Impregnation of peat soils using polyethylene glycol 4000 for the preparation of thin sections

A method was developed to impregnate peat soils for the preparation of thin sections. Feat soil samples used consisted of wet tropical peat collected from Indonesia. To allow miscible impregnation without prior water replacem ent from the sample, polyethylene glycol 4000 was used as the impregnant be cause this material is soluble in water in all proportions. The impregnatio n procedure consisted of consecutive heat-immersion of the samples at 60 to 70 degreesC in polyethylene glycol 4000 solutions with increasing concentr ations. Consecutive impregnation for 2, 3, 4, and 5 d in 25, 50, 75, and 10 0% polyethylene glycol 4000 solutions, respectively, was found to be suitab le for impregnating and hardening the samples. The heating temperature duri ng the period of impregnation should be properly kept so as to avoid too fa st vaporization, bubbling, or even boiling, while maintaining polyethylene glycol 4000 always under solution conditions. Immersed conditions should be maintained in order to avoid air trapping. After the impregnation was comp leted, the samples should be cooled slowly to allow homogeneous solidificat ion of polyethylene glycol 4000, For the preparation of thin sections, a sl iding microtome was used to obtain slices as thick as 20-30 mum after coati ng with a cellulose adhesive. The proposed method was found to be convenien t for, and applicable to the preparation of high quality thin sections of p eat soils.