrical signal and scanned by a millivoltmeter installed in a neighboring laboratory (Siemens Kom-pensograph, maximum deflection 250 mm. with a signal of 5 mv.). When the pen reaches full deflection, the meter is compensated automatically back to zero, there resuming scanning. Thus, a considerable ordinate expansion can be achieved. 

The apparatus used at the BurMines consists of one 10-ml Machlett buret which is automatic filling, self-zeroing and made of Pyrex glass. 

With this apparatus, constant pH can be maintained by using a combination glass electrode along with an automatic titrimeter and digital buret. 

Much of what has been said about automatic pipets can be extended to burets. However, since the buret is conventionally used in titrations, it is felt necessary to include additional discussion of automatic titrators which have shown considerable advance in the production of automated designs. 

For microchemical work there is quite a variety of automatic or semiautomatic buret available. The Schellbach and Squibb types which have already been described have been adapted to microdispensing. These... 

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