SWEETENED CONDENSED Mil,.K—CONDENSING 71 
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circulation of the milk over the heating surface is indispensable. 
It is further obvious that the rapidity of evaporation is in direct 
relation to the area of the heating surlace. 
Rapidity of circulation of the milk demands that there be 
no hindering counter currents and that the milk be permitted 
to circulate with maximum freedom in one direction. ‘This can 
best be accomplished by leaving a large open space in the center 
for the milk to return to the bottom after it has boiled up and 
over the coils from the periphery. 
In order to have the coils so ar- 
ranged as to permit this maximum and 
unhindered circulation of the milk, the 
pan must have a certain height or 
depth, so as to admit the necessary 
heating surface. 
With the growing recognition of 
these principles, vacuum pan manufac- 
turers are therefore more and more 
tending toward the stvle of pan with a 
tall body in proportion to its diameter. 
The vacuum pan consists of four 
main parts, namely, the jacket or bot- 
tom, the body or vapor belt, the dome 
and the condenser. 
The Jacket forms the bottom oi 
the pan. The inside wall is copper, the 
outside cast iron. It generally is con- 
cave, the curve varying in different 
types of pans from a depth of a few 
inches to two and one-half feet. The 
steam space in the jacket between 
inner and outer walls is about two 
inches wide. It is equipped with two 
steam inlets and one or two steam 
outlets. In some pans some or all of 
Vacuum pan and condenser 
Geurtess Of C: Ih. Rovers the steam outlets of the coils also ex- 
haust through the jacket. 
In the center of the bottom there is an opening, irom two 
to three inches in diameter, for the discharge of the condensed 
