Beckman pH meter

Benchtop centrifuge lEC Model HN-SII 6 x 50-mL fixed-angle solid rotor, 15-mL adapter sleeves Beckman pH meter... 

Beckman pH Meter Measured Calculated pH200°C EMF (mV) Solution chemistry... 

The Plexiglas Box. A Plexiglas box surrounds the artificial uterus and the manifold. Hot air is introduced through an opening in the side to maintain the placenta and the amniotic fluid at 37 °C. Other equipment used included a Beckman pH meter, Beckman 02 electrode, and C02 and C02-02 tanks. 

The Classical Age, the end of which I witnessed briefly in the early 1940 s, featured personal skill, precise techniques, and style...With the instrumentation of the Beckman pH meter in 1940, every laboratory could estimate the pH of solution almost as easily as measuring its temperature. In retrospect, the introduction of the pH meter signaled a new era in biochemistry. 

Ref 4 contains the following requirements and criteria for silica (1) finely divided similar to Cab-O-Sil , Grade M-5, made by the Cabot Corp of Boston, Mass, (2) surface area as ml of NaOH titrant used to achieve a pH of 9.0 175 to 225m2/g, (3) density as the wt of a known vol of silica 2.31bs/cu ft max, (4) moisture as loss in wt 1.5% max, (5) pH as the measurement made using a Beckman Model G pH Meter with glass vs calomel electrodes ... 

In most experiments the smallest amount of electrolyte needed to coagulate the sols measured after 2 hours standing was chosen as the CCC. When using HC1, this point is the critical coagulation pH. A constant temperature water bath was used for temperature different than 23°C. The pH values were measured with a Beckman Model 96A pH meter and a Fisher combination electrode. The electrophoretic mobility measurements were made with a Laser Doppler Electrophoresis apparatus. These experiments were performed by Mr. J. Klein of the Chemistry Department, Syracuse University. 

It would not be until the development of the pH meter and pH electrode that soil scientists had a good way to measure soil pH. In 1934, A. O. Beckman introduced the first pH meter and started a company to build and sell the meter. This sparked an intense study of soil pH and its relationship to plant nutrient availability [14],... 

Note 1 A Beckman Industrial Model M pH Meter (Fisher Scientific Co Catalogue 90, p577) is satisfactory for detn of pH Note 2 Prepare stock and buffer spins having the pH values listed below in the following manner ... 

The surface trough was made of Lucite, 45 X 15 X 1.5 cm. and was divided into two compartments of equal size by a septum of Lucite, 1.5 cm. high. Cooling channels for temperature control were milled into the bottom of the trough. The monolayer was spread inside a paraffined mica frame which floated on the water and was firmly positioned by external mounts. The surface tension was measured with a double-hook torsion balance and a sand-blasted platinum Wilhemy plate. A Beckman model G pH meter with standard glass and KC1 electrodes was used to measure pH. 

So little current flows across a glass electrode that it was not practical when discovered in 1906. One of the first people to use a vacuum tube amplifier to measure pH with a glass electrode was an undergraduate, W. H. Wright at the University of Illinois in 1928, who knew about electronics from amateur radio. Arnold Beckman at Caltech invented a portable, rugged, vacuum tube pH meter In 1935, which revolutionized chemical instrumentation.16... 

The range of pH and total acid values found in commercial musts of five native and two hybrid varieties for a six-year period (18) are given in Table III. Total acidity and pH were determined in filtered must samples representative of each day s total production, first noting pH then titrating to pH 8.2 using a Beckman Zeromatic pH meter (27). Only the Niagara grape consistently had a total acid content below 1.000... 

