EVAPORATED M1t,.K—HoMOGENIZING 125 
force, they cannet rise to the surface and therefore remain in 
homogeneous emulsion. The value of the homogenizer les in 
removing the fundamental cause of this separation. It reduces 
the fat globules to such small size that their buoyancy, or grav- 
ity force, is not great enough to overcome the resistance of the 
surrounding liquid. 
The earlier theories concerning the action of the homogen- 
izer were that the milk had to pass through openings so mui- 
nute, that the fat globules, in order to be able to pass through, 
were crushed, torn and divided into much smaller units, hence 
their fine state of division in the homogenized milk. 
Later study of the principles of homogenization has revealed 
facts and probabilities which do not bear out the earlier assump- 
tions. Men who have subjected the construction and operation 
of homogenizers to intensive study claim, that the openings or 
orifices through which the milk passes in the machines in com- 
mercial use when operating at capacity, range in size from about 
.003 inch to .O1 inch. If these findings are correct, then it is ob- 
vious that the fat globules and even clusters of fat globules can 
pass through the homogenizer as entire units and without being 
broken up, for the average fat globule measures about .OOOL inch 
in diameter. 
It is not improbable that the homogenizing action is very 
similar in its atomizing cause and effect, as that which takes 
place in the spray-drying process, only the homogenizing action 
is more intensive because of the smaller size of the openings 
through which the milk must pass. The atomized spray in 
the spray-drying process is formed, not in the spray nozzle, but 
as soon as the pressure is released, or as soon as the milk 
escapes from the nozzle. 
In the case of the spray-drying process, the atomized spray 
is discharged into a medium of heated air, while in the homogen- 
izing process, the atomized spray is discharged into a liquid 
medium, milk. 
The degree of fineness of the atoms in either case depends 
on the speed with which the liquid passes through the orifice; 
the higher the speed the finer and more minute the atoms. And 
the speed of passage in turn depends on the degree of pressure 
and the size of the orifice. ‘The greater the pressure and the 
