This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
In using whitewash much difficulty is experienced in making it stick to the substance covered. A good way to prevent the coating from cracking and peeling off is to add 2 oz. of pure sodium chloride to every 1 gal. of whitewash mixture. This is not expensive, but should be secured at a drug store because some salts of sodium are not pure and will darken the whitewash. The sodium chloride should be added after the whitewash solution is made up. When this mixture is used in buildings it will destroy All vermin which it touches.