ANALYSIS OF WOOD ASHES 609 



efficient in respect of nitrogen not much inferior to most organic 

 bodies. 



In comparative trials with sodium nitrate it was demonstrated 

 that nitrogen in leather, previously dissolved in sulfuric acid, 

 has a rank of about 60 when it is rated at 100 in the soda salt. 



For the estimation of the nitrogen in leather the moist com- 

 bustion process is to be preferred. 



516. Hair and Horn. Waste hair and horn also have a high ni- 

 trogen content, and in certain circumstances this may become valu- 

 able for manurial purposes. To this end, however, a treatment 

 similar to that prescribed for leather is imperative. In the nat- 

 ural state, hair and horn decay so slowly as to be of little conse- 

 quence for plant food within any reasonable time in so far as 

 practical agriculture is concerned. The preliminary digestion 

 of these substances with sulfuric acid brings a large proportion 

 of their nitrogen within reach of the growing crop. 



517. Analysis of Wood Ashes. The only kinds of ashes used 

 extensively for manurial purposes are those derived from the 

 burning of hard woods. The ash of soft woods, such as the pine, 

 is too poor in plant foods to warrant its transportation to any 

 great distance for manurial purposes. The methods of incinera- 

 tion of organic bodies for the purpose of obtaining and estimat- 

 ing their mineral contents will be fully discussed in the third 

 volume of this work. 



It is important in ash analysis to know whether there be 

 enough of iron present to combine with all the phosphoric acid. 

 For manurial purposes it will be found sufficient to determine 

 the percentages of potash and phosphoric acid alone. For hy- 

 gienic purposes it is advisable to examine the ash qualitatively 

 and, if necessary, quantitatively for zinc, lead, copper, boric acid, 

 and other bodies of a similar character which may be naturally 

 present in the ash, or may have been added to the organic sub- 

 stance from which it was prepared for preservation or other 

 purposes. The methods of making these special investigations 

 will be discussed in the succeeding volume. At present will be 

 given, however, not only the methods for detecting phosphoric 



