1. Preheat oven to 250 degrees.
2. Beat egg whites and salt until foamy.
3. Add gelatin and sugar gradually and beat until stiff and sugar is dissolved.
4. Mix in vinegar and fold in chocolate chips.
5. Drop tablespoonfuls on cookie sheet lined with brown paper.
6. Bake for 25 minutes, then turn off the heat and leave the cookies in the oven for another 20 minutes.