Table 1. Effect of a Solvent on the Sulfur Content in DEAE-Cellulose Sulfates during Sulfation with Sulfamic Acid in the Presence of Urea at 90 °C for 3.0 h.

no.	solvent	permittivity	Kb	sulfur content (wt %)
1	1,4-dioxane	2.3	1.2 × 10–17	10.1
2	pyridine	12.5	1.5 × 10–9	8.9
3	morpholine	7.3	2.1 × 10–6	7.2
4	piperidine	5.9	1.3 × 10–3	7.9
5	diglyme	7.4	2.0 × 10–18	9.4