Wash spinach, trim off any heavy stems and break into pieces. Crisp overnight in dish towel if you wish. Fry bacon until crisp, drain and crumble.
Combine sugar, salt, dry mustard, onion juice, lemon juice, vinegar and sald oil. Mix well. Add sliced water chestnuts and let marinate util ready to serve. When ready to serve, sprinkle bacon over spinach. Toss lightly with dressing. Serves 8.