MIXED FERTILIZERS 13 



tions in which the deposits were made. As large a quantity of the 

 material as can be conveniently obtained and transported should 

 be secured. Where a large quantity of mineral matter is at hand 

 it should first be put through a crusher. Many forms of 'crusher, 

 driven by hand and other power, are on the market. They are all 

 constructed essentially -on the same principle, the pieces of mineral 

 being broken into small fragments between two heavy vibrating 

 steel plates. The general form of these crushers is seen in Fig. i. 



The fragments coming from the crusher can be reduced to a 

 coarse powder by means of the iron plate and crusher shown in 

 Fig. 2. 



Where only a small quantity of mineral is at hand the appa- 

 ratus just mentioned may be used at once after breaking the 

 sample into small fragments by means of a hammer. 



Finally the sample, if to be dissolved in an acid for sol- 

 uble materials only, is reduced to a powder in an iron mortar 

 until it will pass a sieve with a one, or, better, one-half millimeter 



Fig. 2. Plate Grinder for Minerals. 



circular mesh. The powder thus obtained must be stirred with 

 a magnet to remove all iron particles that may have been incor- 

 porated with the mass by abrasion of the instruments employed. 



If a complete mineral analysis of the sample is to be secured, 

 the material freed from iron, as above described, is to be rubbed 

 to an impalpable powder in an agate mortar. 



16. Mixed Fertilizers. In securing a sample of mixed fertiliz- 

 ers the first requisite is that they should be homogeneous. If a part 

 of one kind of a fertilizer be in excess in any part of the whole, 



