The importance of vigorous stirring cannot be overemphasized. If too much iron remains on the bottom, it can cause a runaway reaction, which you will regret. To avoid this, keep the iron in suspension and the reactants moving. This writer has determined experimentally that about 150 rpm is a good speed for stirring, but this can vary depending upon the effectiveness of the stirring vanes. The vanes on the reaction vessel shown were a simple plate welded onto the bottom of the shaft, insuring that it did not contact the thermometer shaft inserted through the pot wall.
Now that we have a bearing and driveshaft, we must design a bracket that will hold our gearmotor firmly in line with the bearing and driveshaft. The picture above shows the gearmotor without the bracket, as the unit has been disassembled for storage. The reader will be left to his own devices in this bracket design since there is little chance that your gearmotor will be exactly like mine. Since there are two more attachments which must be placed on the top cover, one should locate an adequate gearmotor early on in the design and then wait until the end to fit the motor and bracket. The motor should have a shaft speed of about 150 rpm and a torque of 32 inch-pounds or better, keeping in mind that the more reaction mixture being turned, the more torque is required.
A 2" stainless nipple must be welded to the top plate to accommodate the condenser and it's fittings. In addition, a threaded ¼" hole must be placed in a location near the outside of the top plate. A ¼" NPT stainless nipple screws in here and is attached to 5/16 Tygon tubing leading to the acid reservoir. This is where the acid enters the reaction vessel.
The condenser and its fittings are fairly straightforward. Four 5' sections of ½" thinwall stainless tubing are grouped within a 2" diameter circle and welded into a flat flange with outside boltholes. Use ½" bolts for strength and a thick rubber gasket. The outside waterjacket is 4" thinwall truck exhaust tubing which is light and cheap. It is fitted with ¼ " NPT bushings at each end for water circulation. It is sealed at the end with another flange, leaving 6-9" of tubing sticking out the end. The waterjacket should be 4' long. Use dishwasher hoses found at the hardware store that have ¼" NPT thread on one end and hose thread on the other for circulating water through the system. The condenser will need to be supported with chains due to it's weight when full of water. In order to use the condenser in both distillation and reflux modes, another flange must be fabricated which can be moved around in combination with standard pipe fittings. A combination of 2" stainless "T" , a 2" plug, and a 6" long nipple with an angled flange of about 20°C on the end worked well for this writer. The adapter flange must mate well with the condenser flange to avoid leaks.
The following diagrams show how the condenser is configured for both distillation and reflux modes:
A container to hold and dispense the muriatic acid is required. This writer uses a small(5gal) plastic garbage can with a Tygon tubing siphon hole drilled just above the acid line. A 1/8" stainless-steel flow valve is required to control the flow of acid into the reaction. These valves may be found at industrial supply houses like W.W. Grainger, etc. One should use only Tygon tubing as most other types will soon harden and crack.