tar formation was evidenced the method of example 1 was repeated except that the concentration of the sulfuric acid was maintained at 4 5 percent based on the weight of the diethylene glycol and the reaction was conducted at 146 u00b0 c and a pressure of 547 mm hg the productivity of the reaction measured as the amount of reaction product including water produced per cubic meter of reactor volume per hour was measured at steady state operation and is set forth in table iii a series of experiments were conducted using the method of example 7 except that the reactor pressure was maintained at the pressure specified in table iii the productivity for the reaction at each pressure was measured and is also set forth in table iii a test run was conducted using the method of example 7 except that the reactor pressure was maintained at atmospheric pressure i e 760 mm hg the productivity of this test run is measured and also set forth in table iii table iii______________________________________ com example parativeno 7 8 9 10 11 example c______________________________________reactor 547 479 304 129 15 760pressure mm hg productivity 115 150 176 203 238 84kg m sup 3 hr______________________________________ as evidenced by the data in table iii due to the increased catalyst efficiency the productivity of the reaction increased as the reactor pressure decreased moreover although examples 7 12 exhibited no tar formation or excessive foaming noticable tar formation.