L.A. Douglas
Iowa State University
6 Papers
5 Citations
L.A. Douglas is an academic researcher from Iowa State University. The author has contributed to research in topics: Urea & Urease. The author has an hindex of 5, co-authored 6 publications.
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Papers
Use of plastic films for aeration in soil incubation experiments
J. M. Bremner,L.A. Douglas +1 more
TL;DR: This article showed that polyethylene film having a thickness of 0.5 mil (1 mil = 10−3 in) is considerably more permeable to oxygen and carbon dioxide than is the 1-mil film commonly used for aeration in soil incubation experiments.
52
Colorimetric Determination of Microgram Quantities of Urea
L.A. Douglas,J. M. Bremner +1 more
TL;DR: In this article, a sensitive colorimetric method for determining urea is described, which involves measurement of the absorbance of the red color formed when urea was heated with diacetyl monoxime and thiosemicarbazide under acidic conditions (phosphoric acid-sulfuric acid medium).
49
An evaluation of the barium peroxide method of maintaining aerobic conditions and determining carbon dioxide evolved during incubation of soils treated with organic materials
L.A. Douglas,J. M. Bremner +1 more
TL;DR: In this paper, gas chromatographic investigations showed that the barium peroxide technique is not satisfactory for maintenance of aerobic conditions or for determination of carbon dioxide evolved during incubation of soils treated with organic materials.
5
Extraction and colorimetric determination of urea in soils.
L.A. Douglas,J. M. Bremner +1 more
TL;DR: In this paper, a simple colorimetric method of determining urea in soils is described, where the soil sample is extracted with 2M KCl containing a urease inhibitor (phenylmercuric acetate), and the extract is analyzed for urea by measurement of the red color formed when an aliquot is heated with diacetyl monoxime and thiosemicarbazide under acidic conditions (phosphoric acid-sulfuric acid medium).
A rapid method of evaluating different compounds as inhibitors of urease activity in soils
L.A. Douglas,J. M. Bremner +1 more
TL;DR: In this paper, a simple method of studying the abilities of different compounds to inhibit urease activity in soils is described, which involves determination of the effect of the test compound on the amount of urea hydrolyzed by incubation of soils with urea and toluene at 37°C for 5 hours, urea hydrysis being estimated by colorimetric determination of urerea in the extracts obtained by treatment of the incubated samples with 2 M KC1 containing a urea inhibitor (phenylmercuric acetate).