LOSS ON IGNITION

S. D. Carroll, C. G. Herron, D. C. Lafex    
University of Arkansas Soil Testing and Research Laboratory    
P. O. Drawer 767    
Marianna, AR 72360    
Phone 870-295-2851 email soiltest@uark.edu    

 

Crucible Preparation

1. Crucibles were numbered and placed into trays that were to be prepared for LOI.

2. They were placed into an oven and heated for 360 °C for 2 hours. Crucibles are never to be touched with the naked hand.

3. Crucibles are to be weighed numerically and the weights recorded.

 

Routine Analysis

1. Scoop 5.0 g of soil into each crucible.

2. Heat samples in 120 °C oven for 2 hours.

3. Remove racks from oven numerically.

4. Place in desiccation cabinet for 10 minutes.

5. Take one tray of crucibles out of cabinet at a time, weigh crucibles numerically, and record gross weight (GW) to ± 0.001.

6. Place each tray back into desiccation cabinet until you are finished recording all weights.

7. Place trays in 360°C oven for 2 hours to remove all organic matter.

8. Remove racks from oven numerically and cool in desiccation rack for 25 minutes.

9. Weigh crucibles and record net weights (NW).

10.When all weights have been taken, the soil is discarded from each crucible in sequence and replaced in its original position in the rack. When all the crucibles in the rack are emptied, gently blow any remaining dust from the crucible set.

 

Calculation
%LOI = (Wt at 120°C - Wt of Crucible) - (Wt at 360°C - Wt of Cruc.) *100/ (Wt at 120°C - Wt of Cruc.)
 

Modifications: We modified heating the samples the first time from 105°C to 120°C. The original directions also said to cool to 105°C after the second heating, but we cool 25 minutes in a desiccation cabinet.

 
References:
Combs, S. M. and M. V. Nathan. 1998. Soil organic matter. p. 53-58. Recommended Chemical Soil Test Procedures for the North Central Region. Missouri Agricultural Experiment Station SB 1001. Columbia, MO.
 
Wolf, A.M. and R. O. Miller. 1998. Development of a North American Proficiency Testing Program for soil and plant analysis. Commun. Soil Sci. Plant Anal., 29:1685-1690.

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