Tertiary amyl phenol sulfides are made in flaked form by reacting tertiary amyl phenol with sulfur monochloride at a mole ratio of to moles of the phenol to one mole of sulfur monochloride. The hot liquid reaction product is then flaked on a cooled surface. The use of tertiary amyl phenol sulfides as a sulfur donor in the vulcanization of rubber is facilitated by .