558 The Storage of Farmyard Manure 



material for the actual determinations, these final samples were passed 

 through a large meat mincing machine and about one-tenth of the 

 product taken for the working sample in each case. 



It is important to note that the whole of the dung was treated in 

 this manner so that a reall)^ representative sample should be obtained. 

 From six to fifteen tons were thus handled in each experiment. 



2. The analytical methods. The laboratory analyses were all 

 made in duplicate. Thus for each item four values were obtained, 

 two from each of the separate samples drawn as described above. 

 Table VIII shows that a satisfactory degree of agreement can be 

 attained. 



The nitrogen was determined by the Kjeldahl-Gunning method. 

 The ammonia was estimated as follows: 10 grams of the manure 

 Avere added to 500 c.c. of distilled water and sufficient magnesia (about 

 3 grams) to make the whole alkaline to litmus. It was then distilled 

 at ordinary pressure. This method is quicker than distillation in vacuo 

 and while it does not give absolutely sharp results it works sufficiently 

 well. The end point is sufficiently sharp when tested by titration: 

 it is not, however, sharp to the Nessler test. 



The amide nitrogen was estimated by digesting 10 grams of the 

 manure with 200 c.c. of 10 % sulphuric acid for 10 hours on the water 

 bath, making just alkaline with caustic soda and distilHng. The 

 ammonia figure has to be deducted from the value thus obtained. 

 The "other nitrogen compounds" are arrived at by difference. 

 The nitrate was estimated by the zinc-couple reduction method 

 when sufficient was present, but small quantities were approximately 

 estimated by the phenol sulphonic acid method. For qualitative 

 te.sting, Letts' diphenylbenzidine method gave good results. 



3. The average comfosition of farmyard manure. Although it is 

 obviously impossible to speak definitely of an average composition of «bo 

 variable a material as farmyard manure its composition as made on 

 different farms differs less than might be expected. So much of it is 

 litter, and so httle does the indigestible material of the sohd faeces 

 vary, that the only notable cause of variation is the urine. The results 

 of some of the most complete analyses are given in Table X. 



