Large-Scale Methamphetamine Manufacture

3.3 Pre-reduction of platinum dioxide

Much of the existing literature concerning Adam's catalyst describes pre-reducing the catalyst in ethanol and/or allowing the catalyst to pre-reduce in situ. My experience indicates both techniques are wrong. Attempting to pre-reduce this catalyst in ethanol resulted in several small fires and explosions. Attempting to pre-reduce the catalyst in situ worked on only one batch of catalyst, which was the poorest catalyst made.
The procedure that works reliably, every time, is to pre-reduce in distilled water. The pre-reduction process involves exposing the catalyst to hydrogen gas under pressure, resulting in a change in both color and character of the platinum dioxide. Carefully weigh out 1g of catalyst on a triple-beam scale. Place the catalyst into a small (50ml) beaker and add 10ml of distilled water. Carefully pour the resulting slurry into the small pre-reduction vessel through a small funnel, chasing the slurry into the vessel with an additional 10ml of distilled water. Place a small Teflon-coated stirbar into the vessel and seal by carefully cinching down on the retaining nuts on the top plate. Make sure the hydrogen gas valve is closed and the vacuum valve with the nipple is open. Attach the 3/8" hose from your vacuum aspirator and pull a vacuum in the vessel to about 25"Hg. Close the vacuum valve and watch the gauge for a minute. If it doesn't move, your vessel is holding a vacuum. Now open the hydrogen tank valve and increase the pressure at the second stage of the regulator to 30psi maximum. Open the hydrogen inlet valve on the catalyst vessel, pressurizing to 30psi. Close the vessel hydrogen valve and watch the gauge for a drop in pressure. If there is a leak, one can find it rapidly using dishwashing soap mixed with water in a squirt bottle. Once the vessel is pressurized with no leaks, begin stirring as rapidly as possible. The catalyst will be thrown against the interior wall of the vessel as it is splashed around. Adjust the position of the vessel on the stir-plate to maximize the splash. The catalyst will begin to turn from brown to black in color. After an additional amount of time, small particles of catalyst will begin "sticking" to the vessel wall, soon forming a "ring" of tiny black flakes or particles. Once most of the catalyst is in the "flake" form and all of the catalyst has turned from brown to black, it is pre-reduced.
Over-reduction can easily take place, and as this drastically decreases the activity level of the catalyst and reduces it's useful life, this is to be avoided. The catalyst will pre-reduce more quickly during warm weather, but the pre- reduction time varies more from batch-to-batch than with any other factor. One should use 20ml of distilled water for every gram of catalyst. Using less increases the chance of over-reduction while excessive water requires the addition of more ethanol to the reaction solution to maintain homogeneity, thus decreasing catalyst density and increasing reduction time. Typical pre-reduction times are 10-25 minutes.
Once the chemist is satisfied that his catalyst is pre-reduced, he makes sure all hydrogen valves are closed and then slowly opens the vacuum valve to release the excess hydrogen. One should keep in mind that hydrogen reacts with oxygen to make water, with an accompanying release of energy--one should be careful when opening hydrogen gas valves into an atmosphere containing oxygen. Once the pressurized hydrogen has been released, it is time to move the catalyst to the reaction vessel. The best way to do this is to partly fill the pre-reduction vessel with 95% ethanol, then pour the slurry into the reaction vessel using a funnel. Repeat until all the catalyst is picked up. The chemist is now ready to make his product.