102-103] TESTING MANURES 39 



phosphate ; if the liquid be at all brown then the soluble 

 phosphate was most probably dissolved bones. From this 

 experiment, therefore, we learn first, whether the manure 

 contains soluble phosphate, and secondly, whether that 

 phosphate was prepared from bones or from a mineral 

 phosphate. 



* 102. Test for Insoluble Phosphate. — Should 

 soluble phosphate have been found in paragraph ioi, we are 

 pretty certain to find insoluble phosphate also. This is 

 tested for in the substance saved on the filter-paper from 

 the last experiment. Scrape the mud off the filter-paper 

 and place in a 3 -inch evaporating-dish ; just cover the 

 substance with strong hydrochloric acid and warm for a few 

 minutes. When as much has dissolved as is possible fill 

 the dish nearly full of distilled water and stir well. Filter. 

 The residue will be the sand which was present in the 

 manure. Divide the liquid which comes through into two 

 portions. Boil one portion with ammonium molybdate. 

 Should a yellow precipitate form, then insoluble phosphate 

 was present. To the other portion add ammonia, and 

 notice the colour of the precipitate. If the insoluble phos- 

 phate has been derived from bones the precipitate will be 

 quite white. If it has been derived from mineral phosphate 

 the precipitate will probably contain phosphate of iron, and 

 be more or less brown. From this experiment we learn 

 whether the manure contains insoluble phosphate, and, if so, 

 whether it is made from bones or mineral. 



* 103. Test for Organic Nitrogen.— Boil up a small 

 quantity of the manure with water in a 3-inch evaporating- 

 basin. Filter and wash with the spray from a wash- bottle ; 

 keep the liquid for paragraph 105. When the liquid 

 and washings have all run through, take the filter and its 

 contents out of the funnel and place them in a dry evapo- 

 rating-basin, and put this to dry in a steam-oven. (Whilst 

 the substance is drying proceed with the next experiment) 



