Preheat oven to 350 degrees F (175 degrees C), grease and flour pan.
In a large bowl, sift together flour, cocoa powder, soda and salt.
Add sugar and mix together.
Beat and add oil, water and vanilla and lemon juice mix thoroughly.
Pour into a 9×13 inch pan. Bake at 350 degrees F (175 degrees C) for 1 hour or until toothpick inserted in center comes out clean.