92 AGRICULTURAL ANALYSIS 



and closed with rubber stoppers. They are placed upon a shaking 

 rack, as indicated in Fig. 3, which is also furnished with an ap- 

 paratus for separating the fine meal from the basic slag. 



On a table, as shown in the figure, is fastened a movable hori- 

 zontal board by means of hinges. On one side of this movable 

 board is placed an open wooden box in which is a perforated 

 shelf for the purpose of holding the flasks, so as to prevent their 

 striking together during the shaking. On the other side is placed 

 the sifting apparatus above mentioned. The to and fro move- 

 ment of the shaker is imparted by any convenient mechanism. 



Good results are obtained by placing the substance to be exam- 



Fig. 3. Shaking Apparatus for Superphosphates. 



ined in the flask in a dry state, adding 800 cubic centimeters of 

 water and shaking by means of the machine indicated for half 

 an hour. Afterwards the flasks are filled up to the mark, well 

 shaken and their contents filtered through double folded filters into 

 ordinary flasks of about 400 cubic centimeters capacity. Before any 

 of the filtrate is collected the first that runs through should 'be 

 well shaken in the receiving flasks and rejected. Fifty cubic centi- 

 meters of the filtrate thus collected, corresponding to one gram 

 of the substance, should be used for the determination. 



(2) Total Acid. For total phosphoric acid, including the in- 

 soluble portions, except in the case of basic slags, the material is 

 treated as follows : Five grams of the substance are placed in a 



