It looks like there’s trouble in China.  Supplies of milk powder meant for Chinese infants are tainted with melamine – the same chemical found in last year’s dog-food scare.

On Sept. 17, China’s minister of health, Chen Zhu, announced that three babies had died, more than 150 were suffering from acute kidney failure, and an additional 6,000 infants had become sick after drinking milk made from milk powder tainted with melamine.

Now you might be wondering why on earth a company would add melamine to powdered milk.  Could it have been accidental?  Or was there some reason to add this compound?

Consider this:  The amount of protein in foods is often determined based on total nitrogen content.  That’s because proteins contain a fairly regular amount of nitrogen – about 16% by mass.  Take the total nitrogen content, multiply by a conversion factor, and you have a good estimate of protein content of the food.

Take a look at melamine.

Melamine, C3H6N6. Nitrogen atoms are indicated in blue.

Simple assay methods for total nitrogen content can’t distinguish the nitrogen in melamine – which is about 67% nitrogen by mass – from the nitrogen in proteins.

The tested substance appears to have a higher protein content than it actually does – since analysts assume that almost all the measured nitrogen comes from actual protein.  This is a reasonable assumption for uncontaminated materials, but is open to abuse by the amoral.