Use an ammonia electrode (Orion Model 95-10, Beckman Model 39565 or equivalent) along with a readout device, such as a pH meter with expanded millivolt scale between -700 mV and +700 mV or a specific ion meter. The electrode assembly consists of a sensor glass electrode and a reference electrode mounted behind a hydrophobic gas-permeable membrane. The membrane separates the aqueous sample from an ammonium chloride internal solution. Before analysis, the sample is treated with caustic soda to convert any NH4+ ion present in the sample into NH3. The dissolved NH3 in the sample diffuses through the membrane until the partial pressure of NH3 in the sample becomes equal to that in the internal solution. The partial pressure of ammonia is proportional to its concentration in the sample. The diffusion of NH3 into the internal solution increases its pH, which is measured by a pH electrode. The chloride level in the internal standard solution remains constant. It is sensed by a chloride ion-selective electrode which serves as the reference electrode. 

A book dealing with instruments that have been developed by a community connected to both science and industry (termed the research-technology community ) has chapters on Fourier-transform spectrometers and liquid scintillation counters.309,310 Precision scientific instruments were produced by specialist manufacturers the growth of the instruments industry in Britain and France between 1870 and 1939 has been the subject of a book.311 Of the analytical instruments developed in the 20th century, the most widely used has been the pH meter, and its invention and marketing by A. O. Beckman has been described.312... 

In contrast is the hugely successful American firm of Beckman Instruments, which constructed and marketed pH meters from 1935 and the DU Spectrophotometer from 1941. Papers of a biographical nature based on interviews with Arnold Beckman have been published.104,105 The development of nuclear magnetic resonance spectrometers by the firm of Varian is considered in another paper, with emphasis on the introduction of the Varian A-60, the first commercial instrument intended for the broadly trained chemist as opposed to the custom-built tools for the research specialist.106... 

Meanwhile, Arnold Beckman (b.1900), hitherto a manufacturer of electronic pH meters, had joined forces with Robert Brattain - the brother of Walter Brattain of transistor fame - at Shell Research, with the encouragement of the U. S. Government s Rubber Reserve Company. Beckman s first commercial infrared spectrometer, the IR-1, was developed in 1942 and was used by the wartime synthetic rubber research program. However, the classified nature of this and similar work meant that Beckman spectrometers were not generally available until 1945, when the IR-2 was marketed. Meanwhile, in Britain, Adam Hilger and Grubb Parsons independ-... 

Beckman, Arnold Orville — (April 10,1900, Cullom, Illinois, USA - May 18, 2004, La Jolla, California, USA) Earned his B.Sc. and M.Sc. degrees from the University of Illinois. Received a Ph.D. from the California Institute of Technology in 1928. He founded what eventually became Beckman Instruments in 1935 with the invention of the acidimeter which was later called a -> pH meter. Beckman developed also the UV-VIS (1940) and IR spectrophotometers (1942) and the Helipot (helical potentiometer) (1940) as well as a dosimeter (1942). 

Because of the high resistance of the glass membrane (10 to 100 MO), it is not practical to measure the emf directly. Instead, pH meters either use a direct-reading electronic voltmeter or electronically amplify the small current that flows through the cell and detect the voltage drop across a standard resistor potentiometrically. Both battery-operated and ac line-operated pH meters are available connnercially from such firms as Beckman Coulter, Thermo Orion, and Coming. Such pH meters are calibrated to read directly in pH units, have internal compensation for the temperature coefficient of emf, and have provision for scale adjustments. 

Oxidation-reduction potential measurements were made with a platinum-calomel electrode system connected to a Beckman Model H-2 pH meter. The buffered bacterial suspensions were similar to those in the dose-contact time experiments. To these suspensions, successive equal aliquots of an ozone solution were added at 1°, and the oxidation-reduction potential was measured in millivolts. 

Solutions were prepared from triply distilled water with the purest chemicals usually available commercially. Measurements of pH were made with Beckman Zeromatic and Model G pH meters, and electrodes suitable for alkaline solutions. Solutions with pH greater than 11.4 were made immediately prior to the experiment. All solutions were saturated with Matheson N20 (minimum purity 98% ) by bubbling for at least 20 minutes. The N20 was pre-saturated with water vapor to minimize concentration changes during bubbling. 

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