604 AGRICULTURAL ANALYSIS 



sulfuric acid. The moisture may be ascertained by drying the 

 finely powdered sample over sulfuric acid for a few hours. The 

 water of crystallization is separated by exposing the sample to a 

 temperature of 285 for two hours. The iron may be determined 

 by oxidizing to the ferrous state by boiling with nitric acid 

 and then precipitating with ammonia, and proceeding as directed 

 for iron analysis. The sulfuric acid is separated as barium sul- 

 fate and determined as already directed. 



510. Pyrites. The existence of iron pyrites in a soil in any 

 notable quantity is injurious. The pyrites, which is sulfid of iron, 

 FeS 2 , is converted into copperas, (ferrous sulfate or green vitriol) 

 in which state before passing to a state of higher oxidation, it is 

 quite injurious. Iron pyrites is easily recognized by its crystalline 

 form and golden luster. It has often been mistaken for gold, and 

 to this fact is due its common name, "fool's gold." It often oc- 

 curs in globular masses in marls, and in this state is known as 

 "sulfur balls." When heated, pyrites takes fire and burns with 

 a pale blue flame (sulfur flame), and the iron is converted into 

 ferric hydrate. 



511. Stall Manures. There are no definite methods to be 

 described for the analysis of that large class of valuable fertilizer 

 produced in the stable and pen, and which collectively may be 

 called stall manures. The methods of sampling have already 

 been described, but only patience and tact will enable the col- 

 lector to get a fair representation of the whole mass. 80 These 

 manures are a mixture of urine, excrement, waste fragments of 

 fodder, and the bedding used for the animals. With them may 

 also be included the night soil and waste from human habita- 

 tions and the garbage fro'm cities. All of these bodies contain 

 valuable plant foods, and the phosphoric acid, potash, and nitro- 

 gen therein are to be determined by the methods already given 

 for these bodies when they occur in, or are mixed with, organic 

 matter. In general, stall manures are found to have a higher 

 manurial value than is indicated by the amount of phosphorus, 

 potash, and nitrogen which they contain. Through them there 



80 Wiley, Principles and Practice of Agricultural Analysis, 2nd Edition, 

 1908, 2 : 16. 



