How Do You Convert PPM to mg/oz

["Snodgrass, Bonnie" <snodgrab@ncr.disa.mil>]

I've been spending some time analyzing my horses feed and I have a chart
that shows how to make almost every type of conversion there is except
"parts per million" aka ppm. I've been looking at the trace mineral salt I
use, the electrolytes I prefer and the mineral supplement I'm using.  

I feed Buckeye Harvest Salt and all of the ingredients are listed as ppm. I
would like to convert this to mg per oz.  

Another thing that has me stumped is the electrolytes I use list salt,
sodium and chloride as three different ingredients while some electrolytes
will list just sodium and others list sodium chloride. What is the
difference between these minerals and does a horse need all three? 

Bonnie Snodgrass