use of variable substitution for curl in bash -

i trying cas registry numbers nist webbook. have large file of chemical compounds search. find example:

eval curl -o tmp --data-urlencode name=barium webbook.nist.gov/cgi/cbook.cgi 

works fine, reading file in

while read line    eval curl -o tmp --data-urlencode name=$line webbook.nist.gov/cgi/cbook.cgi done<inventory.txt 

fails--the html output says "the requested name (barium)" not found. ideas how proceed?

thanks!