108 



HATCH EXPERIMENT STATION. 



[Jan. 



in our general markets. In this article we pointed out the 

 special modes of analysis that were in use in testing this 

 material, also certain changes that have taken place in many 

 localities in preparing the phosphatic slag by the addition 

 of silica in a fusing process to change the free lime which is 

 present in the slag to a silicate of lime, thus showing, it is 

 claimed, a larger percentage of available phosphoric acid. 



Samples of phosphatic slag have been collected in our 

 general markets during the past year. This would indicate 

 that this class of material was claimino: the attention of ao;ri- 

 culturists more than in the past. The extensive introduction 

 of new methods of iron mamifacture has largely increased 

 the su})ply of phosphatic slag. Results of field experiments 

 have shown the superior value of this material and demon- 

 strated its fitness as a manurial matter. In view of the 

 above facts, we have again taken this subject up for dis- 

 cussion. 



The following table gives the results of analysis of samples 

 of phosphatic slag made at the laboratory during 1904, in 

 comparison with the average of analyses of slags made at 

 the station in years past. Sample I. was imported from 

 England in 1904; Sample II. was collected in our general 

 markets during the spring of 1904 ; Sample IH. was the 

 average of all previous analyses made at the station. 



Analysis of Sanqiles (Per Cent.). 



Sample I. 



Sample II. 



Sample III. 



Moisture, . . . . 

 Total phosphoric- acid, 

 Available phosphoric acid. 

 Insoluble phosphoric acid, 

 Calcium oxide, 

 Insoluble matter, . 



18.61 



50.. 'jS 



none 

 20.52 

 4.96 

 15.. 56 



.99 

 20.61 



4.05 

 19.02 

 50.82 



6.59 



From the results of the above compilation of analyses it 

 will be seen that the present phosphatic slag does not differ 

 materially from that of the past. The two samples analyzed 

 during the year showed the presence of free lime, which fact 

 was recognized and the mode of analysis was so modified as to 



