From the Economist….

But something fishy seems to be going on here. For one thing, melamine is not all that easy to dissolve into milk. For another, there’s been a worldwide shortage of melamine for some time now. Its price has shot up to more than $1,750 per tonne from $1,100 a few years ago.

So why use an expensive industrial chemical that’s in short supply to dilute a dirt cheap product like milk? The answer can only be that either some flaw rendered the melamine industrially worthless, or it wasn’t melamine at all. The first suggestion is scary enough; the second is even more ominous.

The only thing your correspondent can imagine that would render melamine industrially worthless is if it were reclaimed waste from the production process.

Industrially, melamine is usually made by heating urea in the presence of a catalyst. Because large amounts of ammonia and carbon dioxide are given off in the process, most modern plants now combine melamine production with urea production, which uses ammonia and carbon dioxide as feedstocks. As the two processes feed off one another, a combined plant is considerably more efficient than two separate ones.

But the final stage—washing the melamine and turning it into crystal form—produces lots of effluent that needs treating before releasing into the environment. The usual way to do that is to filter the waste water and pipe that away, and then dispose of the concentrated solids separately.

Those accumulated solids are around 70% melamine, with the rest being made up of various by-products, including our old friend cyanuric acid. As mentioned before, a mixture of melamine and cyanuric acid can be a nasty witches’ brew, especially when ingested by infants.

But what if it’s not melamine that’s being used to spike China’s diluted milk? Urea may be not as rich in nitrogen, but it’s certainly a whole lot cheaper (around $650 per tonne). Sprayed into the milk at the temperature used to create a powdered product for baby food and confectionery, enough of the urea would be converted into melamine to show up in tests.