The Viscosity of Liquid Sulfur

The viscosity of pure sulfur and the effect of selenium, arsenic, and the organic substances on its viscosity were determined in the temperature range between 120 and 160℃. The viscosity of pure sulfur versus temperature is normally represented by the experimental formula of η=Be^ until the ascending temperature reaches about 155℃. In the equation, which directs the linear relation between the logalithm of the viscosity and the reciprocal of the absolute temperature, the viscosity is reduced to minimum near about 155℃, and then gradually rises to the neighbourhood of 159℃. Further, a sudden increase of the viscosity is observed when temperature reaches 160℃. It is considered that the critical point of the formation of polymer sulfur exists in the temperature defined by these narrow ranges. Selenium dissolved in sulfur causes no remarkable change in viscosity, but it is considered to cause a slight depression in the above critical point whose temperature is seen to lie in the neighbourhood of 159 to 160℃ of pure sulfur. The viscosity of sulfur containing arsenic has a value noticeably higher than that of pure sulfur. The change in viscosity should be demonstrated in other phase such as the equilibrium system on the variation of the molecular species of sulfur and arsenic. The results show that a minimum point is reduced to lower temperature, according to the increase in arsenic content in sulfur. The organic substances from the source of charcoal tar or that of coal tar cause no change in viscosity. Further, distinct differences are not observed in various heat treated samples below 160℃. So, the effect of the organic substances is considered to be small in experiments