The film is Curse of the Crying Woman, a Mexican horror pict which includes many of the things i remember as a child. The film was released in the USA in 1969 which is the year I was born. I can only imagine that I saw it years later on Creature Feature or some other television program.
Here is the sequence that I believe is the one that i have searched for all these years.
This sequence also reminds me of another similar all time favorite from "I Married a Monster from Outer Space" where the aliens, in their death throes dissolve into a rice crispy and goo kind of substance that flows out of their clothing.