x i i r n 1 1 < . 





.id from the longer part of the bar in such i \toMon 

 as to counterbalance the weight on the shorter part 

 The reading gives the weight of the specimen in air. The 



:rom the bar, is then immcr 



a tumbler ! tiiMillcd water at a temperature of 60' Fahr. 

 ami moved along until it again counterbalances the 

 weight. This new reading gives the weight of the 

 specimen in water. The specific gravity is obtained by 



ng the weight in air by the loss of weight in water. 

 In conned u >n with the determination of specific gr:> 

 reference may be made here to a convenient method of 

 making use of the relative weights of minerals as a means 

 of readily separating them when they are constituents of 

 rocks. It is often desirable to isolate the various minerals 

 in a crystalline rock, not only for chemical analysis but 

 for ex i with the microscope. For this purpose, 



liquids of high specific gravity are used, in which some 

 of the minerals will float, while others sink. By v 

 the density of the solution, the various ingredients of a 

 rock, when they are of different specific gravities, may be 

 obtained separately. The rock to be examined is crushed 

 in a metal mortar, care being taken to prevent any of the 

 steel of the mortar from being removed. The liquids in 

 most general use are Sonstadt's solution of potassium - 



iric iodide, with a maximum density of 5.196, and 



m's Solution" of cadmiunvborotungstate, which has 

 a density of 3.28, and is more serviceable than Sonstadt's. 

 Both these solutions can readily be diluted with water. 

 Mcthylene iodide is also available with a density of 3.33, 

 which can be increased to 3.65. 



3. TrtatmtKt witk AM In the list of a field 



