DRY GRINDING OF SOIL THIN SECTIONS

Thin Sections

Knowledge of the thickness of sections is important for proper interpretation of electron micrographs. Therefore, the thicknesses of sections of n-butyl methacrylate polymer were determined by ellipsometry, and correlated with the color shown in reflected light. The results are: gray, thinner than 60 mmicro; silver, 60 to 90 mmicro; gold, 90 to 150 mmicro; purple, 150 to 190 mmicro; blue, 190 t...

Educational Meteorite Thin Sections

Routine Preparation of Potished Thin-sections

The colour plate which appears in this number of the Canadian Mineralogist iliustrates the advantage of microscopic observation of mineralized rocks in polished thin-section by incident and transmitted cross-polarized light simultaneously: the identities and relationships of opuqrr" and translucent minerals in contact are immediately evident. The principle is not ne.w; more than a hundred years...

The Permeability of Thin Dry Collodion Membranes

Dry thin collodion membranes have been prepared which are permeable to water, ammonia, weak acids of low molecular weight, HCl gas, O(2), CO(2), and H(2)S, but are impermeable to strong electrolytes and substances of high molecular weight. The permeability to gases does not depend on the density, so that the gases do not pass through pores in the membrane.

Survival of Azotobacter in dry soil.

Detection of viable Azotobacter in soils stored in the laboratory for more than 10 years suggests that these bacteria can remain dormant in nature for prolonged periods of time. Studies of dried cultures show that cysts of A. vinelandii 12837 remain viable for at least 10 years, whereas vegetative cells do not survive for even 1 year under the same conditions.