COMPOSITION AND PROPERTIES OF Miut POWDERS 323 



called solution is a factor which does not always depend on their 

 actual solubility. 



Other conditions being the same, it is obvious that the finer the 

 particles of the powder the more rapidly will it dissolve. This fact 

 is based on the well-known physical law that the smaller a body the 

 larger is its surface in proportion to its cubic contents. The sur- 

 faces of two spheres are to each other as the squares of their diame- 

 ters and the cubic contents of two spheres are to each other as the 

 cubes of their diameters. This is clearly demonstrated in the fol- 

 lowing example : 



One sphere has a diameter of 2 inches and the other sphere has 

 a diameter of 4 inches. The surfaces and the cubic contents of 

 these spheres are as follows : 



Fig*. 108. 



Sphere with Sphere with 



2-inch dia. 4-inch dia. 



Surfaces 2x2 = 4 4X4= 16 



Cubic contents =2x2X2 = 8 4X4X4 = 64 



The surface of the sphere with the 4-inch diameter is four 

 times as large as the surface of the sphere with the 2-inch diameter. 

 But the cubic content of the sphere with the 4-inch diameter is 

 eight times as great as the cubic content of the sphere with the 2-inch 

 diameter. 



And again, the cube and circular shape of a body has a smaller 

 surface than the oblong and flake shape body. 



The greater the area or surface of a body with a given cubic 

 content, the more surface is exposed to the solvent and the more 

 rapidly will it dissolve. Therefore, the finer and more flaky the 

 particles of milk powder, the more readily and more rapidly will 

 they dissolve. 



The spray-process powders usually are finer and more flaky 



