Yale University School of Forestry & Environmental Studies FES519B - Methods of Ecosystem Analysis 1998

Weighing and ashing samples

    Oven dried samples from each jar were weighed in crucibles. First, each empty crucible was given a unique batch and sample number, and weighed. Next, samples of wood (1.0 g), branch (0.5 g) or bark (0.3 g) were placed into individual crucibles. These samples, weighed to 0.1 mg, were then placed in dessicators with a blank (empty crucible) and a 0.3 g sample of NBS apple leaves in each batch (a batch is 14 crucibles). Crucibles were then removed from dessicators, placed in a muffle furnace at 500 degrees Celcius, and left overnight to ash. Each crucible was then weighed again. The empty crucible was included in each batch to indicate the weight reduction from each sample's crucible alone. This value was subtracted from sample weights later:

Sample Weight = Crucible and Dried Sample - Empty Crucible

Ash Weight = Crucible and ash - Empty Crucible weight (pre-ash) - Weight reduction in blank crucible

Organic Matter = Sample Weight - Ash