Volt-hours

Regulated direct current (DC) power supplies designed for electrophoresis allow control of every electrophoretic mode. Constant voltage, constant current, or constant power conditions can be selected. Many power supplies have timers and some have integrators allowing runs to be automatically terminated after a set time or number of volt-hours (important in IEF). All modes of operation can produce satisfactory results, but for best results and good reproducibility some form of electrical control is important. The choice of which electrical parameter to control is almost a matter of preference. The major limitation is the ability of the chamber to dissipate the heat generated by the electrical current. 

Figure 27-31, p. 331, shows one of the more sophisticated power supplies for electrophoresis. This unit can supply up to 3,500 V, and 150 ma at 100 watt operation. It has nine programs, each with nine phases. It can control time (hr, min) current ( 1 A to 150 mA) volts (volt hr) and break times. According to the manufacturer," The volt-hour mode automatically compensates for differences in field strength caused by variations in the gel thickness or ionic strength. The mA-hr mode can be used to compensate for differences in field strength caused by temperature variations." Much less expensive supplies are available. 

Initial studies were made with the Rank Bros, electrophoresis unit, using the dilute supernatant suspension over a dispersion of 3.33g of carbon black per liter of dodecane equilibrated for 24 hours with the added 0L0A-1200. The electrophoretic mobility (u) of 1-3 pm clumps of particles was observed at a field of 100 volts per centimeter. The zeta-potentials ( ) were calculated... 

A mixture of 105.7 g. (0.55 mole) of ethyl benzoylacetate and 46.6 g. (0.5 mole) of aniline (Note 1) is placed in the dropping funnel D (Fig. 1) at the top of the continuous reactor (Notes 2 and 3) after the column has been heated to 135° (transformer set at 80 volts) (Notes 4 and 5). The reactants are then admitted to the column during about 15 minutes (this corresponds to a rate of amide formation of 396-400 g. per hour). Alcohol distils (Note 5) noticeably from the column during the addition and collects in flask G. At the completion of the reaction,... 

Ford s Think NEV came in two and four passenger models with a range of 30 miles. It had a 72 volt battery with a 5,000 watt DC motor. The charging time was 4 to 8 hours and it had regenerative braking with hydraulic drum brakes. The price range was 8,000 to 10,000. 

Figure 12. Plot of the Fe/ Fe ratio of an Fe standard, analyzed at 200 to 600 ppb concentrations, relative to the average Fe/ Fe of bracketing 400 ppb an Fe standard, versus the measured Fe volts (10 fl resistor). The measured Fe isotope composition varies relative to Fe concentration, which reflects differences in instrumental mass bias as a function of concentration. Data were taken over a 24 hour period using the University of Wisconsin-Madison Micromass IsoProbe.

Now it has been previously deduced from Faraday s ws that a current of one ampere for one hour should oduce 0147 cubic foot of hydrogen (at 0° C. and 760 m. pressure), but if a solution of caustic soda was used e current would have had to be supplied at i 6g volts, erefore i x 1 69 watt-hour produces 0147 cubic foot hydrogen, or... 

The atmospheric pressure on-site short stack consisting of 32 cells obtained an initial performance of 0.65 volts/cell at 200 ASF (215 mA/cm ) or 0.139 W/cm. The performance degradation rate was less than 4 mV/1000 hours during the 4500 hour test. Single cells tested at atmospheric conditions achieved a 500 hour performance of approximately 0.75 volts/cell at 225 ASF... 

The checkers found that after 5.5 hours the current dropped below 3 amperes at 75 volts. Addition of 25 ml. of 2N potassium hydroxide in methanol to the anode solution increased the current to 6 amperes. Subsequent additions of 10-15 ml. of base were made approximately every 30 minutes. The total volume of base added was 80 ml. 

A portion of the solution was subjected to a qualitative electrical migration experiment using a three-component cell similar to that described by Hardwick and Robertson (79). The solution under investigation was placed in the center compartment, and in the outer compartments were placed sulfuric acid solutions of concentrations similar to that of the test solution. No diffusion occurred over a period of 24 hours. Application of about 50 volts d.c. across the electrodes caused migration of violet color to the cathode and no violet color to the anode. The results indicate a positively charged chromium species. 

Two gallons of waste were filtered using a Whatman glass microfibre filter (GF/D 9.0 cm), and poured into the chamber. The electrodes were connected to a power supply, (B K Precision Model 1601 Regulated DC), supplying two volts and a current of about 100 mA. The pH of the solution was decreased to pH 3.6-3.8 with hydrochloric acid. 5-10 g of calcium chloride were added. The bath was agitated by a stirrer and the plating process was allowed to continue for 8 hours. 

Cone., 0.16M (sat.) applied potential, 300 volts current, 0.1S amp. time, about 3.3 hours. 

Divided cell applied potential, 185 volts current, 0.3 amp. time, about 1.7 hours. 

The stirrers are started, the current (no volt D.C.) turned on, and the resistance so adjusted that the ammeter records io-i 2 amperes. The temperature of the solution in the cells is maintained at 20-30° by surrounding them with a bath of cool water (Note 4). The reduction is complete after 60-70 ampere-hours. This fact is indicated by the increased evolution of hydrogen and the complete solution of the anthranilic acid. 

---