From: Mars Society
Posted: Tuesday, July 24, 2001
Soil samples were analyzed using a professional soil testing outfit from LaMotte.
In order to test the pH, a distilled water extraction procedure with a flocculating reagent was used to obtain a clear liquid extract, to which a wide range indicator was added. The resulting color was matched to a color standard to determine the pH.
The Melich 1 extracting solution (an acid extracting solution composed of 0.5N hydrochloric acid and 0.025N sulfuric acid) was used to produce a clear extract (the soil filtrate) necessary for most of the tests. The filtrate was neutralized before testing for ammonia nitrogen and iron. A different extraction method was carried out to test for sulfur. Nitrate nitrogen was tested for by a cadmium reduction method which produces a red dye through a diazotization reaction. Nessler's reagent was used to test for ammonia. A diazotization reaction in which nitrite reacts with sulfanilamide was carried out to test for nitrite. Phosphorus was tested for using its reaction with molybdate and reduction with stannous chloride. A bipyridal indicator was used to test for iron at the proper pH. Sulfur was tested for using barium chloride. The results are summarized in the following table using soil samples from near the Hab (Hayne's ridge) and from the northern edge of the von Braun planitia, about 3 km northwest of the Hab (Marine rock).
|Parameter||Haynes Ridge||Marine Rock|
|Nitrate||less then 1.25 ppm||less than 1.25 ppm|
|Amonia||almost 5 ppm||slightly below 5 ppm|
|Nitrite||much less than 0.25 ppm||much less than 0.25 ppm|
|Phosphorous||less than 7.5 ppm||less than 7.5 ppm|
|Sulfur||almost 0 ppm||0 ppm|
|Iron||much less than 2.5 ppm||much less than 2.5 ppm|
Soil samples from the two above areas produced similar chemical results for the above parameters, indicating that the soil is poor in nitrogen, phosphorus, sulfur, and iron.
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