1 62 Soil Analysis [270 



(b) Determination of moisture. This determination is of 

 no value to the farmer, since the moisture in any soil ex- 

 posed to the weather is, perforce, a very variable quantity. It 

 is therefore only made to enable the operator to calculate 

 out his results as parts per hundred of the perfectly dry 

 sample. 



Remove the clip, and place the watch glasses containing 

 the soil in the steam oven. In two hours replace the clip, 

 allow to cool in a desiccator, and weigh. Repeat the dry- 

 ing operation for half-an-hour at a time until the weight is 

 constant. 



(c) Determination of sulphuric and phosphoric acids. Add 

 to the soil in the beaker 5 c.c. dilute HC1, cover with a clock 

 glass, and allow it to stand on the top of the steam oven until 

 effervescence ceases. Remove the clock glass, washing any 

 liquid condensed on it back into the beaker, and add 25 c.c. 

 strong HC1. Evaporate to dryness on the water bath. Heat 

 for a minute or two on the sand bath until completely dry, 

 cool, moisten with strong HC1, add 25 c.c. dilute HC1 (1-2), 

 mix thoroughly with a short glass rod, heat on the water bath 

 until the sediment settles, and decant through a filter into a 

 12-oz beaker. Wash by decantation until the washings are no 

 longer acid, reject the precipitate, and treat the liquid as 

 directed in the following table : 



Raise nearly to boiling, add ammonia in slight excess, boil, allow to 

 settle, filter, washing by decantation. 



Precipitate. Make a hole through the 

 paper ; wash the ppt. into a 16-oz. 

 beaker with dilute HN0 3 , removing the 

 last traces by dropping strong HNO s 

 into the filter, then washing with hot 

 water. Heat to 85°C. Add 25 c.c. 

 ammonium molybdate solution, allow 

 to stand one hour in a warm place, and determine P 2 5 as described in 

 paragraph 209. 



Filtrate. Add HC1 until 

 acid, boil, add hot BaCL. 

 Allow to stand on water 

 bath for an hour, filter, 

 and weigh BaSO., as in 

 paragraphs 29 and 30. 



