152 Analysis and Valuation of Manures [259 



salts of potassium, and sometimes nitrates. The first thing to 

 do is, of course, to find out what the manure consists of. The 

 following tests may be used : 



Experiment I. — Make into a paste with water and add a 

 piece of blue litmus paper. If it be strongly acid, the soluble 

 P 2 5 must be estimated. 



Experiment II. — Boil a small quantity (about 4 grams) 

 with 100 c.c. distilled water ; filter, and divide the filtrate into 

 two parts, A and B. 



(A) Add 1 c.c. indigo solution and 50 c.c. strong H 2 S0 4 . 

 Should the indigo bleach, the manure contains nitrates. 



(B) Add 5 c.c. strong H 2 S0 4 . Boil to dryness in a 

 platinum dish ; ignite the residue until it no longer fumes. 

 Dissolve in alcohol; filter. To the filtrate add 1 c.c. of 

 PtCl 4 solution. A yellow precipitate indicates potash. 



If the substance contain soluble phosphoric acid, it must 

 be analysed exactly like a superphosphate. 



If the substance be not acid, it must be analysed exactly 

 like a sample of bones. 



If the substance contain N 2 5 the nitrogen must be esti- 

 mated by the modified acid method. 



If the substance contain potash, 2 grams of the substance 

 are ignited at a dull red heat until all the organic matter and 

 salts of ammonia have been driven off. The residue is boiled 

 with water, filtered, and washed. The K 2 in the washings is 

 estimated by one of the two methods given under potash 

 manures, paragraphs 250 and 251. 



VALUATION OF MANURES BY ANALYSIS 



259. The word value has two very distinct meanings. It 

 may either indicate the price which must be paid when purchas- 

 ing a manure, or it may mean the profit which is to be obtained 



