24a Soluble mineral salt occurring in arid soils? (6) 28a Two opposite electric charges separated by a short distance? (6) 29a First name of actor Hopper and occult writer Wheatley? (6) 2d Hairball in an animal's stomach? (6) 19d Speech defect in pronouncing the letters S and Z? (4) Is that lisp? 40d The oldester of Dumas' Three Musketeers? (5)