Commodity money cans or foil pouches of mackerel fish fillets, which have a fairly standard cost and are easy to store. These may be exchanged for many services in prisons where personal possession of currency is prohibited. In situations where the commodity is metal, typically gold or silver, a government mint will often coin money by placing a mark on the metal that serves as a guarantee of the weight and purity of the metal. In doing so, the government will often impose a fee which is known as seigniorage. The role of a mint and of coin differs between commodity money
Ultra-high-purity steam for oxidation and annealing high temperature combustion. Within its optimal operating range, torches deliver good purity. Pyrolytic systems can support a middle range of flow but have a difficult time with very low flow rates and low steam to hydrogen ratios when adding water vapor to a carrier gas. Also, thermal management of the heat profile of the furnace and incomplete combustion affect furnace performance. In selective oxidation processes, water vapor is needed with hydrogen and without molecular to oxygen. This allows for the oxidation of specific metals. Torches and catalytic system are not 100% efficient so low levels of oxygen may still enter