Refrigerated Slaw

8 C cabbage, shredded

1 large onion, thinly sliced

1 or 1 1/2 C sugar

1 C vinegar

3/4 C salad oil

1 t celery seed

1 t salt

1 t dry mustard powder

Alternate layers of cabbage, onion and sugar. Combine remaining ingredients. Bring to boil. Simmer until well blended. Pour boiling liquid over cabbage mixture. Cover and let set for about 3 hours. Stir. Let set for 2 or 3 hours. Refrigerate. Will keep for 5-6 weeks if refrigerated. 15-20 servings