I've always found it extremely difficult to try and equate salaries across different countries, as there are many factors to consider. Your primary concern is making sure that what you are offered is comparable to what other chemical engineers in comparable positions are making in the part of Switzerland in which you will be located.

What some (unscrupulous) employers will do is take your US salary, add a percentage to it, then convert that to the local currency (SFr in your case). The problem with that is that the resulting figure may put you considerably higher or lower than what the guy working next to you in virtually the same job is making - particularly if he's from another foreign country and they pulled the same thing on him.

For salary negotiations, you want to determine whether you'll be on an expat package or on the local payroll, then determine exactly what is included in whichever you're looking at - health insurance, a company car, retirement plans, etc.

If you can, try and take a stroll around before you meet with your potential employer and try to get a feel for what things cost - rentals, groceries, etc. When you work overseas, you spend your money on very different things and it's admittedly hard to get a good sense about that beforehand. It can also depend on how long you're planning on staying in Switzerland - whether you need to maintain your US based insurance or retirement or not.
Cheers,
Bev