(Continued from page 24)

gress to authorize limited military strikes against Syrian President Bashar Assad's government in retaliation for a deadly Aug. 21 chemical weapons attack.
• The proposal to use the U.S. military to train the rebels -- something the administration has resisted through more than two years of civil war -- would answer the demands of some lawmakers, including Sen. John McCain, R-Ariz., to do more to train and equip the Syrian opposition. President Barack Obama in June decided to provide lethal aid to the rebels, but so far none of that assistance has gotten to the opposition.
• Officials said Thursday that talk about a military training mission has increased but that there have been no specific Pentagon recommendations forwarded to the White House on how big it should be or how many troops it should involve.
• ___

• WASHINGTON (AP) -- Three simple numbers will prove whether sarin was used to gas Syrians last month: 99-125-81.
• Chemists this week around Europe are feeding samples of bodily tissue and dirt collected after chemical attacks in Syria into sophisticated machines, waiting for those three numbers to read out in a bar graph on a computer screen. The numbers are sarin's fingerprint, said Carlos Fraga, a chemist who specializes in nerve agent forensics at the Pacific Northwest National Laboratory in Richland, Wash. "You're always going to see that."
• In a process that takes about two weeks, chemists have to turn that solid dirt and tissue first into liquid and then into gas.
• Chemists dissolve the samples by putting them into a solvent, such as methanol, and shaking them, Fraga said. Then that's injected into a gas chromatograph, which looks like a big oven. It heats the liquid, turning it into a gas, then acts as a giant sorting machine. The suspected sarin is separated, but at this point scientists still can't figure out what it is. It's just not mixed up with everything else anymore.
• The separated chemicals are injected into a mass spectrometer, which hits the molecules with an electron beam that knocks out an electron to give the molecule a positive charge. The machine can't analyze sarin when it is in its normal neutral level, Fraga said, but when ionized, it breaks apart into a telltale pattern. It's that pattern, shown as a bar graph on a computer screen,that reads the atomic masses of the chemical fragments -- the molecular fingerprint.
• ___

(Continued on page 26)