Variac

Many forms and sizes of magnetic stirring apparatus are available commercially. These include those fitted with an electric hot plate attached to the flat top the hot plate is controlled by an energy regulator or variable transformer (Variac). 

The submitters used a transformer purchased from the Franklin Transformer Company, Minneapolis, Minnesota, for 25-30. It was provided with taps so that secondary voltages of 5500, 6600, 7700, 8800, 9900, and 11,000 could be obtained. These transformers do not always deliver the rated voltage and hence should be calibrated by actual measurement. The checkers used a luminous tube transformer obtained from the Jefferson Electric Company, Bellwood, Illinois, Cat. No. 721-411. Cap. 825 VA. Primary 115 V.A.C. 60 cycles. Secondary 15,000 V. 60 M.A. Price 19.60. The variable transformer used to regulate the voltage should be rated at 7.5 amperes and may be a Varitran, Adjustavolt, or Variac. 

A bench-top power supply that can simulate the input power source. This will be a large dc power supply with voltage and current ratings in excess of what is needed. For off-line power supplies, use a variac with a current rating in excess of what is needed. 

Using an 8-in. Nichrome wire strip connected with springs to a variac, organic decomposition can be carried out in a very fine line to locate zones. The resulting carbon is small in quantity and will not interfere in subsequent elutions. 

GC-MS Experiments. GC-MS pyrolyses were carried out using a Porapak Q column 6-ft (flow rate 35 mL/min) attached to a Finnigan 4000 quadrupole GC-MS. The sample was placed in a stainless steel tube 10 cm long connected to a 4 way valve. One of the outlets was attached to a Porapak Q column interfaced with the M.S. The stainless steel tube containing a portion of Au colloid film was placed in a furnace connected to a Variac provided with a digitial quartz pyrometer to measure the temperature. Three pyrolyses were performed at 100, 200 and 350°C with the Au-acetone film. 

Boss Ng Hey Yongyi, I just walked past your bench I turned down the variac just a tiny little bit. 

The growth rate is quite sensitive to the axial temperature profile. An axial temperature profile that increases along the reactor because it improves the deposition uniformity is commonly used in industry. The temperature of each successive zone in the furnace (defined by the furnace elements in Figure E14.5a) can be adjusted by voltage applied to variac heaters. The zone temperatures are assumed constant within each zone, T-,j = 1,..., ntv where ntz is the number of temperature zones to be used,... 

Variac General Radio Company, Concord, Massachusetts... 

Electric tube furnaces of appropriate dimensions are available from various manufacturers. A model RO 4/25 by Heraeus GmbH, Hanau, FRG is suitable. However, a very satisfactory furnace can be built by any well equipped laboratory workshop at little cost and effort. The material required consists of thin walled ceramic tubing, 3.5 cm i.d., nichrome resistance wire, heat resistant insulation, and ordinary hardware material. A technical drawing will be provided by the submitters upon request. The temperature of the furnace can be adjusted by an electronic temperature controller using a thermocouple sensor. A 1.5 kW-Variac transformer and any high temperature thermometer would do as well for the budget-minded chemist. 

One bank was connected to the spark coil and the other to the output of my microwave oven transformer. The variac was set to just below the arcing of the spark plug. Then firing the spark coil caused the plasma to start the arc from the microwave transformer. If we set the variac low enough the plasma would stay for a few seconds and then stop until the spark coil was fired again. Then it would stay again for a few seconds and so on. 

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