146 Analysis and Valuation of Manures [236-239 



236. Moisture. — Two grams are dried at ioo° C. as 

 usual. 



2 37- Organic Matter.— Two grams are weighed out in a 

 platinum dish, and ignited until of constant weight. The loss 

 gives moisture and organic matter. 



238. Sand. — The ash left after burning is dissolved in 

 strong HO, diluted, and filtered. The sand on the filter is 

 washed, ignited, and weighed. 



239. Phosphoric Acid.— The filtrate from the sand is 

 raised to a boil and excess of ammonia added. The precipi- 

 tate is allowed to settle and washed twice by decantation. It is 

 then dissolved in HC1, boiled, re-precipitated with ammonia, 

 allowed to settle again, and washed well by decantation. When 

 fairly clean it is transferred to the filter, washed with hot water, 

 dried, ignited, and weighed, the amount being entered as 

 ammonia precipitate. The ignited mass is then re-dissolved by 

 digestion on the water bath with strong HC1. The solution is 

 boiled down nearly to dryness. Ten c.c. of dilute HN0 3 (3-i) 

 are added with 50 c.c. of water, then ammonia until nearly neutral. 

 Excess of HNO3 is next added, and the solution heated to 

 85 ° C. This heating and the next operation are most con- 

 veniently carried out in an 8-oz. conical flask fitted with an 

 india-rubber stopper. Forty c.c. of ammonium molybdate solu- 

 tion are added to the liquid and the whole shaken up well for 

 three minutes, then placed on the water bath for twenty minutes 

 to settle. The yellow precipitate is filtered off and washed with 

 dilute HNO3. To the filtrate another 10 c.c. of molybdate 

 solution are added, and if further precipitation occurs it is heated 

 to 85°C, shaken up again, and the operation repeated. The 

 washed precipitate is dissolved in dilute ammonia, which must be 

 poured into the filter so that only the soluble portion may come 

 through. To the ammoniacal solution 10 c.c. of magnesia 

 mixture are added, drop by drop, stirring all the while ; 10 c.c. of 



