§ 128. ASHES OF FUEL. 249 



This process, will, however, hardly succeed in many 

 cases, and usually only when the ash yielded by the sub- 

 stance is rich in alkaline carbonates or sodic chloride, or 

 when but a small quantity of the substance is incinerated 

 in order to determine the total amount of ash. Since a 

 considerable proportion of alkaline phosphates is often 

 present, which is converted into pyrophosphate during 

 the incineration, it is generally necessary to treat the 

 charred substance ^ith baryta water, in the manner di- 

 rected for the incineration of vegetable substances rich in 

 phosphates. 



In the analysis of the ash, proceed as directed for the 

 analysis of ashes of plants, with the exception that, since 

 silicic acid and sand are rarely present, the work is some- 

 what simplified. The total sul])hur should be determined 

 in a portion of the substance that has been heated with 

 potassic hydrate and nitrate (§ 92). 



III. 



ASHES OF FUEL. 



128. a. Carbonic Acid, — Determine this in 2 grms. 

 h. Clllorine* — Determine this in the nitric-acid solution 

 obtained in a. 



c. Complete Analysis. — Conduct this as directed for the 

 analysis of the ash of plants poor in silica. (§ 124, c, d.) 

 The estimation of potassa and phosphoric acid is of most 

 importance in respect to the agricultural value of the 

 ashes. 10-15 grms. of wood ashes, or 15-25 grms. of 

 peat or coal ashes, should be treated with acid, in order to 

 prepare a sufficient quantity of the solution. 



d. Potassa. — For a volumetric determination of potassa 

 that will answer very well for practical purposes, treat 

 6.91 grms. of the wood ashes in a flask of about 300 c.c. 

 capacity with 5-6 grms. of caustic lime and 40-60 c.c. of 



11* 



