Ultrapure

ultrapure water

To quote Doctor Taylor further: "Certainly the laboratory and the factory which have cheapened food by canning and preserving it and the well-meaning legislator who has purified it, in some cases, perhaps, to the exclusion of the vitamines, owe to the public the corrective for machine-made, ultrapure and deceptive products."

We will see on the other hand that when the symbiotic association has continued for a long time it may be very difficult to obtain ultrapure colonies. In this last case it is necessary to adopt special methods of isolation.

The very high cost of ultrapure semiconductor silicon has been a barrier to lowering the cost of solar cells. Metallurgical-grade silicon has a purity as high as 99 percent, and it costs 10 to 20 cents per pound, roughly the same cost as steel. The semiconductor-grade silicon, used In solar cells, however, has a purity of 99.99999 percent and costs $10 to $20 a pound.